Impact of Intensity-Specific Aquatic Cycling Training on Muscle Strength, Cardiorespiratory Fitness, Neurotrophic Factors, and Cognitive Function Among Older Women

Impact of Intensity-Specific Aquatic Cycling Training on Muscle Strength, Cardiorespiratory Fitness, Neurotrophic Factors, and Cognitive Function Among Older Women | 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 Impact of Intensity-Specific Aquatic Cycling Training on Muscle Strength, Cardiorespiratory Fitness, Neurotrophic Factors, and Cognitive Function Among Older Women Cheolgyu Yoo, Jihae Park, Taejin Kwak, Gichul Ha This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9285643/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background This study investigated the effects of aquatic cycling training (ACT) at varying intensities on muscle strength, cardiorespiratory fitness, brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), and cognitive function among older women. Methods Forty women aged 65–74 years were randomly assigned to one of four groups: high-intensity interval ACT (HIIT; n = 10), moderate-intensity continuous ACT (MICT; n = 10), progressive-intensity ACT (PICT; n = 10), and control groups (n = 10). The intervention was conducted over 16 weeks, with three sessions weekly. Muscle strength (represented by isokinetic knee strength), cardiorespiratory fitness, BDNF, IGF-1, and cognitive function were measured before and after the intervention. A two-way repeated-measures (RM) analysis of variance (ANOVA) was performed to examine differences across groups and time. Results Knee extensor strength significantly improved across all training groups (p < 0.01), with between-group differences observed. Knee flexor strength significantly increased in the HIIT and PICT groups (p < 0.01), with partial differences between groups. Both BDNF and IGF-1 levels significantly increased across all training groups (p < 0.01), with confirmed group differences. Cognitive function improved significantly across all training groups, but no intensity-based differences were found. Conclusions Sixteen weeks of ACT produces beneficial effects on functional fitness (represented by muscle strength and cardiorespiratory fitness), BDNF, IGF-1, and cognitive function among older women, irrespective of training intensity. Improvements in muscular strength and neurotrophic factors were influenced by exercise intensity, whereas cognitive gains were independent of intensity. These findings indicate that ACT is an effective and safe intervention for enhancing physical fitness and promote neuroplasticity, thereby contributing to improved cognitive function among older women. Trial registration Clinical Research Information Service (CRIS), KCT0011903. Registered 27 April 2026 (Retrospectively registered). Aquatic cycling Fitness Brain-derived neurotrophic factor insulin-like growth factor-1 Cognitive function Figures Figure 1 Background Aging induces numerous physiological changes that affect functional fitness and physical health, which ultimately increase vulnerability to chronic diseases [ 1 ]. In particular, the prevalence of sarcopenia, a key component of frailty, stands at 24% among individuals aged 65–70 years, with total muscle mass declining up to 15% at 70–80 years of age [ 2 , 3 ]. Such age-related declines in muscle mass and functional fitness weaken gait and balance, elevate the risk of falls, and diminish physical and functional independence [ 4 ]. Natural aging entails peripheral muscle atrophy as well as significant neural degradation [ 5 ]. This encompasses decreased brain mass and synaptic loss, coupled with reduced blood supply and altered hippocampal integrity. Such neurological transformations ultimately lead to the deterioration of cognitive performance [ 6 – 8 ]. Age-related cognitive decline is a natural process; however, regular physical exercise exerts beneficial effects on neural function, supporting the maintenance and even improvement of cognitive capacity [ 6 , 9 – 11 ]. Exercise stimulates brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1), which promote neurogenesis, neuronal development, cerebrovascular integrity [ 12 – 14 ], and neural plasticity, ultimately improving cognitive function [ 13 , 15 – 17 ]. Therefore, regular exercise is essential in old age to prevent and mitigate declines in physical and cognitive function. Aerobic exercise strengthens brain plasticity and contributes to cognitive improvement [ 18 , 19 ]. Additionally, compared with low-intensity exercise, high-intensity exercise produces greater benefits for the cardiovascular, metabolic, and musculoskeletal health of older adults [ 18 ]. In this context, aquatic exercise serves as a safe and effective modality for older adults, especially those with lower-limb dysfunction or those at risk of osteoporosis, because it allows high-intensity training without imposing excessive joint stress [ 20 , 21 ]. Numerous studies have examined aquatic exercise among older populations. However, most have either compared aquatic exercise with land-based or combined exercise [ 22 – 26 ] or investigated different exercise intensities within a single aquatic exercise [ 27 – 31 ]. Furthermore, research focusing on neurotrophic factors and cognitive function has primarily employed aquatic aerobics or resistance training with equipment or water resistance [ 31 , 32 ]. Aquatic cycling training (ACT) has been identified as an alternative that may improve cognitive function [ 33 ] as well as reduce joint load, thereby facilitating safe participation [ 34 , 35 ]. Nevertheless, few studies have investigated ACT among older women [ 36 ]. Considering that the benefits for cognitive and various physical functions in older women may differ according to exercise intensity [ 8 , 37 , 38 ], further research is required to verify the effects of intensity on functional fitness, BDNF levels, and cognitive performance. Therefore, this study examined the effects of ACT on muscle strength, cardiorespiratory fitness (CRF), neurotrophic factors (BDNF and IGF-1), and cognitive function among older women. With this aim, we sought to provide empirical evidence of ACT as a safe exercise prescription that prevents and improves age-related cognitive decline, thereby promoting health and independence in later life. Methods Participants A total of 40 women aged 65–74 years were recruited from A Sports Center in Hanam, Gyeonggi Province, and randomly assigned to four groups: high-intensity interval ACT group (HIIT group; n = 10), moderate-intensity continuous ACT group (MICT group; n = 10), progressive-intensity ACT group (PICT group; n = 10), and control group (n = 10). To ensure unbiased allocation, a simple randomization was performed by drawing numbered lots from an opaque container. Individuals were excluded if they had engaged in regular exercise within the previous 6 months; had received pharmacological treatment for cardiovascular disease; had uncontrolled hypertension; had used sex hormones or other relevant medication; or experienced chest pain, dyspnea, arrhythmia, or musculoskeletal disorders during exercise. Table 1 lists the demographic and physical characteristics of the final sample. This study was approved by the Institutional Review Board (IRB) of Korea National Sport University (No. 20210817-116) and conducted in accordance with the ethical principles of the Declaration of Helsinki. There were no important changes to the methods after trial commencement. Table 1 Demographic and physical characteristics of the participants Group Age (years) Height (cm) Weight (kg) BMI (kg/m2) Body fat (%) HIIT 70.30 ± 2.75 154.80 ± 6.25 53.21 ± 2.87 23.12 ± 2.06 32.80 ± 3.96 MICT 70.20 ± 2.53 155.02 ± 8.02 57.34 ± 7.15 23.78 ± 0.77 32.85 ± 0.80 PICT 69.40 ± 3.20 154.44 ± 8.13 57.60 ± 6.32 24.74 ± 1.65 31.04 ± 3.50 Control 70.00 ± 2.82 151.80 ± 6.18 54.64 ± 4.60 23.12 ± 2.06 32.80 ± 3.96 p 0.899 0.733 0.244 0.134 0.588 Values are presented as the mean ± SD HIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training Exercise Program Following orientation, intensity setting, and adaptation sessions, ACT was performed three times weekly for 16 weeks. All steps were conducted under controlled conditions (indoor temperature, 33–35°C; humidity, 70–75%; water temperature, 30–31°C; water depth, 1.2 m). Participants used an Aquabike V4 (AquaNess, France), with submersion between the navel and sternum. Each session comprised a 10-min warm-up, 30-min primary exercise, and 10-min cool-down. Warm-up and cool-down included slow forward/backward pedaling and static stretching. The exercise intensity was set based on the heart rate reserve (HRR) of each individual, which was derived from their maximal heart rate during a graded exercise test. Heart rate was continuously monitored (Polar RS400sd, USA), recording peak and average values. The program was adapted from Rewald, Mesters [ 35 ]. Figure 1 shows the protocol of high-intensity interval ACT, moderate-intensity continuous ACT, and progressive-intensity ACT. The protocol for the HIIT group was adapted from Keogh et al. [ 39 ]. We alternated 85% HRR (high) and 40% HRR (low), with 30-s bouts at up to 110 rpm, followed by 90 s at < 70 rpm, for a total of 30 min. In the MICT group, participants cycled continuously at approximately 60% HRR, with a rating of perceived exertion (RPE) of 12–14, at 60–80 rpm for a total of 30 min [ 39 ]. In the PICT group, the exercise intensity increased every 4 weeks [ 40 ]: 40–50% HRR during weeks 1–4; 50–60% HRR during weeks 5–8; 60–65% HRR during weeks 9–12; and 65–75% HRR during weeks 13–16. Measurements Body Composition Weight and height were measured (Jenix, Seoul, Republic of Korea), and BMI was calculated (kg/m²). Body composition was determined using bioelectrical impedance analysis (X-Scan II, Jawon Medical, Republic of Korea). Muscle Strength Muscle strength was determined by assessing the isokinetic knee strength of participants (Biodex System 3, USA). After warm-up, participants were aligned with the dynamometer axis and stabilized using Velcro straps. Then, we performed three maximal extension/flexion trials at 60°/s. Cardiorespiratory Fitness CRF was evaluated with an automated gas-analysis system (Q4500, Quinton, Bothell, WA, USA), using a modified Balke treadmill protocol to assess maximal oxygen uptake (VO₂max). Termination criteria included a respiratory exchange ratio (RER) of > 1.15, heart rate (HR) of ≥ 90% of the age-predicted maximum (220 − age), or the request of the participant to stop. BDNF and IGF-1 After an overnight fast of at least 8 h, venous blood was collected from the participants. BDNF was measured using Total BDNF Quantikine ELISA (R&D Systems, Minneapolis, MN, USA) and spectrophotometry (Thermo Scientific Multiskan Go). IGF-1 was measured by operating the LIAISON IGF-1 kit (DiaSorin, Saluggia, Italy) on the Liaison XL analyzer (DiaSorin, Stillwater, MN, USA) using chemiluminescent immunoassay. Cognitive Function Cognitive function was assessed using the Mini-Mental State Examination (MMSE). In particular, we used the standardized Korean version of the MMSE (MMSE-K), which was translated and validated by Folstein [ 41 ]. Item scoring included adjustments for illiteracy (+ 1 orientation; +2 attention/calculation; +1 language). The assessment utilizes a 30-point scale (0–30), where elevated scores are directly associated with superior cognitive performance. Scores of ≤ 23 indicate cognitive impairment. Statistical Analysis The required sample size was determined using G*Power 3.1.9.7. To detect a within-between interaction effect in a two-way repeated measures (RM) analysis of variance (ANOVA), the calculation was based on a medium effect size (f) of 0.25, a significance level (α) of 0.05, and a statistical power (1- β) of 0.70. Because of the four groups, two measurement points, and a correlation of 0.5 among RM, the minimum sample size was identified as 40 (n = 10 per group). All data were analyzed using SPSS for Windows version 21.