Fast-Acting Caffeine Strategy: A Systematic Review and Meta-Analysis of the Ergogenic Effects of Caffeine Chewing Gum on Physical Performance

Fast-Acting Caffeine Strategy: A Systematic Review and Meta-Analysis of the Ergogenic Effects of Caffeine Chewing Gum on Physical Performance | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Fast-Acting Caffeine Strategy: A Systematic Review and Meta-Analysis of the Ergogenic Effects of Caffeine Chewing Gum on Physical Performance Hossein Miraftabi, Erfan Berjisian, Craig Pickering, Alvaro Lopez-Samanes, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9461741/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Background: Caffeine gum is a fast‑acting delivery method that rapidly elevates circulating caffeine levels and may improve physical performance. Given the recent growth in research, an updated systematic review and meta-analysis is warranted. Objectives: To evaluate the acute effects of caffeine gum on physical performance compared with placebo, and investigate potential moderators including (1) training status, (2) exercise type, (3) chewing duration, (4) caffeine habituation (i.e., habitual intake), (5) caffeine dosage, and (6) timing of administration relative to exercise. Methods: The review followed the Cochrane Handbook for Systematic Reviews of Interventions and PRISMA guidelines. PubMed, Web of Science, Scopus and SPORTDiscus were searched up to February 2026. Three-level meta-analyses were synthesized for outcomes. Sensitivity analyses addressed assumptions within-subject correlations, outliers, and influential cases. Results: Thirty-one studies met the inclusion criteria, with 25 included in the meta-analysis. Caffeine gum produced a trivial but significant improvement in physical performance (SMD = 0.195, 95% CI [0.115 to 0.275] p < 0.05). Aerobic endurance showed a small significant effect, whereas trivial but significant effects were observed for anaerobic performance and vertical jump outcomes (p < 0.05). These effects were consistent across chewing durations of 5 and 10 min and across individuals with low to moderate habitual caffeine intake. In contrast, trivial and non-significant effects were observed in recreationally active participants, for muscular strength/endurance outcomes, and among high caffeine users (p > 0.05) . Meta‑regression showed a significant dose–response relationship (p = 0.031), but no effect of timing of administration relative to exercise (p = 0.683). Sensitivity analyses confirmed the robustness of findings across correlation assumptions and leave‑one‑out procedures. Overall risk of bias was mostly low , with some concerns related to randomization, blinding, and selective reporting. Conclusion: Caffeine gum produced trivial but significant ergogenic effects on physical performance and may represent a practical strategy for athletes, particularly in time‑sensitive situations, due to its rapid buccal absorption and quick onset of action. Registration: The protocol was prospectively registered in the PROSPERO database (CRD420251086458). ergogenic aids nutrition caffeine caffeine chewing gum exercise performance Figures Figure 1 Figure 2 Figure 3 Figure 4 Key Points Caffeine chewing gum produces a trivial but statistically significant improvement in physical performance, including aerobic endurance, anaerobic, and vertical jump performance. Training status and caffeine habituation influence responses, with greater effects in trained individuals and low–moderate caffeine users, but not in highly habituated or recreational participants. Ergogenic effects are evident with typical doses of ~2–4 mg·kg⁻¹ body mass and chewing durations of 5–10 min, Due to its rapid buccal absorption and fast onset, caffeine gum is a practical ergogenic option in time-sensitive or competition settings. 1 Introduction Caffeine (1,3,7-trimethylxanthine) is one of the most widely used ergogenic aids across sports and competitive levels. Since early work over a century ago first demonstrated its performance-enhancing effects on muscular work [1], extensive research has consistently confirmed caffeine's ergogenic effects across diverse exercise modalities. Caffeine intake can improve muscular strength and power [2], endurance capacity [3], and performance in intermittent and team sports [4]. These effects are primarily mediated through antagonism of adenosine receptors (A 1 and A 2 A) in the central nervous system, which increases alertness, promotes arousal, and reduces fatigue perception [5]. Beyond this central action, caffeine stimulates catecholamine release (e.g., adrenaline and noradrenaline) [6], activates dopamine D2 receptors to enhance motivation and reward pathways [7], and lowers pain and effort perceptions during exercise [5]. It may also increase fat oxidation and consequent glycogen sparing during prolonged aerobic exercise [8]. Peripheral mechanisms likely contribute, including enhanced calcium mobilization within muscle fibres during excitation-contraction coupling [9] and improved neuromuscular transmission efficiency [10], leading to improved strength and sprint performance [11]. Together, these central and peripheral actions underpin caffeine’s status as an effective, safe, and widely accessible ergogenic aid. However, responses may vary considerably between individuals. Factors such as genetic polymorphisms (e.g., CYP1A2 and ADORA2A), habitual caffeine intake, and expectancy‑related placebo or nocebo effects [12, 13] can influence metabolism, sensitivity, and perceived performance benefits, partly explaining variability in responses across individuals and studies [14, 15]. Traditionally, caffeine is consumed in capsule form [16], with peak absorption occurring 45-60 min after ingestion [3]. In time-constrained scenarios (e.g., warm-ups, early-morning training, or half-time), faster delivery methods are desirable. Caffeine gum has therefore gained attention due to its rapid absorption kinetics [16]. Caffeine delivered via caffeine gum is partially absorbed through the buccal mucosa, resulting in a faster rise in plasma caffeine concentrations (~5–10 min) compared with traditional ingestion methods [17, 18]. This rapid availability may be advantageous when the time between ingestion and exercise is limited, although pre‑match ingestion remains the most common strategy to ensure adequate circulating caffeine levels at the start of competition [17]. In addition, caffeine gum may be associated with a lower incidence of commonly reported side effects (e.g., anxiety, headaches, gastrointestinal disorders, and sleep disturbances) compared with traditional forms of ingestion [19]. Numerous studies have investigated the effects of caffeine gum across a range of doses (i.e., 1.35 to 6.4 mg/kg BM) [20, 21], ingestion timings (5-120 min) [22, 23], and exercise protocols (e.g., resistance training, vertical jump, cycling performance, and agility) [22, 24]. Additional factors that have been explored include chewing duration (e.g., 5 vs. 10 min) [25, 26], habitual caffeine intake (low, moderate, and high) [25, 27], and participant characteristics (trained and recreationally active individuals) [18, 28]. Despite the growing body of work on caffeine gum, findings remain inconsistent, likely due to methodological heterogeneity. A comprehensive synthesis is therefore needed to clarify the ergogenic potential of caffeine gum, inform future research, and support evidence-based recommendations for athletes and coaches. An earlier meta-analysis by Barreto et al. [29] demonstrated improvements in both endurance and strength/power performance, supporting caffeine gum as a fast-acting and practical delivery method. Since its publication in 2023, the number of studies on caffeine gum has more than doubled, warranting an updated synthesis. Importantly, key moderators such as chewing duration and habitual caffeine intake require investigation through subgroup analyses. These factors have not been examined in previous meta-analyses [29] and may help explain heterogeneity in the observed effects of caffeine gum. Accordingly, this systematic review and three‑level meta‑analysis aimed to quantify the effects of caffeine gum on exercise performance compared with placebo. Subgroup analyses examined potential moderators, including training status, exercise type, chewing duration, and habitual caffeine intake. Meta‑regression analyses were conducted to further explore the influence of caffeine dose (mg/kg) and timing of administration relative to exercise. By clarifying the magnitude and consistency of these effects across conditions, this work aims to inform the practical use of caffeine gum as a rapid caffeine delivery strategy for performance enhancement. 2 Methods This systematic review and meta-analysis were conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions [30] and followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to ensure transparency and methodological rigour [31]. The protocol was prospectively registered in the PROSPERO database (CRD420251086458). 2.1 Eligibility Criteria This review followed the PICO framework: (1) Participants: healthy adults; (2) Intervention: caffeine gum; (3) Comparison: non-caffeinated placebo chewing gum; (4) Outcomes: physical performance. Studies were included if they met all of the following criteria: (1) randomized controlled trials (RCTs) published in peer-reviewed journals; (2) investigated the effects of caffeine gum on physical performance outcomes; (3) involved healthy human participants; (4) included a non-caffeine control condition such as water or non-caloric placebo gum; and (5) reported original experimental data in English. Exclusion criteria were: (1) interventions involving ingestion or mouth rinsing of caffeine; (2) co-interventions with other active ingredients (e.g. carbohydrate, menthol); (3) studies without exercise performance-related outcomes; (4) reviews, abstracts, or non-original reports; or (5) insufficient methodological information. 2.2 Data Sources and Search All databases were searched from the start of their indexing period to September 2025, with a final updated search conducted in February 2026. The search was performed across four electronic databases: PubMed, Web of Science, Scopus, and SPORTDiscus, using the following terms: ("Caffeinated chewing gum" OR "Caffeine gum" OR "Caffeine chewing gum" OR "Caffeinated gum" OR "Caffeine-containing chewing gum") AND ("Exercise performance" OR "Performance" OR "Exercise" OR "Cycling" OR "Running" OR "Sprint" OR "Time trial" OR "Time to exhaustion" OR "Endurance" OR "Resistance" OR "Strength" OR "Power"). All retrieved records were imported into EndNote 21 (Clarivate, Philadelphia, PA, USA) for reference management, and duplicates were removed using EndNote’s built-in “Remove Duplicates” function. Following deduplication and title and abstract screening, full-text articles were independently assessed by two authors ([H.M.] and [E.B.]). During full-text screening, the reference lists of eligible studies were also examined to identify any additional relevant articles. The lists of included and excluded studies were then compared for accuracy, and any disagreements were resolved through consultation with a third author ([A.S.]). Only peer-reviewed original articles were included in the final analysis; conference abstracts, review articles, and non-peer-reviewed sources were excluded. The search strategy and study selection process are summarized in the PRISMA flow diagram (Figure 1) 2.3 Study Selection and Data Collection For each included study, data were extracted on: (i) title, year, and publication type; (ii) study design and participant characteristics, including sample size, sex, age, training status, caffeine habituation, chewing duration, caffeine dose, and timing of administration relative to exercise; and (iii) intervention details, including caffeine gum, exercise type, and performance outcomes (i.e., aerobic endurance, anaerobic performance, jump performance, and muscular strength/endurance). All studies reported data as mean ± standard deviation (SD). For one study [20], the corresponding author was contacted to obtain missing data; however, no response was received, and the required information could not be obtained. Consequently, this study was excluded. 2.4 Quality Assessment The quality of the included studies was assessed using a modified version of the Quality Criteria Checklist: Primary Research [32], following previously published approaches [33]. The initial quality assessment was conducted by one author (H.M.) and independently cross-checked by a second author (E.B.) to ensure accuracy and consistency. Any disagreements were resolved through discussion until a consensus was reached. 2.5 Risk of Bias Assessment A risk of bias assessment was conducted for all studies included in the meta-analysis in accordance with the Cochrane Collaboration’s recommendation for systematic reviews [34]. The assessment categories included: (i) random sequence generation (selection bias); (ii) blinding of participants and personnel (performance bias); (3) blinding of outcome assessment (detection bias); (4) incomplete outcome data (attrition bias), and (5) selective reporting (reporting bias). Each category was rated as low risk , high risk , or some concerns . The initial assessment was carried out by one author (H.M.) and independently verified by a second author (E.B.) to ensure accuracy. Any disagreements were discussed and resolved by consensus. 2.6 Statistical Analysis 2.6.1 Effect size calculation and data synthesis Data analysis was performed by one author (H.M.). For each included study, mean values, standard deviations (SD), and sample sizes (n) were extracted for meta-analysis. Standardized mean differences (SMDs) were calculated using Hedges’ g to account for small-sample bias. For time-based outcomes, where lower values indicate better performance, the direction of the effect size was reversed so that positive SMD values consistently represented performance improvements. When data were available only in graphical form, values were digitized using WebPlotDigitizer (Version 4.3), and corresponding mean and SD values were extracted from the figures [24, 28, 35-37]. One study was excluded because the data could not be extracted from the figure and the corresponding author did not respond to requests for the original data [20]. All effect size calculations were conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions (Version 6.5, 2024) [38]. As all included studies used within-subject crossover designs, the paired nature of the data was accounted for in the effect size calculations [39]. For studies reporting both pre- and post-exercise values, SMDs were calculated using the mean change scores between the caffeine gum and placebo conditions. The same assumed correlation coefficient was applied to pre-post comparisons to ensure methodological consistency across studies. When only post-intervention values were reported, effect sizes were calculated directly from the difference between caffeine gum and placebo means while still accounting for the within-subject dependency inherent in crossover designs. Because most studies did not report the correlation between paired measurements, a correlation coefficient of r = 0.50 was assumed for the primary analysis [40]. Effect sizes (g) were also interpreted according to conventional thresholds: trivial (0.8) [41]. 2.6.2 Three-level meta-analysis and heterogeneity To account for multiple outcomes nested within studies, a three-level meta-analysis was performed using the metafor package in R version 4.5.2 for Windows (R Core Team, 2024), with restricted maximum likelihood estimation (REML) [42-44]. Variance was partitioned into sampling error (level 1), within-study variance (level 2), and between- study variance (level 3) [45]. Heterogeneity was assessed using I² statistics, categorized as low (0–25%), moderate (25–50%), substantial (50–75%), or considerable (>75%) [40-43, 46]. 2. 6 .3 Moderators and subgroup analysis Moderator analyses were conducted to explore potential sources of variability in effect sizes and to identify conditions under which caffeine gum may influence physical performance. These analyses were performed using weighted random‑effects meta‑regression models, and moderators were selected based on theoretical relevance and data availability. The examined moderators included training status, exercise type, chewing duration, habitual caffeine intake, caffeine dose, and timing of administration relative to exercise. Subgroup analysis by sex was not conducted because only one study included female participants (k = 1). Participants’ training status was harmonized into two categories: recreationally active (including recreationally active or physically active participants) and trained (including trained or highly trained participants). This harmonization reduced category fragmentation while preserving meaningful differences in training level. Exercise outcomes were classified into four categories based on the predominant physiological demands of the performance task: jump performance (e.g., countermovement jump and Sargent jump), aerobic endurance (e.g., 5‑km running, Yo‑Yo Intermittent Recovery Test, cycling time trials, and time‑to‑exhaustion protocols), anaerobic performance (e.g., sprint tests, agility tests, rowing ergometer tests, and RAST), and muscular strength and endurance (e.g., 1RM tests, repetitions to failure, handgrip strength, and Romanian deadlift tests ([ 47]. Chewing duration was categorized as short exposure (5 min) or long exposure (10 min) based on the most frequently reported durations across studies. Habitual caffeine intake was also estimated using reference values from the U.S. Department of Agriculture Food Data Central database and categorized as low (0–150 mg/day), moderate (150–300 mg/day), high (>300 mg/day), or unclear when intake was not reported [48]. Caffeine dose was analyzed to explore potential dose–response relationships and was treated as a continuous moderator because the reported relative doses (mg/kg) showed substantial variability across the included studies. Therefore, rather than categorizing doses into arbitrary groups, the full range of reported values was retained to capture better potential linear associations between caffeine dose and performance outcomes. Timing of caffeine administration relative to exercise was analyzed as a continuous moderator, given that the included studies reported a wide range of ingestion times before exercise. Treating this variable as continuous enabled the analysis to capture variability in timing protocols across studies and to more closely examine potential relationships between the timing of caffeine gum administration and performance outcomes. Mixed‑effects multilevel meta‑regression models were fitted using restricted maximum likelihood (REML) estimation with the rma.mv function from the metafor package. Effect sizes were nested within studies to account for statistical dependence among multiple outcomes within the same study, and statistical inference for moderators was obtained from model‑based tests within the multilevel framework. Continuous moderators, including caffeine dose (mg/kg) and the timing of administration relative to exercise, were entered as continuous predictors in the meta‑regression models. Categorical moderators (e.g., training status, exercise type, chewing duration and caffeine habituation) were included as factor variables, and models were specified without an intercept to obtain separate pooled estimates for each category [49, 50]. Forest plots were generated using the forest function from the metafor package in R. Effect sizes were reported as standardized mean differences (SMDs) with their corresponding confidence intervals (CIs). Study labels included the subgroup analysis, and additional study information (n = number of participants and k = number of effect sizes) was presented alongside each effect size estimate. 