The Effect of Blood Flow Restriction Pressure on Acute and 24-Hour Recovery Following Upper-Limb Repeated High-Intensity Exercise in Boxers 

The Effect of Blood Flow Restriction Pressure on Acute and 24-Hour Recovery Following Upper-Limb Repeated High-Intensity Exercise in Boxers | 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 The Effect of Blood Flow Restriction Pressure on Acute and 24-Hour Recovery Following Upper-Limb Repeated High-Intensity Exercise in Boxers Qinglou Xu, Siyi Leng, Ruiqiu Mao, Aiqin Sun This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8489574/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract PURPOSE To investigate the acute and 24-hour effects of different blood flow restriction (BFR) pressures on recovery following a single session of boxing-specific repeated high-intensity exercise. METHODS Fifteen boxers performed the exercise under four randomly ordered conditions: non-BFR, and BFR at 40%, 60%, and 80% arterial occlusion pressure (AOP). Heart rate (HR), blood lactate (BLA), muscle oxygen saturation (SmO 2 ), punching speed, and force were measured at baseline, immediately post-exercise, and at 5 minutes, 20 minutes, and 24 hours post-exercise. Statistical significance was set at p < 0.05. RESULTS The 80% AOP condition elicited significantly higher HR and slower HR recovery (% baseline) compared to other conditions immediately post-exercise and at 5 minutes and 20 minutes post-exercise (p < 0.001). BLA concentrations were significantly lower under all BFR conditions than non-BFR throughout recovery ( p < 0.001), with the lowest values observed at 80% AOP, which also exhibited the highest lactate clearance rate at 20 minutes post-exercise. SmO 2 recovery slowed progressively with increasing BFR pressure ( p < 0.001). Punching performance decreased immediately post-exercise in a pressure-dependent manner ( p < 0.001), with performance at 80% AOP remaining impaired at 24 hours. CONCLUSION BFR alters post-exercise physiological responses and impairs punching performance, with effects magnified at 80% AOP. Pressures of 40–60% AOP may offer an optimal balance between physiological stimulus and performance recovery. Therefore, BFR at high pressures should be avoided within 24 hours prior to competition. combat sports upper-limb training blood lactate punching performance muscle oxygen saturation Figures Figure 1 Figure 2 Figure 3 Introduction Blood flow restriction (BFR) training involves the application of external pressure to the proximal limbs to partially restrict arterial inflow and occlude venous outflow, and has emerged as a potent training methodology. When combined with low-load resistance exercise, BFR induces muscular hypertrophy and strength gains comparable to high-load training ( 20 ) . More recently, the application of BFR has expanded to high-intensity exercise modalities ( 23 ) . Studies integrating BFR with sprint or repeated high-intensity efforts have reported enhanced metabolic stress ( 2 ) , improved vascular function ( 40 ) , and potential benefits for aerobic and anaerobic capacities in athletes ( 6 ) , highlighting its acute physiological effectiveness. Boxing is an intermittent sport requiring both aerobic and anaerobic capacities. Athletes typically perform repeated short-duration, high-intensity actions (≤ 10 seconds), such as punching, footwork, and defensive maneuvers. These actions involve almost all muscle groups, and the brief rest periods (≤ 30 seconds) between efforts are insufficient for complete recovery. Thus, improving the upper limbs’ capacity to repeatedly perform high-intensity actions is essential for continuous, powerful strikes during training and competitions. Consequently, combining upper-limb BFR with repeated high-intensity effort training (hereafter referred to as BFR-RST) may offer beneficial training outcomes ( 23 ) . Although research indicates that BFR-RST could be a promising training method, considerable controversy remains. The physiological responses to BFR-RST are complex and occasionally paradoxical. Some studies report that BFR during high-intensity exercise modifies muscle oxygenation kinetics, for instance, by increasing deoxygenated hemoglobin and slowing reoxygenation rates ( 37 ) , which may ultimately facilitate beneficial physiological adaptations ( 24 ) . In contrast, other studies have reported conflicting results ( 14 ) , indicating that the interplay between exercise intensity and BFR pressure makes outcomes difficult to predict. Additionally, other studies reported suboptimal performance outcomes ( 29 ) . A recent narrative review indicated that BFR-RST could benefit sports requiring high glycolytic demands by enhancing repeated sprint ability (RSA) within a short period ( 30 ) . Nevertheless, previous studies mostly employed tests involving specific sprint movements. Differences in training movement patterns may influence muscle recruitment and energy consumption ( 28 ) . It is widely recognized that training modes closely matching sport-specific actions facilitate the transfer of training effects to competition scenarios. Therefore, appropriate RST modalities should be selected according to specialized sport movements. Moreover, selecting an appropriate BFR pressure is crucial for achieving optimal training outcomes. Significant discrepancies exist among studies regarding pressure application, participant selection, training frequency, and intensity, complicating comparisons and applications of research findings. If the BFR pressure is too low, muscle and cardiovascular stimuli may be insufficient for inducing desired physiological adaptations. Conversely, excessive pressure may negatively affect sprint performance, exacerbate fatigue, and decrease training intensity. These consequences not only counteract potential BFR benefits but may also impair single-session effectiveness and pose physical risks to athletes ( 21 ) . Current research suggests that training with BFR pressures ranging from 40% to 80% limb occlusion pressure is safe and effective, with the specific pressure selected based on training mode, cuff width, training load, and participant fitness level ( 35 ) . However, combining BFR with high-intensity training further complicates the scenario. Such combined training, characterized by maximal efforts dependent on anaerobic energy systems, may elicit metabolic, neuromuscular, and perceptual responses distinct from those observed with submaximal exercise ( 3 ) . Additionally, RST studies indicate potentially greater adaptive benefits for the upper limbs ( 38 ) . Thus, understanding the physiological effects of specialized upper-limb RST combined with BFR is essential for developing targeted training programs and optimizing athletic performance. In summary, this study aimed to investigate the acute recovery characteristics and delayed effects of combining different BFR pressures with specialized upper-limb RST. Dynamic recovery monitoring was conducted at multiple time points. Identifying the optimal BFR pressure could enable more precise upper-limb BFR-RST, providing evidence for safe and efficient medium- to long-term training interventions. Method Experimental Approach to the Problem A randomized crossover design within subjects was adopted for this study. Over a four-week period, participants underwent upper-limb RST under four BFR pressure conditions (non-BFR, 40% AOP, 60% AOP, and 80% AOP). Each condition was separated by a washout period of at least 72 hours to minimize carryover effects ( 17 ) . For all participants, testing sessions were consistently conducted on Monday and Tuesday of each week, resulting in a 5-day interval between sessions for each participant. Pressure conditions were randomly assigned for each participant using a computer-generated randomization method (Microsoft Excel RAND function) to determine the order of the four conditions. Each experimental round occurred at consistent times (baseline testing at 8:00 AM, training intervention at 2:00 PM) and under identical environmental conditions to ensure experimental consistency. The detailed experimental procedure was as follows (Fig. 1 ): Baseline data (T0) were collected at 8:00 AM on each testing day. At 2:00 PM on the same day, participants performed specialized BFR-RST at a boxing training venue. Participants initially performed a standardized 15-minute warm-up consisting of 5 minutes of jogging, 5 minutes of dynamic stretching (e.g., arm circles, torso twists, leg swings), and 5 minutes of sport-specific movements (e.g., shadow boxing, light punching combinations). This was followed by brief static stretching of the upper limbs, after which the randomly assigned BFR pressure condition was applied. They then performed three sets of repeated maximal-effort punches (hitting a sandbag), each set consisting of 14 repetitions of 3 seconds, with 10 seconds of passive recovery between repetitions and 1-minute intervals between sets. Training intensity was monitored using a modified Borg CR-10 scale (RPE 0–10) ( 33 ) . Prior to the study, all participants attended a familiarization session during which the scale was thoroughly explained, with '0' representing no effort and '10' representing maximal effort. Participants were instructed to report their overall perception of exertion immediately following each set. This protocol was adapted from Kamandulis et al. ( 13 ) and aligns with boxing-specific demands. Similar protocols have been employed in previous studies ( 40 ) . Data collection occurred immediately post-training (T1), after 5 minutes of recovery (standing or slow walking, T2), 20 minutes (T3), and 24 hours (T4) after training completion. Measurements included HR, BLA, SmO 2 , and punching performance. The chosen recovery modality (standing or slow walking at T2) was selected to replicate typical low-intensity activities (e.g., standing in a corner, light footwork) experienced during brief rest intervals in boxing matches. Although differences between standing and slow walking might introduce variability in recovery measures, participants were explicitly instructed to maintain consistent activity (either standing or very slow pacing) across all testing sessions to minimize intra-participant variability. Following the training session and subsequent assessments (T1–T3), participants were instructed to abstain from any structured exercise, upper-body resistance training, or high-impact activities until after the final measurement at T4 (24 hours). They were advised to maintain normal dietary and hydration practices but to avoid caffeine and alcohol consumption. Compliance was verbally confirmed at T4. Participants Using G*Power 3.1.9 software, sample size estimation indicated that at a significance level of α = 0.05 and a medium effect size (η² = 0.25), a minimum of 12 participants was required to achieve 95% statistical power ( 18 ) . Ultimately, 15 male collegiate boxers (mean ± SD; age: 20.81 ± 1.0 years, height: 175.5 ± 4.6 cm, weight: 67.4 ± 7.9 kg) voluntarily participated after recruitment and screening. Participants had competed in at least 10 official amateur or university-level boxing matches and received boxing training since high school or earlier. According to the participant classification framework by Kay et al., participants were categorized as Tier 2 ( 25 ) . Before testing, all participants received full information about experimental procedures and potential risks and provided written informed consent. Ethical approval was granted by the Ethics Committee of Shenyang Sport University (Ethics [2024] No. 12). Prior to inclusion, all participants completed a health screening questionnaire (see