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were determined and reported as the mean ± standard deviation (SD). A two-way RM ANOVA was performed to determine group (HIIT, MICT, PICT, and control) × time (pre and post) effects. When significant primary or interaction effects were detected, post-hoc analyses were performed. Statistical significance was consistently set at α = 0.05. Results Change in Muscle Strength Based on ACT Intensity A two-way RM ANOVA of knee extensor strength showed a significant interaction effect (p < 0.001) and significant primary effects of both group and time (both p < 0.001; Table 2 ). Paired t-tests indicated significant pre-to-post increases in the HIIT, PICT, and MICT groups (p < 0.01). Between-group differences post-intervention were significant (p < 0.01). Regarding knee flexor strength, a significant interaction effect (p < 0.01) and a significant primary effect of time (p < 0.01) were observed. Paired t-tests showed significant gains in the HIIT and PICT groups (p < 0.01). Between-group differences post-intervention were significant (p < 0.01). Table 2 Changes in muscle strength based on aquatic cycling training intensity Pre Post‡ Δ% F p Post-hoc Knee extensor strength (%BW) HIIT a 106.32 ± 5.36 151.98 ± 18.66† 42.94 G 22.400 0.001** d < b<a, c MICT b 106.46 ± 5.28 122.80 ± 12.53† 15.34 T 138.452 0.001** PICT c 106.28 ± 5.41 150.50 ± 10.63† 41.60 G*T 29.262 0.001** Control d 108.02 ± 4.81 105.62 ± 9.68 -2.24 Knee flexor strength (%BW) HIIT a 53.48 ± 2.66 70.16 ± 10.85† 31.18 G 1.646 0.196 NS MICT b 55.80 ± 17.73 58.91 ± 9.58 5.57 T 18.983 0.001** PICT c 54.98 ± 13.60 70.22 ± 13.41† 27.71 G*T 5.464 0.003** Control d 53.55 ± 15.58 52.01 ± 12.51 -2.87 Values are presented as the mean ± SD G: group; T: time; G*T: group*time; Δ%=[(post - pre)/pre] × 100 HIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training † difference between pre- and post-test, ‡ difference between groups *p < 0.05, **p < 0.01, ***p 0.05; Table 3 ). Table 3 Changes in cardiorespiratory fitness based on aquatic cycling training intensity Pre Post‡ Δ% F p Post-hoc HIIT a 22.68 ± 3.06 22.98 ± 2.57 1.32 G 0.176 0.001** NS MICT b 22.26 ± 2.11 22.56 ± 2.64 1.34 T 0.733 0.398 PICT c 22.91 ± 2.40 23.32 ± 1.88 1.78 G*T 0.538 0.660 Control d 22.90 ± 1.29 22.62 ± 1.82 -1.22 Values are presented as mean ± SD G: group; T: time; G*T: group*time; Δ%=[(post - pre)/pre] × 100 HIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training †difference between pre- and post-test, ‡ difference between groups *p < 0.05, **p < 0.01, ***p < 0.001 Changes in BDNF Based on ACT Intensity A two-way RM ANOVA of BDNF indicated a significant interaction effect (p < 0.05) and significant primary effects of both group (p < 0.05) and time (p < 0.01; Table 4 ). Paired t-tests showed significant pre-to-post increases in BDNF in the HIIT, MICT, and PICT groups (p < 0.01). Between-group differences post-intervention were significant (p < 0.01). Table 4 Changes in BDNF based on aquatic cycling training intensity Pre Post‡ Δ% F p Post-hoc HIIT a 18636.87 ± 1971.26 24266.86 ± 2656.18† 30.20 G 3.222 0.034* b,d < a<c MICT b 18473.27 ± 3696.37 23067.27 ± 2431.21† 24.86 T 45.068 0.001** PICT c 18618.97 ± 2742.43 24906.24 ± 2908.10† 33.76 G*T 3.462 0.026* Control d 18518.97 ± 2998.61 19406.24 ± 4135.04 4.79 Values are presented as the mean ± SD G: group; T: time; G*T: group*time; Δ%=[(post - pre)/pre] × 100 HIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training † difference between pre- and post-test, ‡ difference between groups *p < 0.05, **p < 0.01, ***p < 0.001 Changes in IGF-1 Based on ACT Intensity Two-way RM ANOVA of IGF-1 showed a significant interaction effect (p < 0.01) and a significant primary effect of time (p < 0.01; Table 5 ). Paired t-tests revealed significant pre-to-post increases in IGF-1 in the HIIT, MICT, and PICT groups (p < 0.01). Between-group differences post-intervention were significant (p < 0.01). Table 5 Changes in IGF-1 based on aquatic cycling training intensity Pre Post‡ Δ% F p Post-hoc HIIT a 115.02 ± 16.69 151.73 ± 11.12† 31.91 G 2.395 0.084 b,d < a,c MICT b 118.44 ± 16.52 140.81 ± 17.87† 18.88 T 91.022 0.001** PICT c 117.68 ± 26.21 154.62 ± 16.86† 31.39 G*T 12.725 0.001** Control d 118.58 ± 17.07 117.72 ± 18.21 -0.72 Values are presented as the mean ± SD G: group; T: time; G*T: group*time; Δ%= [(post - pre)/pre] × 100 HIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training † difference between pre- and post-test, ‡ difference between groups * p < 0.05, ** p < 0.01, *** p < 0.001 Changes in Cognitive Function Based on ACT Intensity A two-way RM ANOVA of MMSE scores identified a significant interaction effect (p < 0.05) and a significant primary effect of time (p < 0.01; Table 6 ). Paired t-tests showed that MMSE scores increased significantly in the HIIT (p < 0.01), PICT (p < 0.01), and MICT groups (p < 0.05). Between-group differences post-intervention were significant (p < 0.01). Table 6 Changes in cognitive function based on aquatic cycling training intensity Pre Post ‡ Δ% F p Post-hoc HIIT a 24.40 ± 2.75 28.20 ± 1.31 † 15.57 G 1.129 0.250 NS MICT b 24.60 ± 2.87 27.10 ± 2.88 † 10.16 T 35.349 0.001** PICT c 24.30 ± 3.74 28.30 ± 1.33 † 16.46 G*T 3.675 0.006* Control d 24.35 ± 3.09 24.20 ± 2.61 -0.61 Values are presented as the mean ± SD G: group; T: time; G*T: group*time; Δ%= [(post - pre) / pre] × 100 HIIT: High-intensity interval aquatic cycling training, MICT: Moderate-intensity continuous aquatic cycling training, PICT: Progressive-intensity aquatic cycling training, CG: control group † difference between pre- and post- test, ‡ difference between groups * p < 0.05, ** p < 0.01, *** p < 0.001 Discussion This study investigated the effects of ACT at different intensities on functional fitness, BDNF, IGF-1, and cognitive function among older women. Functional fitness, encompassing muscle strength, CRF, flexibility, agility, and balance, is essential for independent living [ 42 ]; however, it declines with aging [ 43 ]. Aquatic exercise leverages buoyancy (reducing joint loading) and multidirectional resistance (increasing energy cost and heart-rate response) to improve physical function [ 44 ], thus making it suitable for insufficiently active older adults [ 45 ]. In this study, moderate-intensity continuous ACT significantly improved knee extensor strength but did not induce significant gains in knee flexor strength. Notably, progressive-intensity ACT improved both extensors and flexors. These findings align with prior reports revealing that appropriately loaded, faster-paced aquatic exercise enhances strength and functional fitness among older women [ 30 , 46 ]. ACT promotes core stability and closed-kinetic-chain movement patterns, which can enhance balance, improve gait, and reduce the risk of falls. Although no significant between-group differences were observed for CRF, all training groups showed rising statistics. Literature indicates that high-intensity interval training, dynamic, whole-body work involving upper and lower limbs, improves aerobic capacity and CRF [ 47 ]. It also reports that progressive aquatic resistance/interval training benefits cardiovascular health and fitness [ 48 – 52 ]. Therefore, high-intensity interval ACT, moderate-intensity continuous ACT, and progressive-intensity ACT all appear effective for improving physical fitness among older women; however, further research is warranted to refine training intensity, frequency, duration, and modality. BDNF increased significantly across all training groups, with some intensity-based differences. This result is consistent with the notion that BDNF responses dependent on intensity [ 53 , 54 ]. Because of the central role of BDNF in neuroplasticity and cognition and its age-related decline [ 7 , 55 ], regular exercise-induced increases are meaningful for cognitive health [ 56 – 60 ]. Similar to BDNF, IGF-1 increased significantly across all groups, with larger gains in the HIIT and PICT groups. Because IGF-1 supports muscle maintenance, metabolism, and strength but declines with age [ 61 – 63 ], exercise-related upregulation, especially at higher intensities, aligns with prior findings [ 64 , 65 ]. The energetic demands of water-based training (arising from buoyancy and multidirectional resistance) may further stimulate IGF-1 [ 66 ], thereby supporting neural plasticity and cognitive improvement [ 20 , 67 ]. MMSE scores improved significantly across all training groups, with no differences based on intensity. This finding aligns with previous research reporting that aquatic aerobics and psychomotor programs enhance cognition among older adults [ 32 , 68 – 70 ]. In this study, ACT incorporated various upper-limb patterns in addition to pedaling, thus providing diverse, repetitive stimuli that may have supported cognitive gains. Accordingly, ACT aimed at cognitive improvement should pair sufficient repetition with varied motor challenges. Overall, intensity-specific ACT improved muscular function, neurotrophic profiles (IGF-1 and BDNF), and cognitive function among older women. The aquatic environment minimized joint stress, while supporting strength gains. These findings reveal that ACT may be a viable strategy to prevent age-related muscle loss, maintain independence, and promote healthy aging. In addition, its multimodal sensory input may enhance cognitive outcomes. Conclusions Over 16 weeks, high-intensity interval ACT, moderate-intensity continuous ACT, and progressive-intensity ACT all improved isokinetic knee extensor strength. Knee flexor strength improved markedly with high-intensity interval ACT and progressive-intensity ACT (and to a lesser extent with moderate-intensity continuous ACT). BDNF and IGF-1 increased significantly across all training groups. Cognitive function improved across groups without intensity-based differences. These findings indicate that, irrespective of intensity, ACT enhances muscular fitness and promotes neuroplasticity (through increased BDNF and IGF-1), thereby contributing to improved cognitive function among older women. Abbreviations ACT aquatic cycling training BDNF brain-derived neurotrophic factor IGF-1 insulin-like growth factor-1 CRF cardiorespiratory fitness HRR heart rate reserve PICT progressive-intensity training HIIT high-intensity interval training MMSE mini-mental state examination MICT moderate-intensity continuous RPE rating of perceived exertion Declarations Ethics approval and consent to participate Write text here Ethical approval for this study was obtained from the Institutional Review Board of Korea National Sport University (No. 20210817-116). All subjects voluntarily signed a written informed consent form before participating, having been fully briefed on the research objectives and protocols. 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. Clinical trial number Not applicable Competing interests The authors declare no conflicts of interest. Funding This research received no external funding. Author Contributions Conceptualization, C.Y., G.H.; methodology, C.Y., T.K.; investigation, C.Y., J.P, T.K. and G.H; data curation: J.P; writing—original draft preparation, C.Y.; writing—editing, T.K., G.H.; project administration, C.Y. All authors have read and agreed to the final version of the manuscript for publication. Acknowledgements The authors extend their sincere gratitude to all participants in the exercise program. References Hallal PC, Andersen LB, Bull FC, Guthold R, Haskell W, Ekelund U. Global physical activity levels: surveillance progress, pitfalls, and prospects. Lancet. 2012;380:247–57. Xu J, Wan CS, Ktoris K, Reijnierse EM, Maier AB. Sarcopenia is associated with mortality in adults: a systematic review and meta-analysis. Gerontology. 2022;68:361–76. Han A, Bokshan SL, Marcaccio SE, DePasse JM, Daniels AH. Diagnostic criteria and clinical outcomes in sarcopenia research: a literature review. J Clin Med. 2018;7:70. Collino S, Martin F-P, Karagounis LG, Horcajada MN, Moco S, Franceschi C, et al. Musculoskeletal system in the old age and the demand for healthy ageing biomarkers. Mech Ageing Dev. 2013;134:541–7. Clouston SA, Brewster P, Kuh D, Richards M, Cooper R, Hardy R, et al. The dynamic relationship between physical function and cognition in longitudinal aging cohorts. Epidemiol Rev. 2013;35:33–50. Bherer L, Erickson KI, Liu-Ambrose T. Physical exercise and brain functions in older adults. J Aging Res. 2013;2013:197326. Byun J-E, Kang E-B. The effects of senior brain health exercise program on basic physical fitness, cognitive function and BDNF of elderly women-a feasibility study. J Exerc Nutr Biochem. 