2.6.4 Publication Bias and Sensitivity Analyses Publication bias was assessed using Egger’s regression test for outcomes with at least ten effect sizes. Several sensitivity analyses were conducted to evaluate the robustness of the findings. First, leave‑one‑out analyses were performed to examine the influence of each individual study on the pooled estimates for both the overall effect and subgroup analyses. Additional sensitivity analyses were conducted for categorical moderators (e.g., training status, exercise type, chewing duration, and caffeine habituation) as well as for continuous moderators, including caffeine dose (mg/kg) and the timing of administration relative to exercise. Because several included studies used crossover designs, sensitivity analyses were also performed using alternative assumed within‑subject correlations (r = 0.20 and r = 0.80) to evaluate the robustness of the meta‑analytic estimates. 2.6.5 Certainty of Evidence The certainty of the evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework. This approach considers several domains, including risk of bias, inconsistency, indirectness, imprecision, and publication bias [51]. Based on these criteria, the certainty of evidence was classified as high , moderate , low , or very low . All GRADE assessments were initially performed by one reviewer and subsequently checked by a second reviewer. Any discrepancies were resolved through discussion until consensus was achieved. 3 Results 3.1 Systematic Review Results 3.1.1 Search Results A total of 25 studies met the eligibility criteria for inclusion in the meta-analysis. These studies provided 47 effect size estimates (k = 47) that examined physical performance. The main findings and methodological characteristics of the included studies are summarized in Table 1. 3.1.2 Characterization of Participants Across all studies, a total of 390 participants were included (359 males, 31females), with sample sizes ranging from 8 to 27. Most of exercise performance studies recruited only males (n = 22, k = 42), two studies recruited mixed-sex samples (k = 4), and one study recruited exclusively female participants. For training level, 21 studies (k = 40) included trained participants, four studies (k = 7) included recreationally active individuals, and one study did not specify (k = 1). According to the type of exercise categorized by the primary underlying energy system or neuromuscular mechanism, nine studies investigated aerobic endurance (k = 11 ), 10 examined anaerobic performance (k = 14 ), 1 2 assessed jump (k = 13 ), and six evaluated muscular strength and endurance (k = 9) . Chewing duration was categorized according to the time of chewing before expectoration, with studies grouped into short exposure (5 min; n =12, k =22) and longer exposure (10 min; n = 11, k = 19) conditions. Three studies did not report the time of chewing gum (k = 6). Some studies did not report participants’ habitual caffeine intake (n = 6, k = 13). Among those that did, the majority primarily included low‑caffeine consumers (n = 11, k = 21), whereas eight studies involved participants with moderate caffeine intake (n = 8, k = 12). Notably, only one study recruited high-caffeine consumers (n = 1, k = 2). Caffeine dose ranged from 1.35 to 6.4 mg/kg across studies. Most effect sizes were derived from doses between 2 and 4 mg/kg, with values around 3 mg/kg being most frequently reported. Timing of caffeine administration relative to exercise was predominantly clustered at shorter pre‑exercise intervals, with most effect sizes reported for ingestion within 0–10 min before exercise (commonly 5 and 10 min). Fewer observations were available at 15 min, and only isolated cases were reported at longer intervals (30–35 min and 60 min before exercise). For more details, please refer to Table 1. Table 1. Summary of studies included in the meta-analyses for caffeinated chewing gum (n = 25) Authors Exercise Protocol Population (n) Chewing Duration (min) Mean age (y); Body weight (kg); Caffeine habituation status Dose (mg/kg) Time of Consumption Before Exercise (min) Main Outcomes Li Ding et al. [ 52 ] RDB Crossover 1 RM Bench Press/Squat Male / Trained / Resistance Training (16) 5 min 20.8 ± 1.6; 72.9 ± 6.1; Low 4 (mg/kg) 5min Bench Press↑ Squat ↑ Li Ding et al. [ 36 ] RDB Crossover 1 RM Bench Press/Squat Male / Trained / Resistance Training (16) 5 min 21.6 ± 2.0; 79.6 ± 8.8; Low 3 (mg/kg) 5min Bench Press ↑ Squat ↑ Li Ding et al. [53] RDB Crossover 1 RM Bench Press/Squat Male / Trained / Resistance Training (16) 5 min 21.6 ± 2.0; 79.6 ± 8.8; Low 3 (mg/kg) 10 min Bench Press↔ Squat ↑ Teimouri-Korani et al. [ 24 ] RDB Crossover Sargent Male / Trained / Resistance Training (15) 10 min 25 ± 4; 75 ± 11; Low 3-4.5 (mg/kg) NA Sargent↑ Lynn et.al [ 28 ] RDB Crossover 5 km Running Male / Recreational / Running (14) 5 min 33.7 ± 10.7; NA; Low 2.48–3.79 (mg/kg) 30min 5 km Running↑ Tsai et al. [ 26 ] RDB Crossover Yo-Yo IR1/CMJ/35 m Sprint Elite / Ice Hockey (14) 10 min 25.2 ± 5.4; 78.1 ± 13.4; NA 3 (mg/kg) Immediately Before Warm-up Yo-Yo IR1↔ 35 m Sprint ↔ CMJ ↑ Tallis et al. [ 25 ] RDB Crossover CMJ Male / Rugby (27) 5 min 20 ± 2; 96.6 ± 18.2; Moderate 3 (mg/kg) 10min CMJ ↔ Yi-Jie Shiu et al. [ 54 ] RDB Crossover 400 m sprint Male / Trained / Sprinting (19) 10 min 20.9 ± 1.0; 66.5 ± 5.6; NA 3 (mg/kg) 15min 400 m sprint↑ Liu et al. [ 27 ] RDB Crossover CMJ/ T-Agility Test/ Rast Male / Trained / Basketball (15) 10 min 20.9 ± 1.0; 77.2 ± 7.5; Low 3 (mg/kg) 15min CMJ/ T-Agility ↔ Rast ↑ Farmani et al. [ 55 ] RDB Crossover Bruce / Sargent Male / Professional / Table Tennis (18) 10 min 21.86 ± 2.40; 61.81 ± 10.32; Low 3–4.6 (mg/kg) 10min Bruce ↑ Sargent↔ Pirmohammadi et al. [ 56 ] RDB Crossover Edgren’s Agility Test Female / Professional / Table Tennis (18) 10 min 20.50 ± 3.05; 56.83 ± 6.50; NA 3–4.7 (mg/kg) 10min Edgren’s Agility Test ↑ Yildirim et al. [ 21 ] RDB Crossover 15 s CMJ Male / Trained / Soccer (14) 5 min 22 ± 2; 74.2 ± 7.1; High 2.68 or 1.34 (mg/kg) 10min 15 s CMJ ↔ Kaszuba et al. [ 57 ] RDB Crossover CMJ/ T-Agility Test/10 m sprint Male, Female / Trained / Volleyball (12) 5 min 23 ± 3; 85.9 ± 11.2; Moderate 3.2 (mg/kg) 15min CMJ↔ T-Agility Test↔ 10 m sprint ↔ Filip Stachnik et al. [ 58 ] RDB Crossover Special Judo Fitness Test Male / Elite / Judo (9) 5 min 23.7 ± 4.4; 73.5 ± 7.4; Moderate 2.7 or 5.4 (mg/kg) 15min Special Judo Fitness Test ↔ Dittrich et al. [ 59 ] RDB Crossover Treadmill Run at 15.4 ± 0.7 km/h Male / Well-Trained / Running (12) 5 min 31.3 ± 6.4; 70.5 ± 6.6; Low 4.26 (mg/kg) N/A Treadmill Run test↑ Veiner et al. [ 60 ] RDB Crossover CMJ/ Rowing Ergometer Peak Power Output Male / Trained / Resistance Training (19) 10 min 24±5; 83±10; Low 3.61 (mg/kg) Before Starting the Tests CMJ↑ Rowing Ergometer Peak Power Output ↑ Ranchordas et al. [ 61 ] RDB Crossover CMJ/ Yo-Yo IR2/Illinois Agility Test/6×30m Sprint Male / Trained / Rugby (17) 5 min 20.4 ± 1.2; 85.6 ± 6.3; NA 2.3 (mg/kg) after the warm-up CMJ ↑ Illinois Agility Test ↔ Yo-Yo IR2 ↑ 6×30m Sprint ↔ Ranchordas et al. [ 62 ] RDB Crossover 20 meter Sprint/ Yo-Yo IR1/CMJ Male / Trained / Soccer (10) 5 min 19 ± 1; 75.5 ± 4.8; NA 2.7 (mg/kg) 5min Yo-Yo IR1↑ CMJ ↑ 20 meter Sprint ↔ Russell et al. [ 37 ] RDB Crossover 2 Repeated sprint tests: 6 × 40 m sprints Male / Professional / Rugby (14) 5 min 18 ±1; 98.6 ± 10.9; Moderate 4.1 (mg/kg) 15min 2 Repeated sprint tests: 6 × 40 m sprints ↔ Evans et al. [ 23 ] RDB Crossover 10x40 m maximal shuttle run test Male / Team Sport (18) 10 min 21.2 ± 1; 80.4 ± 6.6; Low and Moderate 2.5 (mg/kg) 5min 10x40 m maximal shuttle run test (Moderate) ↔ 10x40 m maximal shuttle run test (Low)↑ Ryan et al. [ 22 ] RDB Crossover Cycling to Volitional Exhaustion Male / Recreational / Cycling (8) 5 min 25 ± 5; NA; Moderate 2 (mg/kg) 120, 60, 5min Cycling to Volitional Exhaustion↔ Paton et al. [ 18 ] RDB Crossover 30-km cycling time trial Trained / Cycling (20) 5 min 30 ± 10; 69 ± 10; Moderate 3-4 (mg/kg) NA First 20-km ↔ Final 10-km ↑ Chen et al. [ 35 ] RDB Crossover Romanian deadlift Recreational/ Resistance training (19) 5 min 22.5 ± 3.5; 78.8 ±13.2; Low 2.5 (mg/kg) 10 Romanian deadlift performance on the flywheel machine ↑ Tzeng et al. [ 63 ] RDB Crossover Hand grip strength Male/ Wrestler/Trained (16) 10 min 21.8 ± 1.0; 68.2 ± 8.7; Low 3 (mg/kg) 15 grip strength↔ Vargas-Molina et al. [ 64 ] RDB Crossover Total Number of Repetitions (Pull-ups, Push-ups, and Squats) CMJ Male/ CrossFit ® (14) NA 30.9 ± 5.62; 78 ± 5.75; NA 3 (mg/kg) NA Total Number of Repetitions ↔ CMJ↑ 3.1.3 Meta‑analysis Analysis of 47 outcomes using a multilevel meta-analytic model indicated a trivial but statistically significant positive effect of caffeine gum on physical performance compared with placebo (k = 47, n = 390, SMD = 0.195, 95% CI [0.115 to 0.275], p = 0.001, GRADE: high). Heterogeneity across studies was very low (I² = 4% [low], Q = 37.53, df = 46, p = 0.809). Variance decomposition from the three‑level meta‑analytic model indicated that 64.6% of the total variability was attributable to differences between studies (Level 3; τ² = 0.002), while no variability was observed at the within‑study level (Level 2; τ² = 0.000; 0%). Nevertheless, moderator analyses were conducted to further explore potential sources of variability across studies. 3.1.4 Moderator analysis The overall test of moderators indicated that training status significantly moderates the effect of caffeine gum on exercise performance (QM (1) = 29.83, p = 0.001). Moderator analyses based on training status indicated that caffeine gum was associated with a trivial , non‑significant improvement in exercise performance among recreationally active participants (k = 7, n = 59, SMD = −0.038, 95% CI [−0.244, 0.167], p = 0.713, I² = 26% [moderate], GRADE: low) [22, 23, 28]. In contrast, a small but statistically significant ergogenic effect was observed in trained participants (k = 40, n = 304, SMD = 0.228, 95% CI [0.146, 0.310], p0.001 = , I² = 0% [low], GRADE: high) [18, 21, 24-27, 36, 37, 52-64]. A multilevel meta‑analysis was conducted to examine whether the type of exercise outcome moderated the ergogenic effects of caffeine gum. The test of moderators was significant (QM (4) = 21.18, p = 0.001), indicating that the effect of caffeine gum differed across exercise outcome categories. Subgroup analyses showed a small but significant positive effect for aerobic endurance outcomes (k = 11, n = 122, SMD = 0.258, 95% CI [0.081, 0.436], p = 0.004, I² = 0% [low], GRADE: moderate) [18, 22, 26-28, 55, 59, 61, 62]. Similarly, a trivial but statistically significant improvements were observed for anaerobic performance (k = 14, n = 156, SMD = 0.186, 95% CI [0.042, 0.340], p = 0.011, I² = 0% [low], GRADE: moderate) [23, 26, 27, 37, 56-58, 61, 62, 65] and trivial significant for jump performance (k = 13, n=195, SMD = 0.183, 95% CI [0.037, 0.330], p = 0.014, I² = 0% [low], GRADE: moderate) [25-27, 55, 57, 61, 62, 64, 66]. In contrast, the effect for muscular strength and endurance was trivial but non - significant (k = 9, n = 97, SMD = 0.142, 95% CI [−0.038, 0.322], p = 0.127, I² = 35% [moderate], GRADE: low) [24, 35, 36, 52, 53, 63, 64]. A moderator analysis was conducted to examine the effect of chewing duration (5 vs. 10 min), and a significant moderating effect of chewing duration was observed (QM (1) = 28.58, p = 0.001). For the 10‑min chewing duration (k = 19, n = 190, SMD = 0.262, 95% CI [0.151, 0.384], p = 0.001, I² = 0% [low], GRADE: high), the effect was small significant [23-27, 54-56, 60, 63]. Similarly, for the 5‑min chewing duration (k = 22, n =110, SMD = 0.142, 95% CI [0.030, 0.262], p = 0.017, I² = 7% [low], GRADE: moderate), a trivial but statistically significant effect was observed [18, 28, 35-37, 53, 57-59, 61, 62, 67]. Across strata of habitual caffeine intake, the ergogenic effects of caffeine gum differed by intake level (QM (2) = 10.43, p = 0.015). A small, non-significant performance improvement was observed among individuals with high habitual caffeine intake (k = 2, n = 14, SMD = −0.203, 95% CI [−0.67, 0.26], p = 0.39, I² = 0% [low], GRADE: low) [21] . In contrast, small but statistically significant improvements were observed among participants with moderate (k = 12, n = 130, SMD = 0.187, 95% CI [0.038, 0.336], p = 0.026, I² = 12% [low], GRADE: moderate) [23, 24, 36, 52, 53, 60, 62, 67, 68] and a small but statistically significant effect for low habitual caffeine intake (k = 21, n=153, SMD = 0.207, 95% CI [0.091, 0.323], p = 0.030, I² = 10% [low], GRADE: moderate) [18, 23, 25, 37, 55, 57, 59, 69]. For a summary of subgroup results for physical performance outcomes, see figure 2. A meta‑regression analysis was conducted to examine whether caffeine dose moderated the effect size. The results indicated a significant positive association between caffeine dose and effect size (β = 0.100, p = 0.031, 95% CI [0.002, 0.192]). Residual heterogeneity for that was not significant (QE (44) = 31.17, p = 0.927). Meta‑regression analysis showed that timing of administration relative to exercise was not a significant moderator of the effect size. The regression coefficient indicated a non‑significant association between timing of administration relative to exercise and performance outcomes (β = −0.002, p = 0.683, 95% CI [−0.010 to 0.006]). Residual heterogeneity for that was not significant as well (QE = 32.38, p = 0.799). 3.1.5 Sensitivity analysis 3.1.6 Sensitivity analysis for primary effect Sensitivity analyses using different assumed within‑subject correlations (r = 0.2 and r = 0.8) yielded consistent findings for overall effect size. Under these assumptions, the ergogenic effect of caffeine gum remained significant (r = 0.2: SMD = 0.156, p < 0.001; r = 0.8: SMD = 0.282, p < 0.001). A leave‑one‑study‑out sensitivity analysis also was conducted to assess the robustness of the pooled effect. The results indicated that the overall effect size remained stable when each study was removed in turn, with pooled estimates ranging from SMD = 0.182 to SMD = 0.215. All models remained statistically significant (all p < 0.001). In addition, heterogeneity remained very low across all iterations, with I² values ranging from 0% to 7.51%. 3.1.7 Sensitivity analysis for moderator effect Sensitivity analyses using different assumed within-subject correlations (r = 0.2 and 0.8) yielded consistent findings for the training status subgroup. A significant ergogenic effect of caffeine gum was observed in trained participants across all correlation assumptions (r = 0.2: SMD = 0.184, p < 0.001; r = 0.8: SMD = 0.344, p < 0.001). In contrast, no significant effects were observed in recreationally active individuals (r = 0.2: SMD = −0.034, p = 0.746; r = 0.8: SMD = −0.083, p = 0.595). Leave‑one‑out sensitivity analysis showed that results in the trained subgroup were highly robust, and all models remained statistically significant. In contrast, in the recreationally active subgroup the effect size varied slightly although remained non‑significant in all models. Sensitivity analyses using different assumed within‑subject correlations (r = 0.2 and 0.8) showed consistent findings across exercise modes. Significant ergogenic effects of caffeine gum were observed for aerobic endurance (r = 0.2: SMD = 0.212, p = 0.013; r = 0.8: SMD = 0.402, p < 0.001), anaerobic performance (r = 0.2: SMD = 0.153, p = 0.025; r = 0.8: SMD = 0.271, p = 0.008), and jump performance (r = 0.2: SMD = 0.156, p = 0.037; r = 0.8: SMD = 0.293, p = 0.004). In contrast, no significant effect was observed for muscle strength and endurance tasks (r = 0.2: SMD = 0.121, p = 0.158; r = 0.8: SMD = 0.161, p = 0.124). Leave‑one‑out sensitivity analyses across exercise‑type subgroups showed that the pooled effects for aerobic endurance, jump, and anaerobic performance remained stable and statistically significant after removing individual studies, indicating robust results. In contrast, the muscle strength and endurance subgroup showed some variability, with the effect becoming significant after the removal of one study [35], suggesting sensitivity to individual studies. Across all assumed within‑subject correlations (r = 0.2 and 0.8), chewing duration demonstrated consistent effects. At r = 0.2, the 10 min condition showed a significant ergogenic effect (SMD = 0.210, p = 0.001), whereas the 5 min condition was borderline non‑significant (SMD = 0.120, p = 0.051). At r = 0.8, effect sizes were larger for both conditions, with significant improvements observed for 10 min (SMD = 0.393, p < 0.001) and 5 min (SMD = 0.210, p = 0.015). Leave‑one‑out sensitivity analyses for caffeine gum chewing duration showed different patterns between conditions. For the 10 min condition, the pooled effect size remained stable and statistically significant after removing individual studies, indicating robust results. In contrast, the 5 min condition exhibited greater variability in the leave‑one‑out analyses. Although the overall effect remained statistically significant, the magnitude of the estimate fluctuated when individual study [35] were removed, indicating some sensitivity to study‑level influence. Using alternative assumed correlations (r = 0.2 and r = 0.8) did not materially alter the conclusions of the habituation subgroup analysis. For low habitual caffeine intake, the ergogenic effect remained small but statistically significant across both correlations (SMD range: 0.165 to 0.289; all p < 0.010), indicating high robustness. For the moderate habituation subgroup, effects were likewise stable and consistently significant (SMD range: 0.153 to 0.308). Leave‑one‑out sensitivity analyses for the low and moderate habitual caffeine intake subgroups showed that the effects were highly robust, remaining stable and statistically significant across all iterations. Meta‑regression analyses examined the association between caffeine gum dose (mg/kg) and performance outcomes across different assumed within‑subject correlations. For r = 0.2, the relationship between dose and effect size showed non‑significant trend (β = 0.083, p = 0.063,), while for r = 0.8, a significant positive dose–response relationship was observed (β = 0.162, p = 0.008), indicating significantly larger ergogenic effects with increasing caffeine dose. A leave‑one‑out sensitivity analysis was conducted to examine the robustness of the meta‑regression for caffeine dose (mg/kg). The results showed the effect remained statistically significant in nearly all iterations, except when study [21] and study [35] were removed, where the association was no longer statistically significant. Across the sensitivity analyses using r = 0.2 and r = 0.8, meta‑regression indicated that the timing of administration relative to exercise was not significantly associated with performance outcomes. The regression coefficients (r = 0.2: β = −0.001, p = 0.712; r = 0.8: β = −0.002, p = 0.702), suggesting that variations in timing of administration relative to exercise did not meaningfully influence the ergogenic effect. A leave‑one‑out sensitivity analysis was also conducted for the meta‑regression examining the timing of administration relative to exercise. The results showed that the regression coefficient remained relatively stable across iterations and the association remained statistically non‑significant after the removal of individual studies. 