Additional File 1) designed to exclude individuals with contraindications to BFR training, such as a history of deep vein thrombosis, cardiovascular or cerebrovascular diseases, peripheral vascular disease, or hypertension (defined as systolic blood pressure > 140 mmHg or diastolic > 90 mmHg). No participant reported any of these conditions or other injuries that would limit participation. Participants were instructed to avoid alcohol or substances potentially affecting test outcomes the day before each session, refrain from additional high-intensity physical activities beyond the training sessions during the two testing days, and maintain regular sleep patterns and dietary habits. To maximize compliance, the study was conducted during the participants' off-season. Participants were reminded verbally before each session and via text message to adhere to the activity restrictions. Procedures Measurement of Upper-Limb AOP Participants’ resting AOP was assessed before initial testing (161 ± 13 mmHg) using an established protocol ( 15 ) . An upper-limb pressure cuff (Theratools, China; length: 68 cm, width: 7.5 cm) was positioned around the upper biceps brachii region for BFR. AOP was measured using Doppler ultrasound (Swedish PF6001, Perimed, Sweden) by detecting radial artery pulsations. The cuff pressure was first inflated to 70 mmHg, then increased incrementally by 5 mmHg until the pulse disappeared. The pressure at pulse disappearance was recorded as the AOP. This procedure was repeated three times with 2-minute rest intervals, and the mean value was recorded as each participant’s upper-limb AOP. Subsequently, pressures corresponding to 40%, 60%, and 80% AOP were calculated individually and recorded for each athlete. Before the experimental sessions, participants were familiarized with the sensation of BFR at a low pressure (20% AOP). During experimental sessions, the pressure cuff was inflated to the target pressure (0%, 40%, 60%, or 80% AOP) immediately before the first set of punches and deflated immediately after the final set. Thus, BFR was applied continuously throughout the entire exercise protocol, including inter-set rest periods. HR Monitoring During testing, HR was continuously recorded using a HR monitor (Polar Accurex Plus, Finland). Resting HR was measured after participants had been seated quietly for 10 minutes during baseline (T0) data collection in the morning. HR values at each specified time point (T1, T2, T3, and T4) were extracted for analysis. To quantify recovery at each time point, HR was expressed as a percentage of the baseline resting value using the following formula: ( 1 ) $$\:\:\:\:\:\:\:HR\:recovery\:rate\:\left(expressed\:as\:\%\:of\:baseline\right)\:=\frac{HR\:immediately\:after\:exercise-HR\:at\:N\:minutes\:after\:exercise}{HR\:immediately\:after\:exercise-Resting\:HR}\times\:100％$$ SmO 2 Testing Changes in SmO 2 in the anterior deltoid muscle of the upper limb were monitored using a wireless muscle oxygenation device (Moxy, Fortiori Design LLC, USA). The anterior deltoid was selected because it contributes the highest proportion of mechanical work during rear-hand straight punches in both male and female boxers ( 7 , 39 ) . Near-infrared spectroscopy (NIRS) technology provides a non-invasive measurement of tissue hemodynamics. NIRS detects changes in absorbance between oxygenated and deoxygenated states of hemoglobin and myoglobin at specific wavelengths. SmO 2 typically indicates the percentage of oxygenated hemoglobin/myoglobin relative to total hemoglobin, ranging from 0% to 100%. To quantify recovery at each time point, SmO 2 was expressed as a percentage of the baseline resting value using the following formula ( 1 ) : $$\:SMO2\:recovery\:rate\left(expressed\:as\:\%\:of\:baseline\right)=\frac{SMO2\:at\:N\:min\:after\:exercise\:}{Resting\:SMO2}\times\:100％$$ BLA Testing Ear blood samples (10 µL per sample) were collected at multiple stages (pre-training, immediately post-training, 5 min post-training, 20 min post-training, and 24 h post-training). BLA levels were measured using a lactate analyzer (EKF Biosen-S Line, Germany), and specific values were recorded. The sampling procedure was as follows: participants’ earlobes were sterilized with alcohol using cotton swabs; gentle thumb pressure was applied to obtain blood at the sampling site; samples were collected with capillary tubes and transferred to centrifuge tubes containing a lactate inhibitor. Tubes were then sealed, gently shaken, and labeled. To quantify recovery at each time point, BLA was expressed as a percentage of the baseline resting value using the following formula: $$\:BLA\:recovery\:rate\left(expressed\:as\:\%\:of\:baseline\right)=\frac{Peak\:post\:-exercise\:BLA\left(T2\right)-BLA\:at\:N\:min\:post\:-exercise}{Peak\:post-exercise\:BLA\left(T2\right)}\times\:100％$$ Punching Performance Testing Punching indicators, including punching speed and force, were measured using Strike Tec boxing sensors (Strike Tec, Dallas, USA; version 1.4.4). Data derived from acceleration measurements were extracted via an accompanying mobile application ( 41 ) . Punching force calculated from acceleration (typical measurement error: 0.57) ( 16 ) and punching speed (ICC: 0.853; 95% CI: 0.650–0.942) ( 9 ) have demonstrated high reliability. Punching force was expressed in relative values to eliminate body-weight effects. Sensors were securely attached to athletes’ wrists. Athletes were instructed to adopt an orthodox stance and perform three maximal-effort rear-hand straight punches ( 22 ) . This punch type was selected due to its frequent use in competition ( 5 ) and simplicity, facilitating consistent assessment. Professional researchers trained participants in proper punching technique before testing to ensure reliable data collection. Statistical Analysis Statistical analysis was performed using SPSS version 26.0 software (IBM Corp., Armonk, NY, USA). All data are presented as mean ± standard deviation (mean ± SD). A two-way repeated-measures analysis of variance (ANOVA) was conducted to evaluate the overall effects of independent variables (pressure × time) on each dependent variable. Mauchly’s test of sphericity was applied, and the Greenhouse-Geisser correction was used when the sphericity assumption was violated. When significant interaction effects were identified, simple effects analysis with Bonferroni adjustments was conducted for post-hoc comparisons. Effect sizes (partial eta squared, η² ) were categorized as trivial (< 0.04), small (0.04–0.25), moderate (0.25–0.64), and large (≥ 0.64). Statistical significance was set at p < 0.05. In all figures and text, data are presented as mean ± standard deviation (SD). Results All fifteen participants completed all four experimental conditions and all measurement timepoints. Therefore, the analysis was conducted on a complete dataset with no missing values. Although not systematically quantified, several participants informally reported transient sensations of numbness and discomfort in the arm during the training sessions under the BFR conditions, particularly at 80% AOP. These sensations resolved promptly upon cuff deflation. No other adverse events were reported. Two-way repeated-measures ANOVA indicated significant main effects for pressure conditions (non-BFR, AOP 40%, AOP 60%, AOP 80%), time points (T0–T4), and their interaction on HR, BLA, SmO 2 , punching speed, and punching force ( p < 0.001). The effect sizes and key statistical characteristics are detailed below (Fig. 2 – 3 , Table 1 ). Table 1 Comparison of recovery rate (% of baseline) in HR, BLA, and SmO2 under different treatment conditions Treatment Conditions HR recovery rate (%) BLA recovery rate (%) SmO 2 recovery rate (%) 5min 20min 24h 20min 24h 5min 20min 24h NO-BFR 52.28 ± 8.21 60.65 ± 5.98 99.69 ± 1.00 18.28 ± 11.09 80.74 ± 3.57 97.67 ± 2.49 96.42 ± 4.57 97.62 ± 2.81 AOP45 49.76 ± 6.79 61.46 ± 4.60 99.51 ± 0.81 28.54 ± 15.76 84.25 ± 4.27 85.73 ± 9.17 * 91.24 ± 4.71 * 96.88 ± 3.59 AOP60 48.54 ± 6.62 60.92 ± 5.19 99.67 ± 0.51 27.96 ± 15.04 83.72 ± 8.73 85.86 ± 8.49 * 90.64 ± 6.30 * 97.69 ± 2.03 AOP80 42.79 ± 8.29 *#∆ 55.77 ± 6.19 *#∆ 99.74 ± 0.81 33.92 ± 11.59 * 84.93 ± 7.18 85.09 ± 9.60 * 89.22 ± 5.75 * 97.44 ± 4.52 f 4.276 3.415 0.238 3.474 1.286 8.666 5.116 0.179 p 0.009 0.023 0.870 0.022 0.288 < 0.001 0.003 0.910 Note: “*” denotes significant difference compared to NO-BFR group ( p < 0.05); “#” indicates significant difference compared to 40% AOP ( p < 0.05); “∆” denotes significant difference compared to 60% AOP ( p < 0.05). No significant HR differences were observed among the non-BFR, 40% AOP, and 60% AOP groups across all time points. However, the 80% AOP condition elicited a significantly higher HR at T1, T2, and T3 ( p < 0.001) compared to the other conditions, with lower HR recovery rates (% of baseline) at T2 ( p = 0.009) and T3( p = 0.023). All groups returned to baseline HR at T4. Regarding statistical effects, time had a large main effect ( η 2 = 0.990), group had a moderate main effect ( η 2 = 0.448), and interaction exhibited a small effect ( η 2 = 0.181). All BFR groups exhibited significantly lower BLA levels from T1 to T4 compared to the non-BFR group ( p < 0.001), with the 80% AOP group demonstrating significantly lower values than the 40% AOP and 60% AOP groups ( p < 0.001). Additionally, the 80% AOP group showed a higher lactate clearance rate at T3 (33.92% vs. 18.28%–27.96%, p = 0.022). The main effect for group was large ( η² = 0.637), the main effect for time was large (η² = 0.951), and their interaction effect was moderate ( η² = 0.257). SmO 2 showed no significant group differences at T0, T1, and T4. However, from T2 to T3, SmO 2 recovery in all BFR groups (40%–80% AOP) was significantly slower compared to the non-BFR group (T2: 85.09%–85.73% vs. 97.67%, p < 0.001; T3: 89.22%–91.24% vs. 96.42%, p = 0.003). SmO 2 values converged among groups at T4 (96.88%–97.69%, p = 0.910). The main effect of group was small ( η 2 = 0.232), the main effect of time was large ( η 2 = 0.936), and their interaction was small ( η 2 = 0.124). Punching speed and force trends were consistent across groups. From T1 to T3, punching speed and force in BFR groups significantly decreased compared to the non-BFR group ( p < 0.001), with the 80% AOP group performing worse than the 40% AOP and 60% AOP groups. At T4, although all groups returned close to baseline levels with no significant inter-group differences, punching performance in the 80% AOP group remained slightly below baseline (within-group difference, speed: p = 0.008, force: p = 0.012). The main effect of group was moderate for speed ( η 2 = 0.575) and large for force ( η 2 = 0.680), time showed moderate-to-large effects (speed: η 2 = 0.681, force: η 2 = 0.696), and interaction effects were small. Discussion This study aimed to examine the effects of different BFR pressures combined with upper-limb RST on acute physiological recovery and delayed effects in boxers, and to identify an optimal BFR intensity to enhance training outcomes. Through multi-timepoint monitoring of 15 boxers under four conditions (non-BFR, 40% AOP, 60% AOP, and 80% AOP), significant associations emerged between BFR pressure, physiological indicators, and performance recovery. Higher pressures (particularly 80% AOP) notably increased HR responses and delayed SmO 2 recovery during acute recovery (T1–T3), although they also promoted greater BLA clearance. Meanwhile, punching speed and force acutely decreased with increasing pressure intensity. Athletic performance recovery in the 80% AOP group remained delayed at 24 hours. These findings provide empirical evidence on the