2016;20:8. Hogan M. Physical and cognitive activity and exercise for older adults: a review. Int J Aging Hum Dev. 2005;60:95–126. Lista I, Sorrentino G. Biological mechanisms of physical activity in preventing cognitive decline. Cell Mol Neurobiol. 2010;30:493–503. Etnier JL, Chang Y-K. Exercise, cognitive function, and the brain: Advancing our understanding of complex relationships. J Sport Health Sci. 2019;8:299. Zigmond M, Smeyne RJ. Foreword: exercise and the brain. Brain Res. 2010;1341:1–2. Loprinzi PD, Herod SM, Cardinal BJ, Noakes TD. Physical activity and the brain: a review of this dynamic, bi-directional relationship. Brain Res. 2013;1539:95–104. Skriver K, Roig M, Lundbye-Jensen J, Pingel J, Helge JW, Kiens B, et al. Acute exercise improves motor memory: exploring potential biomarkers. Neurobiol Learn Mem. 2014;116:46–58. Van Praag H. Exercise and the brain: something to chew on. Trends Neurosci. 2009;32:283–90. Whiteman AS, Young DE, He X, Chen TC, Wagenaar RC, Stern CE, et al. Interaction between serum BDNF and aerobic fitness predicts recognition memory in healthy young adults. Behav Brain Res. 2014;259:302–12. Voss MW, Erickson KI, Prakash RS, Chaddock L, Kim JS, Alves H, et al. Neurobiological markers of exercise-related brain plasticity in older adults. Brain Behav Immun. 2013;28:90–9. Ratey JJ, Loehr JE. The positive impact of physical activity on cognition during adulthood: a review of underlying mechanisms, evidence and recommendations. Rev Neurosci. 2011;22(2):171–85. Petzinger GM, Fisher BE, McEwen S, Beeler JA, Walsh JP, Jakowec MW. Exercise-enhanced neuroplasticity targeting motor and cognitive circuitry in Parkinson's disease. Lancet Neurol. 2013;12:716–26. Kang D-w, Bressel E, Kim D-y. Effects of aquatic exercise on insulin-like growth factor-1, brain-derived neurotrophic factor, vascular endothelial growth factor, and cognitive function in elderly women. Exp Gerontol. 2020;132:110842. Clerici I, Maestri R, Bonetti F, Ortelli P, Volpe D, Ferrazzoli D, et al. Land plus aquatic therapy versus land-based rehabilitation alone for the treatment of freezing of gait in Parkinson disease: a randomized controlled trial. Phys Ther. 2019;99:591–600. Perkins KM, Munguia N, Angulo A, Anaya C, Rios R, Velazquez L. Evaluation of aquafitness exercise on the physical and mental health of older women: a pilot study. J Women Aging. 2021;33:569–82. Bergamin M, Ermolao A, Tolomio S, Berton L, Sergi G, Zaccaria M. Water-versus land-based exercise in elderly subjects: effects on physical performance and body composition. Clin Interv Aging. 2013:1109–17. de Castro LA, Felcar JM, de Carvalho DR, Vidotto LS, da Silva RA, Pitta F, et al. Effects of land-and water-based exercise programmes on postural balance in individuals with COPD: additional results from a randomised clinical trial. Physiotherapy. 2020;107:58–65. Heywood S, McClelland J, Geigle P, Rahmann A, Villalta E, Mentiplay B, et al. Force during functional exercises on land and in water in older adults with and without knee osteoarthritis: Implications for rehabilitation. Knee. 2019;26:61–72. Naylor LH, Maslen BA, Cox KL, Spence AL, Robey E, Haynes A, et al. Land-versus water-walking interventions in older adults: Effects on body composition. J Sci Med Sport. 2020;23:164–70. Oh S, Lim J-M, Kim Y, Kim M, Song W, Yoon B. Comparison of the effects of water-and land-based exercises on the physical function and quality of life in community-dwelling elderly people with history of falling: a single-blind, randomized controlled trial. Arch Gerontol Geriatr. 2015;60:288–93. Alberton CL, Zaffari P, Pinto SS, Reichert T, Bagatini NC, Kanitz AC, et al. Water-based exercises in postmenopausal women: Vertical ground reaction force and oxygen uptake responses. Eur J Sport Sci. 2021;21:331–40. Andrade LS, Pinto SS, Silva MR, Schaun GZ, Portella EG, Nunes GN, et al. Water-based continuous and interval training in older women: Cardiorespiratory and neuromuscular outcomes (WATER study). Exp Gerontol. 2020;134:110914. Graef FI, Pinto RS, Alberton CL, De Lima WC, Kruel LF. The effects of resistance training performed in water on muscle strength in the elderly. J Strength Cond Res. 2010;24:3150–6. Moreira NB, da Silva LP, Rodacki ALF. Aquatic exercise improves functional capacity, perceptual aspects, and quality of life in older adults with musculoskeletal disorders and risk of falling: A randomized controlled trial. Exp Gerontol. 2020;142:111135. Silva LAd, Tortelli L, Motta J, Menguer L, Mariano S, Tasca G, et al. Effects of aquatic exercise on mental health, functional autonomy and oxidative stress in depressed elderly individuals: A randomized clinical trial. Clin (Sao Paulo). 2019;74:e322. Kim J-H, Kim D-Y. Aquarobic exercises improve the serum blood irisin and brain-derived neurotrophic factor levels in elderly women. Exp Gerontol. 2018;104:60–5. Lippi G, Mattiuzzi C, Sanchis-Gomar F. Updated overview on interplay between physical exercise, neurotrophins, and cognitive function in humans. J Sport Health Sci. 2020;9:74–81. Lopez JF, Espinoza RV, Alvear-Vasquez F, Macedo LS, Velasquez DM, Pacco WR, et al. Systematic review of aquatic physical exercise programs on functional fitness in older adults. Eur J Transl Myol. 2021;31:10006. Rewald S, Mesters I, Lenssen A, Emans PJ, Wijnen W, de Bie RA. Effect of aqua-cycling on pain and physical functioning compared with usual care in patients with knee osteoarthritis: study protocol of a randomised controlled trial. BMC Musculoskelet Disord. 2016;17:88. Rewald S, Mesters I, Lenssen AF, Bansi J, Lambeck J, de Bie RA, et al. Aquatic cycling—What do we know? A scoping review on head-out aquatic cycling. PLoS ONE. 2017;12:e0177704. Karabulut M, Abe T, Sato Y, Bemben MG. The effects of low-intensity resistance training with vascular restriction on leg muscle strength in older men. Eur J Appl Physiol. 2010;108:147–55. Macaluso A, De Vito G. Muscle strength, power and adaptations to resistance training in older people. Eur J Appl Physiol. 2004;91:450–72. Keogh JW, Grigg J, Vertullo CJ. Is high-intensity interval cycling feasible and more beneficial than continuous cycling for knee osteoarthritic patients? Results of a randomised control feasibility trial. PeerJ. 2018;6:e4738. Medicine ACS. ACSM's guidelines for exercise testing and prescription. Lippincott williams & wilkins; 2013. Folstein MF, Folstein SE, McHugh PR. Mini-mental state: a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res. 1975;12:189–98. Rikli RE, Jones CJ. Senior fitness test manual: Human kinetics; 2013. Riebe D, Blissmer BJ, Greaney ML, Ewing Garber C, Lees FD, Clark PG. The relationship between obesity, physical activity, and physical function in older adults. J Aging Health. 2009;21:1159–78. Tamin TZ, Loekito N. Aquatic versus land-based exercise for cardiorespiratory endurance and quality of life in obese patients with knee osteoarthritis: a randomized controlled trial. Med J Indones. 2018;27:284–92. Rezaeipour M, Nychyporuk VI, Raghi Z. Study of Anthropometric and Body Composition Variables in the Overweight/Obese, Sedentary Elderly Men Using WATERinMOTION Aqua Training: A Cross-sectional Study. Asian J Sports Med. 2021;12. Bento PCB, Rodacki ALF. Muscle function in aged women in response to a water-based exercises program and progressive resistance training. Geriatr Gerontol Int. 2015;15:1193–200. Ross LM, Porter RR, Durstine JL. High-intensity interval training (HIIT) for patients with chronic diseases. J Sport Health Sci. 2016;5:139–44. Munukka M, Waller B, Rantalainen T, Häkkinen A, Nieminen MT, Lammentausta E, et al. Efficacy of progressive aquatic resistance training for tibiofemoral cartilage in postmenopausal women with mild knee osteoarthritis: a randomised controlled trial. Osteoarthritis Cartilage. 2016;24:1708–17. Depiazzi JE, Forbes RA, Gibson N, Smith NL, Wilson AC, Boyd RN, et al. The effect of aquatic high-intensity interval training on aerobic performance, strength and body composition in a non-athletic population: systematic review and meta-analysis. Clin Rehabil. 2019;33:157–70. Broman G, Quintana M, Lindberg T, Jansson E, Kaijser L. High intensity deep water training can improve aerobic power in elderly women. Eur J Appl Physiol. 2006;98:117–23. Kwok MM, Ng SS, Man SS, So BC. The effect of aquatic High Intensity Interval Training on cardiometabolic and physical health markers in women: A systematic review and meta-analysis. J Exerc Sci Fit. 2022;20:113–27. Nagle EF, Sanders ME, Franklin BA. Aquatic high intensity interval training for cardiometabolic health: benefits and training design. Am J Lifestyle Med. 2017;11:64–76. Ferris LT, Williams JS, Shen C-L. The effect of acute exercise on serum brain-derived neurotrophic factor levels and cognitive function. Med Sci Sports Exerc. 2007;39:728–34. Knaepen K, Goekint M, Heyman EM, Meeusen R. Neuroplasticity—exercise-induced response of peripheral brain-derived neurotrophic factor: a systematic review of experimental studies in human subjects. Sports Med. 2010;40:765–801. Leckie RL, Oberlin LE, Voss MW, Prakash RS, Szabo-Reed A, Chaddock-Heyman L, et al. BDNF mediates improvements in executive function following a 1-year exercise intervention. Front Hum Neurosci. 2014;8:985. de Melo Coelho FG, Gobbi S, Andreatto CAA, Corazza DI, Pedroso RV, Santos-Galduróz RF. Physical exercise modulates peripheral levels of brain-derived neurotrophic factor (BDNF): a systematic review of experimental studies in the elderly. Arch Gerontol Geriatr. 2013;56:10–5. Duman CH, Schlesinger L, Russell DS, Duman RS. Voluntary exercise produces antidepressant and anxiolytic behavioral effects in mice. Brain Res. 2008;1199:148–58. Khalil MH. The BDNF-Interactive Model for Sustainable Hippocampal Neurogenesis in Humans: Synergistic Effects of Environmentally-Mediated Physical Activity, Cognitive Stimulation, and Mindfulness. Int J Mol Sci. 2024;25:12924. Piepmeier AT, Etnier JL. Brain-derived neurotrophic factor (BDNF) as a potential mechanism of the effects of acute exercise on cognitive performance. J Sport Health Sci. 2015;4:14–23. Jiménez-Maldonado A, Rentería I, García-Suárez PC, Moncada-Jiménez J, Freire-Royes LF. The impact of high-intensity interval training on brain derived neurotrophic factor in brain: a mini-review. Front Neurosci. 2018;12:839. Manini TM, Druger M, Ploutz-Snyder L. Misconceptions about strength exercise among older adults. J Aging Phys Act. 2005;13:422–33. Frater J, Lie D, Bartlett P, McGrath JJ. Insulin-like growth factor 1 (IGF-1) as a marker of cognitive decline in normal ageing: a review. Ageing Res Rev. 2018;42:14–27. Nakamura Y, Tanaka K, Yabushita N, Sakai T, Shigematsu R. Effects of exercise frequency on functional fitness in older adult women. Arch Gerontol Geriatr. 2007;44:163–73. Rubin MR, Kraemer WJ, Maresh CM, Volek JS, Ratamess NA, Vanheest JL, et al. High-affinity growth hormone binding protein and acute heavy resistance exercise. Med Sci Sports Exerc. 2005;37:395–403. Tsai C-L, Wang C-H, Pan C-Y, Chen F-C. The effects of long-term resistance exercise on the relationship between neurocognitive performance and GH, IGF-1, and homocysteine levels in the elderly. Front Behav Neurosci. 2015;9:23. Shafei A, Fathi M, Ziaaldini MM. Comparison of the Effect of Eight Weeks of Water-Based Versus Land-Based Cycling on Serum Levels of Testosterone and IGF-1 in Elderly Men. Gene Cell Tissue. 2021;8. Barker AL, Talevski J, Morello RT, Nolan GA, De Silva RD, Briggs AM. Jumping into the deep-end: results from a pilot impact evaluation of a community-based aquatic exercise program. Clin Rheumatol. 2016;35:1593–601. Henwood T, Neville C, Baguley C, Beattie E. Aquatic exercise for residential aged care adults with dementia: benefits and barriers to participation. Int Psychogeriatr. 2017;29:1439–49. Cheol-Gyu Y, Hyo-Ji P, Shin-Young L, Kang-Min L, Gi-Chul H, Jae-Ryang Y. Effects of Dementia Prevention Program according to the Type of Aquatic Exercise on Cognitive Function, Grip Strength and Risk Factors of Metabolic Syndrome in Elderly Women. Korean J Sport. 2020;18:499–510. Won-Suk J, Cheol-Gyo Y, Gi-Chul H, Jae-Ryang Y. Effect of aquatic interval training on muscle strength, cranial nerve growth factor (IGF-1) and cognitive function. Sport Sci. 2021;39:63–70. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 18 May, 2026 Reviewers agreed at journal 17 May, 2026 Reviews received at journal 15 May, 2026 Reviewers agreed at journal 06 May, 2026 Reviewers invited by journal 05 May, 2026 Editor invited by journal 29 Apr, 2026 Editor assigned by journal 29 Apr, 2026 Submission checks completed at journal 28 Apr, 2026 First submitted to journal 28 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9285643","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":635511379,"identity":"405a3857-ff9e-4bbe-b6eb-4e6ac3c8b5af","order_by":0,"name":"Cheolgyu Yoo","email":"","orcid":"","institution":"AquaBalance Association","correspondingAuthor":false,"prefix":"","firstName":"Cheolgyu","middleName":"","lastName":"Yoo","suffix":""},{"id":635511380,"identity":"bab962f9-72f6-47b8-bbb9-e755eaa3ab6e","order_by":1,"name":"Jihae Park","email":"","orcid":"","institution":"Korea National Sport University","correspondingAuthor":false,"prefix":"","firstName":"Jihae","middleName":"","lastName":"Park","suffix":""},{"id":635511382,"identity":"44a53cf4-5a39-4a8c-8b9d-4acde6358e44","order_by":2,"name":"Taejin Kwak","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYBACCQaGBCBlwcBPvBY2sBYJBskGErRALDM4QKwWyfkNzyQ+tknYG99uBjL2MMjzixHQLM3GkGw4s00icdudY2aSM54xGM6cnYBfixwbQ+Jj3m0SCWY3EoyNeQ4wJBjcJqwl4TBQi73xjPTPxn+I0SINtYVxg0SO4WMGYrRItiUA/fJPInHGjZzChz0HJAj7ReLwmTSJD2ds7PlnpG848OOAjTy/NAEtDAw8KCokCCkHAfYDxKgaBaNgFIyCkQwATl4/rrSQRikAAAAASUVORK5CYII=","orcid":"","institution":"Korea Institute of Sport Science","correspondingAuthor":true,"prefix":"","firstName":"Taejin","middleName":"","lastName":"Kwak","suffix":""},{"id":635511383,"identity":"3fd9914a-fc91-41d3-8268-08f7c6780133","order_by":3,"name":"Gichul Ha","email":"","orcid":"","institution":"National Fitness Center","correspondingAuthor":false,"prefix":"","firstName":"Gichul","middleName":"","lastName":"Ha","suffix":""}],"badges":[],"createdAt":"2026-04-01 02:40:01","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9285643/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9285643/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109281052,"identity":"34afba07-cf83-4a27-a0e1-ceb9c754733f","added_by":"auto","created_at":"2026-05-14 17:42:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":172960,"visible":true,"origin":"","legend":"\u003cp\u003eProtocol of the aquatic cycling training program\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9285643/v1/6135394079a98501fda17cde.png"},{"id":109296950,"identity":"6664326e-da7f-47eb-9ed1-f574c221a5d8","added_by":"auto","created_at":"2026-05-15 08:52:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":512745,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9285643/v1/2304bbe2-6704-41a1-9ade-028ca8c6c7fb.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Impact of Intensity-Specific Aquatic Cycling Training on Muscle Strength, Cardiorespiratory Fitness, Neurotrophic Factors, and Cognitive Function Among Older Women","fulltext":[{"header":"Background","content":"\u003cp\u003eAging induces numerous physiological changes that affect functional fitness and physical health, which ultimately increase vulnerability to chronic diseases [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In particular, the prevalence of sarcopenia, a key component of frailty, stands at 24% among individuals aged 65\u0026ndash;70 years, with total muscle mass declining up to 15% at 70\u0026ndash;80 years of age [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Such age-related declines in muscle mass and functional fitness weaken gait and balance, elevate the risk of falls, and diminish physical and functional independence [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Natural aging entails peripheral muscle atrophy as well as significant neural degradation [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This encompasses decreased brain mass and synaptic loss, coupled with reduced blood supply and altered hippocampal integrity. Such neurological transformations ultimately lead to the deterioration of cognitive performance [\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAge-related cognitive decline is a natural process; however, regular physical exercise exerts beneficial effects on neural function, supporting the maintenance and even improvement of cognitive capacity [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Exercise stimulates brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1), which promote neurogenesis, neuronal development, cerebrovascular integrity [\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and neural plasticity, ultimately improving cognitive function [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Therefore, regular exercise is essential in old age to prevent and mitigate declines in physical and cognitive function.\u003c/p\u003e \u003cp\u003eAerobic exercise strengthens brain plasticity and contributes to cognitive improvement [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Additionally, compared with low-intensity exercise, high-intensity exercise produces greater benefits for the cardiovascular, metabolic, and musculoskeletal health of older adults [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In this context, aquatic exercise serves as a safe and effective modality for older adults, especially those with lower-limb dysfunction or those at risk of osteoporosis, because it allows high-intensity training without imposing excessive joint stress [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eNumerous studies have examined aquatic exercise among older populations. However, most have either compared aquatic exercise with land-based or combined exercise [\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] or investigated different exercise intensities within a single aquatic exercise [\u003cspan additionalcitationids=\"CR28 CR29 CR30\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Furthermore, research focusing on neurotrophic factors and cognitive function has primarily employed aquatic aerobics or resistance training with equipment or water resistance [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Aquatic cycling training (ACT) has been identified as an alternative that may improve cognitive function [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] as well as reduce joint load, thereby facilitating safe participation [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Nevertheless, few studies have investigated ACT among older women [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Considering that the benefits for cognitive and various physical functions in older women may differ according to exercise intensity [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], further research is required to verify the effects of intensity on functional fitness, BDNF levels, and cognitive performance.\u003c/p\u003e \u003cp\u003eTherefore, this study examined the effects of ACT on muscle strength, cardiorespiratory fitness (CRF), neurotrophic factors (BDNF and IGF-1), and cognitive function among older women. With this aim, we sought to provide empirical evidence of ACT as a safe exercise prescription that prevents and improves age-related cognitive decline, thereby promoting health and independence in later life.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eParticipants\u003c/h2\u003e \u003cp\u003eA total of 40 women aged 65\u0026ndash;74 years were recruited from A Sports Center in Hanam, Gyeonggi Province, and randomly assigned to four groups: high-intensity interval ACT group (HIIT group; n\u0026thinsp;=\u0026thinsp;10), moderate-intensity continuous ACT group (MICT group; n\u0026thinsp;=\u0026thinsp;10), progressive-intensity ACT group (PICT group; n\u0026thinsp;=\u0026thinsp;10), and control group (n\u0026thinsp;=\u0026thinsp;10). To ensure unbiased allocation, a simple randomization was performed by drawing numbered lots from an opaque container. Individuals were excluded if they had engaged in regular exercise within the previous 6 months; had received pharmacological treatment for cardiovascular disease; had uncontrolled hypertension; had used sex hormones or other relevant medication; or experienced chest pain, dyspnea, arrhythmia, or musculoskeletal disorders during exercise. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e lists the demographic and physical characteristics of the final sample. This study was approved by the Institutional Review Board (IRB) of Korea National Sport University (No. 20210817-116) and conducted in accordance with the ethical principles of the Declaration of Helsinki. There were no important changes to the methods after trial commencement.\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\u003eDemographic and physical characteristics of the participants\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHeight (cm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWeight (kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBMI (kg/m2)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eBody fat (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHIIT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e70.30\u0026thinsp;\u0026plusmn;\u0026thinsp;2.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e154.80\u0026thinsp;\u0026plusmn;\u0026thinsp;6.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53.21\u0026thinsp;\u0026plusmn;\u0026thinsp;2.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.12\u0026thinsp;\u0026plusmn;\u0026thinsp;2.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e32.80\u0026thinsp;\u0026plusmn;\u0026thinsp;3.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMICT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e70.20\u0026thinsp;\u0026plusmn;\u0026thinsp;2.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e155.02\u0026thinsp;\u0026plusmn;\u0026thinsp;8.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e57.34\u0026thinsp;\u0026plusmn;\u0026thinsp;7.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.78\u0026thinsp;\u0026plusmn;\u0026thinsp;0.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e32.85\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePICT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e69.40\u0026thinsp;\u0026plusmn;\u0026thinsp;3.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e154.44\u0026thinsp;\u0026plusmn;\u0026thinsp;8.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e57.60\u0026thinsp;\u0026plusmn;\u0026thinsp;6.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e24.74\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e31.04\u0026thinsp;\u0026plusmn;\u0026thinsp;3.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eControl\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e70.00\u0026thinsp;\u0026plusmn;\u0026thinsp;2.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e151.80\u0026thinsp;\u0026plusmn;\u0026thinsp;6.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e54.64\u0026thinsp;\u0026plusmn;\u0026thinsp;4.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.12\u0026thinsp;\u0026plusmn;\u0026thinsp;2.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e32.80\u0026thinsp;\u0026plusmn;\u0026thinsp;3.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.899\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.244\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.134\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.588\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003eValues are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eHIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eExercise Program\u003c/h3\u003e\n\u003cp\u003eFollowing orientation, intensity setting, and adaptation sessions, ACT was performed three times weekly for 16 weeks. All steps were conducted under controlled conditions (indoor temperature, 33\u0026ndash;35\u0026deg;C; humidity, 70\u0026ndash;75%; water temperature, 30\u0026ndash;31\u0026deg;C; water depth, 1.2 m). Participants used an Aquabike V4 (AquaNess, France), with submersion between the navel and sternum. Each session comprised a 10-min warm-up, 30-min primary exercise, and 10-min cool-down. Warm-up and cool-down included slow forward/backward pedaling and static stretching. The exercise intensity was set based on the heart rate reserve (HRR) of each individual, which was derived from their maximal heart rate during a graded exercise test. Heart rate was continuously monitored (Polar RS400sd, USA), recording peak and average values. The program was adapted from Rewald, Mesters [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the protocol of high-intensity interval ACT, moderate-intensity continuous ACT, and progressive-intensity ACT.