3.1.8 Risk of bias and quality of methods Across the included studies, most domains were judged as low risk of bias, particularly for missing outcome data (D3) and measurement of outcomes (D4). However, Domains 1 (randomization process) and 5 (selection of the reported result) showed the highest proportion of some concerns , mainly due to insufficient reporting of randomization methods and lack of pre‑specified analysis plans. A high risk of bias was observed in a few studies in Domain 2 (deviations from intended interventions), primarily related to unclear blinding procedures (Figure 3). The mixed-effects meta-regression model assessing funnel plot asymmetry showed no statistically significant evidence of publication bias. Egger’s regression test yielded a non‑significant result (z = −0.19, p = 0.848), indicating that the relationship between effect size and its standard error was not systematic. The limit estimate as the standard error approached zero was b = 0.251 (95% CI: −0.33 to 0.84), further suggesting the absence of small‑study effects. Overall, these findings imply that the likelihood of publication bias influencing the pooled effect size is low. Egger’s regression tests were conducted to assess potential publication bias across all examined subgroups. Egger’s tests across subgroups based on training status, exercise type, caffeine habituation level, and chewing duration also showed no significant funnel plot asymmetry (all p > 0.05), suggesting no evidence of publication bias; however, the test could not be calculated for some subgroups due to an insufficient number of studies. Additionally, Egger’s regression tests conducted for meta regression models including caffeine gum dose and timing of administration relative to exercise as moderators showed no significant funnel plot asymmetry (caffeine dose: z = −0.67, p = 0.502; timing of administration relative to exercise: z = −0.07, p = 0.951). However, these results should be interpreted cautiously because the meta‑analysis included dependent effect sizes and a relatively small number of independent studies, which may limit the reliability of regression‑based tests for publication bias. The certainty of evidence was not downgraded for publication bias, as there was no evidence of funnel plot asymmetry or small-study effects based on Egger’s regression analyses. 4 Discussion This systematic review and meta-analysis provide updated evidence on the ergogenic potential of caffeine gum on physical performance. Caffeine gum produced a trivial but meaningful improvement in overall physical performance. A small yet significant effect was noted in trained individuals, whereas no meaningful benefit was evident in recreationally active participants. Regarding exercise outcomes, small but significant improvements were observed for aerobic endurance, with trivial but significant benefits for anaerobic performance and jump performance, while muscular strength and endurance showed no significant changes. Responses were influenced by chewing duration, with a small but significant benefit for 10 min and trivial effects for 5 min. Habitual caffeine intake also moderated outcomes, with small significant improvements in low and moderate consumers, but no effect in high consumers. In addition, higher caffeine doses were associated with greater performance improvements, while timing of administration did not significantly influence outcomes. The overall standardized mean differences (SMD) observed with caffeine gum were comparable to those reported for caffeine capsules [2]. This similarity was expected, as both forms produce equivalent plasma caffeine concentrations despite differing absorption rates [17]. Our findings indicate that caffeine gum significantly enhances physical performance, consistent with the meta-analysis by Barreto et al. [29], which identified caffeine gum as an effective ergogenic strategy for both aerobic and anaerobic exercise. Supporting this, several studies [22, 37] show that consuming caffeine gum 5-15 min before exercise can enhance aerobic endurance [70], cycling time-trial performance [18, 59] , repeated sprint ability [18], muscular power (e.g., jumping) [61], maximal strength [36], and team-sport-specific performance [61]. This rapid effect is likely due to buccal absorption, bypassing first-pass hepatic metabolism and allowing caffeine to enter the bloodstream within 5-10 min, thereby producing a quicker ergogenic response than traditional ingestion methods. Trained individuals showed a significant benefit from caffeine gum supplementation, whereas no meaningful effect was observed in recreationally active participants. This aligns with Barreto et al. [29], who observed clear enhancements in trained but not untrained individuals. The broader literature, however, demonstrates inconsistent ergogenic based on training status. For example, beta-alanine tends to produce smaller effects in highly trained individuals [71], whereas sodium bicarbonate shows diminished effects in untrained participants [72]. Whether caffeine exhibits comparable training status-specific effects remains unclear [73]. This interpretation is limited by the small number of outcomes in the recreationally active group (40 from trained individuals versus 7 from recreationally active participants) and the low total sample size of recreationally active participants (n =59), which likely reduced statistical power and precision. Beyond caffeine gum administration, the broader caffeine literature suggests that training status is not a consistent moderator of resistance-type outcomes [74]. Accordingly, the apparent trained–untrained differences in our dataset should be interpreted cautiously, as they may reflect sampling and design features rather than systematic physiological moderation by training status. Current evidence indicates that caffeine gum produces significant improvements in aerobic endurance, anaerobic performance and vertical jump ability, but no meaningful effects on muscular strength or endurance. Consistent with our findings, Barreto et al. [29] reported improvements in exercise performance, particularly for endurance and power‑related outcomes. However, our findings diverge for muscular strength, as their meta-analysis identified a positive effect of caffeine gum on strength performance, whereas ours did not. Broader meta-analytic evidence suggests that caffeine exerts greater ergogenic effects in endurance than strength-based tasks [73]. This pattern was also reflected in our findings, where the effect for aerobic endurance outcomes was small , whereas effects for jumping and anaerobic measures were trivial , and muscular strength and endurance outcomes did not show a significant improvement. However, these findings should be interpreted cautiously, as the sensitivity analysis indicated that excluding a single study revealed a small positive effect, suggesting that the ergogenic benefit may become evident when methodological variability is reduced, particularly in muscular‑related performance task. In addition, differences in delivery method, timing of ingestion, or participant characteristics may contribute to discrepancies among studies [15]. Mechanistically, improvements in endurance performance may be mediated by both central and peripheral mechanisms, whereas improvements in power‑related tasks are more likely linked to direct effects on muscle contractile processes. In addition, enhanced sympathetic nervous system activation and increased central motor drive may contribute to performance during short‑duration anaerobic efforts. Together, these mechanisms may partly explain the improvements observed in some physical performance outcomes in the present analysis [75]. Moderator analysis showed that chewing duration significantly influenced the ergogenic effect of caffeine gum. Both 5 and 10 min chewing durations improved performance, but the longer duration produced a small rather than trivial effect. Barreto et al. [29] did not examine chewing duration as a moderator, which makes direct comparison challenging. Nevertheless, individual studies report improvements in physical performance with both shorter [28, 36] and longer chewing [24, 76] periods . To date, no investigation has directly compared these durations, so interpretations should be made with caution. However, the slightly larger effect associated with longer chewing may reflect increased caffeine release and enhanced buccal absorption, resulting in greater plasma availability and stronger adenosine receptor antagonism [77]. Together, these mechanisms provide a plausible explanation for the augmented physiological impact of prolonged chewing on physical performance. The ergogenic effects of caffeine gum appeared to depend on habitual caffeine intake. Individuals with high habitual consumption showed no clear performance benefits, possibly due to tolerance, whereas those with low and moderate intake demonstrated significant improvements. However, evidence for high habitual consumers remains limited. The only dataset representing high consumers originated from a subgroup analysis including just fourteen participants, making any conclusions tentative. Caffeine habituation has been proposed to attenuate the ergogenic effects of acute caffeine ingestion [3], although current evidence remains inconsistent. Chronic caffeine intake may induce tolerance through physiological adaptations, such as the upregulation of adenosine receptors, potentially requiring higher acute doses to elicit similar effects [3]. For example, one study [78] reported that 28 days of caffeine consumption abolishes the performance benefit of 3 mg/kg caffeine, whereas another [79] found no influence of habitual intake on the ergogenic effect of a higher dose (6 mg/kg) during a cycling time trial. These findings suggest that acute caffeine dose may partly explain conflicting results related to habituation. Overall, individuals with low and moderate habitual caffeine consumption are more likely to benefit from caffeine gum. However, limitations in dietary reporting and other methodological constraints complicate interpretation, reducing confidence in these conclusions. Caffeine gum dosage ranged from 1.35 to 6.4 mg/kg across included studies. Meta‑regression indicated that dosage significantly moderated effect size, showing a positive association such that higher doses were linked to slightly larger ergogenic effects. This finding suggests that increasing caffeine dose may modestly enhance exercise performance when delivered via caffeine gum. Our findings are consistent with Barreto et al. [29], who reported no significant effect at doses <3 mg/kg body mass, but a clear benefit at ≥3 mg/kg. However, one study comparing 2.7 and 5.4 mg/kg body mass reported that both caffeine gum administration did not improve performance in the Special Judo Fitness Test [58]. Another investigation evaluating 100 mg and 200 mg caffeine gum reported greater quadriceps strength with the higher dose, but no effect on isometric handgrip strength, hamstring strength, ball‑kicking speed, or performance in a 15‑s countermovement jump test [21]. Discrepancies across studies may reflect differences in methodological factors, such as participant characteristics, habitual caffeine intake, and overall study quality . Overall, the observed dose range (1.35 to 6.4 mg/kg) revealed a meaningful dose–response association, while further original dose–response studies with caffeine gum on physical performance are required to confirm these findings and to help provide accurate practical recommendations. Our data showed that exercise performance is not significantly moderated by the timing of caffeine gum administration before exercise. This contrasts with Barreto et al. [29], who found that caffeine gum was ergogenic only when consumed within 15 min before exercise. In our analysis, however, most outcomes involved ingestion within this 15-min window (k = 35), with no difference observed across timings. This pattern aligns with the pharmacokinetics of caffeine gum, as caffeine absorbed through the buccal mucosa reaches detectable plasma concentrations within ~15 min [17], considerably faster than traditional capsule forms. The limited data available beyond 15 min pre-exercise (k = 3) reduced statistical power and prevented firm conclusions regarding longer pre-exercise intervals. Nonetheless, ingestion beyond 15 min before exercise may still confer performance benefits, as plasma caffeine concentrations remain elevated for several hours despite peaking within ∼45–105 min depending on the dose [17]. Overall, these findings suggest that consuming caffeine gum within 15 min of exercise is an effective and practical strategy for enhancing performance. The overall risk of bias was low, particularly for outcome measurement and missing data, supporting the general reliability of the findings. However, recurring concerns in the randomization process and selective reporting highlight limitations in study design transparency. In addition, unclear blinding contributed to a high risk in some studies. Taking together, the evidence base is methodologically acceptable, but improvements in randomization and reporting practices are needed to strengthen confidence in future findings. 4.3 Practical applications Caffeine gum represents a viable strategy for athletes requiring rapid caffeine delivery, particularly when traditional capsule or liquid ingestion is impractical (e.g., halftime, substitutions, or early-morning training). It may be preferable for longer events, as its rapid buccal absorption and high bioavailability help sustain plasma caffeine levels [17]. This makes caffeine gum especially useful when a rapid ergogenic effect is desired or during prolonged exercise. Figure 4 represents a schematic overview of caffeine gum as a fast-acting strategy in sport and physical performance. 4.4 Limitations Although this study provides new insights into the effects of caffeine gum on physical performance, several limitations should be acknowledged. First, heterogeneity across studies in training status, exercise type, chewing duration, caffeine habituation, caffeine dosage, and timing of administration relative to exercise across studies may have contributed to variability in effect sizes. Second, most studies included only male participants, with limited representation of females, which restricts the generalizability of the findings. Third, although overall methodological quality was acceptable, concerns were identified regarding the randomization process, blinding procedures, and pre‑registration practices in some studies. Finally, the small number of independent studies may compromise the stability and reliability of regression‑based publication bias analyses. 5 Conclusion This systematic review and meta-analysis demonstrate that caffeine gum produces trivial but statistically significant improvements in physical performance. The rapid buccal absorption of caffeine from chewing gum offers a practical and well-tolerated ergogenic strategy, particularly when traditional caffeine intake is impractical or undesirable. Although the overall magnitude of effect is trivial , these improvements may still be meaningful in competitive settings where marginal gains can influence performance outcomes. Abbreviations SMD Standardized Mean Difference CI Confidence Interval BM Body Mass RCTs Randomized Controlled Trials 1RM One‑Repetition Maximum CYP1A2 Cytochrome P450 1A2 Gene GRADE Grading of Recommendations Assessment, Development, and Evaluation PICO Population, Intervention, Comparison, Outcome REML Restricted Maximum Likelihood SD Standard Deviation PRISMA Referred Reporting Items for Systematic Reviews and Meta-Analyses PROSPER International Prospective Register of Systematic Reviews I² I‑squared (statistical measure of heterogeneity) Q Cochran’s Q statistic (test for heterogeneity) QM Test statistic for moderators in meta‑analysis (Cochran’s Q for moderators) QE Residual heterogeneity statistic (Cochran’s Q for residual heterogeneity) β Regression Coefficient (beta coefficient in meta‑regression) b Intercept estimate (limit estimate in Egger’s regression) Declarations Acknowledgments We gratefully acknowledge the researchers and authors of the original studies included in this meta-analysis for their valuable contributions to scientific literature. We also thank the librarians and research support staff who assisted with database searches and resource access. Special thanks to our colleagues for their insightful feedback during the development of this manuscript. Funding There is no funding for the current article. Conflict of Interest The authors declare that they have no competing interests. Availability of Data and Materials All data relevant to the study are included in the article. Ethics Approval Not required. Consent to Participate Not required. Consent for Publication Not required. Author details [1] Department of Exercise Physiology, Faculty of Sport Sciences and Health, University of Tehran, Tehran, Iran 2 School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia 3Australian Athletics, Melbourne, Australia 4 GICAF Research Group, Department of Education Research Methods and Evaluation, Faculty of Human and Social Sciences, Universidad Pontificia Comillas, 28049 Madrid, Spain 5 School of Human Sciences, Exercise and Sport Science, University of Western Australia, Perth, WA 6009, Australia Author Contributions HM and EB conceptualized and designed the study, collected data, carried out the analyses, drafted the initial manuscript, and reviewed and revised the manuscript. HM and EB conceptualized and designed the study and reviewed and revised the manuscript. AS, OG, and CP supervised the analyses and reviewed and revised the manuscript. 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The Acute Impact of a Single Taurine Dose on Exercise Performance: A Meta‐Analytic Review. Scandinavian Journal of Medicine & Science in Sports. 2025;35(9):e70123. Souza DB, Del Coso J, Casonatto J, Polito MD. Acute effects of caffeine-containing energy drinks on physical performance: a systematic review and meta-analysis. European Journal of Nutrition. 2017;56(1):13-27. Pataky MW, Womack CJ, Saunders MJ, Goffe JL, D'Lugos AC, El-Sohemy A, et al. Caffeine and 3-km cycling performance: Effects of mouth rinsing, genotype, and time of day. Scandinavian Journal of Medicine and Science in Sports. 