physiological effects of boxing-specific BFR-RST. Physiological Indicators Only partial differences in HR responses were observed across the four testing rounds. Apart from differences between the 80% AOP and non-BFR conditions during T1–T3, HR was similar at other time points regardless of BFR application. Enhanced exercise pressor reflex (EPR) induced by the 80% AOP condition might explain this observation. Studies indicated that mechanical restriction of blood flow to exercising muscles during BFR activates the EPR ( 31 ) . Increased sympathetic nerve activity from the EPR elevates mean arterial pressure (MAP), primarily due to increased cardiac output (CO) rather than peripheral vascular resistance. The elevated CO was likely driven predominantly by pronounced tachycardia (increased HR), a common cardiovascular response to the combined stress of high-intensity exercise and external pressure ( 31 ) . Additionally, higher HR and impaired performance at 80% AOP suggest greater overall physiological stress. Although BLA was lower, this might reflect a different form of fatigue (e.g., accelerated peripheral fatigue due to metabolite accumulation not fully represented by BLA, or heightened discomfort from cuff pressure itself), thus limiting total work output and lactate production. Previous studies reported that repeated exposure to progressively overloaded BFR-RST increases the internal-to-external workload ratio at a given exercise load ( 24 ) . The lack of differences at T4 supports this hypothesis, suggesting that high BFR pressures induce greater subjective load, temporarily affecting exercise intensity and performance, as confirmed by subsequent analyses. BLA commonly serves to monitor training intensity and metabolic function, given its sensitivity to lactate production and clearance ( 12 ) . Results indicated that BLA was elevated at T2 in all conditions, including the non-BFR group, during acute recovery, irrespective of BFR application, followed by a decrease at T3 and returning to approximately 97% of baseline at T4. This trend likely reflects delayed lactate clearance driven by diffusion from muscle lactate. Elevated muscle lactate during intense exercise diffuses into blood circulation, influenced by muscle cell membrane lactate transport ( 32 ) . Equilibrium timing depends on exercise intensity and duration ( 32 ) ; higher intensities yield higher BLA peaks 5–12 min post-exercise ( 8 ) . Notably, BFR groups demonstrated significantly lower BLA levels and higher lactate clearance rates from T1–T3 compared to the non-BFR group. The lower BLA concentrations in BFR groups, despite participants perceiving maximal effort (RPE = 10), likely occurred because external pressure mechanically limited absolute work output (as evidenced by acutely reduced punching speed and force), thereby reducing glycolytic flux and lactate production compared to the non-BFR condition. Consistent with these findings, Valenzuela et al. also reported lower BLA levels in badminton players after specific BFR-RST at 40% AOP ( 34 ) . Additionally, this study found significantly lower lactate levels during acute recovery (T2–T3) in the 80% AOP condition compared to 40% and 60% AOP groups. Extreme BFR pressures may impede oxygen delivery and restrict phosphocreatine (PCr) resynthesis, potentially causing premature muscle fatigue and limiting work output, thereby paradoxically reducing glycolysis and lactate production despite the hypoxic stimulus. Reduced lactate levels, however, do not imply reduced fatigue but reflect disrupted energy metabolism, confirmed by decreased punching performance. Given ongoing debates surrounding local metabolic responses to BFR, future research should examine muscle lactate concentrations and metabolic acidosis markers (e.g., blood hydrogen ions, bicarbonate ions, and base excess) to clarify metabolic regulatory mechanisms underlying BFR-RST. SmO 2 represents the ratio of oxygenated hemoglobin to total hemoglobin (oxygenated and deoxygenated) in local skeletal muscle, reflecting dynamic muscle oxygenation and deoxygenation changes. Typically, increased BFR pressure reduces SmO 2 due to its close correlation with blood perfusion ( 10 ) . However, this study observed no significant SmO 2 changes at T1, despite increased BFR pressure. Even at 80% AOP, SmO 2 did not significantly differ from the non-BFR condition. During acute recovery (T2–T3), SmO 2 changes under BFR conditions were significantly greater than the non-BFR condition, with noticeable effects starting at 40% AOP. However, this difference disappeared at T4 (24 hours later). Cockfield et al. ( 4 ) reported similar findings, indicating no significant differences in deoxygenated hemoglobin concentrations between upper-limb cycling groups with varying pressures. Nonetheless, during intervals, the 70% AOP group exhibited higher deoxygenated hemoglobin levels than the 50% AOP group. They speculated that BFR restricts venous outflow, reducing tissue oxygen saturation and increasing deoxygenated hemoglobin concentrations. In contrast, Valenzuela et al. observed no significant SmO 2 differences between BFR and control groups during badminton-specific RST ( 34 ) . This discrepancy could result from maximal RST intensity masking BFR-induced hypoxia or biomechanical differences affecting SmO 2 kinetics. Additionally, some lower-limb BFR-RST studies reported no significant SmO 2 differences during exercise but noted greater changes during recovery compared to controls ( 14 ) . The absence of SmO 2 differences at T1, despite high BFR pressures, may indicate that intense muscle contractions partially mitigate the BFR during exercise. However, after exercise cessation, persistent vascular occlusion under BFR conditions likely impaired post-exercise hemodynamics, resulting in slower SmO 2 recovery compared to the unrestricted flow condition (non-BFR). Additionally, we speculate intense muscle contractions during training activate a “muscle pump” effect ( 26 ) , increasing intramuscular blood flow and aiding venous return, thus mitigating BFR-induced blood flow limitations. Reduced blood flow lowers tissue oxygenation and causes metabolite accumulation, explaining greater SmO 2 recovery in the non-BFR group than in BFR groups during acute recovery. Under higher pressure (80% AOP), SmO 2 recovery is further impeded. Punching Performance Only rear-hand straight punches were assessed for punching speed and force. Punching speed and force significantly decreased at T1 under BFR conditions compared to non-BFR conditions, decreasing further as pressure increased. These trends persisted throughout acute recovery (T2–T3). Punching speed and force in the 80% AOP condition were significantly lower than the 40% and 60% AOP conditions at T1 and T2. Although no significant inter-group differences existed at T4, within-group differences from baseline persisted in the 80% AOP condition (Force: 45.34 ± 2.04 N∙kg − 1 vs. 44.26 ± 1.63 N∙kg − 1 , p < 0.001; Speed: 9.81 ± 0.69 m/s vs. 9.56 ± 0.60 m/s, p < 0.001), indicating greater and prolonged muscle fatigue at higher BFR pressures. Although the absolute reduction in punching force at 24 hours for the 80% AOP group was relatively small (~ 1 N·kg − 1 ), it represented a consistent and statistically significant within-group decline from baseline. For elite athletes, even minor performance decrements could be meaningful competitively. Likely explanations include impaired oxygen and nutrient delivery, metabolite accumulation, limited PCr recovery, and accelerated peripheral fatigue. Although perceived fatigue and muscle soreness were not directly assessed, decreased punching force and speed at higher BFR pressures imply increased fatigue levels ( 3 ) . Considering reduced BLA concentrations under BFR conditions, we speculate higher subjective loads induced by BFR ( 24 ) , ultimately impairing subsequent punching performance. Consistent with our findings, previous studies on lower-limb BFR-RST have also reported fewer sprint repetitions, lower mean power, and reduced total work under 45% AOP BFR-RST compared to controls ( 11 ) . Similar findings emerged from an acute intervention study using upper-limb 45% AOP combined with RST ( 37 ) . Various hypoxia forms reduce muscle high-intensity work capacity through distinct mechanisms. One study comparing upper-limb 45% AOP and systemic hypoxia training found reduced sprint repetitions and mean power output in both, but BFR had greater peripheral impacts, particularly impaired muscle excitation-contraction coupling ( 27 ) . Although Peyrard et al.’s study differed slightly in design, they reported a 23% reduction in sprint repetitions after upper-limb BFR-RST (BFR: 10 repetitions; Control: 13 repetitions) ( 27 ) . Similar effects appeared in lower-limb RST, where BFR significantly reduced total repetitions and work ( 26 , 36 ) . Additionally, lower-limb cycling studies found greater declines in power output with increasing BFR intensity (75% > 60% > 45% > 30% > control), alongside increased muscle soreness post-training ( 19 ) . Physiological responses during BFR training, including increased vascular shear stress, reduced SmO 2 , and metabolite accumulation ( 3 , 27 , 38 ) , could induce beneficial long-term adaptations, enhancing metabolic function and repeated sprint performance. However, short-term outcomes may vary individually and depend on the sport or training protocol. In conclusion, single-session upper-limb BFR-RST at 40%, 60%, or 80% AOP reduces punching performance during acute recovery. The 80% AOP condition also delays performance recovery up to 24 hours post-exercise. Limitations Several limitations of this study are acknowledged. First, the study focused exclusively on male collegiate boxers, limiting generalizability to female boxers and other populations. Second, acute physiological responses do not necessarily reflect potential long-term adaptations; therefore, results regarding long-term effects and performance improvements may differ. Third, only one punching technique (rear-hand straight punch) was examined. Boxing involves various striking techniques, which might respond differently to BFR training. Lastly, measurement variables were limited. During high-pressure (AOP) training, some participants reported upper-limb discomfort such as pain and numbness. However, the lack of subjective measures (e.g., perceived exertion [RPE], delayed-onset muscle soreness [DOMS]) prevented correlating physiological responses with subjective sensations. Additionally, cardiovascular parameters (e.g., blood pressure, HR variability) were not assessed, precluding comprehensive evaluation of cardiovascular risk associated with BFR. Future research should include mixed-gender cohorts, longer intervention periods, multiple punching techniques, and multidimensional assessments to enhance evaluation comprehensiveness. Practical Applications Based on the study findings, practical applications for integrating upper-limb blood flow restriction repeated sprint training (BFR-RST) into boxing regimens are as follows. Coaches and athletes should apply BFR pressure set at 40–60% of the individually measured arterial occlusion pressure (AOP) during upper-limb RST sessions. This pressure range effectively enhances metabolic stress (as indicated by improved lactate clearance) while minimizing acute negative impacts on punching speed, force, and physiological recovery compared to higher pressures. Critically, pressure at 80% AOP should be avoided, as it causes excessive cardiovascular strain, significantly impairs acute punching performance, and delays recovery beyond 24 hours post-exercise. Furthermore, all