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe protocol for the HIIT group was adapted from Keogh et al. [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. We alternated 85% HRR (high) and 40% HRR (low), with 30-s bouts at up to 110 rpm, followed by 90 s at \u0026lt;\u0026thinsp;70 rpm, for a total of 30 min. In the MICT group, participants cycled continuously at approximately 60% HRR, with a rating of perceived exertion (RPE) of 12\u0026ndash;14, at 60\u0026ndash;80 rpm for a total of 30 min [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In the PICT group, the exercise intensity increased every 4 weeks [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]: 40\u0026ndash;50% HRR during weeks 1\u0026ndash;4; 50\u0026ndash;60% HRR during weeks 5\u0026ndash;8; 60\u0026ndash;65% HRR during weeks 9\u0026ndash;12; and 65\u0026ndash;75% HRR during weeks 13\u0026ndash;16.\u003c/p\u003e\n\u003ch3\u003eMeasurements\u003c/h3\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eBody Composition\u003c/h2\u003e \u003cp\u003eWeight and height were measured (Jenix, Seoul, Republic of Korea), and BMI was calculated (kg/m\u0026sup2;). Body composition was determined using bioelectrical impedance analysis (X-Scan II, Jawon Medical, Republic of Korea).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMuscle Strength\u003c/h3\u003e\n\u003cp\u003eMuscle strength was determined by assessing the isokinetic knee strength of participants (Biodex System 3, USA). After warm-up, participants were aligned with the dynamometer axis and stabilized using Velcro straps. Then, we performed three maximal extension/flexion trials at 60\u0026deg;/s.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCardiorespiratory Fitness\u003c/h2\u003e \u003cp\u003eCRF was evaluated with an automated gas-analysis system (Q4500, Quinton, Bothell, WA, USA), using a modified Balke treadmill protocol to assess maximal oxygen uptake (VO₂max). Termination criteria included a respiratory exchange ratio (RER) of \u0026gt;\u0026thinsp;1.15, heart rate (HR) of \u0026ge;\u0026thinsp;90% of the age-predicted maximum (220\u0026thinsp;\u0026minus;\u0026thinsp;age), or the request of the participant to stop.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eBDNF and IGF-1\u003c/h3\u003e\n\u003cp\u003eAfter an overnight fast of at least 8 h, venous blood was collected from the participants. BDNF was measured using Total BDNF Quantikine ELISA (R\u0026amp;D Systems, Minneapolis, MN, USA) and spectrophotometry (Thermo Scientific Multiskan Go). IGF-1 was measured by operating the LIAISON IGF-1 kit (DiaSorin, Saluggia, Italy) on the Liaison XL analyzer (DiaSorin, Stillwater, MN, USA) using chemiluminescent immunoassay.\u003c/p\u003e\n\u003ch3\u003eCognitive Function\u003c/h3\u003e\n\u003cp\u003eCognitive function was assessed using the Mini-Mental State Examination (MMSE). In particular, we used the standardized Korean version of the MMSE (MMSE-K), which was translated and validated by Folstein [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Item scoring included adjustments for illiteracy (+\u0026thinsp;1 orientation; +2 attention/calculation; +1 language). The assessment utilizes a 30-point scale (0\u0026ndash;30), where elevated scores are directly associated with superior cognitive performance. Scores of \u0026le;\u0026thinsp;23 indicate cognitive impairment.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eThe required sample size was determined using G*Power 3.1.9.7. To detect a within-between interaction effect in a two-way repeated measures (RM) analysis of variance (ANOVA), the calculation was based on a medium effect size (f) of 0.25, a significance level (α) of 0.05, and a statistical power (1- β) of 0.70. Because of the four groups, two measurement points, and a correlation of 0.5 among RM, the minimum sample size was identified as 40 (n\u0026thinsp;=\u0026thinsp;10 per group).\u003c/p\u003e \u003cp\u003eAll data were analyzed using SPSS for Windows version 21.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were determined and reported as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD). A two-way RM ANOVA was performed to determine group (HIIT, MICT, PICT, and control) \u0026times; time (pre and post) effects. When significant primary or interaction effects were detected, post-hoc analyses were performed. Statistical significance was consistently set at α\u0026thinsp;=\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eChange in Muscle Strength Based on ACT Intensity\u003c/h2\u003e \u003cp\u003eA two-way RM ANOVA of knee extensor strength showed a significant interaction effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and significant primary effects of both group and time (both p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Paired t-tests indicated significant pre-to-post increases in the HIIT, PICT, and MICT groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Between-group differences post-intervention were significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Regarding knee flexor strength, a significant interaction effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and a significant primary effect of time (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) were observed. Paired t-tests showed significant gains in the HIIT and PICT groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Between-group differences post-intervention were significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in muscle strength based on aquatic cycling training intensity\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\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePost\u0026Dagger;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eΔ%\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cem\u003ePost-hoc\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eKnee extensor strength\u003c/p\u003e \u003cp\u003e(%BW)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHIIT\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e106.32\u0026thinsp;\u0026plusmn;\u0026thinsp;5.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e151.98\u0026thinsp;\u0026plusmn;\u0026thinsp;18.66\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e42.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22.400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003ed\u0026thinsp;\u0026lt;\u0026thinsp;b\u0026lt;a, c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMICT\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e106.46\u0026thinsp;\u0026plusmn;\u0026thinsp;5.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e122.80\u0026thinsp;\u0026plusmn;\u0026thinsp;12.53\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e15.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e138.452\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePICT\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e106.28\u0026thinsp;\u0026plusmn;\u0026thinsp;5.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e150.50\u0026thinsp;\u0026plusmn;\u0026thinsp;10.63\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e41.60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eG*T\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e29.262\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eControl\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e108.02\u0026thinsp;\u0026plusmn;\u0026thinsp;4.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e105.62\u0026thinsp;\u0026plusmn;\u0026thinsp;9.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-2.24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eKnee flexor strength\u003c/p\u003e \u003cp\u003e(%BW)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHIIT\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e53.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e70.16\u0026thinsp;\u0026plusmn;\u0026thinsp;10.85\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.646\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.196\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMICT\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e55.80\u0026thinsp;\u0026plusmn;\u0026thinsp;17.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e58.91\u0026thinsp;\u0026plusmn;\u0026thinsp;9.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e5.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e18.983\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePICT\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e54.98\u0026thinsp;\u0026plusmn;\u0026thinsp;13.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e70.22\u0026thinsp;\u0026plusmn;\u0026thinsp;13.41\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e27.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eG*T\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e5.464\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.003**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eControl\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e53.55\u0026thinsp;\u0026plusmn;\u0026thinsp;15.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e52.01\u0026thinsp;\u0026plusmn;\u0026thinsp;12.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-2.87\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003eValues are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eG: group; T: time; G*T: group*time; Δ%=[(post - pre)/pre] \u0026times; 100\u003c/p\u003e \u003cp\u003eHIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training\u003c/p\u003e \u003cp\u003e\u0026dagger; difference between pre- and post-test, \u0026Dagger; difference between groups\u003c/p\u003e \u003cp\u003e*p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, ***p\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eChanges in Cardiorespiratory Fitness based on ACT Intensity\u003c/h2\u003e \u003cp\u003eA two-way RM ANOVA of CRF revealed no significant interaction effect (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05; Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in cardiorespiratory fitness based on aquatic cycling training intensity\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePost\u0026Dagger;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eΔ%\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ePost-hoc\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHIIT\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.68\u0026thinsp;\u0026plusmn;\u0026thinsp;3.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.98\u0026thinsp;\u0026plusmn;\u0026thinsp;2.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.176\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMICT\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22.26\u0026thinsp;\u0026plusmn;\u0026thinsp;2.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22.56\u0026thinsp;\u0026plusmn;\u0026thinsp;2.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eT\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.398\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePICT\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22.91\u0026thinsp;\u0026plusmn;\u0026thinsp;2.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e23.32\u0026thinsp;\u0026plusmn;\u0026thinsp;1.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.78\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG*T\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.538\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.660\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eControl\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.90\u0026thinsp;\u0026plusmn;\u0026thinsp;1.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.62\u0026thinsp;\u0026plusmn;\u0026thinsp;1.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-1.