2016;26(6):613-9. Zuur AF, Ieno EN, Walker NJ, Saveliev AA, Smith GM. Mixed effects models and extensions in ecology with R: Springer; 2009. Harrell Jr FE. General aspects of fitting regression models. Regression modeling strategies: with applications to linear models, logistic regression, and survival analysis: Springer; 2001. p. 11-40. Schünemann HJ, Higgins JPT, Vist GE, Glasziou P, Akl EA, Skoetz N, et al. Completing ‘Summary of findings’ tables and grading the certainty of the evidence. Cochrane Handbook for Systematic Reviews of Interventions; 2019. p. 375-402. Ding L, Liu J, Ma YX, Bai LT, Guo L, Chen B, et al. Caffeinated chewing gum produces comparable strength and power gains to capsules with fewer side effects in resistance-trained men. Journal of the International Society of Sports Nutrition. 2025 DEC 31;22(1). Ding L, Liu J, Ma YX, Lei TH, Barnes M, Guo L, et al. Effect of Caffeinated Chewing Gum on Maximal Strength, Muscular Power, and Muscle Recruitment During Bench Press and Back Squat Exercises. Nutrients. 2025 JUL 28;17(15). Shiu Y-J, Chen C-H, Tao W-S, Nai H-F, Yu C-Y, Chiu C-H. Acute ingestion of caffeinated chewing gum reduces fatigue index and improves 400-meter performance in trained sprinters: a double-blind crossover trial. Journal of the International Society of Sports Nutrition. 2024;21(1):1-13. Farmani A, Hemmatinafar M, Jahromi MK, Pirmohammadi S, Imanian B, Jahan Z. The effect of repeated coffee mouth rinsing and caffeinated gum consumption on aerobic capacity and explosive power of table tennis players: a randomized, double-blind, placebo-controlled, crossover study. Journal of the International Society of Sports Nutrition . 2024 DEC 31;21(1). Pirmohammadi S, Hemmatinafar M, Nemati J, Imanian B, Abdollahi MH. Early absorption sources of caffeine can be a useful strategy for improving female table tennis players-specific performance. Journal of the International Society of Sports Nutrition. 2023;20(1):1-19. Kaszuba M, Klocek O, Spieszny M, Filip-Stachnik A. The Effect of Caffeinated Chewing Gum on Volleyball-Specific Skills and Physical Performance in Volleyball Players. Nutrients. 2022 Dec 24;15(1). Filip-Stachnik A, Krawczyk R, Krzysztofik M, Rzeszutko-Belzowska A, Dornowski M, Zajac A, et al. Effects of acute ingestion of caffeinated chewing gum on performance in elite judo athletes. Journal of the International Society of Sports Nutrition. 2021 Jun 19;18(1):49. Dittrich N, Serpa MC, Lemos EC, De Lucas RD, Guglielmo LGA. Effects of Caffeine Chewing Gum on Exercise Tolerance and Neuromuscular Responses in Well-Trained Runners. J Strength Cond Res. 2021 Jun 1;35(6):1671-6. Venier S, Grgic J, Mikulic P. Acute Enhancement of Jump Performance, Muscle Strength, and Power in Resistance-Trained Men After Consumption of Caffeinated Chewing Gum. International Journal of Sports Physiology & Performance. 2019;14(10):1415-21. Ranchordas MK, Pratt H, Parsons M, Parry A, Boyd C, Lynn A. Effect of caffeinated gum on a battery of rugby-specific tests in trained university-standard male rugby union players. Journal of the International Society of Sports Nutrition. 2019;16(1):N.PAG-N.PAG. Ranchordas MK, King G, Russell M, Lynn A, Russell M. Effects of Caffeinated Gum on a Battery of Soccer-Specific Tests in Trained University-Standard Male Soccer Players. International Journal of Sport Nutrition & Exercise Metabolism. 2018;28(6):629-34. Tzeng G-J, Lin H-Y, Shiu Y-J, Hsieh M-H, Chen Z-C, Chiu C-H. Caffeinated Chewing Gum Improves Sympathetic Nerve Activity and Wrestling Performance: A Double-Blind Crossover Trial. International Journal of Sports Physiology & Performance. 2026;21(1):41-8. Vargas-Molina S, Bonilla DA, García-Sillero M, Iglesias-Placed S, Murri M, Martín-Rivera F, et al. Comparing Acute Effects of Caffeine Delivery Forms on Cross-Training Performance: A Randomized Placebo-Controlled Crossover Trial. Nutrients. 2026 FEB 17;18(4). Shiu YJ, Chen FY, Chen CH, Chen MY, Lee WC, Lin YZ, et al. Caffeinated chewing gum improves the batting and pitching performance of female softball players: a randomized crossover study. Journal of Sports Medicine and Physical Fitness. 2024 NOV;64(11):1118-26. Yildirim UC, Akcay N, Alexe DI, Esen O, Gulu M, Cîrtita-Buzoianu C, et al. Acute effect of different doses of caffeinated chewing gum on exercise performance in caffeine-habituated male soccer players. Frontiers in Nutrition . 2023 OCT 18;10. Ryan EJ, Kim CH, Fickes EJ, Williamson M, Muller MD, Barkley JE, et al. CAFFEINE GUM AND CYCLING PERFORMANCE: A TIMING STUDY. Journal of Strength and Conditioning Research. 2013 JAN;27(1):259-64. Liu HS, Liu CC, Shiu YJ, Lan PT, Wang AY, Chiu CH. Caffeinated Chewing Gum Improves Basketball Shooting Accuracy and Physical Performance Indicators of Trained Basketball Players: A Double-Blind Crossover Trial. Nutrients. 2024 MAY;16(9). Filip-Stachnik A, Kaszuba M, Dorozynski B, Komarek Z, Gawel D, Del Coso J, et al. Acute Effects of Caffeinated Chewing Gum on Volleyball Performance in High-Performance Female Players. Journal of Human Kinetics. 2022 NOV 8;84(1):92-102. Whalley PJ, Dearing CG, Paton CD. The effects of different forms of caffeine supplement on 5-km running performance. International Journal of Sports Physiology and Performance. 2020;15(3):390-4. Saunders B, Elliott-Sale K, Artioli GG, Swinton PA, Dolan E, Roschel H, et al. β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis. British journal of Sports edicine. 2017;51(8):658-69. Carr AJ, Hopkins WG, Gore CJ. Effects of acute alkalosis and acidosis on performance: a meta-analysis. Sports medicine. 2011;41(10):801-14. Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z. Wake up and smell the coffee: caffeine supplementation and exercise performance—an umbrella review of 21 published meta-analyses. British journal of Sports Medicine. 2020;54(11):681-8. Warren GL, Park ND, Maresca RD, McKibans KI, Millard-Stafford ML. Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis. Med Sci Sports Exerc. 2010 Jul;42(7):1375-87. Bowtell JL, Mohr M, Fulford J, Jackman SR, Ermidis G, Krustrup P, et al. Improved exercise tolerance with caffeine is associated with modulation of both peripheral and central neural processes in human participants. Frontiers in Nutrition. 2018;5:6. Deng H, Wang L, Liu P, Bin Naharudin MN, Fan X. Caffeine and taurine: a systematic review and network meta-analysis of their individual and combined effects on physical capacity, cognitive function, and physiological markers. Journal of the International Society of Sports Nutrition. 2025;22(1):2566371. Morris C, Viriot SM, Farooq Mirza QUA, Morris GA, Lynn A. Caffeine release and absorption from caffeinated gums. Food Funct. 2019 Apr 1;10(4):1792-6. Beaumont R, Cordery P, Funnell M, Mears S, James L, Watson P. Chronic ingestion of a low dose of caffeine induces tolerance to the performance benefits of caffeine. Journal of Sports Sciences. 2017;35(19):1920-7. Gonçalves LdS, Painelli VdS, Yamaguchi G, Oliveira LFd, Saunders B, Da Silva RP, et al. Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation. Journal of Applied Physiology. 2017;123(1):213-20. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 06 May, 2026 Reviewers invited by journal 30 Apr, 2026 Editor invited by journal 29 Apr, 2026 Editor assigned by journal 22 Apr, 2026 First submitted to journal 21 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9461741","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":632719853,"identity":"7d0a9b47-87b9-4ed9-9858-7b56381a1e88","order_by":0,"name":"Hossein Miraftabi","email":"","orcid":"","institution":"University of Tehran","correspondingAuthor":false,"prefix":"","firstName":"Hossein","middleName":"","lastName":"Miraftabi","suffix":""},{"id":632719854,"identity":"829f0994-2a82-4201-9400-316f5a2dfc28","order_by":1,"name":"Erfan Berjisian","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+ElEQVRIiWNgGAWjYFACHhCWYGBjYGB8ABFJIF4LswEJWiCATYIoLfwMvAcfV8hY2POxnz1W8aHmMAM/e44Bw8823FokG/iSDc/wSCS28eSl3Zxx7DCDZM8bA8ZePFoMDvCYSTbwSCSwMeSY3eZtOMxgcANoCy8eLfYHeMx/ArXYs/G/MSv+C9RiD9TC+BefLQw8ZoxALYxtEjlmzIwgWyRyDJjx2SJxmC8Z5LDENok3xpI9x9J5JM48Kzgscw63Fv723oMfG3vq7OX7cww//KixluNvT9748E0Zbi0MzEDM2IPgg6PpAB4NUPCDsJJRMApGwSgYwQAAu6NFXP0msrsAAAAASUVORK5CYII=","orcid":"https://orcid.org/0009-0001-4886-7063","institution":"Edith Cowan University School of Medical and Health Sciences","correspondingAuthor":true,"prefix":"","firstName":"Erfan","middleName":"","lastName":"Berjisian","suffix":""},{"id":632719855,"identity":"357fedf9-0032-4636-aee9-72710851b894","order_by":2,"name":"Craig Pickering","email":"","orcid":"","institution":"Australian Athletics","correspondingAuthor":false,"prefix":"","firstName":"Craig","middleName":"","lastName":"Pickering","suffix":""},{"id":632719856,"identity":"78d526d8-1a3a-4027-9e0e-581596b78848","order_by":3,"name":"Alvaro Lopez-Samanes","email":"","orcid":"","institution":"Universidad Pontificia de Comillas: Universidad Pontificia Comillas","correspondingAuthor":false,"prefix":"","firstName":"Alvaro","middleName":"","lastName":"Lopez-Samanes","suffix":""},{"id":632719857,"identity":"e9206c14-00ee-4c14-bb43-25ed8f1d257a","order_by":4,"name":"Olivier Girard","email":"","orcid":"","institution":"UWA: University of Western Australia","correspondingAuthor":false,"prefix":"","firstName":"Olivier","middleName":"","lastName":"Girard","suffix":""}],"badges":[],"createdAt":"2026-04-19 11:51:00","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9461741/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9461741/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108974256,"identity":"7e015d99-faaa-494c-850c-4cc811069bb8","added_by":"auto","created_at":"2026-05-11 10:50:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":57629,"visible":true,"origin":"","legend":"\u003cp\u003eStrategy carried out in this systematic review following PRISMA guidelines\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9461741/v1/d46ac1efa98c7e6d9f58e7c6.png"},{"id":108974259,"identity":"9c591438-13e9-4959-aa5f-f58c0bbcb9c2","added_by":"auto","created_at":"2026-05-11 10:50:20","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":455909,"visible":true,"origin":"","legend":"\u003cp\u003eModerator analysis for physical performance results.\u003c/p\u003e\n\u003cp\u003eNotes: k, the total number of effects included in the pooled effect size; SMD, the effect size indicators used in the pooled; 95% CI, 95% confidence interval; P-value, statistically significant P values for pooled results; I\u003csup\u003e2\u003c/sup\u003e, quantitative indicators of heterogeneity; GRADE, grading of recommendations assessment, development, and evaluation, a system for evaluating the quality of evidence and strength of recommendations.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9461741/v1/ccdccfc109d49eb83accd617.png"},{"id":109067275,"identity":"682b08a4-c306-404d-a072-0c14462cfe5c","added_by":"auto","created_at":"2026-05-12 09:30:44","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":283048,"visible":true,"origin":"","legend":"\u003cp\u003eRisk of bias for caffeinated chewing gum\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9461741/v1/afd0bd646016fa83b25cd38a.png"},{"id":108974257,"identity":"f20e8cc8-8a34-4c5e-9a1e-b7a64295c4d2","added_by":"auto","created_at":"2026-05-11 10:50:20","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1295235,"visible":true,"origin":"","legend":"\u003cp\u003eschematic overview of the applications of caffeine gum in sports, its mechanisms, and associated performance benefits.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-9461741/v1/b64670c3a5e279a2592c0996.png"},{"id":109069252,"identity":"b901148b-3c09-45f9-860a-803f1ed1d141","added_by":"auto","created_at":"2026-05-12 10:22:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2779421,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9461741/v1/a2d6476b-c415-49a6-8e01-b1070056b2ce.pdf"}],"financialInterests":"","formattedTitle":"Fast-Acting Caffeine Strategy: A Systematic Review and Meta-Analysis of the Ergogenic Effects of Caffeine Chewing Gum on Physical Performance","fulltext":[{"header":"Key Points","content":"\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"660\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 660px;\"\u003e\n \u003cp\u003eCaffeine chewing gum produces a trivial but statistically significant improvement in physical performance, including\u0026nbsp;aerobic endurance, anaerobic, and vertical jump performance.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 660px;\"\u003e\n \u003cp\u003eTraining status and caffeine habituation influence responses, with greater effects in trained individuals and low\u0026ndash;moderate caffeine users, but not in highly habituated or recreational participants.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 660px;\"\u003e\n \u003cp\u003eErgogenic effects are evident with typical doses of ~2\u0026ndash;4 mg\u0026middot;kg⁻\u0026sup1; body mass and chewing durations of 5\u0026ndash;10 min,\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 660px;\"\u003e\n \u003cp\u003eDue to its rapid buccal absorption and fast onset, caffeine gum is a practical ergogenic option in time-sensitive or competition settings.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"1 Introduction","content":"\u003cp\u003eCaffeine (1,3,7-trimethylxanthine) is one of the most widely used ergogenic aids across sports and competitive levels. Since early work over a century ago first demonstrated its performance-enhancing effects on muscular work [1], extensive research has consistently confirmed caffeine\u0026apos;s ergogenic effects across diverse exercise modalities. Caffeine intake can improve muscular strength and power [2], endurance capacity [3], and performance in intermittent and team sports [4]. These effects are primarily mediated through antagonism of adenosine receptors (A\u003csub\u003e1\u003c/sub\u003e and A\u003csub\u003e2\u003c/sub\u003eA) in the central nervous system,\u0026nbsp;which increases alertness, promotes arousal, and reduces fatigue perception [5]. Beyond this central action, caffeine stimulates catecholamine release (e.g., adrenaline and noradrenaline) [6], activates dopamine D2 receptors to enhance motivation and reward pathways [7], and lowers pain and effort perceptions during exercise [5].\u0026nbsp;It may also increase fat oxidation and consequent glycogen sparing during prolonged aerobic exercise [8]. Peripheral mechanisms likely contribute, including enhanced calcium mobilization within muscle fibres during excitation-contraction coupling [9]\u0026nbsp;and improved neuromuscular transmission efficiency [10], leading to improved strength and sprint performance [11]. Together, these central and peripheral actions underpin caffeine\u0026rsquo;s status as an effective, safe, and widely accessible ergogenic aid. However, responses may vary considerably between individuals. Factors such as genetic polymorphisms (e.g., CYP1A2 and ADORA2A), habitual caffeine intake, and expectancy‑related placebo or nocebo effects [12, 13] can influence metabolism, sensitivity, and perceived performance benefits, partly explaining variability in responses across individuals and studies [14,\u0026nbsp;15].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTraditionally, caffeine is consumed in capsule form [16], with peak absorption occurring \u0026nbsp;45-60 min after ingestion [3]. In time-constrained scenarios (e.g., warm-ups, early-morning training, or half-time), faster delivery methods are desirable. Caffeine gum has therefore gained attention due to its rapid absorption kinetics [16]. Caffeine delivered via\u0026nbsp;caffeine gum is partially absorbed through the buccal mucosa, resulting in a faster rise in plasma caffeine concentrations (~5\u0026ndash;10 min) compared with traditional ingestion methods [17,\u0026nbsp;18]. This rapid availability may be advantageous when the time between ingestion and exercise is limited, although pre‑match ingestion remains the most common strategy to ensure adequate circulating caffeine levels at the start of competition [17].\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eIn addition, caffeine gum may be associated with a lower incidence of commonly reported side effects (e.g., anxiety, headaches, gastrointestinal disorders, and sleep disturbances)\u0026nbsp;compared with traditional forms of ingestion\u0026nbsp;[19].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNumerous studies have investigated the effects of caffeine gum across a range of doses (i.e., 1.35 to 6.4 mg/kg BM) [20, 21], ingestion timings (5-120 min) [22,\u0026nbsp;23], and exercise protocols (e.g., resistance training, vertical jump, cycling performance, and agility) [22,\u0026nbsp;24].\u0026nbsp;Additional factors that have been explored include chewing duration (e.g., 5 vs. 10 min) [25,\u0026nbsp;26], habitual caffeine intake (low, moderate, and high) [25,\u0026nbsp;27], and participant characteristics (trained and recreationally active individuals) [18,\u0026nbsp;28].\u0026nbsp;Despite the growing body of work on caffeine gum, findings remain inconsistent, likely due to methodological heterogeneity. A comprehensive synthesis is therefore needed to clarify the ergogenic potential of caffeine gum, inform future research, and support evidence-based recommendations for athletes and coaches. An earlier meta-analysis by Barreto et al.\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e[29]\u0026nbsp;demonstrated improvements in both endurance and strength/power performance, supporting caffeine gum as a fast-acting and practical delivery method. Since its publication in 2023, the number of studies on caffeine gum has more than doubled, warranting an updated synthesis. Importantly, key moderators such as chewing duration and habitual caffeine intake require investigation through subgroup analyses. These factors have not been examined in previous meta-analyses [29]\u0026nbsp;and may help explain heterogeneity in the observed effects of caffeine gum.\u003c/p\u003e\n\u003cp\u003eAccordingly, this systematic review and three‑level meta‑analysis aimed to quantify the effects of caffeine gum on exercise performance compared with placebo. Subgroup analyses examined potential moderators, including training status, exercise type, chewing duration, and habitual caffeine intake. Meta‑regression analyses were conducted to further explore the influence of caffeine dose (mg/kg) and timing of administration relative to exercise. By clarifying the magnitude and consistency of these effects across conditions, this work aims to inform the practical use of caffeine gum as a rapid caffeine delivery strategy for performance enhancement.\u0026nbsp;\u003c/p\u003e"},{"header":"2 Methods","content":"\u003cp\u003eThis systematic review and meta-analysis were conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions [30] and followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to ensure transparency and methodological rigour [31].\u0026nbsp;The protocol was prospectively registered in the PROSPERO database (CRD420251086458).