BFR-RST must be discontinued at least 48 hours prior to competition to ensure full recovery of punching capabilities for peak performance. When programming BFR-RST, anticipate acute reductions in punch performance immediately after training; therefore, avoid scheduling these sessions before technical or high-intensity sessions requiring maximal power output. Strategically implement this method during training phases focused on metabolic adaptation. Conclusions During the acute recovery phase, HR responses and BLA clearance rates in the BFR groups (particularly at 80% AOP) were significantly higher than in the non-BFR group. However, BLA levels, HR and SmO 2 recovery rates (% of baseline), punching speed, and punching force decreased with increasing BFR pressure. At 24 hours post-training, all parameters recovered to baseline except punching speed and force at 80% AOP. It is recommended to select 40%–60% AOP for upper-limb BFR-RST in daily training to balance metabolic benefits and performance outcomes, although coaches should individually assess tolerance and recovery. Additionally, BFR training should be avoided within 24 hours before competition. Future studies should investigate the long-term physiological effects of BFR-RST across diverse populations, including elite athletes, to further clarify physiological adaptations and enhance scientific training practices. Declarations The authors would like to thank the boxers who volunteered their time and effort to participate in this study. Ethics approval and consent to participate This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee (Institutional Review Board) of Shenyang Sport University (Approval No. Ethics [2024] No. 12). Prior to participation, all subjects were fully informed of the purpose, procedures, potential risks, and benefits of the study. Written informed consent was obtained from all individual participants included in the study. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Declaration of interests The authors declare no competing interests. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Authors' contributions Q.X. and A.S. conceived and designed the study. Q.X., S.L., and R.M. performed the experiments and data collection. Q.X. and S.L. conducted the statistical analysis. Q.X. wrote the original draft of the manuscript. S.L., R.M., and A.S. critically reviewed and edited the manuscript. A.S. provided supervision and project administration. 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Supplementary Files Supplementarymaterial1.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 03 Mar, 2026 Reviewers agreed at journal 26 Feb, 2026 Reviewers invited by journal 09 Jan, 2026 Editor assigned by journal 09 Jan, 2026 Editor invited by journal 07 Jan, 2026 Submission checks completed at journal 06 Jan, 2026 First submitted to journal 06 Jan, 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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2","display":"","copyAsset":false,"role":"figure","size":231838,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of changes in HR, BLA, and SmO\u003csub\u003e2\u003c/sub\u003e under different treatment conditions\u003c/p\u003e\n\u003cp\u003eNote: “a” indicates significant within-group difference compared to T0 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “b” compared to T1 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “c” compared to T2 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “d” compared to T3 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05). “*” denotes significant difference compared to NO-BFR group (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “#” indicates significant difference compared to 40% AOP (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “∆” denotes significant difference compared to 60% AOP (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8489574/v1/50c823253aafdd8c5e4fb1a3.png"},{"id":100368857,"identity":"57f24a7c-26b3-409d-80d0-d2d5377f5083","added_by":"auto","created_at":"2026-01-16 07:58:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":181835,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of changes in Punching speed and force under different treatment conditions\u003c/p\u003e\n\u003cp\u003eNote: “a” indicates significant within-group difference compared to T0 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “b” compared to T1 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “c” compared to T2 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “d” compared to T3 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05). “*” denotes significant difference compared to NO-BFR group (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “#” indicates significant difference compared to 40% AOP (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05); “∆” denotes significant difference compared to 60% AOP (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8489574/v1/88d4d113ebdbe91b37acc53c.png"},{"id":100406047,"identity":"6bf1ef33-9942-45f9-8f15-ea0497f955d4","added_by":"auto","created_at":"2026-01-16 12:36:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1216891,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8489574/v1/b299d053-273f-48a7-aeba-ca325f4e23d9.pdf"},{"id":100164991,"identity":"2efc8152-6f33-4aa3-ba91-a6ce411b3d7a","added_by":"auto","created_at":"2026-01-13 15:27:31","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":19952,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial1.docx","url":"https://assets-eu.researchsquare.com/files/rs-8489574/v1/cff35532375b8e94a3943c02.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Effect of Blood Flow Restriction Pressure on Acute and 24-Hour Recovery Following Upper-Limb Repeated High-Intensity Exercise in Boxers ","fulltext":[{"header":"Introduction","content":"\u003cp\u003eBlood flow restriction (BFR) training involves the application of external pressure to the proximal limbs to partially restrict arterial inflow and occlude venous outflow, and has emerged as a potent training methodology. When combined with low-load resistance exercise, BFR induces muscular hypertrophy and strength gains comparable to high-load training \u003csup\u003e(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e)\u003c/sup\u003e. More recently, the application of BFR has expanded to high-intensity exercise modalities \u003csup\u003e(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e)\u003c/sup\u003e. Studies integrating BFR with sprint or repeated high-intensity efforts have reported enhanced metabolic stress \u003csup\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e)\u003c/sup\u003e, improved vascular function \u003csup\u003e(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e)\u003c/sup\u003e, and potential benefits for aerobic and anaerobic capacities in athletes \u003csup\u003e(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e)\u003c/sup\u003e, highlighting its acute physiological effectiveness.\u003c/p\u003e \u003cp\u003eBoxing is an intermittent sport requiring both aerobic and anaerobic capacities. Athletes typically perform repeated short-duration, high-intensity actions (\u0026le;\u0026thinsp;10 seconds), such as punching, footwork, and defensive maneuvers. These actions involve almost all muscle groups, and the brief rest periods (\u0026le;\u0026thinsp;30 seconds) between efforts are insufficient for complete recovery. Thus, improving the upper limbs\u0026rsquo; capacity to repeatedly perform high-intensity actions is essential for continuous, powerful strikes during training and competitions. Consequently, combining upper-limb BFR with repeated high-intensity effort training (hereafter referred to as BFR-RST) may offer beneficial training outcomes \u003csup\u003e(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e)\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAlthough research indicates that BFR-RST could be a promising training method, considerable controversy remains. The physiological responses to BFR-RST are complex and occasionally paradoxical. Some studies report that BFR during high-intensity exercise modifies muscle oxygenation kinetics, for instance, by increasing deoxygenated hemoglobin and slowing reoxygenation rates \u003csup\u003e(\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e)\u003c/sup\u003e, which may ultimately facilitate beneficial physiological adaptations \u003csup\u003e(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e. In contrast, other studies have reported conflicting results \u003csup\u003e(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e)\u003c/sup\u003e, indicating that the interplay between exercise intensity and BFR pressure makes outcomes difficult to predict. Additionally, other studies reported suboptimal performance outcomes \u003csup\u003e(\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e)\u003c/sup\u003e. A recent narrative review indicated that BFR-RST could benefit sports requiring high glycolytic demands by enhancing repeated sprint ability (RSA) within a short period \u003csup\u003e(\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e)\u003c/sup\u003e. Nevertheless, previous studies mostly employed tests involving specific sprint movements. Differences in training movement patterns may influence muscle recruitment and energy consumption \u003csup\u003e(\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e)\u003c/sup\u003e. It is widely recognized that training modes closely matching sport-specific actions facilitate the transfer of training effects to competition scenarios. Therefore, appropriate RST modalities should be selected according to specialized sport movements.\u003c/p\u003e \u003cp\u003eMoreover, selecting an appropriate BFR pressure is crucial for achieving optimal training outcomes. Significant discrepancies exist among studies regarding pressure application, participant selection, training frequency, and intensity, complicating comparisons and applications of research findings. If the BFR pressure is too low, muscle and cardiovascular stimuli may be insufficient for inducing desired physiological adaptations. Conversely, excessive pressure may negatively affect sprint performance, exacerbate fatigue, and decrease training intensity. These consequences not only counteract potential BFR benefits but may also impair single-session effectiveness and pose physical risks to athletes \u003csup\u003e(\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e)\u003c/sup\u003e. Current research suggests that training with BFR pressures ranging from 40% to 80% limb occlusion pressure is safe and effective, with the specific pressure selected based on training mode, cuff width, training load, and participant fitness level \u003csup\u003e(\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e)\u003c/sup\u003e. However, combining BFR with high-intensity training further complicates the scenario. Such combined training, characterized by maximal efforts dependent on anaerobic energy systems, may elicit metabolic, neuromuscular, and perceptual responses distinct from those observed with submaximal exercise \u003csup\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/sup\u003e. Additionally, RST studies indicate potentially greater adaptive benefits for the upper limbs \u003csup\u003e(\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e)\u003c/sup\u003e. Thus, understanding the physiological effects of specialized upper-limb RST combined with BFR is essential for developing targeted training programs and optimizing athletic performance.