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eValues are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eG: group; T: time; G*T: group*time; Δ%=[(post - pre)/pre] \u0026times; 100\u003c/p\u003e \u003cp\u003eHIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training\u003c/p\u003e \u003cp\u003e\u0026dagger;difference between pre- and post-test, \u0026Dagger; difference between groups\u003c/p\u003e \u003cp\u003e*p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, ***p\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eChanges in BDNF Based on ACT Intensity\u003c/h2\u003e \u003cp\u003eA two-way RM ANOVA of BDNF indicated a significant interaction effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and significant primary effects of both group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and time (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01; Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Paired t-tests showed significant pre-to-post increases in BDNF in the HIIT, MICT, and PICT groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Between-group differences post-intervention were significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in BDNF based on aquatic cycling training intensity\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePost\u0026Dagger;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eΔ%\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ePost-hoc\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHIIT\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18636.87\u0026thinsp;\u0026plusmn;\u0026thinsp;1971.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24266.86\u0026thinsp;\u0026plusmn;\u0026thinsp;2656.18\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3.222\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.034*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eb,d\u0026thinsp;\u0026lt;\u0026thinsp;a\u0026lt;c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMICT\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e18473.27\u0026thinsp;\u0026plusmn;\u0026thinsp;3696.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e23067.27\u0026thinsp;\u0026plusmn;\u0026thinsp;2431.21\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e24.86\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eT\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e45.068\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePICT\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e18618.97\u0026thinsp;\u0026plusmn;\u0026thinsp;2742.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e24906.24\u0026thinsp;\u0026plusmn;\u0026thinsp;2908.10\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e33.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG*T\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3.462\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.026*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eControl\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18518.97\u0026thinsp;\u0026plusmn;\u0026thinsp;2998.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19406.24\u0026thinsp;\u0026plusmn;\u0026thinsp;4135.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eValues are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eG: group; T: time; G*T: group*time; Δ%=[(post - pre)/pre] \u0026times; 100\u003c/p\u003e \u003cp\u003eHIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training\u003c/p\u003e \u003cp\u003e\u0026dagger; difference between pre- and post-test, \u0026Dagger; difference between groups\u003c/p\u003e \u003cp\u003e*p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, ***p\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eChanges in IGF-1 Based on ACT Intensity\u003c/h2\u003e \u003cp\u003eTwo-way RM ANOVA of IGF-1 showed a significant interaction effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and a significant primary effect of time (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01; Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Paired t-tests revealed significant pre-to-post increases in IGF-1 in the HIIT, MICT, and PICT groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Between-group differences post-intervention were significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in IGF-1 based on aquatic cycling training intensity\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePost\u0026Dagger;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eΔ%\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ePost-hoc\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHIIT\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e115.02\u0026thinsp;\u0026plusmn;\u0026thinsp;16.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e151.73\u0026thinsp;\u0026plusmn;\u0026thinsp;11.12\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e2.395\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.084\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eb,d\u0026thinsp;\u0026lt;\u0026thinsp;a,c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMICT\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e118.44\u0026thinsp;\u0026plusmn;\u0026thinsp;16.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e140.81\u0026thinsp;\u0026plusmn;\u0026thinsp;17.87\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e18.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eT\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e91.022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePICT\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e117.68\u0026thinsp;\u0026plusmn;\u0026thinsp;26.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e154.62\u0026thinsp;\u0026plusmn;\u0026thinsp;16.86\u0026dagger;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e31.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG*T\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e12.725\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eControl\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e118.58\u0026thinsp;\u0026plusmn;\u0026thinsp;17.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e117.72\u0026thinsp;\u0026plusmn;\u0026thinsp;18.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.72\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eValues are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eG: group; T: time; G*T: group*time; \u003cem\u003eΔ%=\u003c/em\u003e[(post - pre)/pre] \u0026times; 100\u003c/p\u003e \u003cp\u003eHIIT: high-intensity interval aquatic cycling training, MICT: moderate-intensity continuous aquatic cycling training, PICT: progressive-intensity aquatic cycling training\u003c/p\u003e \u003cp\u003e\u003csup\u003e\u0026dagger;\u003c/sup\u003e difference between pre- and post-test, \u003csup\u003e\u0026Dagger;\u003c/sup\u003e difference between groups\u003c/p\u003e \u003cp\u003e*\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.05, **\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.01, ***\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eChanges in Cognitive Function Based on ACT Intensity\u003c/h2\u003e \u003cp\u003eA two-way RM ANOVA of MMSE scores identified a significant interaction effect (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and a significant primary effect of time (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01; Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Paired t-tests showed that MMSE scores increased significantly in the HIIT (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), PICT (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and MICT groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Between-group differences post-intervention were significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in cognitive function based on aquatic cycling training intensity\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePost\u003csup\u003e\u0026Dagger;\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eΔ%\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ePost-hoc\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHIIT\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.40\u0026thinsp;\u0026plusmn;\u0026thinsp;2.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28.20\u0026thinsp;\u0026plusmn;\u0026thinsp;1.31\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e1.129\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eNS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMICT\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e24.60\u0026thinsp;\u0026plusmn;\u0026thinsp;2.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e27.10\u0026thinsp;\u0026plusmn;\u0026thinsp;2.88\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e10.16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eT\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e35.349\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.001**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePICT\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e24.30\u0026thinsp;\u0026plusmn;\u0026thinsp;3.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e28.30\u0026thinsp;\u0026plusmn;\u0026thinsp;1.33\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e16.46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eG*T\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3.675\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.006*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eControl\u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.35\u0026thinsp;\u0026plusmn;\u0026thinsp;3.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24.20\u0026thinsp;\u0026plusmn;\u0026thinsp;2.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c8\" namest=\"c1\"\u003e \u003cp\u003eValues are presented as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003cp\u003eG: group; T: time; G*T: group*time; \u003cem\u003eΔ%=\u003c/em\u003e[(post - pre) / pre] \u0026times; 100\u003c/p\u003e \u003cp\u003eHIIT: High-intensity interval aquatic cycling training, MICT: Moderate-intensity continuous aquatic cycling training, PICT: Progressive-intensity aquatic cycling training, CG: control group\u003c/p\u003e \u003cp\u003e\u003csup\u003e\u0026dagger;\u003c/sup\u003edifference between pre- and post- test, \u003csup\u003e\u0026Dagger;\u003c/sup\u003edifference between groups\u003c/p\u003e \u003cp\u003e*\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.05, **\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.01, ***\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study investigated the effects of ACT at different intensities on functional fitness, BDNF, IGF-1, and cognitive function among older women. Functional fitness, encompassing muscle strength, CRF, flexibility, agility, and balance, is essential for independent living [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]; however, it declines with aging [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. Aquatic exercise leverages buoyancy (reducing joint loading) and multidirectional resistance (increasing energy cost and heart-rate response) to improve physical function [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], thus making it suitable for insufficiently active older adults [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, moderate-intensity continuous ACT significantly improved knee extensor strength but did not induce significant gains in knee flexor strength. Notably, progressive-intensity ACT improved both extensors and flexors. These findings align with prior reports revealing that appropriately loaded, faster-paced aquatic exercise enhances strength and functional fitness among older women [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. ACT promotes core stability and closed-kinetic-chain movement patterns, which can enhance balance, improve gait, and reduce the risk of falls.\u003c/p\u003e \u003cp\u003eAlthough no significant between-group differences were observed for CRF, all training groups showed rising statistics. Literature indicates that high-intensity interval training, dynamic, whole-body work involving upper and lower limbs, improves aerobic capacity and CRF [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. It also reports that progressive aquatic resistance/interval training benefits cardiovascular health and fitness [\u003cspan additionalcitationids=\"CR49 CR50 CR51\" citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. Therefore, high-intensity interval ACT, moderate-intensity continuous ACT, and progressive-intensity ACT all appear effective for improving physical fitness among older women; however, further research is warranted to refine training intensity, frequency, duration, and modality.