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.1 Eligibility Criteria\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis review followed the PICO framework: (1) Participants: healthy adults; (2) Intervention: caffeine gum; (3) Comparison: non-caffeinated placebo chewing gum; (4) Outcomes: physical performance. Studies were included if they met all of the following criteria: (1) randomized controlled trials (RCTs) published in peer-reviewed journals; (2) investigated the effects of caffeine gum on physical performance outcomes; (3) involved healthy human participants; (4) included a non-caffeine control condition such as water or non-caloric placebo gum; and (5) reported original experimental data in English. Exclusion criteria were: (1) interventions involving ingestion or mouth rinsing of caffeine; (2) co-interventions with other active ingredients (e.g. carbohydrate, menthol); (3) studies without exercise performance-related outcomes; (4) reviews, abstracts, or non-original reports; or (5) insufficient methodological information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2 Data Sources and Search\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll databases were searched from the start of their indexing period to September 2025, with a final updated search conducted in February 2026. The search was performed across four electronic databases: PubMed, Web of Science, Scopus, and SPORTDiscus, using the following terms: (\u0026quot;Caffeinated chewing gum\u0026quot; OR \u0026quot;Caffeine gum\u0026quot; OR \u0026quot;Caffeine chewing gum\u0026quot; OR \u0026quot;Caffeinated gum\u0026quot; OR \u0026quot;Caffeine-containing chewing gum\u0026quot;) AND (\u0026quot;Exercise performance\u0026quot; OR \u0026quot;Performance\u0026quot; OR \u0026quot;Exercise\u0026quot; OR \u0026quot;Cycling\u0026quot; OR \u0026quot;Running\u0026quot; OR \u0026quot;Sprint\u0026quot; OR \u0026quot;Time trial\u0026quot; OR \u0026quot;Time to exhaustion\u0026quot; OR \u0026quot;Endurance\u0026quot; OR \u0026quot;Resistance\u0026quot; OR \u0026quot;Strength\u0026quot; OR \u0026quot;Power\u0026quot;). All retrieved records were imported into EndNote 21 (Clarivate, Philadelphia, PA, USA) for reference management, and duplicates were removed using EndNote\u0026rsquo;s built-in \u0026ldquo;Remove Duplicates\u0026rdquo; function. Following deduplication and title and abstract screening, full-text articles were independently assessed by two authors ([H.M.] and [E.B.]). During full-text screening, the reference lists of eligible studies were also examined to identify any additional relevant articles. The lists of included and excluded studies were then compared for accuracy, and any disagreements were resolved through consultation with a third author ([A.S.]). Only peer-reviewed original articles were included in the final analysis; conference abstracts, review articles, and non-peer-reviewed sources were excluded. The search strategy and study selection process are summarized in the PRISMA flow diagram (Figure 1)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.3 Study Selection and Data Collection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor each included study, data were extracted on: (i) title, year, and publication type; (ii) study design and participant characteristics, including sample size, sex, age, training status, caffeine habituation, chewing duration, caffeine dose, and timing of administration relative to exercise; and (iii) intervention details, including caffeine gum, exercise type, and performance outcomes (i.e., aerobic endurance, anaerobic performance, jump performance, and muscular strength/endurance). All studies reported data as mean \u0026plusmn; standard deviation (SD). For one study\u0026nbsp;[20], the corresponding author was contacted to obtain missing data; however, no response was received, and the required information could not be obtained. Consequently, this study was excluded.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.4 Quality Assessment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe quality of the included studies was assessed using a modified version of the Quality Criteria Checklist: Primary Research [32], following previously published approaches [33]. The initial quality assessment was conducted by one author (H.M.) and independently cross-checked by a second author (E.B.) to ensure accuracy and consistency. Any disagreements were resolved through discussion until a consensus was reached.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.5 Risk of Bias Assessment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA risk of bias assessment was conducted for all studies included in the meta-analysis in accordance with \u0026nbsp;the Cochrane Collaboration\u0026rsquo;s recommendation for systematic reviews [34]. The assessment categories included: (i) random sequence generation (selection bias); (ii) blinding of participants and personnel (performance bias); (3) blinding of outcome assessment (detection bias); (4) incomplete outcome data (attrition bias), and (5) selective reporting (reporting bias). Each category was rated as \u003cem\u003elow risk\u003c/em\u003e, \u003cem\u003ehigh risk\u003c/em\u003e, or \u003cem\u003esome concerns\u003c/em\u003e. The initial assessment was carried out by one author (H.M.) and independently verified by a second author (E.B.) to ensure accuracy. Any disagreements were discussed and resolved by consensus.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.6 Statistical Analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.6.1\u003c/strong\u003e \u003cstrong\u003eEffect size calculation and data synthesis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData analysis was performed by one author (H.M.). For each included study, mean values, standard deviations (SD), and sample sizes (n) were extracted for meta-analysis. Standardized mean differences (SMDs) were calculated using Hedges\u0026rsquo; g to account for small-sample bias. For time-based outcomes, where lower values indicate better performance, the direction of the effect size was reversed so that positive SMD values consistently represented performance improvements.\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eWhen data were available only in graphical form, values were digitized using WebPlotDigitizer (Version 4.3), and corresponding mean and SD values were extracted from the figures\u0026nbsp;[24,\u0026nbsp;28,\u0026nbsp;35-37].\u0026nbsp;One study was excluded because the data could not be extracted from the figure and the corresponding author did not respond to requests for the original data\u0026nbsp;[20].\u0026nbsp;All effect size calculations were conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions (Version 6.5, 2024) [38]. As all included studies used within-subject crossover designs, the paired nature of the data was accounted for in the effect size calculations [39]. For studies reporting both pre- and post-exercise values, SMDs were calculated using the mean change scores between the caffeine gum and placebo conditions. The same assumed correlation coefficient was applied to pre-post comparisons to ensure methodological consistency across studies. When only post-intervention values were reported, effect sizes were calculated directly from the difference between caffeine gum and placebo means while still accounting for the within-subject dependency inherent in crossover designs. Because most studies did not report the correlation between paired measurements, a correlation coefficient of r = 0.50 was assumed for the primary analysis [40]. Effect sizes (g) were also interpreted according to conventional thresholds: \u003cem\u003etrivial\u003c/em\u003e (\u0026lt;0.2), \u003cem\u003esmall\u003c/em\u003e (0.2\u0026ndash;0.5), \u003cem\u003emoderate\u003c/em\u003e (0.5\u0026ndash;0.8), and\u003cem\u003e\u0026nbsp;large\u003c/em\u003e (\u0026gt;0.8) [41].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.6.2 Three-level meta-analysis and heterogeneity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo account for multiple outcomes nested within studies, a three-level meta-analysis was performed using the \u003cem\u003emetafor\u0026nbsp;\u003c/em\u003epackage in\u0026nbsp;R version 4.5.2 for Windows (R Core Team, 2024), with restricted maximum likelihood estimation (REML) [42-44]. Variance was partitioned into sampling error (level 1), within-study variance (level 2), and between- study variance (level 3) [45]. Heterogeneity was assessed using I\u0026sup2; statistics, categorized as low (0\u0026ndash;25%), moderate (25\u0026ndash;50%), substantial (50\u0026ndash;75%), or considerable (\u0026gt;75%) [40-43,\u0026nbsp;46].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.\u003c/strong\u003e\u003cstrong\u003e\u003cspan dir=\"RTL\"\u003e6\u003c/span\u003e\u003c/strong\u003e\u003cstrong\u003e.3 Moderators and subgroup analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eModerator analyses were conducted to explore potential sources of variability in effect sizes and to identify conditions under which caffeine gum may influence physical performance. These analyses were performed using weighted random‑effects meta‑regression models, and moderators were selected based on theoretical relevance and data availability. The examined moderators included training status, exercise type, chewing duration, habitual caffeine intake, caffeine dose, and timing of administration relative to exercise.\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003eSubgroup\u0026nbsp;analysis by sex was not conducted because only one study included female participants (k = 1). Participants\u0026rsquo; training status was harmonized into two categories: recreationally active (including recreationally active or physically active participants) and trained (including trained or highly trained participants). This harmonization reduced category fragmentation while preserving meaningful differences in training level.\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003eExercise outcomes were classified into four categories based on the predominant physiological demands of the performance task: jump performance (e.g., countermovement jump and Sargent jump), aerobic endurance (e.g., 5‑km running, Yo‑Yo Intermittent Recovery Test, cycling time trials, and time‑to‑exhaustion protocols), anaerobic performance (e.g., sprint tests, agility tests, rowing ergometer tests, and RAST), and muscular strength and endurance (e.g., 1RM tests, repetitions to failure, handgrip strength, and Romanian deadlift tests\u003cspan dir=\"RTL\"\u003e\u0026nbsp;([\u003c/span\u003e47].\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003eChewing duration was categorized as short exposure (5 min) or long exposure (10 min) based on the most frequently reported durations across studies.\u0026nbsp;\u0026nbsp;Habitual caffeine intake was also estimated using reference values from the U.S. Department of Agriculture Food Data Central database and categorized as low (0\u0026ndash;150 mg/day), moderate (150\u0026ndash;300 mg/day), high (\u0026gt;300 mg/day), or unclear when intake was not reported\u0026nbsp;[48].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCaffeine dose was analyzed to explore potential dose\u0026ndash;response relationships and was treated as a continuous moderator because the reported relative doses (mg/kg) showed substantial variability across the included studies. Therefore, rather than categorizing doses into arbitrary groups, the full range of reported values was retained to capture better potential linear associations between caffeine dose and performance outcomes.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTiming of caffeine administration relative to exercise was analyzed as a continuous moderator, given that the included studies reported a wide range of ingestion times before exercise. Treating this variable as continuous enabled the analysis to capture variability in timing protocols across studies and to more closely examine potential relationships between the timing of caffeine gum administration and performance outcomes.\u003c/p\u003e\n\u003cp\u003eMixed‑effects multilevel meta‑regression models were fitted using restricted maximum likelihood (REML) estimation with the rma.mv function from the \u003cem\u003emetafor\u0026nbsp;\u003c/em\u003epackage. Effect sizes were nested within studies to account for statistical dependence among multiple outcomes within the same study, and statistical inference for moderators was obtained from model‑based tests within the multilevel framework. Continuous moderators, including caffeine dose (mg/kg) and the timing of administration relative to exercise, were entered as continuous predictors in the meta‑regression models. Categorical moderators (e.g., training status, exercise type, chewing duration and caffeine habituation) were included as factor variables, and models were specified without an intercept to obtain separate pooled estimates for each category [49,\u0026nbsp;50]. Forest plots were generated using the \u003cem\u003eforest\u003c/em\u003e function from the \u003cem\u003emetafor\u003c/em\u003e package in R. Effect sizes were reported as standardized mean differences (SMDs) with their corresponding confidence intervals (CIs). Study labels included the subgroup analysis, and additional study information (n = number of participants and k = number of effect sizes) was presented alongside each effect size estimate.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.6.4 Publication Bias and Sensitivity Analyses\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePublication bias was assessed using Egger\u0026rsquo;s regression test for outcomes with at least ten effect sizes. Several sensitivity analyses were conducted to evaluate the robustness of the findings. First, leave‑one‑out analyses were performed to examine the influence of each individual study on the pooled estimates for both the overall effect and subgroup analyses. Additional sensitivity analyses were conducted for categorical moderators (e.g., training status, exercise type, chewing duration, and caffeine habituation) as well as for continuous moderators, including caffeine dose (mg/kg) and the timing of administration relative to exercise. Because several included studies used crossover designs, sensitivity analyses were also performed using alternative assumed within‑subject correlations (r = 0.20 and r = 0.80) to evaluate the robustness of the meta‑analytic estimates.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.6.5 Certainty of Evidence\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe certainty of the evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework. This approach considers several domains, including risk of bias, inconsistency, indirectness, imprecision, and publication bias [51]. Based on these criteria, the certainty of evidence was classified as \u003cem\u003ehigh\u003c/em\u003e, \u003cem\u003emoderate\u003c/em\u003e, \u003cem\u003elow\u003c/em\u003e, or \u003cem\u003every low\u003c/em\u003e. All GRADE assessments were initially performed by one reviewer and subsequently checked by a second reviewer. Any discrepancies were resolved through discussion until consensus was achieved.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cp\u003e\u003cstrong\u003e3.1 Systematic Review Results\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.1 Search Results\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 25 studies met the eligibility criteria for inclusion in the meta-analysis. These studies provided 47 effect size estimates (k = 47) that examined physical performance. The main findings and methodological characteristics of the included studies are summarized in Table\u0026nbsp;1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.2 Characterization of Participants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAcross all studies, a total of 390 participants were included (359 males, 31females), with sample sizes ranging from 8 to 27. Most of exercise performance studies recruited only males (n = 22, k = 42), two studies recruited mixed-sex samples (k = 4), and one study recruited exclusively female participants. For training level, 21 studies (k = 40) included trained participants, four studies (k = 7) included recreationally active individuals, and one study did not specify (k = 1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to the type of exercise categorized by the primary underlying energy system or neuromuscular mechanism, nine studies investigated aerobic endurance (k = \u003cspan dir=\"RTL\"\u003e11\u003c/span\u003e), \u003cspan dir=\"RTL\"\u003e10\u003c/span\u003e examined anaerobic performance (k = \u003cspan dir=\"RTL\"\u003e14\u003c/span\u003e), 1\u003cspan dir=\"RTL\"\u003e2\u003c/span\u003e assessed jump (k = \u003cspan dir=\"RTL\"\u003e13\u003c/span\u003e), and six evaluated muscular strength and endurance (k = 9)\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eChewing duration was categorized according to the time of chewing before expectoration, with studies grouped into short exposure (5 min; n =12, k =22) and longer exposure (10 min; n = 11, k = 19) conditions. Three studies did not report the time of chewing gum (k = 6).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSome studies did not report participants\u0026rsquo; habitual caffeine intake (n = 6, k = 13). Among those that did, the majority primarily included low‑caffeine consumers (n = 11, k = 21), whereas eight studies involved participants with moderate caffeine intake (n = 8, k = 12). Notably, only one study recruited high-caffeine consumers (n = 1, k = 2).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCaffeine dose ranged from 1.35 to 6.4 mg/kg across studies. Most effect sizes were derived from doses between 2 and 4 mg/kg, with values around 3 mg/kg being most frequently reported.\u003c/p\u003e\n\u003cp\u003eTiming of caffeine administration relative to exercise was predominantly clustered at shorter pre‑exercise intervals, with most effect sizes reported for ingestion within 0\u0026ndash;10 min before exercise (commonly 5 and 10 min). Fewer observations were available at 15 min, and only isolated cases were reported at longer intervals (30\u0026ndash;35 min and 60 min before exercise). For more details, please refer to Table\u0026nbsp;1.