\u003c/p\u003e \u003cp\u003eIn summary, this study aimed to investigate the acute recovery characteristics and delayed effects of combining different BFR pressures with specialized upper-limb RST. Dynamic recovery monitoring was conducted at multiple time points. Identifying the optimal BFR pressure could enable more precise upper-limb BFR-RST, providing evidence for safe and efficient medium- to long-term training interventions.\u003c/p\u003e"},{"header":"Method","content":"\u003cp\u003eExperimental Approach to the Problem\u003c/p\u003e \u003cp\u003eA randomized crossover design within subjects was adopted for this study. Over a four-week period, participants underwent upper-limb RST under four BFR pressure conditions (non-BFR, 40% AOP, 60% AOP, and 80% AOP). Each condition was separated by a washout period of at least 72 hours to minimize carryover effects \u003csup\u003e(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e)\u003c/sup\u003e. For all participants, testing sessions were consistently conducted on Monday and Tuesday of each week, resulting in a 5-day interval between sessions for each participant. Pressure conditions were randomly assigned for each participant using a computer-generated randomization method (Microsoft Excel RAND function) to determine the order of the four conditions. Each experimental round occurred at consistent times (baseline testing at 8:00 AM, training intervention at 2:00 PM) and under identical environmental conditions to ensure experimental consistency.\u003c/p\u003e \u003cp\u003eThe detailed experimental procedure was as follows (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e): Baseline data (T0) were collected at 8:00 AM on each testing day. At 2:00 PM on the same day, participants performed specialized BFR-RST at a boxing training venue. Participants initially performed a standardized 15-minute warm-up consisting of 5 minutes of jogging, 5 minutes of dynamic stretching (e.g., arm circles, torso twists, leg swings), and 5 minutes of sport-specific movements (e.g., shadow boxing, light punching combinations). This was followed by brief static stretching of the upper limbs, after which the randomly assigned BFR pressure condition was applied. They then performed three sets of repeated maximal-effort punches (hitting a sandbag), each set consisting of 14 repetitions of 3 seconds, with 10 seconds of passive recovery between repetitions and 1-minute intervals between sets. Training intensity was monitored using a modified Borg CR-10 scale (RPE 0\u0026ndash;10) \u003csup\u003e(\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e)\u003c/sup\u003e. Prior to the study, all participants attended a familiarization session during which the scale was thoroughly explained, with '0' representing no effort and '10' representing maximal effort. Participants were instructed to report their overall perception of exertion immediately following each set. This protocol was adapted from Kamandulis et al. \u003csup\u003e(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e)\u003c/sup\u003e and aligns with boxing-specific demands. Similar protocols have been employed in previous studies \u003csup\u003e(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e)\u003c/sup\u003e. Data collection occurred immediately post-training (T1), after 5 minutes of recovery (standing or slow walking, T2), 20 minutes (T3), and 24 hours (T4) after training completion. Measurements included HR, BLA, SmO\u003csub\u003e2\u003c/sub\u003e, and punching performance. The chosen recovery modality (standing or slow walking at T2) was selected to replicate typical low-intensity activities (e.g., standing in a corner, light footwork) experienced during brief rest intervals in boxing matches. Although differences between standing and slow walking might introduce variability in recovery measures, participants were explicitly instructed to maintain consistent activity (either standing or very slow pacing) across all testing sessions to minimize intra-participant variability. Following the training session and subsequent assessments (T1\u0026ndash;T3), participants were instructed to abstain from any structured exercise, upper-body resistance training, or high-impact activities until after the final measurement at T4 (24 hours). They were advised to maintain normal dietary and hydration practices but to avoid caffeine and alcohol consumption. Compliance was verbally confirmed at T4.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eParticipants\u003c/p\u003e \u003cp\u003eUsing G*Power 3.1.9 software, sample size estimation indicated that at a significance level of α\u0026thinsp;=\u0026thinsp;0.05 and a medium effect size (η\u0026sup2; = 0.25), a minimum of 12 participants was required to achieve 95% statistical power \u003csup\u003e(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u003c/sup\u003e. Ultimately, 15 male collegiate boxers (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD; age: 20.81\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0 years, height: 175.5\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6 cm, weight: 67.4\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9 kg) voluntarily participated after recruitment and screening. Participants had competed in at least 10 official amateur or university-level boxing matches and received boxing training since high school or earlier. According to the participant classification framework by Kay et al., participants were categorized as Tier 2 \u003csup\u003e(\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e)\u003c/sup\u003e. Before testing, all participants received full information about experimental procedures and potential risks and provided written informed consent. Ethical approval was granted by the Ethics Committee of Shenyang Sport University (Ethics [2024] No. 12). Prior to inclusion, all participants completed a health screening questionnaire (see Additional File 1) designed to exclude individuals with contraindications to BFR training, such as a history of deep vein thrombosis, cardiovascular or cerebrovascular diseases, peripheral vascular disease, or hypertension (defined as systolic blood pressure\u0026thinsp;\u0026gt;\u0026thinsp;140 mmHg or diastolic\u0026thinsp;\u0026gt;\u0026thinsp;90 mmHg). No participant reported any of these conditions or other injuries that would limit participation. Participants were instructed to avoid alcohol or substances potentially affecting test outcomes the day before each session, refrain from additional high-intensity physical activities beyond the training sessions during the two testing days, and maintain regular sleep patterns and dietary habits. To maximize compliance, the study was conducted during the participants' off-season. Participants were reminded verbally before each session and via text message to adhere to the activity restrictions.\u003c/p\u003e \u003cp\u003eProcedures\u003c/p\u003e \u003cp\u003eMeasurement of Upper-Limb AOP\u003c/p\u003e \u003cp\u003eParticipants\u0026rsquo; resting AOP was assessed before initial testing (161\u0026thinsp;\u0026plusmn;\u0026thinsp;13 mmHg) using an established protocol \u003csup\u003e(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u003c/sup\u003e. An upper-limb pressure cuff (Theratools, China; length: 68 cm, width: 7.5 cm) was positioned around the upper biceps brachii region for BFR. AOP was measured using Doppler ultrasound (Swedish PF6001, Perimed, Sweden) by detecting radial artery pulsations. The cuff pressure was first inflated to 70 mmHg, then increased incrementally by 5 mmHg until the pulse disappeared. The pressure at pulse disappearance was recorded as the AOP. This procedure was repeated three times with 2-minute rest intervals, and the mean value was recorded as each participant\u0026rsquo;s upper-limb AOP. Subsequently, pressures corresponding to 40%, 60%, and 80% AOP were calculated individually and recorded for each athlete.\u003c/p\u003e \u003cp\u003eBefore the experimental sessions, participants were familiarized with the sensation of BFR at a low pressure (20% AOP). During experimental sessions, the pressure cuff was inflated to the target pressure (0%, 40%, 60%, or 80% AOP) immediately before the first set of punches and deflated immediately after the final set. Thus, BFR was applied continuously throughout the entire exercise protocol, including inter-set rest periods.\u003c/p\u003e \u003cp\u003eHR Monitoring\u003c/p\u003e \u003cp\u003eDuring testing, HR was continuously recorded using a HR monitor (Polar Accurex Plus, Finland). Resting HR was measured after participants had been seated quietly for 10 minutes during baseline (T0) data collection in the morning. HR values at each specified time point (T1, T2, T3, and T4) were extracted for analysis. To quantify recovery at each time point, HR was expressed as a percentage of the baseline resting value using the following formula: \u003csup\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/sup\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\:\\:\\:\\:\\:\\:HR\\:recovery\\:rate\\:\\left(expressed\\:as\\:\\%\\:of\\:baseline\\right)\\:=\\frac{HR\\:immediately\\:after\\:exercise-HR\\:at\\:N\\:minutes\\:after\\:exercise}{HR\\:immediately\\:after\\:exercise-Resting\\:HR}\\times\\:100％$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eSmO\u003csub\u003e2\u003c/sub\u003e Testing\u003c/p\u003e \u003cp\u003eChanges in SmO\u003csub\u003e2\u003c/sub\u003e in the anterior deltoid muscle of the upper limb were monitored using a wireless muscle oxygenation device (Moxy, Fortiori Design LLC, USA). The anterior deltoid was selected because it contributes the highest proportion of mechanical work during rear-hand straight punches in both male and female boxers \u003csup\u003e(\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e)\u003c/sup\u003e. Near-infrared spectroscopy (NIRS) technology provides a non-invasive measurement of tissue hemodynamics. NIRS detects changes in absorbance between oxygenated and deoxygenated states of hemoglobin and myoglobin at specific wavelengths. SmO\u003csub\u003e2\u003c/sub\u003e typically indicates the percentage of oxygenated hemoglobin/myoglobin relative to total hemoglobin, ranging from 0% to 100%. To quantify recovery at each time point, SmO\u003csub\u003e2\u003c/sub\u003e was expressed as a percentage of the baseline resting value using the following formula \u003csup\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/sup\u003e:\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:SMO2\\:recovery\\:rate\\left(expressed\\:as\\:\\%\\:of\\:baseline\\right)=\\frac{SMO2\\:at\\:N\\:min\\:after\\:exercise\\:}{Resting\\:SMO2}\\times\\:100％$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eBLA Testing\u003c/p\u003e \u003cp\u003eEar blood samples (10 \u0026micro;L per sample) were collected at multiple stages (pre-training, immediately post-training, 5 min post-training, 20 min post-training, and 24 h post-training). BLA levels were measured using a lactate analyzer (EKF Biosen-S Line, Germany), and specific values were recorded. The sampling procedure was as follows: participants\u0026rsquo; earlobes were sterilized with alcohol using cotton swabs; gentle thumb pressure was applied to obtain blood at the sampling site; samples were collected with capillary tubes and transferred to centrifuge tubes containing a lactate inhibitor. Tubes were then sealed, gently shaken, and labeled. To quantify recovery at each time point, BLA was expressed as a percentage of the baseline resting value using the following formula:\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:BLA\\:recovery\\:rate\\left(expressed\\:as\\:\\%\\:of\\:baseline\\right)=\\frac{Peak\\:post\\:-exercise\\:BLA\\left(T2\\right)-BLA\\:at\\:N\\:min\\:post\\:-exercise}{Peak\\:post-exercise\\:BLA\\left(T2\\right)}\\times\\:100％$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ePunching Performance Testing\u003c/p\u003e \u003cp\u003ePunching indicators, including punching speed and force, were measured using Strike Tec boxing sensors (Strike Tec, Dallas, USA; version 1.4.4). Data derived from acceleration measurements were extracted via an accompanying mobile application \u003csup\u003e(\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e)\u003c/sup\u003e. Punching force calculated from acceleration (typical measurement error: 0.57) \u003csup\u003e(\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e)\u003c/sup\u003e and punching speed (ICC: 0.853; 95% CI: 0.650\u0026ndash;0.942) \u003csup\u003e(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)\u003c/sup\u003e have demonstrated high reliability. Punching force was expressed in relative values to eliminate body-weight effects. Sensors were securely attached to athletes\u0026rsquo; wrists. Athletes were instructed to adopt an orthodox stance and perform three maximal-effort rear-hand straight punches \u003csup\u003e(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e)\u003c/sup\u003e. This punch type was selected due to its frequent use in competition \u003csup\u003e(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e)\u003c/sup\u003e and simplicity, facilitating consistent assessment. Professional researchers trained participants in proper punching technique before testing to ensure reliable data collection.