\u003c/p\u003e \u003cp\u003eBDNF increased significantly across all training groups, with some intensity-based differences. This result is consistent with the notion that BDNF responses dependent on intensity [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. Because of the central role of BDNF in neuroplasticity and cognition and its age-related decline [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e], regular exercise-induced increases are meaningful for cognitive health [\u003cspan additionalcitationids=\"CR57 CR58 CR59\" citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. Similar to BDNF, IGF-1 increased significantly across all groups, with larger gains in the HIIT and PICT groups. Because IGF-1 supports muscle maintenance, metabolism, and strength but declines with age [\u003cspan additionalcitationids=\"CR62\" citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e], exercise-related upregulation, especially at higher intensities, aligns with prior findings [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e, \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e]. The energetic demands of water-based training (arising from buoyancy and multidirectional resistance) may further stimulate IGF-1 [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e], thereby supporting neural plasticity and cognitive improvement [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMMSE scores improved significantly across all training groups, with no differences based on intensity. This finding aligns with previous research reporting that aquatic aerobics and psychomotor programs enhance cognition among older adults [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan additionalcitationids=\"CR69\" citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e]. In this study, ACT incorporated various upper-limb patterns in addition to pedaling, thus providing diverse, repetitive stimuli that may have supported cognitive gains. Accordingly, ACT aimed at cognitive improvement should pair sufficient repetition with varied motor challenges.\u003c/p\u003e \u003cp\u003eOverall, intensity-specific ACT improved muscular function, neurotrophic profiles (IGF-1 and BDNF), and cognitive function among older women. The aquatic environment minimized joint stress, while supporting strength gains. These findings reveal that ACT may be a viable strategy to prevent age-related muscle loss, maintain independence, and promote healthy aging. In addition, its multimodal sensory input may enhance cognitive outcomes.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOver 16 weeks, high-intensity interval ACT, moderate-intensity continuous ACT, and progressive-intensity ACT all improved isokinetic knee extensor strength. Knee flexor strength improved markedly with high-intensity interval ACT and progressive-intensity ACT (and to a lesser extent with moderate-intensity continuous ACT). BDNF and IGF-1 increased significantly across all training groups. Cognitive function improved across groups without intensity-based differences. These findings indicate that, irrespective of intensity, ACT enhances muscular fitness and promotes neuroplasticity (through increased BDNF and IGF-1), thereby contributing to improved cognitive function among older women.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eACT \u0026nbsp; \u0026nbsp;aquatic cycling training\u003c/p\u003e\n\u003cp\u003eBDNF \u0026nbsp; brain-derived neurotrophic factor\u003c/p\u003e\n\u003cp\u003eIGF-1 \u0026nbsp; \u0026nbsp; insulin-like growth factor-1\u003c/p\u003e\n\u003cp\u003eCRF \u0026nbsp; \u0026nbsp; \u0026nbsp;cardiorespiratory fitness\u003c/p\u003e\n\u003cp\u003eHRR \u0026nbsp; \u0026nbsp; \u0026nbsp;heart rate reserve\u003c/p\u003e\n\u003cp\u003ePICT \u0026nbsp; \u0026nbsp; \u0026nbsp;progressive-intensity training\u003c/p\u003e\n\u003cp\u003eHIIT \u0026nbsp; \u0026nbsp; \u0026nbsp;high-intensity interval training\u003c/p\u003e\n\u003cp\u003eMMSE \u0026nbsp; \u0026nbsp;mini-mental state examination\u003c/p\u003e\n\u003cp\u003eMICT \u0026nbsp; \u0026nbsp; moderate-intensity continuous\u003c/p\u003e\n\u003cp\u003eRPE \u0026nbsp; \u0026nbsp; \u0026nbsp;rating of perceived exertion\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate\u003c/p\u003e\n\u003cp\u003eWrite text here Ethical approval for this study was obtained from the Institutional Review Board of Korea National Sport University (No. 20210817-116). All subjects voluntarily signed a written informed consent form before participating, having been fully briefed on the research objectives and protocols.\u003c/p\u003e\n\u003cp\u003eConsent for publication\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003eClinical trial number\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eConceptualization, C.Y., G.H.; methodology, C.Y., T.K.; investigation, C.Y., J.P, T.K. and G.H; data curation: J.P; writing\u0026mdash;original draft preparation, C.Y.; writing\u0026mdash;editing, T.K., G.H.; project administration, C.Y.\u003c/p\u003e\n\u003cp\u003eAll authors have read and agreed to the final version of the manuscript for publication.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThe authors extend their sincere gratitude to all participants in the exercise program.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHallal PC, Andersen LB, Bull FC, Guthold R, Haskell W, Ekelund U. Global physical activity levels: surveillance progress, pitfalls, and prospects. Lancet. 2012;380:247\u0026ndash;57.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu J, Wan CS, Ktoris K, Reijnierse EM, Maier AB. Sarcopenia is associated with mortality in adults: a systematic review and meta-analysis. Gerontology. 2022;68:361\u0026ndash;76.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHan A, Bokshan SL, Marcaccio SE, DePasse JM, Daniels AH. Diagnostic criteria and clinical outcomes in sarcopenia research: a literature review. J Clin Med. 2018;7:70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCollino S, Martin F-P, Karagounis LG, Horcajada MN, Moco S, Franceschi C, et al. Musculoskeletal system in the old age and the demand for healthy ageing biomarkers. Mech Ageing Dev. 2013;134:541\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eClouston SA, Brewster P, Kuh D, Richards M, Cooper R, Hardy R, et al. The dynamic relationship between physical function and cognition in longitudinal aging cohorts. Epidemiol Rev. 2013;35:33\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBherer L, Erickson KI, Liu-Ambrose T. Physical exercise and brain functions in older adults. J Aging Res. 2013;2013:197326.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eByun J-E, Kang E-B. The effects of senior brain health exercise program on basic physical fitness, cognitive function and BDNF of elderly women-a feasibility study. J Exerc Nutr Biochem. 2016;20:8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHogan M. Physical and cognitive activity and exercise for older adults: a review. Int J Aging Hum Dev. 2005;60:95\u0026ndash;126.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLista I, Sorrentino G. Biological mechanisms of physical activity in preventing cognitive decline. Cell Mol Neurobiol. 2010;30:493\u0026ndash;503.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEtnier JL, Chang Y-K. Exercise, cognitive function, and the brain: Advancing our understanding of complex relationships. J Sport Health Sci. 2019;8:299.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZigmond M, Smeyne RJ. Foreword: exercise and the brain. Brain Res. 2010;1341:1\u0026ndash;2.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLoprinzi PD, Herod SM, Cardinal BJ, Noakes TD. Physical activity and the brain: a review of this dynamic, bi-directional relationship. Brain Res. 2013;1539:95\u0026ndash;104.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSkriver K, Roig M, Lundbye-Jensen J, Pingel J, Helge JW, Kiens B, et al. Acute exercise improves motor memory: exploring potential biomarkers. Neurobiol Learn Mem. 2014;116:46\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan Praag H. Exercise and the brain: something to chew on. Trends Neurosci. 2009;32:283\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWhiteman AS, Young DE, He X, Chen TC, Wagenaar RC, Stern CE, et al. Interaction between serum BDNF and aerobic fitness predicts recognition memory in healthy young adults. Behav Brain Res. 2014;259:302\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVoss MW, Erickson KI, Prakash RS, Chaddock L, Kim JS, Alves H, et al. Neurobiological markers of exercise-related brain plasticity in older adults. Brain Behav Immun. 2013;28:90\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRatey JJ, Loehr JE. The positive impact of physical activity on cognition during adulthood: a review of underlying mechanisms, evidence and recommendations. Rev Neurosci. 2011;22(2):171\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePetzinger GM, Fisher BE, McEwen S, Beeler JA, Walsh JP, Jakowec MW. Exercise-enhanced neuroplasticity targeting motor and cognitive circuitry in Parkinson's disease. Lancet Neurol. 2013;12:716\u0026ndash;26.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKang D-w, Bressel E, Kim D-y. Effects of aquatic exercise on insulin-like growth factor-1, brain-derived neurotrophic factor, vascular endothelial growth factor, and cognitive function in elderly women. Exp Gerontol. 2020;132:110842.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eClerici I, Maestri R, Bonetti F, Ortelli P, Volpe D, Ferrazzoli D, et al. Land plus aquatic therapy versus land-based rehabilitation alone for the treatment of freezing of gait in Parkinson disease: a randomized controlled trial. Phys Ther. 2019;99:591\u0026ndash;600.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePerkins KM, Munguia N, Angulo A, Anaya C, Rios R, Velazquez L. Evaluation of aquafitness exercise on the physical and mental health of older women: a pilot study. J Women Aging. 2021;33:569\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBergamin M, Ermolao A, Tolomio S, Berton L, Sergi G, Zaccaria M. Water-versus land-based exercise in elderly subjects: effects on physical performance and body composition. Clin Interv Aging. 2013:1109\u0026ndash;17.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Castro LA, Felcar JM, de Carvalho DR, Vidotto LS, da Silva RA, Pitta F, et al. Effects of land-and water-based exercise programmes on postural balance in individuals with COPD: additional results from a randomised clinical trial. Physiotherapy. 2020;107:58\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeywood S, McClelland J, Geigle P, Rahmann A, Villalta E, Mentiplay B, et al. Force during functional exercises on land and in water in older adults with and without knee osteoarthritis: Implications for rehabilitation. Knee. 2019;26:61\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNaylor LH, Maslen BA, Cox KL, Spence AL, Robey E, Haynes A, et al. Land-versus water-walking interventions in older adults: Effects on body composition. J Sci Med Sport. 2020;23:164\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOh S, Lim J-M, Kim Y, Kim M, Song W, Yoon B. Comparison of the effects of water-and land-based exercises on the physical function and quality of life in community-dwelling elderly people with history of falling: a single-blind, randomized controlled trial. Arch Gerontol Geriatr. 2015;60:288\u0026ndash;93.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlberton CL, Zaffari P, Pinto SS, Reichert T, Bagatini NC, Kanitz AC, et al. Water-based exercises in postmenopausal women: Vertical ground reaction force and oxygen uptake responses. Eur J Sport Sci. 2021;21:331\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAndrade LS, Pinto SS, Silva MR, Schaun GZ, Portella EG, Nunes GN, et al. Water-based continuous and interval training in older women: Cardiorespiratory and neuromuscular outcomes (WATER study). Exp Gerontol. 2020;134:110914.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGraef FI, Pinto RS, Alberton CL, De Lima WC, Kruel LF. The effects of resistance training performed in water on muscle strength in the elderly. J Strength Cond Res. 2010;24:3150\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoreira NB, da Silva LP, Rodacki ALF. Aquatic exercise improves functional capacity, perceptual aspects, and quality of life in older adults with musculoskeletal disorders and risk of falling: A randomized controlled trial. Exp Gerontol. 