\u003c/p\u003e\n\u003cp\u003eTable 1. Summary of studies included in the meta-analyses for caffeinated chewing gum (n = 25)\u003c/p\u003e\n\u003ctable style=\"width: 128%;\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eAuthors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eExercise Protocol\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003ePopulation (n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eChewing Duration (min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMean age (y); Body weight (kg); Caffeine habituation status\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eDose (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTime of Consumption Before Exercise (min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMain Outcomes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eLi Ding et al. \u003cstrong\u003e[\u003c/strong\u003e52\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1 RM Bench Press/Squat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Resistance Training (16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;20.8 \u0026plusmn; 1.6;\u003c/p\u003e\n \u003cp\u003e72.9 \u0026plusmn; 6.1;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBench Press\u0026uarr;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eSquat \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eLi Ding et al. \u003cstrong\u003e[\u003c/strong\u003e36\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1 RM Bench Press/Squat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Resistance Training (16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21.6 \u0026plusmn; 2.0;\u003c/p\u003e\n \u003cp\u003e79.6 \u0026plusmn; 8.8;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBench Press \u0026uarr;\u003c/p\u003e\n \u003cp\u003eSquat \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eLi Ding et al. [53] \u003cstrong\u003e\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/strong\u003eRDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e1 RM Bench Press/Squat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Resistance Training (16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21.6 \u0026plusmn; 2.0;\u003c/p\u003e\n \u003cp\u003e79.6 \u0026plusmn; 8.8; \u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBench Press\u0026harr;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eSquat \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eTeimouri-Korani et al. \u003cstrong\u003e[\u003c/strong\u003e24\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSargent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Resistance Training (15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e25\u0026thinsp;\u0026plusmn;\u0026thinsp;4;\u003c/p\u003e\n \u003cp\u003e75\u0026thinsp;\u0026plusmn;\u0026thinsp;11;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3-4.5 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSargent\u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eLynn et.al \u003cstrong\u003e[\u003c/strong\u003e28\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 km Running\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Recreational / Running (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e33.7 \u0026plusmn; 10.7;\u003c/p\u003e\n \u003cp\u003eNA;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.48\u0026ndash;3.79 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e30min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 km Running\u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eTsai et al. \u003cstrong\u003e[\u003c/strong\u003e26\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eYo-Yo IR1/CMJ/35 m Sprint\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eElite / Ice Hockey (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e25.2 \u0026plusmn; 5.4;\u003c/p\u003e\n \u003cp\u003e78.1 \u0026plusmn; 13.4;\u003c/p\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eImmediately Before Warm-up\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eYo-Yo IR1\u0026harr;\u003c/p\u003e\n \u003cp\u003e35 m Sprint \u0026harr;\u003c/p\u003e\n \u003cp\u003eCMJ \u0026uarr;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eTallis et al. \u003cstrong\u003e[\u003c/strong\u003e25\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Rugby (27)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20\u0026thinsp;\u0026plusmn;\u0026thinsp;2;\u003c/p\u003e\n \u003cp\u003e96.6\u0026thinsp;\u0026plusmn;\u0026thinsp;18.2;\u003c/p\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ \u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eYi-Jie Shiu et al. \u003cstrong\u003e[\u003c/strong\u003e54\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e400 m sprint\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Sprinting (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20.9 \u0026plusmn; 1.0;\u003c/p\u003e\n \u003cp\u003e66.5 \u0026plusmn; 5.6;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e400 m sprint\u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eLiu et al. \u003cstrong\u003e[\u003c/strong\u003e27\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ/ T-Agility Test/ Rast\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Basketball (15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20.9 \u0026plusmn; 1.0;\u003c/p\u003e\n \u003cp\u003e77.2 \u0026plusmn; 7.5;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ/ T-Agility \u0026harr;\u003c/p\u003e\n \u003cp\u003eRast \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eFarmani et al. \u003cstrong\u003e[\u003c/strong\u003e55\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBruce / Sargent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Professional / Table Tennis (18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21.86 \u0026plusmn; 2.40;\u003c/p\u003e\n \u003cp\u003e61.81 \u0026plusmn; 10.32;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3\u0026ndash;4.6 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBruce \u0026uarr;\u003c/p\u003e\n \u003cp\u003eSargent\u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003ePirmohammadi et al. \u003cstrong\u003e[\u003c/strong\u003e56\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eEdgren\u0026rsquo;s Agility Test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eFemale / Professional / Table Tennis (18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20.50\u0026thinsp;\u0026plusmn;\u0026thinsp;3.05;\u003c/p\u003e\n \u003cp\u003e56.83\u0026thinsp;\u0026plusmn;\u0026thinsp;6.50;\u003c/p\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3\u0026ndash;4.7 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eEdgren\u0026rsquo;s Agility Test \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eYildirim et al. \u003cstrong\u003e[\u003c/strong\u003e21\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15\u0026thinsp;s CMJ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Soccer (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e22\u0026thinsp;\u0026plusmn;\u0026thinsp;2;\u003c/p\u003e\n \u003cp\u003e74.2\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1;\u003c/p\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.68 or 1.34 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15\u0026thinsp;s CMJ \u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eKaszuba et al. \u003cstrong\u003e[\u003c/strong\u003e57\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ/ T-Agility Test/10 m sprint\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale, Female / Trained / Volleyball (12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e23 \u0026plusmn; 3;\u003c/p\u003e\n \u003cp\u003e85.9 \u0026plusmn; 11.2;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.2 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ\u0026harr;\u003c/p\u003e\n \u003cp\u003eT-Agility Test\u0026harr;\u003c/p\u003e\n \u003cp\u003e10 m sprint \u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eFilip Stachnik et al. \u003cstrong\u003e[\u003c/strong\u003e58\u003cstrong\u003e]\u003c/strong\u003e\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eRDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSpecial Judo Fitness Test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Elite / Judo (9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e23.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4;\u003c/p\u003e\n \u003cp\u003e73.5\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4;\u003c/p\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.7 or 5.4 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSpecial Judo Fitness Test \u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eDittrich et al. \u003cstrong\u003e[\u003c/strong\u003e59\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTreadmill Run at 15.4 \u0026plusmn; 0.7 km/h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Well-Trained / Running (12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e31.3 \u0026plusmn; 6.4;\u003c/p\u003e\n \u003cp\u003e70.5 \u0026plusmn; 6.6;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4.26 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\"\u003e\n \u003cp\u003eTreadmill Run test\u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eVeiner et al. \u003cstrong\u003e[\u003c/strong\u003e60\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ/ Rowing Ergometer Peak Power Output\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Resistance Training (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e24\u0026plusmn;5;\u003c/p\u003e\n \u003cp\u003e83\u0026plusmn;10; \u0026nbsp;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3.61 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eBefore Starting the Tests\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ\u0026uarr;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;Rowing Ergometer Peak Power Output \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eRanchordas et al. \u003cstrong\u003e[\u003c/strong\u003e61\u003cstrong\u003e]\u003c/strong\u003e\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eRDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ/ Yo-Yo IR2/Illinois Agility Test/6\u0026times;30m Sprint\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Rugby (17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2;\u003c/p\u003e\n \u003cp\u003e85.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.3;\u0026thinsp;\u003c/p\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eafter the warm-up\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCMJ \u0026uarr;\u003c/p\u003e\n \u003cp\u003eIllinois Agility Test \u0026harr;\u003c/p\u003e\n \u003cp\u003eYo-Yo IR2 \u0026uarr;\u003c/p\u003e\n \u003cp\u003e6\u0026times;30m Sprint \u0026harr;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eRanchordas et al. \u003cstrong\u003e[\u003c/strong\u003e62\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e20 meter Sprint/ Yo-Yo IR1/CMJ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Trained / Soccer (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e19 \u0026plusmn; 1;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e75.5 \u0026plusmn; 4.8;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.7 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eYo-Yo IR1\u0026uarr;\u003c/p\u003e\n \u003cp\u003eCMJ \u0026uarr;\u003c/p\u003e\n \u003cp\u003e20 meter Sprint \u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eRussell et al. \u003cstrong\u003e[\u003c/strong\u003e37\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2 Repeated sprint tests: 6 \u0026times; 40 m sprints\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Professional / Rugby (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e18 \u0026plusmn;1;\u003c/p\u003e\n \u003cp\u003e98.6 \u0026plusmn; 10.9;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e4.1 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2 Repeated sprint tests: 6 \u0026times; 40 m sprints \u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eEvans et al. \u003cstrong\u003e[\u003c/strong\u003e23\u003cstrong\u003e]\u003c/strong\u003e\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eRDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10x40 m maximal shuttle run test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Team Sport (18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21.2 \u0026plusmn; 1;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e80.4 \u0026plusmn; 6.6; \u0026nbsp;\u003c/p\u003e\n \u003cp\u003eLow and Moderate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.5 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10x40 m maximal shuttle run test (Moderate) \u0026harr;\u003c/p\u003e\n \u003cp\u003e10x40 m maximal shuttle run test (Low)\u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eRyan et al. \u003cstrong\u003e[\u003c/strong\u003e22\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCycling to Volitional Exhaustion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale / Recreational / Cycling (8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e25 \u0026plusmn; 5;\u003c/p\u003e\n \u003cp\u003eNA;\u003c/p\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e120, 60, 5min\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eCycling to Volitional Exhaustion\u0026harr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003ePaton et al.\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003cstrong\u003e[\u003c/strong\u003e18\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e30-km cycling time trial\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTrained / Cycling (20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e30 \u0026plusmn; 10;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e69 \u0026plusmn; 10;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3-4 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eFirst 20-km \u0026harr;\u003c/p\u003e\n \u003cp\u003eFinal 10-km \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eChen et al. \u003cstrong\u003e[\u003c/strong\u003e35\u003cstrong\u003e]\u003c/strong\u003e\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eRDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eRomanian deadlift\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;Recreational/ Resistance training (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e5 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e22.5 \u0026plusmn; 3.5;\u003c/p\u003e\n \u003cp\u003e78.8 \u0026plusmn;13.2;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e2.5 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eRomanian deadlift performance on the flywheel machine \u0026uarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eTzeng et al. \u003cstrong\u003e[\u003c/strong\u003e63\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eHand grip strength\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale/ Wrestler/Trained (16)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e10 min\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e21.8 \u0026plusmn; 1.0;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e68.2 \u0026plusmn; 8.7;\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003egrip strength\u0026harr;\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eVargas-Molina et al. \u003cstrong\u003e[\u003c/strong\u003e64\u003cstrong\u003e]\u003c/strong\u003e RDB Crossover\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTotal Number of Repetitions (Pull-ups, Push-ups, and Squats)\u003c/p\u003e\n \u003cp\u003eCMJ\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMale/ CrossFit\u003csup\u003e\u0026reg;\u0026nbsp;\u003c/sup\u003e(14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e30.9 \u0026plusmn; 5.62;\u003c/p\u003e\n \u003cp\u003e78 \u0026plusmn; 5.75;\u003c/p\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e3 (mg/kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eTotal Number of Repetitions \u0026harr;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp dir=\"RTL\"\u003e\u003cspan dir=\"LTR\"\u003eCMJ\u0026uarr;\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.3 Meta‑analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAnalysis of 47 outcomes using a multilevel meta-analytic model indicated a \u003cem\u003etrivial\u003c/em\u003e but statistically significant positive effect of caffeine gum on physical performance compared with placebo (k = 47, n = 390, SMD = 0.195, 95% CI [0.115 to 0.275], p = 0.001, GRADE: high). Heterogeneity across studies was very low (I\u0026sup2; = 4% [low], Q = 37.53, df = 46, p = 0.809). Variance decomposition from the three‑level meta‑analytic model indicated that 64.6% of the total variability was attributable to differences between studies (Level 3; \u0026tau;\u0026sup2; = 0.002), while no variability was observed at the within‑study level (Level 2; \u0026tau;\u0026sup2; = 0.000; 0%). Nevertheless, moderator analyses were conducted to further explore potential sources of variability across studies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.4 Moderator analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe overall test of moderators indicated that training status significantly moderates the effect of caffeine gum on exercise performance (QM (1) = 29.83, p = 0.001). Moderator analyses based on training status indicated that caffeine gum was associated with a \u003cem\u003etrivial\u003c/em\u003e, non‑significant improvement in exercise performance among recreationally active participants (k = 7, n = 59, SMD = \u0026minus;0.038, 95% CI [\u0026minus;0.244, 0.167], p = 0.713, I\u0026sup2; = 26% [moderate], GRADE: low) [22, 23, 28]. In contrast, a \u003cem\u003esmall\u003c/em\u003e but statistically significant ergogenic effect was observed in trained participants (k = 40, n = 304, SMD = 0.228, 95% CI [0.146, 0.310], p0.001 = , I\u0026sup2; = 0% [low], GRADE: high) [18, 21, 24-27, 36, 37, 52-64].\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;A multilevel meta‑analysis was conducted to examine whether the type of exercise outcome moderated the ergogenic effects of caffeine gum. The test of moderators was significant (QM\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e(4) = 21.18, \u003cem\u003ep\u003c/em\u003e = 0.001), indicating that the effect of caffeine gum differed across exercise outcome categories. Subgroup analyses showed a \u003cem\u003esmall\u003c/em\u003e but significant positive effect for aerobic endurance outcomes (k = 11, n = 122, SMD = 0.258, 95% CI [0.081, 0.436], \u003cem\u003ep\u003c/em\u003e = 0.004, I\u0026sup2; = 0% [low], GRADE: moderate) [18, 22, 26-28, 55, 59, 61, 62]. Similarly, a \u003cem\u003etrivial\u003c/em\u003e but statistically significant improvements were observed for anaerobic performance (k = 14, n = 156, SMD = 0.186, 95% CI [0.042, 0.340], \u003cem\u003ep\u003c/em\u003e = 0.011, I\u0026sup2; = 0% [low], GRADE: moderate) [23, 26, 27, 37, 56-58, 61, 62, 65] and\u003cem\u003e\u0026nbsp;trivial\u003c/em\u003e significant for jump performance (k = 13, n=195, SMD = 0.183, 95% CI [0.037, 0.330], \u003cem\u003ep\u003c/em\u003e = 0.014, I\u0026sup2; = 0% [low], GRADE: moderate) [25-27, 55, 57, 61, 62, 64, 66]. In contrast, the effect for muscular strength and endurance was \u003cem\u003etrivial\u003c/em\u003e\u0026nbsp; but non\u003cspan dir=\"RTL\"\u003e-\u003c/span\u003esignificant (k = 9, n = 97, SMD = 0.142, 95% CI [\u0026minus;0.038, 0.322], \u003cem\u003ep =\u003c/em\u003e 0.127, I\u0026sup2; = 35% [moderate], GRADE: low) [24, 35, 36, 52, 53, 63, 64].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA moderator analysis was conducted to examine the effect of chewing duration (5 vs. 10 min), and a significant moderating effect of chewing duration was observed (QM (1) = 28.58, p = 0.001). For the 10‑min chewing duration (k = 19, n = 190, SMD = 0.262, 95% CI [0.151, 0.384], p = 0.001, I\u0026sup2; = 0% [low], GRADE: high), the effect was \u003cem\u003esmall\u003c/em\u003e significant [23-27, 54-56, 60, 63]. Similarly, for the 5‑min chewing duration (k = 22, n\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e=110, SMD = 0.142, 95% CI [0.030, 0.262], \u003cem\u003ep\u003c/em\u003e = 0.017, I\u0026sup2; = 7% [low], GRADE: moderate), a \u003cem\u003etrivial\u003c/em\u003e but statistically significant effect was observed [18, 28, 35-37, 53, 57-59, 61, 62, 67].