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using SPSS version 26.0 software (IBM Corp., Armonk, NY, USA). All data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD). A two-way repeated-measures analysis of variance (ANOVA) was conducted to evaluate the overall effects of independent variables (pressure \u0026times; time) on each dependent variable. Mauchly\u0026rsquo;s test of sphericity was applied, and the Greenhouse-Geisser correction was used when the sphericity assumption was violated. When significant interaction effects were identified, simple effects analysis with Bonferroni adjustments was conducted for post-hoc comparisons. Effect sizes (partial eta squared, \u003cem\u003eη\u0026sup2;\u003c/em\u003e) were categorized as trivial (\u0026lt;\u0026thinsp;0.04), small (0.04\u0026ndash;0.25), moderate (0.25\u0026ndash;0.64), and large (\u0026ge;\u0026thinsp;0.64). Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. In all figures and text, data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eAll fifteen participants completed all four experimental conditions and all measurement timepoints. Therefore, the analysis was conducted on a complete dataset with no missing values. Although not systematically quantified, several participants informally reported transient sensations of numbness and discomfort in the arm during the training sessions under the BFR conditions, particularly at 80% AOP. These sensations resolved promptly upon cuff deflation. No other adverse events were reported. Two-way repeated-measures ANOVA indicated significant main effects for pressure conditions (non-BFR, AOP 40%, AOP 60%, AOP 80%), time points (T0\u0026ndash;T4), and their interaction on HR, BLA, SmO\u003csub\u003e2\u003c/sub\u003e, punching speed, and punching force (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The effect sizes and key statistical characteristics are detailed below (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of recovery rate (% of baseline) in HR, BLA, and SmO2 under different treatment conditions\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTreatment\u003c/p\u003e \u003cp\u003eConditions\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eHR recovery rate (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eBLA recovery rate (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c9\" namest=\"c7\"\u003e \u003cp\u003eSmO\u003csub\u003e2\u003c/sub\u003e recovery rate (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24h\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e24h\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20min\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e24h\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNO-BFR\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e52.28\u0026thinsp;\u0026plusmn;\u0026thinsp;8.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60.65\u0026thinsp;\u0026plusmn;\u0026thinsp;5.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e99.69\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18.28\u0026thinsp;\u0026plusmn;\u0026thinsp;11.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e80.74\u0026thinsp;\u0026plusmn;\u0026thinsp;3.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e97.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e96.42\u0026thinsp;\u0026plusmn;\u0026thinsp;4.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e97.62\u0026thinsp;\u0026plusmn;\u0026thinsp;2.81\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAOP45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e49.76\u0026thinsp;\u0026plusmn;\u0026thinsp;6.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e61.46\u0026thinsp;\u0026plusmn;\u0026thinsp;4.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e99.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28.54\u0026thinsp;\u0026plusmn;\u0026thinsp;15.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e84.25\u0026thinsp;\u0026plusmn;\u0026thinsp;4.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e85.73\u0026thinsp;\u0026plusmn;\u0026thinsp;9.17\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e91.24\u0026thinsp;\u0026plusmn;\u0026thinsp;4.71\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e96.88\u0026thinsp;\u0026plusmn;\u0026thinsp;3.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAOP60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48.54\u0026thinsp;\u0026plusmn;\u0026thinsp;6.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60.92\u0026thinsp;\u0026plusmn;\u0026thinsp;5.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e99.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e27.96\u0026thinsp;\u0026plusmn;\u0026thinsp;15.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e83.72\u0026thinsp;\u0026plusmn;\u0026thinsp;8.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e85.86\u0026thinsp;\u0026plusmn;\u0026thinsp;8.49\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e90.64\u0026thinsp;\u0026plusmn;\u0026thinsp;6.30\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e97.69\u0026thinsp;\u0026plusmn;\u0026thinsp;2.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAOP80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42.79\u0026thinsp;\u0026plusmn;\u0026thinsp;8.29\u003csup\u003e*#∆\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55.77\u0026thinsp;\u0026plusmn;\u0026thinsp;6.19\u003csup\u003e*#∆\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e99.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e33.92\u0026thinsp;\u0026plusmn;\u0026thinsp;11.59\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e84.93\u0026thinsp;\u0026plusmn;\u0026thinsp;7.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e85.09\u0026thinsp;\u0026plusmn;\u0026thinsp;9.60\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e89.22\u0026thinsp;\u0026plusmn;\u0026thinsp;5.75\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e97.44\u0026thinsp;\u0026plusmn;\u0026thinsp;4.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ef\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.415\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.238\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.474\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.286\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e8.666\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.116\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.179\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.870\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.288\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.910\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003eNote: \u0026ldquo;*\u0026rdquo; denotes significant difference compared to NO-BFR group (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05); \u0026ldquo;#\u0026rdquo; indicates significant difference compared to 40% AOP (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05); \u0026ldquo;∆\u0026rdquo; denotes significant difference compared to 60% AOP (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eNo significant HR differences were observed among the non-BFR, 40% AOP, and 60% AOP groups across all time points. However, the 80% AOP condition elicited a significantly higher HR at T1, T2, and T3 (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) compared to the other conditions, with lower HR recovery rates (% of baseline) at T2 (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.009) and T3(\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.023). All groups returned to baseline HR at T4. Regarding statistical effects, time had a large main effect (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.990), group had a moderate main effect (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.448), and interaction exhibited a small effect (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.181).\u003c/p\u003e \u003cp\u003eAll BFR groups exhibited significantly lower BLA levels from T1 to T4 compared to the non-BFR group (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with the 80% AOP group demonstrating significantly lower values than the 40% AOP and 60% AOP groups (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Additionally, the 80% AOP group showed a higher lactate clearance rate at T3 (33.92% vs. 18.28%\u0026ndash;27.96%, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.022). The main effect for group was large (\u003cem\u003eη\u0026sup2;\u003c/em\u003e = 0.637), the main effect for time was large (η\u0026sup2; = 0.951), and their interaction effect was moderate (\u003cem\u003eη\u0026sup2;\u003c/em\u003e = 0.257).\u003c/p\u003e \u003cp\u003eSmO\u003csub\u003e2\u003c/sub\u003e showed no significant group differences at T0, T1, and T4. However, from T2 to T3, SmO\u003csub\u003e2\u003c/sub\u003e recovery in all BFR groups (40%\u0026ndash;80% AOP) was significantly slower compared to the non-BFR group (T2: 85.09%\u0026ndash;85.73% vs. 97.67%, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; T3: 89.22%\u0026ndash;91.24% vs. 96.42%, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.003). SmO\u003csub\u003e2\u003c/sub\u003e values converged among groups at T4 (96.88%\u0026ndash;97.69%, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.910). The main effect of group was small (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.232), the main effect of time was large (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.936), and their interaction was small (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.124).\u003c/p\u003e \u003cp\u003ePunching speed and force trends were consistent across groups. From T1 to T3, punching speed and force in BFR groups significantly decreased compared to the non-BFR group (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with the 80% AOP group performing worse than the 40% AOP and 60% AOP groups. At T4, although all groups returned close to baseline levels with no significant inter-group differences, punching performance in the 80% AOP group remained slightly below baseline (within-group difference, speed: \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.008, force: \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.012). The main effect of group was moderate for speed (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.575) and large for force (\u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.680), time showed moderate-to-large effects (speed: \u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.681, force: \u003cem\u003eη\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.696), and interaction effects were small.\u003c/p\u003e "},{"header":"Discussion","content":"\u003cp\u003eThis study aimed to examine the effects of different BFR pressures combined with upper-limb RST on acute physiological recovery and delayed effects in boxers, and to identify an optimal BFR intensity to enhance training outcomes. Through multi-timepoint monitoring of 15 boxers under four conditions (non-BFR, 40% AOP, 60% AOP, and 80% AOP), significant associations emerged between BFR pressure, physiological indicators, and performance recovery. Higher pressures (particularly 80% AOP) notably increased HR responses and delayed SmO\u003csub\u003e2\u003c/sub\u003e recovery during acute recovery (T1\u0026ndash;T3), although they also promoted greater BLA clearance. Meanwhile, punching speed and force acutely decreased with increasing pressure intensity. Athletic performance recovery in the 80% AOP group remained delayed at 24 hours. These findings provide empirical evidence on the physiological effects of boxing-specific BFR-RST.\u003c/p\u003e\n\u003ch3\u003ePhysiological Indicators\u003c/h3\u003e\n\u003cp\u003eOnly partial differences in HR responses were observed across the four testing rounds. Apart from differences between the 80% AOP and non-BFR conditions during T1\u0026ndash;T3, HR was similar at other time points regardless of BFR application. Enhanced exercise pressor reflex (EPR) induced by the 80% AOP condition might explain this observation. Studies indicated that mechanical restriction of blood flow to exercising muscles during BFR activates the EPR \u003csup\u003e(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e)\u003c/sup\u003e. Increased sympathetic nerve activity from the EPR elevates mean arterial pressure (MAP), primarily due to increased cardiac output (CO) rather than peripheral vascular resistance. The elevated CO was likely driven predominantly by pronounced tachycardia (increased HR), a common cardiovascular response to the combined stress of high-intensity exercise and external pressure \u003csup\u003e(\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e)\u003c/sup\u003e. Additionally, higher HR and impaired performance at 80% AOP suggest greater overall physiological stress. Although BLA was lower, this might reflect a different form of fatigue (e.g., accelerated peripheral fatigue due to metabolite accumulation not fully represented by BLA, or heightened discomfort from cuff pressure itself), thus limiting total work output and lactate production. Previous studies reported that repeated exposure to progressively overloaded BFR-RST increases the internal-to-external workload ratio at a given exercise load \u003csup\u003e(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e. The lack of differences at T4 supports this hypothesis, suggesting that high BFR pressures induce greater subjective load, temporarily affecting exercise intensity and performance, as confirmed by subsequent analyses.\u003c/p\u003e \u003cp\u003eBLA commonly serves to monitor training intensity and metabolic function, given its sensitivity to lactate production and clearance \u003csup\u003e(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/sup\u003e. Results indicated that BLA was elevated at T2 in all conditions, including the non-BFR group, during acute recovery, irrespective of BFR application, followed by a decrease at T3 and returning to approximately 97% of baseline at T4. This trend likely reflects delayed lactate clearance driven by diffusion from muscle lactate. Elevated muscle lactate during intense exercise diffuses into blood circulation, influenced by muscle cell membrane lactate transport \u003csup\u003e(\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e)\u003c/sup\u003e. Equilibrium timing depends on exercise intensity and duration \u003csup\u003e(\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e)\u003c/sup\u003e; higher intensities yield higher BLA peaks 5\u0026ndash;12 min post-exercise \u003csup\u003e(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e)\u003c/sup\u003e. Notably, BFR groups demonstrated significantly lower BLA levels and higher lactate clearance rates from T1\u0026ndash;T3 compared to the non-BFR group. The lower BLA concentrations in BFR groups, despite participants perceiving maximal effort (RPE\u0026thinsp;=\u0026thinsp;10), likely occurred because external pressure mechanically limited absolute work output (as evidenced by acutely reduced punching speed and force), thereby reducing glycolytic flux and lactate production compared to the non-BFR condition. Consistent with these findings, Valenzuela et al. also reported lower BLA levels in badminton players after specific BFR-RST at 40% AOP \u003csup\u003e(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e)\u003c/sup\u003e. Additionally, this study found significantly lower lactate levels during acute recovery (T2\u0026ndash;T3) in the 80% AOP condition compared to 40% and 60% AOP groups. Extreme BFR pressures may impede oxygen delivery and restrict phosphocreatine (PCr) resynthesis, potentially causing premature muscle fatigue and limiting work output, thereby paradoxically reducing glycolysis and lactate production despite the hypoxic stimulus. Reduced lactate levels, however, do not imply reduced fatigue but reflect disrupted energy metabolism, confirmed by decreased punching performance. Given ongoing debates surrounding local metabolic responses to BFR, future research should examine muscle lactate concentrations and metabolic acidosis markers (e.g., blood hydrogen ions, bicarbonate ions, and base excess) to clarify metabolic regulatory mechanisms underlying BFR-RST.\u003c/p\u003e \u003cp\u003eSmO\u003csub\u003e2\u003c/sub\u003e represents the ratio of oxygenated hemoglobin to total hemoglobin (oxygenated and deoxygenated) in local skeletal muscle, reflecting dynamic muscle oxygenation and deoxygenation changes. Typically, increased BFR pressure reduces SmO\u003csub\u003e2\u003c/sub\u003e due to its close correlation with blood perfusion \u003csup\u003e(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e)\u003c/sup\u003e. However, this study observed no significant SmO\u003csub\u003e2\u003c/sub\u003e changes at T1, despite increased BFR pressure. Even at 80% AOP, SmO\u003csub\u003e2\u003c/sub\u003e did not significantly differ from the non-BFR condition. During acute recovery (T2\u0026ndash;T3), SmO\u003csub\u003e2\u003c/sub\u003e changes under BFR conditions were significantly greater than the non-BFR condition, with noticeable effects starting at 40% AOP. However, this difference disappeared at T4 (24 hours later). Cockfield et al. \u003csup\u003e(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e)\u003c/sup\u003e reported similar findings, indicating no significant differences in deoxygenated hemoglobin concentrations between upper-limb cycling groups with varying pressures. Nonetheless, during intervals, the 70% AOP group exhibited higher deoxygenated hemoglobin levels than the 50% AOP group. They speculated that BFR restricts venous outflow, reducing tissue oxygen saturation and increasing deoxygenated hemoglobin concentrations. In contrast, Valenzuela et al. observed no significant SmO\u003csub\u003e2\u003c/sub\u003e differences between BFR and control groups during badminton-specific RST \u003csup\u003e(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e)\u003c/sup\u003e. This discrepancy could result from maximal RST intensity masking BFR-induced hypoxia or biomechanical differences affecting SmO\u003csub\u003e2\u003c/sub\u003e kinetics. Additionally, some lower-limb BFR-RST studies reported no significant SmO\u003csub\u003e2\u003c/sub\u003e differences during exercise but noted greater changes during recovery compared to controls \u003csup\u003e(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e)\u003c/sup\u003e. The absence of SmO\u003csub\u003e2\u003c/sub\u003e differences at T1, despite high BFR pressures, may indicate that intense muscle contractions partially mitigate the BFR during exercise. However, after exercise cessation, persistent vascular occlusion under BFR conditions likely impaired post-exercise hemodynamics, resulting in slower SmO\u003csub\u003e2\u003c/sub\u003e recovery compared to the unrestricted flow condition (non-BFR). Additionally, we speculate intense muscle contractions during training activate a \u0026ldquo;muscle pump\u0026rdquo; effect \u003csup\u003e(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e)\u003c/sup\u003e, increasing intramuscular blood flow and aiding venous return, thus mitigating BFR-induced blood flow limitations. Reduced blood flow lowers tissue oxygenation and causes metabolite accumulation, explaining greater SmO\u003csub\u003e2\u003c/sub\u003e recovery in the non-BFR group than in BFR groups during acute recovery. Under higher pressure (80% AOP), SmO\u003csub\u003e2\u003c/sub\u003e recovery is further impeded.\u003c/p\u003e\n\u003ch3\u003ePunching Performance\u003c/h3\u003e\n\u003cp\u003eOnly rear-hand straight punches were assessed for punching speed and force. Punching speed and force significantly decreased at T1 under BFR conditions compared to non-BFR conditions, decreasing further as pressure increased. These trends persisted throughout acute recovery (T2\u0026ndash;T3). Punching speed and force in the 80% AOP condition were significantly lower than the 40% and 60% AOP conditions at T1 and T2. Although no significant inter-group differences existed at T4, within-group differences from baseline persisted in the 80% AOP condition (Force: 45.34\u0026thinsp;\u0026plusmn;\u0026thinsp;2.04 N∙kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e vs. 44.26\u0026thinsp;\u0026plusmn;\u0026thinsp;1.63 N∙kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Speed: 9.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.69 m/s vs. 9.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.60 m/s, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), indicating greater and prolonged muscle fatigue at higher BFR pressures. Although the absolute reduction in punching force at 24 hours for the 80% AOP group was relatively small (~\u0026thinsp;1 N\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), it represented a consistent and statistically significant within-group decline from baseline. For elite athletes, even minor performance decrements could be meaningful competitively. Likely explanations include impaired oxygen and nutrient delivery, metabolite accumulation, limited PCr recovery, and accelerated peripheral fatigue. Although perceived fatigue and muscle soreness were not directly assessed, decreased punching force and speed at higher BFR pressures imply increased fatigue levels \u003csup\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/sup\u003e. Considering reduced BLA concentrations under BFR conditions, we speculate higher subjective loads induced by BFR \u003csup\u003e(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e, ultimately impairing subsequent punching performance.