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAcross strata of habitual caffeine intake, the ergogenic effects of caffeine gum differed by intake level (QM (2) = 10.43, \u003cem\u003ep\u003c/em\u003e = 0.015). A \u003cem\u003esmall,\u003c/em\u003e non-significant performance improvement was observed among individuals with high habitual caffeine intake (k = 2, n = 14, SMD = \u0026minus;0.203, 95% CI [\u0026minus;0.67, 0.26], \u003cem\u003ep\u003c/em\u003e = 0.39, I\u0026sup2; = 0% [low], GRADE: low) [21] . In contrast, \u003cem\u003esmall\u003c/em\u003e but statistically significant improvements were observed among participants with moderate (k = 12, n = 130, SMD = 0.187, 95% CI [0.038, 0.336], \u003cem\u003ep\u003c/em\u003e = 0.026, I\u0026sup2; = 12% [low], GRADE: moderate) [23, 24, 36, 52, 53, 60, 62, 67, 68] and a \u003cem\u003esmall\u003c/em\u003e but statistically significant effect for low habitual caffeine intake (k = 21, n=153, SMD = 0.207, 95% CI [0.091, 0.323], \u003cem\u003ep\u003c/em\u003e = 0.030, I\u0026sup2; = 10% [low], GRADE: moderate) [18, 23, 25, 37, 55, 57, 59, 69]. For a summary of subgroup results for physical performance outcomes, see figure 2.\u003c/p\u003e\n\u003cp\u003eA meta‑regression analysis was conducted to examine whether caffeine dose moderated the effect size. The results indicated a significant positive association between caffeine dose and effect size (\u0026beta; = 0.100, \u003cem\u003ep\u003c/em\u003e = 0.031, 95% CI [0.002, 0.192]). Residual heterogeneity for that was not significant (QE\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e(44) = 31.17, \u003cem\u003ep\u003c/em\u003e = 0.927). Meta‑regression analysis showed that timing of administration relative to exercise was not a significant moderator of the effect size. The regression coefficient indicated a non‑significant association between timing of administration relative to exercise and performance outcomes (\u0026beta; = \u0026minus;0.002, p = 0.683, 95% CI [\u0026minus;0.010 to 0.006]). Residual heterogeneity for that was not significant as well (QE = 32.38, \u003cem\u003ep\u003c/em\u003e = 0.799).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.5 Sensitivity analysis\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.6 Sensitivity analysis for primary effect\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSensitivity analyses using different assumed within‑subject correlations (r = 0.2 and r = 0.8) yielded consistent findings for overall effect size. Under these assumptions, the ergogenic effect of caffeine gum remained significant (r = 0.2: SMD = 0.156, p \u0026lt; 0.001; r = 0.8: SMD = 0.282, p \u0026lt; 0.001). A leave‑one‑study‑out sensitivity analysis also was conducted to assess the robustness of the pooled effect. The results indicated that the overall effect size remained stable when each study was removed in turn, with pooled estimates ranging from SMD = 0.182 to SMD\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e= 0.215. All models remained statistically significant (all p \u0026lt; 0.001). In addition, heterogeneity remained very low across all iterations, with I\u0026sup2; values ranging from 0% to 7.51%.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.7 Sensitivity analysis for moderator effect\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSensitivity analyses using different assumed within-subject correlations (r = 0.2 and 0.8) yielded consistent findings for the training status subgroup. A significant ergogenic effect of caffeine gum was observed in trained participants across all correlation assumptions (r = 0.2: SMD = 0.184, p \u0026lt; 0.001; r = 0.8: SMD = 0.344, p \u0026lt; 0.001). In contrast, no significant effects were observed in recreationally active individuals (r = 0.2: SMD = \u0026minus;0.034, p = 0.746; r = 0.8: SMD = \u0026minus;0.083, p = 0.595). Leave‑one‑out sensitivity analysis showed that results in the trained subgroup were highly robust, and all models remained statistically significant. In contrast, in the recreationally active subgroup the effect size varied slightly although remained non‑significant in all models.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSensitivity analyses using different assumed within‑subject correlations (r = 0.2 and 0.8) showed consistent findings across exercise modes. Significant ergogenic effects of caffeine gum were observed for aerobic endurance (r = 0.2: SMD = 0.212, p = 0.013; r = 0.8: SMD = 0.402, p \u0026lt; 0.001), anaerobic performance (r = 0.2: SMD = 0.153, p = 0.025; r = 0.8: SMD = 0.271, p = 0.008), and jump performance (r = 0.2: SMD = 0.156, p = 0.037; r = 0.8: SMD = 0.293, p = 0.004). In contrast, no significant effect was observed for muscle strength and endurance tasks (r = 0.2: SMD = 0.121, p = 0.158; r = 0.8: SMD = 0.161, p = 0.124). Leave‑one‑out sensitivity analyses across exercise‑type subgroups showed that the pooled effects for aerobic endurance, jump, and anaerobic performance remained stable and statistically significant after removing individual studies, indicating robust results. In contrast, the muscle strength and endurance subgroup showed some variability, with the effect becoming significant after the removal of one study [35], suggesting sensitivity to individual studies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAcross all assumed within‑subject correlations (r = 0.2 and 0.8), chewing duration demonstrated consistent effects. At r = 0.2, the 10 min condition showed a significant ergogenic effect (SMD = 0.210, p = 0.001), whereas the 5 min condition was borderline non‑significant (SMD = 0.120, p = 0.051). At r = 0.8, effect sizes were larger for both conditions, with significant improvements observed for 10 min (SMD = 0.393, p \u0026lt; 0.001) and 5 min (SMD = 0.210, p = 0.015). Leave‑one‑out sensitivity analyses for caffeine gum chewing duration showed different patterns between conditions. For the 10 min condition, the pooled effect size remained stable and statistically significant after removing individual studies, indicating robust results. In contrast, the 5 min condition exhibited greater variability in the leave‑one‑out analyses. Although the overall effect remained statistically significant, the magnitude of the estimate fluctuated when individual study [35] \u0026nbsp;were removed, indicating some sensitivity to study‑level influence.\u003c/p\u003e\n\u003cp\u003eUsing alternative assumed correlations (r = 0.2 and r = 0.8) did not materially alter the conclusions of the habituation subgroup analysis. For low habitual caffeine intake, the ergogenic effect remained \u003cem\u003esmall\u003c/em\u003e but statistically significant across both correlations (SMD range: 0.165 to 0.289; all p \u0026lt; 0.010), indicating high robustness. For the moderate habituation subgroup, effects were likewise stable and consistently significant (SMD range: 0.153 to 0.308). Leave‑one‑out sensitivity analyses for the low and moderate habitual caffeine intake subgroups showed that the effects were highly robust, remaining stable and statistically significant across all iterations.\u003c/p\u003e\n\u003cp\u003eMeta‑regression analyses examined the association between caffeine gum dose (mg/kg) and performance outcomes across different assumed within‑subject correlations. For r = 0.2, the relationship between dose and effect size showed non‑significant trend (\u0026beta; = 0.083, p = 0.063,), while for r = 0.8, a significant positive dose\u0026ndash;response relationship was observed (\u0026beta; = 0.162, p = 0.008), indicating significantly larger ergogenic effects with increasing caffeine dose. A leave‑one‑out sensitivity analysis was conducted to examine the robustness of the meta‑regression for caffeine dose (mg/kg). The results showed the effect remained statistically significant in nearly all iterations, except when study [21] and study [35] were removed, where the association was no longer statistically significant.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAcross the sensitivity analyses using r = 0.2 and r = 0.8, meta‑regression indicated that the timing of administration relative to exercise was not significantly associated with performance outcomes. The regression coefficients (r = 0.2: \u0026beta; = \u0026minus;0.001, p = 0.712; r = 0.8: \u0026beta; = \u0026minus;0.002, p = 0.702), suggesting that variations in timing of administration relative to exercise did not meaningfully influence the ergogenic effect. A leave‑one‑out sensitivity analysis was also conducted for the meta‑regression examining the timing of administration relative to exercise. The results showed that the regression coefficient remained relatively stable across iterations and the association remained statistically non‑significant after the removal of individual studies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1.8 Risk of bias and quality of methods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAcross the included studies, most domains were judged as \u003cem\u003elow risk\u003c/em\u003e of bias, particularly for missing outcome data (D3) and measurement of outcomes (D4). However, Domains 1 (randomization process) and 5 (selection of the reported result) showed the highest proportion of \u003cem\u003esome concerns\u003c/em\u003e, mainly due to insufficient reporting of randomization methods and lack of pre‑specified analysis plans. A \u003cem\u003ehigh risk\u003c/em\u003e of bias was observed in a few studies in Domain 2 (deviations from intended interventions), primarily related to unclear blinding procedures (Figure 3).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe mixed-effects meta-regression model assessing funnel plot asymmetry showed no statistically significant evidence of publication bias. Egger\u0026rsquo;s regression test yielded a non‑significant result (z = \u0026minus;0.19, \u003cem\u003ep\u003c/em\u003e = 0.848), indicating that the relationship between effect size and its standard error was not systematic. The limit estimate as the standard error approached zero was b = 0.251 (95% CI: \u0026minus;0.33 to 0.84), further suggesting the absence of small‑study effects. Overall, these findings imply that the likelihood of publication bias influencing the pooled effect size is low. Egger\u0026rsquo;s regression tests were conducted to assess potential publication bias across all examined subgroups. Egger\u0026rsquo;s tests across subgroups based on training status, exercise type, caffeine habituation level, and chewing duration also showed no significant funnel plot asymmetry (all p \u0026gt; 0.05), suggesting no evidence of publication bias; however, the test could not be calculated for some subgroups due to an insufficient number of studies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAdditionally, Egger\u0026rsquo;s regression tests conducted for meta regression models including caffeine gum dose and timing of administration relative to exercise as moderators showed no significant funnel plot asymmetry (caffeine dose: z = \u0026minus;0.67, p = 0.502; timing of administration relative to exercise: z = \u0026minus;0.07, p = 0.951). However, these results should be interpreted cautiously because the meta‑analysis included dependent effect sizes and a relatively small number of independent studies, which may limit the reliability of regression‑based tests for publication bias. The certainty of evidence was not downgraded for publication bias, as there was no evidence of funnel plot asymmetry or small-study effects based on Egger\u0026rsquo;s regression analyses.\u003c/p\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eThis systematic review and meta-analysis provide updated evidence on the ergogenic potential of caffeine gum on physical performance. Caffeine gum produced a \u003cem\u003etrivial\u003c/em\u003e but meaningful improvement in overall physical performance. A \u003cem\u003esmall\u003c/em\u003e yet significant effect was noted in trained individuals, whereas no meaningful benefit was evident in recreationally active participants. Regarding exercise outcomes, \u003cem\u003esmall\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u003c/em\u003ebut significant improvements were observed for aerobic endurance, with \u003cem\u003etrivial\u003c/em\u003e but significant\u0026nbsp;benefits for anaerobic performance and jump performance, while muscular strength and endurance showed no significant changes. Responses were influenced by chewing duration, with a \u003cem\u003esmall\u003c/em\u003e but significant benefit for 10 min and \u003cem\u003etrivial\u003c/em\u003e effects for 5 min.\u0026nbsp;Habitual caffeine intake also moderated outcomes, with \u003cem\u003esmall\u0026nbsp;\u003c/em\u003esignificant improvements in low and moderate consumers, but no effect in high consumers. In addition, higher caffeine doses were associated with greater performance improvements, while timing of administration did not significantly influence outcomes.\u003c/p\u003e\n\u003cp\u003eThe overall standardized mean differences (SMD) observed with caffeine gum were comparable to those reported for caffeine capsules [2]. This similarity was expected, as both forms produce equivalent plasma caffeine concentrations despite differing absorption rates [17]. Our findings indicate that\u0026nbsp;caffeine gum\u0026nbsp;significantly enhances physical performance, consistent with the meta-analysis by Barreto et al. [29], which identified\u0026nbsp;caffeine gum\u0026nbsp;as an effective ergogenic strategy for both aerobic and anaerobic exercise. Supporting this, several studies [22,\u0026nbsp;37]\u0026nbsp;show that consuming\u0026nbsp;caffeine gum\u0026nbsp;5-15 min before exercise can enhance aerobic endurance [70], cycling time-trial performance [18,\u0026nbsp;59]\u0026nbsp;, repeated sprint ability [18], muscular power (e.g., jumping) [61], maximal strength [36], and team-sport-specific performance [61]. This rapid effect is likely due to buccal absorption, bypassing first-pass hepatic metabolism and allowing caffeine to enter the bloodstream within 5-10 min, thereby producing a quicker ergogenic response than traditional ingestion methods.\u003c/p\u003e\n\u003cp\u003eTrained individuals showed a significant benefit from caffeine gum supplementation, whereas no meaningful effect was observed in recreationally active participants. This aligns with Barreto et al. [29], who observed clear enhancements in trained but not untrained individuals. The broader literature, however, demonstrates inconsistent ergogenic based on training status. For example, beta-alanine tends to produce smaller effects in highly trained individuals [71], whereas sodium bicarbonate shows diminished effects in untrained participants [72]. Whether caffeine exhibits comparable training status-specific effects remains unclear\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e[73]. This interpretation is limited by the small number of outcomes in the recreationally active group (40 from trained individuals versus 7 from recreationally active participants) and the low total sample size of recreationally active participants (n =59), which likely reduced statistical power and precision. Beyond\u0026nbsp;caffeine gum\u0026nbsp;administration, the broader caffeine literature suggests that training status is not a consistent moderator of resistance-type outcomes [74]. Accordingly, the apparent trained\u0026ndash;untrained differences in our dataset should be interpreted cautiously, as they may reflect sampling and design features rather than systematic physiological moderation by training status.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCurrent evidence indicates that caffeine gum produces significant improvements in aerobic endurance, anaerobic performance and vertical jump ability, but no meaningful effects on muscular strength or endurance. Consistent with\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eour findings, Barreto et al.\u0026nbsp;[29]\u0026nbsp;reported improvements in\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eexercise performance, particularly for endurance and power‑related outcomes. However, our findings diverge for muscular strength, as their meta-analysis identified a positive effect of\u0026nbsp;caffeine gum\u0026nbsp;on strength performance, whereas ours did not. Broader meta-analytic evidence suggests that caffeine exerts greater ergogenic effects in endurance than strength-based tasks [73]. This pattern was also reflected in our findings,\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003ewhere the effect for aerobic endurance outcomes was \u003cem\u003esmall\u003c/em\u003e, whereas effects for jumping and anaerobic measures were \u003cem\u003etrivial\u003c/em\u003e, and muscular strength and endurance outcomes did not show a significant improvement. However, these findings should be interpreted cautiously, as the sensitivity analysis indicated that excluding a single study revealed a \u003cem\u003esmall\u003c/em\u003e positive effect, suggesting that the ergogenic benefit may become evident when methodological variability is reduced, particularly in muscular‑related performance task. In addition, differences in delivery method, timing of ingestion, or participant characteristics may contribute to discrepancies among studies [15].\u0026nbsp;Mechanistically, improvements in endurance performance may be mediated by both central and peripheral mechanisms, whereas improvements in power‑related tasks are more likely linked to direct effects on muscle contractile processes. In addition, enhanced sympathetic nervous system activation and increased central motor drive may contribute to performance during short‑duration anaerobic efforts. Together, these mechanisms may partly explain the improvements observed in some physical performance outcomes in the present analysis [75]. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eModerator analysis showed that chewing duration significantly influenced the ergogenic effect of caffeine gum. Both 5 and 10 min chewing durations improved performance, but the longer duration produced a \u003cem\u003esmall\u003c/em\u003e rather than \u003cem\u003etrivial\u003c/em\u003e effect.\u0026nbsp;Barreto et al. [29]\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003edid not examine chewing duration as a moderator, which makes direct comparison challenging. Nevertheless, individual studies report improvements in physical performance with both shorter [28,\u0026nbsp;36]\u0026nbsp;and longer chewing [24,\u0026nbsp;76]\u0026nbsp;periods\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e To date, no investigation has directly compared these durations, so interpretations should be made with caution. However, the slightly larger effect associated with longer chewing may reflect increased caffeine release and enhanced buccal absorption, resulting in greater plasma availability and stronger adenosine receptor antagonism [77]. Together, these mechanisms provide a plausible explanation for the augmented physiological impact of prolonged chewing on physical performance.