\u003c/p\u003e \u003cp\u003eConsistent with our findings, previous studies on lower-limb BFR-RST have also reported fewer sprint repetitions, lower mean power, and reduced total work under 45% AOP BFR-RST compared to controls \u003csup\u003e(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e)\u003c/sup\u003e. Similar findings emerged from an acute intervention study using upper-limb 45% AOP combined with RST \u003csup\u003e(\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e)\u003c/sup\u003e. Various hypoxia forms reduce muscle high-intensity work capacity through distinct mechanisms. One study comparing upper-limb 45% AOP and systemic hypoxia training found reduced sprint repetitions and mean power output in both, but BFR had greater peripheral impacts, particularly impaired muscle excitation-contraction coupling \u003csup\u003e(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e)\u003c/sup\u003e. Although Peyrard et al.\u0026rsquo;s study differed slightly in design, they reported a 23% reduction in sprint repetitions after upper-limb BFR-RST (BFR: 10 repetitions; Control: 13 repetitions)\u003csup\u003e(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e)\u003c/sup\u003e. Similar effects appeared in lower-limb RST, where BFR significantly reduced total repetitions and work \u003csup\u003e(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e)\u003c/sup\u003e. Additionally, lower-limb cycling studies found greater declines in power output with increasing BFR intensity (75% \u0026gt; 60% \u0026gt; 45% \u0026gt; 30% \u0026gt; control), alongside increased muscle soreness post-training \u003csup\u003e(\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e)\u003c/sup\u003e. Physiological responses during BFR training, including increased vascular shear stress, reduced SmO\u003csub\u003e2\u003c/sub\u003e, and metabolite accumulation \u003csup\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e)\u003c/sup\u003e, could induce beneficial long-term adaptations, enhancing metabolic function and repeated sprint performance. However, short-term outcomes may vary individually and depend on the sport or training protocol.\u003c/p\u003e \u003cp\u003eIn conclusion, single-session upper-limb BFR-RST at 40%, 60%, or 80% AOP reduces punching performance during acute recovery. The 80% AOP condition also delays performance recovery up to 24 hours post-exercise.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eSeveral limitations of this study are acknowledged. First, the study focused exclusively on male collegiate boxers, limiting generalizability to female boxers and other populations. Second, acute physiological responses do not necessarily reflect potential long-term adaptations; therefore, results regarding long-term effects and performance improvements may differ. Third, only one punching technique (rear-hand straight punch) was examined. Boxing involves various striking techniques, which might respond differently to BFR training. Lastly, measurement variables were limited. During high-pressure (AOP) training, some participants reported upper-limb discomfort such as pain and numbness. However, the lack of subjective measures (e.g., perceived exertion [RPE], delayed-onset muscle soreness [DOMS]) prevented correlating physiological responses with subjective sensations. Additionally, cardiovascular parameters (e.g., blood pressure, HR variability) were not assessed, precluding comprehensive evaluation of cardiovascular risk associated with BFR. Future research should include mixed-gender cohorts, longer intervention periods, multiple punching techniques, and multidimensional assessments to enhance evaluation comprehensiveness.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePractical Applications\u003c/h3\u003e\n\u003cp\u003eBased on the study findings, practical applications for integrating upper-limb blood flow restriction repeated sprint training (BFR-RST) into boxing regimens are as follows. Coaches and athletes should apply BFR pressure set at 40\u0026ndash;60% of the individually measured arterial occlusion pressure (AOP) during upper-limb RST sessions. This pressure range effectively enhances metabolic stress (as indicated by improved lactate clearance) while minimizing acute negative impacts on punching speed, force, and physiological recovery compared to higher pressures. Critically, pressure at 80% AOP should be avoided, as it causes excessive cardiovascular strain, significantly impairs acute punching performance, and delays recovery beyond 24 hours post-exercise. Furthermore, all BFR-RST must be discontinued at least 48 hours prior to competition to ensure full recovery of punching capabilities for peak performance. When programming BFR-RST, anticipate acute reductions in punch performance immediately after training; therefore, avoid scheduling these sessions before technical or high-intensity sessions requiring maximal power output. Strategically implement this method during training phases focused on metabolic adaptation.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eDuring the acute recovery phase, HR responses and BLA clearance rates in the BFR groups (particularly at 80% AOP) were significantly higher than in the non-BFR group. However, BLA levels, HR and SmO\u003csub\u003e2\u003c/sub\u003e recovery rates (% of baseline), punching speed, and punching force decreased with increasing BFR pressure. At 24 hours post-training, all parameters recovered to baseline except punching speed and force at 80% AOP. It is recommended to select 40%\u0026ndash;60% AOP for upper-limb BFR-RST in daily training to balance metabolic benefits and performance outcomes, although coaches should individually assess tolerance and recovery. Additionally, BFR training should be avoided within 24 hours before competition. Future studies should investigate the long-term physiological effects of BFR-RST across diverse populations, including elite athletes, to further clarify physiological adaptations and enhance scientific training practices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors would like to thank the boxers who volunteered their time and effort to participate in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee (Institutional Review Board) of Shenyang Sport University (Approval No. Ethics [2024] No. 12). Prior to participation, all subjects were fully informed of the purpose, procedures, potential risks, and benefits of the study. Written informed consent was obtained from all individual participants included in the study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of interests\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ.X.\u003c/strong\u003e and \u003cstrong\u003eA.S.\u003c/strong\u003e conceived and designed the study. \u003cstrong\u003eQ.X., S.L.,\u003c/strong\u003e and \u003cstrong\u003eR.M.\u003c/strong\u003e performed the experiments and data collection. \u003cstrong\u003eQ.X.\u003c/strong\u003e and \u003cstrong\u003eS.L.\u003c/strong\u003e conducted the statistical analysis. \u003cstrong\u003eQ.X.\u003c/strong\u003e wrote the original draft of the manuscript. \u003cstrong\u003eS.L., R.M.,\u003c/strong\u003e and \u003cstrong\u003eA.S.\u003c/strong\u003e critically reviewed and edited the manuscript. \u003cstrong\u003eA.S.\u003c/strong\u003e provided supervision and project administration. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBi XC, Zhan JG. Relationship of muscle oxygen saturation, heart rate and blood lactate during high-intensity interval training recovery period. J Chengdu Sport Univ. 2019;45(4):105\u0026ndash;12. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.15942/j.jcsu.2019.04.017\u003c/span\u003e\u003cspan address=\"10.15942/j.jcsu.2019.04.017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChristiansen D, Bishop DJ. 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BMC Sports Sci Med Rehabil. 2022;14(1):161. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1186/s13102-022-00557-4\u003c/span\u003e\u003cspan address=\"10.1186/s13102-022-00557-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\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":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"combat sports, upper-limb training, blood lactate, punching performance, muscle oxygen saturation","lastPublishedDoi":"10.21203/rs.3.rs-8489574/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8489574/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePURPOSE\u003c/h2\u003e \u003cp\u003eTo investigate the acute and 24-hour effects of different blood flow restriction (BFR) pressures on recovery following a single session of boxing-specific repeated high-intensity exercise.\u003c/p\u003e\u003ch2\u003eMETHODS\u003c/h2\u003e \u003cp\u003eFifteen boxers performed the exercise under four randomly ordered conditions: non-BFR, and BFR at 40%, 60%, and 80% arterial occlusion pressure (AOP). Heart rate (HR), blood lactate (BLA), muscle oxygen saturation (SmO\u003csub\u003e2\u003c/sub\u003e), punching speed, and force were measured at baseline, immediately post-exercise, and at 5 minutes, 20 minutes, and 24 hours post-exercise. Statistical significance was set at \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003ch2\u003eRESULTS\u003c/h2\u003e \u003cp\u003eThe 80% AOP condition elicited significantly higher HR and slower HR recovery (% baseline) compared to other conditions immediately post-exercise and at 5 minutes and 20 minutes post-exercise (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). BLA concentrations were significantly lower under all BFR conditions than non-BFR throughout recovery (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with the lowest values observed at 80% AOP, which also exhibited the highest lactate clearance rate at 20 minutes post-exercise. SmO\u003csub\u003e2\u003c/sub\u003e recovery slowed progressively with increasing BFR pressure (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Punching performance decreased immediately post-exercise in a pressure-dependent manner (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with performance at 80% AOP remaining impaired at 24 hours.\u003c/p\u003e\u003ch2\u003eCONCLUSION\u003c/h2\u003e \u003cp\u003eBFR alters post-exercise physiological responses and impairs punching performance, with effects magnified at 80% AOP. Pressures of 40\u0026ndash;60% AOP may offer an optimal balance between physiological stimulus and performance recovery. Therefore, BFR at high pressures should be avoided within 24 hours prior to competition.\u003c/p\u003e","manuscriptTitle":"The Effect of Blood Flow Restriction Pressure on Acute and 24-Hour Recovery Following Upper-Limb Repeated High-Intensity Exercise in Boxers ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-13 15:27:26","doi":"10.21203/rs.3.rs-8489574/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-03-03T18:20:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"200562202442086952148200143158874258537","date":"2026-02-26T17:42:15+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-09T11:43:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-09T11:35:36+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-07T06:47:57+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-06T13:20:10+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Sports Science, Medicine and Rehabilitation","date":"2026-01-06T13:08:56+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f3ac365f-933e-43ac-a39f-bd9780d9e8c2","owner":[],"postedDate":"January 13th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-13T15:27:26+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-13 15:27:26","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8489574","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8489574","identity":"rs-8489574","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}