\u003c/p\u003e\n\u003cp\u003eThe ergogenic effects of caffeine gum appeared to depend on habitual caffeine intake. Individuals with high habitual consumption showed no clear performance benefits, possibly due to tolerance, whereas those with low and moderate intake demonstrated significant improvements. However, evidence for high habitual consumers remains limited. The only dataset representing high consumers originated from a subgroup analysis including just fourteen participants, making any conclusions tentative. Caffeine habituation has been proposed to attenuate the ergogenic effects of acute caffeine ingestion [3], although current evidence remains inconsistent. Chronic caffeine intake may induce tolerance through physiological adaptations, such as the upregulation of adenosine receptors, potentially requiring higher acute doses to elicit similar effects [3]. For example, one study [78]\u0026nbsp;reported that 28 days of caffeine consumption abolishes the performance benefit of 3 mg/kg caffeine, whereas another [79]\u0026nbsp;found no influence of habitual intake on the ergogenic effect of a higher dose (6 mg/kg) during a cycling time trial. These findings suggest that acute caffeine dose may partly explain conflicting results related to habituation. Overall, individuals with low and moderate habitual caffeine consumption are more likely to benefit from\u0026nbsp;caffeine gum. However, limitations in dietary reporting and other methodological constraints complicate interpretation, reducing confidence in these conclusions.\u003c/p\u003e\n\u003cp\u003eCaffeine gum dosage ranged from 1.35 to 6.4 mg/kg across included studies. Meta‑regression indicated that dosage significantly moderated effect size, showing a positive association such that higher doses were linked to slightly larger ergogenic effects. This finding suggests that increasing caffeine dose may modestly enhance exercise performance when delivered via caffeine gum.\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eOur findings are consistent with Barreto et al. [29], who reported no significant effect at doses \u0026lt;3 mg/kg body mass, but a clear benefit at \u0026ge;3 mg/kg.\u0026nbsp;However, one study comparing 2.7 and 5.4 mg/kg body mass reported that both\u0026nbsp;caffeine gum\u0026nbsp;administration did not improve performance in the Special Judo Fitness Test\u0026nbsp;[58].\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eAnother investigation evaluating 100 mg and 200 mg\u0026nbsp;caffeine gum reported\u0026nbsp;greater quadriceps strength with the higher dose, but no effect on isometric handgrip strength, hamstring strength, ball‑kicking speed, or performance in a 15‑s countermovement jump test [21].\u0026nbsp;Discrepancies across studies may reflect differences in methodological factors, such as participant characteristics, habitual caffeine intake, and overall study quality\u003cspan dir=\"RTL\"\u003e.\u003c/span\u003e Overall, the observed dose range (1.35 to 6.4 mg/kg) revealed a meaningful dose\u0026ndash;response association, while further original dose\u0026ndash;response studies with\u0026nbsp;caffeine gum\u0026nbsp;on physical performance are required to confirm these findings and to help provide accurate practical recommendations.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOur data showed that exercise performance is not significantly moderated by the timing of caffeine gum administration before exercise. This contrasts with Barreto et al. [29], who found that caffeine gum was ergogenic only when consumed within 15 min before exercise. In our analysis, however, most outcomes involved ingestion within this 15-min window (k = 35), with no difference observed across timings. This pattern aligns with the pharmacokinetics of\u0026nbsp;caffeine gum, as caffeine absorbed through the buccal mucosa reaches detectable plasma concentrations within ~15 min [17], considerably faster than traditional capsule forms. The limited data available beyond 15 min pre-exercise (k = 3) reduced statistical power and prevented firm conclusions regarding longer pre-exercise intervals. Nonetheless, ingestion beyond 15 min before exercise may still confer performance benefits, as plasma caffeine concentrations remain elevated for several hours despite peaking within\u0026nbsp;\u0026sim;45\u0026ndash;105 min depending on the dose [17]. Overall, these findings suggest that consuming\u0026nbsp;caffeine gum\u0026nbsp;within 15 min of exercise is an effective and practical strategy for enhancing performance.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe overall risk of bias was low, particularly for outcome measurement and missing data, supporting the general reliability of the findings. However, recurring concerns in the randomization process and selective reporting highlight limitations in study design transparency. In addition, unclear blinding contributed to a high risk in some studies. Taking together, the evidence base is methodologically acceptable, but improvements in randomization and reporting practices are needed to strengthen confidence in future findings.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.3 Practical applications\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCaffeine gum represents a viable strategy for athletes requiring rapid caffeine delivery, particularly when traditional capsule or liquid ingestion is impractical (e.g., halftime, substitutions, or early-morning training). It may be preferable for longer events, as its rapid buccal absorption and high bioavailability help sustain plasma caffeine levels [17]. This makes caffeine gum especially useful when a rapid ergogenic effect is desired or during prolonged exercise. Figure 4 represents a schematic overview of caffeine gum as a fast-acting strategy in sport and physical performance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.4\u0026ensp;Limitations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAlthough this study provides new insights into the effects of caffeine gum on physical performance, several limitations should be acknowledged. First, heterogeneity across studies in training status, exercise type, chewing duration, caffeine habituation, caffeine dosage, and timing of administration relative to exercise across studies may have contributed to variability in effect sizes. Second, most studies included only male participants, with limited representation of females, which restricts the generalizability of the findings. Third, although overall methodological quality was acceptable, concerns were identified regarding the randomization process, blinding procedures, and pre‑registration practices in some studies. Finally, the small number of independent studies may compromise the stability and reliability of regression‑based publication bias analyses.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThis systematic review and meta-analysis demonstrate that caffeine gum produces \u003cem\u003etrivial\u003c/em\u003e but statistically significant improvements in physical performance. The rapid buccal absorption of caffeine from chewing gum offers a practical and well-tolerated ergogenic strategy, particularly when traditional caffeine intake is impractical or undesirable. Although the overall magnitude of effect is \u003cem\u003etrivial\u003c/em\u003e, these improvements may still be meaningful in competitive settings where marginal gains can influence performance outcomes.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eSMD\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Standardized Mean Difference\u003c/p\u003e\n\u003cp\u003eCI\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u0026nbsp; Confidence Interval\u003c/p\u003e\n\u003cp\u003eBM\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp; \u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e Body Mass\u003c/p\u003e\n\u003cp\u003eRCTs\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp; \u0026nbsp;Randomized Controlled Trials\u003c/p\u003e\n\u003cp\u003e1RM\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u0026nbsp; \u0026nbsp; One‑Repetition Maximum\u003c/p\u003e\n\u003cp\u003eCYP1A2\u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003e \u003cspan dir=\"RTL\"\u003e\u0026nbsp;\u003c/span\u003eCytochrome P450 1A2 Gene\u003c/p\u003e\n\u003cp\u003eGRADE \u0026nbsp; \u0026nbsp;Grading of Recommendations Assessment, Development, and Evaluation\u003c/p\u003e\n\u003cp\u003ePICO\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp; \u0026nbsp; Population, Intervention, Comparison, Outcome\u003c/p\u003e\n\u003cp\u003eREML\u0026nbsp; \u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp;Restricted Maximum Likelihood\u003c/p\u003e\n\u003cp\u003eSD\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp;Standard Deviation\u003c/p\u003e\n\u003cp\u003ePRISMA \u0026nbsp; \u0026nbsp; Referred Reporting Items for Systematic Reviews and Meta-Analyses\u003c/p\u003e\n\u003cp\u003ePROSPER \u0026nbsp; International Prospective Register of Systematic Reviews\u003c/p\u003e\n\u003cp\u003eI\u0026sup2;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; I‑squared (statistical measure of heterogeneity)\u003c/p\u003e\n\u003cp\u003eQ\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Cochran\u0026rsquo;s Q statistic (test for heterogeneity)\u003c/p\u003e\n\u003cp\u003eQM\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Test statistic for moderators in meta‑analysis (Cochran\u0026rsquo;s Q for moderators)\u003c/p\u003e\n\u003cp\u003eQE\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Residual heterogeneity statistic (Cochran\u0026rsquo;s Q for residual heterogeneity)\u003c/p\u003e\n\u003cp\u003e\u0026beta;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Regression Coefficient (beta coefficient in meta‑regression)\u003c/p\u003e\n\u003cp\u003eb \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Intercept estimate (limit estimate in Egger\u0026rsquo;s regression)\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e We gratefully acknowledge the researchers and authors of the original studies included in this meta-analysis for their valuable contributions to scientific literature. We also thank the librarians and research support staff who assisted with database searches and resource access. Special thanks to our colleagues for their insightful feedback during the development of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e There is no funding for the current article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e The authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u003c/strong\u003e All data relevant to the study are included in the article.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval\u003c/strong\u003e Not required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate\u003c/strong\u003e Not required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for Publication\u003c/strong\u003e Not required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor details\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e[1]\u0026nbsp;Department of Exercise Physiology, Faculty of Sport Sciences and Health, University of Tehran, Tehran, Iran\u003c/p\u003e\n\u003cp\u003e2\u0026nbsp;School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia\u003c/p\u003e\n\u003cp\u003e3Australian Athletics, Melbourne, Australia\u003c/p\u003e\n\u003cp\u003e4\u0026nbsp;GICAF Research Group, Department of Education Research Methods and Evaluation, Faculty of Human and Social Sciences, Universidad Pontificia Comillas, 28049 Madrid, Spain\u003c/p\u003e\n\u003cp\u003e5 School of Human Sciences, Exercise and Sport Science, University of Western Australia, Perth, WA 6009, Australia\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e HM and EB conceptualized and designed the study, collected data, carried out the analyses, drafted the initial manuscript, and reviewed and revised the manuscript. HM and EB conceptualized and designed the study and reviewed and revised the manuscript. AS, OG, and CP supervised the analyses and reviewed and revised the manuscript. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRivers W, Webber H. The action of caffeine on the capacity for muscular work. The Journal of physiology. 1907;36(1):33.\u003c/li\u003e\n\u003cli\u003eGrgic J, Trexler ET, Lazinica B, Pedisic Z. Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition. 2018;15(1):11.\u003c/li\u003e\n\u003cli\u003eGuest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, et al. International society of sports nutrition position stand: caffeine and exercise performance. 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Effect of caffeine ingestion on muscular strength and endurance: a meta-analysis. Med Sci Sports Exerc. 2010 Jul;42(7):1375-87.\u003c/li\u003e\n\u003cli\u003eBowtell JL, Mohr M, Fulford J, Jackman SR, Ermidis G, Krustrup P, et al. Improved exercise tolerance with caffeine is associated with modulation of both peripheral and central neural processes in human participants. Frontiers in Nutrition. 2018;5:6.\u003c/li\u003e\n\u003cli\u003eDeng H, Wang L, Liu P, Bin Naharudin MN, Fan X. Caffeine and taurine: a systematic review and network meta-analysis of their individual and combined effects on physical capacity, cognitive function, and physiological markers. Journal of the International Society of Sports Nutrition. 2025;22(1):2566371.\u003c/li\u003e\n\u003cli\u003eMorris C, Viriot SM, Farooq Mirza QUA, Morris GA, Lynn A. Caffeine release and absorption from caffeinated gums. Food Funct. 2019 Apr 1;10(4):1792-6.\u003c/li\u003e\n\u003cli\u003eBeaumont R, Cordery P, Funnell M, Mears S, James L, Watson P. Chronic ingestion of a low dose of caffeine induces tolerance to the performance benefits of caffeine. Journal of Sports Sciences. 2017;35(19):1920-7.\u003c/li\u003e\n\u003cli\u003eGon\u0026ccedil;alves LdS, Painelli VdS, Yamaguchi G, Oliveira LFd, Saunders B, Da Silva RP, et al. Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation. Journal of Applied Physiology. 2017;123(1):213-20.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"sports-medicine-open","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"smoa","sideBox":"Learn more about [Sports Medicine-Open](http://sportsmedicine-open.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/smoa/default.aspx","title":"Sports Medicine-Open","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"ergogenic aids, nutrition, caffeine, caffeine chewing gum, exercise performance","lastPublishedDoi":"10.21203/rs.3.rs-9461741/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9461741/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e Caffeine gum is a fast‑acting delivery method that rapidly elevates circulating caffeine levels and may improve physical performance. Given the recent growth in research, an updated systematic review and meta-analysis is warranted.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjectives:\u003c/strong\u003e To evaluate the acute effects of caffeine gum on physical performance compared with placebo, and investigate potential moderators including (1) training status, (2) exercise type, (3) chewing duration, (4) caffeine habituation (i.e., habitual intake), (5) caffeine dosage, and (6) timing of administration relative to exercise.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e The review followed the Cochrane Handbook for Systematic Reviews of Interventions and PRISMA guidelines. PubMed, Web of Science, Scopus and SPORTDiscus were searched up to February 2026. Three-level meta-analyses were synthesized for outcomes. Sensitivity analyses addressed assumptions within-subject correlations, outliers, and influential cases.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThirty-one studies met the inclusion criteria, with 25 included in the meta-analysis. Caffeine gum produced a \u003cem\u003etrivial\u003c/em\u003e but significant improvement in physical performance (SMD = 0.195, 95% CI [0.115 to 0.275] p \u0026lt; 0.05). Aerobic endurance showed a \u003cem\u003esmall\u003c/em\u003e significant effect, whereas \u003cem\u003etrivial\u003c/em\u003e but significant effects were observed for anaerobic performance and vertical jump outcomes (p \u0026lt; 0.05). These effects were consistent across chewing durations of 5 and 10 min and across individuals with low to moderate habitual caffeine intake. In contrast, \u003cem\u003etrivial\u003c/em\u003e and non-significant effects were observed in recreationally active participants, for muscular strength/endurance outcomes, and among high caffeine users (p \u0026gt; 0.05)\u003cem\u003e. \u003c/em\u003eMeta‑regression showed a significant dose–response relationship (p = 0.031), but no effect of timing of administration relative to exercise (p = 0.683). Sensitivity analyses confirmed the robustness of findings across correlation assumptions and leave‑one‑out procedures. Overall risk of bias was mostly \u003cem\u003elow\u003c/em\u003e, with \u003cem\u003esome concerns\u003c/em\u003e related to randomization, blinding, and selective reporting.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e Caffeine gum produced \u003cem\u003etrivial\u003c/em\u003ebut significant ergogenic effects on physical performance and may represent a practical strategy for athletes, particularly in time‑sensitive situations, due to its rapid buccal absorption and quick onset of action.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRegistration: \u003c/strong\u003eThe protocol was prospectively registered in the PROSPERO database (CRD420251086458).\u003c/p\u003e","manuscriptTitle":"Fast-Acting Caffeine Strategy: A Systematic Review and Meta-Analysis of the Ergogenic Effects of Caffeine Chewing Gum on Physical Performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-11 10:50:12","doi":"10.21203/rs.3.rs-9461741/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-05-06T04:23:47+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-30T23:33:22+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Sports Medicine-Open","date":"2026-04-30T00:16:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-22T12:34:39+00:00","index":"","fulltext":""},{"type":"submitted","content":"Sports Medicine-Open","date":"2026-04-21T19:56:56+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"sports-medicine-open","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"smoa","sideBox":"Learn more about [Sports Medicine-Open](http://sportsmedicine-open.springeropen.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/smoa/default.aspx","title":"Sports Medicine-Open","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"37b9277c-aa67-4224-ba33-1b7bb8b4404c","owner":[],"postedDate":"May 11th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"","date":"2026-05-06T04:23:47+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-30T23:33:22+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Sports Medicine-Open","date":"2026-04-30T00:16:51+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-11T10:50:12+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-11 10:50:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9461741","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9461741","identity":"rs-9461741","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}