2020;142:111135.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSilva LAd, Tortelli L, Motta J, Menguer L, Mariano S, Tasca G, et al. Effects of aquatic exercise on mental health, functional autonomy and oxidative stress in depressed elderly individuals: A randomized clinical trial. Clin (Sao Paulo). 2019;74:e322.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim J-H, Kim D-Y. Aquarobic exercises improve the serum blood irisin and brain-derived neurotrophic factor levels in elderly women. Exp Gerontol. 2018;104:60\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLippi G, Mattiuzzi C, Sanchis-Gomar F. Updated overview on interplay between physical exercise, neurotrophins, and cognitive function in humans. J Sport Health Sci. 2020;9:74\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLopez JF, Espinoza RV, Alvear-Vasquez F, Macedo LS, Velasquez DM, Pacco WR, et al. Systematic review of aquatic physical exercise programs on functional fitness in older adults. Eur J Transl Myol. 2021;31:10006.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRewald S, Mesters I, Lenssen A, Emans PJ, Wijnen W, de Bie RA. Effect of aqua-cycling on pain and physical functioning compared with usual care in patients with knee osteoarthritis: study protocol of a randomised controlled trial. BMC Musculoskelet Disord. 2016;17:88.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRewald S, Mesters I, Lenssen AF, Bansi J, Lambeck J, de Bie RA, et al. Aquatic cycling\u0026mdash;What do we know? A scoping review on head-out aquatic cycling. PLoS ONE. 2017;12:e0177704.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarabulut M, Abe T, Sato Y, Bemben MG. The effects of low-intensity resistance training with vascular restriction on leg muscle strength in older men. Eur J Appl Physiol. 2010;108:147\u0026ndash;55.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMacaluso A, De Vito G. Muscle strength, power and adaptations to resistance training in older people. Eur J Appl Physiol. 2004;91:450\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKeogh JW, Grigg J, Vertullo CJ. Is high-intensity interval cycling feasible and more beneficial than continuous cycling for knee osteoarthritic patients? Results of a randomised control feasibility trial. PeerJ. 2018;6:e4738.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMedicine ACS. ACSM's guidelines for exercise testing and prescription. Lippincott williams \u0026amp; wilkins; 2013.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFolstein MF, Folstein SE, McHugh PR. Mini-mental state: a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res. 1975;12:189\u0026ndash;98.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRikli RE, Jones CJ. Senior fitness test manual: Human kinetics; 2013.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRiebe D, Blissmer BJ, Greaney ML, Ewing Garber C, Lees FD, Clark PG. The relationship between obesity, physical activity, and physical function in older adults. J Aging Health. 2009;21:1159\u0026ndash;78.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTamin TZ, Loekito N. Aquatic versus land-based exercise for cardiorespiratory endurance and quality of life in obese patients with knee osteoarthritis: a randomized controlled trial. Med J Indones. 2018;27:284\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRezaeipour M, Nychyporuk VI, Raghi Z. Study of Anthropometric and Body Composition Variables in the Overweight/Obese, Sedentary Elderly Men Using WATERinMOTION Aqua Training: A Cross-sectional Study. Asian J Sports Med. 2021;12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBento PCB, Rodacki ALF. Muscle function in aged women in response to a water-based exercises program and progressive resistance training. Geriatr Gerontol Int. 2015;15:1193\u0026ndash;200.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoss LM, Porter RR, Durstine JL. High-intensity interval training (HIIT) for patients with chronic diseases. J Sport Health Sci. 2016;5:139\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMunukka M, Waller B, Rantalainen T, H\u0026auml;kkinen A, Nieminen MT, Lammentausta E, et al. Efficacy of progressive aquatic resistance training for tibiofemoral cartilage in postmenopausal women with mild knee osteoarthritis: a randomised controlled trial. Osteoarthritis Cartilage. 2016;24:1708\u0026ndash;17.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDepiazzi JE, Forbes RA, Gibson N, Smith NL, Wilson AC, Boyd RN, et al. The effect of aquatic high-intensity interval training on aerobic performance, strength and body composition in a non-athletic population: systematic review and meta-analysis. Clin Rehabil. 2019;33:157\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBroman G, Quintana M, Lindberg T, Jansson E, Kaijser L. High intensity deep water training can improve aerobic power in elderly women. Eur J Appl Physiol. 2006;98:117\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKwok MM, Ng SS, Man SS, So BC. The effect of aquatic High Intensity Interval Training on cardiometabolic and physical health markers in women: A systematic review and meta-analysis. J Exerc Sci Fit. 2022;20:113\u0026ndash;27.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNagle EF, Sanders ME, Franklin BA. Aquatic high intensity interval training for cardiometabolic health: benefits and training design. Am J Lifestyle Med. 2017;11:64\u0026ndash;76.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFerris LT, Williams JS, Shen C-L. The effect of acute exercise on serum brain-derived neurotrophic factor levels and cognitive function. Med Sci Sports Exerc. 2007;39:728\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKnaepen K, Goekint M, Heyman EM, Meeusen R. Neuroplasticity\u0026mdash;exercise-induced response of peripheral brain-derived neurotrophic factor: a systematic review of experimental studies in human subjects. Sports Med. 2010;40:765\u0026ndash;801.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeckie RL, Oberlin LE, Voss MW, Prakash RS, Szabo-Reed A, Chaddock-Heyman L, et al. BDNF mediates improvements in executive function following a 1-year exercise intervention. Front Hum Neurosci. 2014;8:985.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Melo Coelho FG, Gobbi S, Andreatto CAA, Corazza DI, Pedroso RV, Santos-Galdur\u0026oacute;z RF. Physical exercise modulates peripheral levels of brain-derived neurotrophic factor (BDNF): a systematic review of experimental studies in the elderly. Arch Gerontol Geriatr. 2013;56:10\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDuman CH, Schlesinger L, Russell DS, Duman RS. Voluntary exercise produces antidepressant and anxiolytic behavioral effects in mice. Brain Res. 2008;1199:148\u0026ndash;58.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhalil MH. The BDNF-Interactive Model for Sustainable Hippocampal Neurogenesis in Humans: Synergistic Effects of Environmentally-Mediated Physical Activity, Cognitive Stimulation, and Mindfulness. Int J Mol Sci. 2024;25:12924.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePiepmeier AT, Etnier JL. Brain-derived neurotrophic factor (BDNF) as a potential mechanism of the effects of acute exercise on cognitive performance. J Sport Health Sci. 2015;4:14\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJim\u0026eacute;nez-Maldonado A, Renter\u0026iacute;a I, Garc\u0026iacute;a-Su\u0026aacute;rez PC, Moncada-Jim\u0026eacute;nez J, Freire-Royes LF. The impact of high-intensity interval training on brain derived neurotrophic factor in brain: a mini-review. Front Neurosci. 2018;12:839.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eManini TM, Druger M, Ploutz-Snyder L. Misconceptions about strength exercise among older adults. J Aging Phys Act. 2005;13:422\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrater J, Lie D, Bartlett P, McGrath JJ. Insulin-like growth factor 1 (IGF-1) as a marker of cognitive decline in normal ageing: a review. Ageing Res Rev. 2018;42:14\u0026ndash;27.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNakamura Y, Tanaka K, Yabushita N, Sakai T, Shigematsu R. Effects of exercise frequency on functional fitness in older adult women. Arch Gerontol Geriatr. 2007;44:163\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRubin MR, Kraemer WJ, Maresh CM, Volek JS, Ratamess NA, Vanheest JL, et al. High-affinity growth hormone binding protein and acute heavy resistance exercise. Med Sci Sports Exerc. 2005;37:395\u0026ndash;403.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTsai C-L, Wang C-H, Pan C-Y, Chen F-C. The effects of long-term resistance exercise on the relationship between neurocognitive performance and GH, IGF-1, and homocysteine levels in the elderly. Front Behav Neurosci. 2015;9:23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShafei A, Fathi M, Ziaaldini MM. Comparison of the Effect of Eight Weeks of Water-Based Versus Land-Based Cycling on Serum Levels of Testosterone and IGF-1 in Elderly Men. Gene Cell Tissue. 2021;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarker AL, Talevski J, Morello RT, Nolan GA, De Silva RD, Briggs AM. Jumping into the deep-end: results from a pilot impact evaluation of a community-based aquatic exercise program. Clin Rheumatol. 2016;35:1593\u0026ndash;601.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHenwood T, Neville C, Baguley C, Beattie E. Aquatic exercise for residential aged care adults with dementia: benefits and barriers to participation. Int Psychogeriatr. 2017;29:1439\u0026ndash;49.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCheol-Gyu Y, Hyo-Ji P, Shin-Young L, Kang-Min L, Gi-Chul H, Jae-Ryang Y. Effects of Dementia Prevention Program according to the Type of Aquatic Exercise on Cognitive Function, Grip Strength and Risk Factors of Metabolic Syndrome in Elderly Women. Korean J Sport. 2020;18:499\u0026ndash;510.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWon-Suk J, Cheol-Gyo Y, Gi-Chul H, Jae-Ryang Y. Effect of aquatic interval training on muscle strength, cranial nerve growth factor (IGF-1) and cognitive function. Sport Sci. 2021;39:63\u0026ndash;70.\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":"Aquatic cycling, Fitness, Brain-derived neurotrophic factor, insulin-like growth factor-1, Cognitive function","lastPublishedDoi":"10.21203/rs.3.rs-9285643/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9285643/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThis study investigated the effects of aquatic cycling training (ACT) at varying intensities on muscle strength, cardiorespiratory fitness, brain-derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1), and cognitive function among older women.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eForty women aged 65\u0026ndash;74 years were randomly assigned to one of four groups: high-intensity interval ACT (HIIT; n\u0026thinsp;=\u0026thinsp;10), moderate-intensity continuous ACT (MICT; n\u0026thinsp;=\u0026thinsp;10), progressive-intensity ACT (PICT; n\u0026thinsp;=\u0026thinsp;10), and control groups (n\u0026thinsp;=\u0026thinsp;10). The intervention was conducted over 16 weeks, with three sessions weekly. Muscle strength (represented by isokinetic knee strength), cardiorespiratory fitness, BDNF, IGF-1, and cognitive function were measured before and after the intervention. A two-way repeated-measures (RM) analysis of variance (ANOVA) was performed to examine differences across groups and time.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eKnee extensor strength significantly improved across all training groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), with between-group differences observed. Knee flexor strength significantly increased in the HIIT and PICT groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), with partial differences between groups. Both BDNF and IGF-1 levels significantly increased across all training groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), with confirmed group differences. Cognitive function improved significantly across all training groups, but no intensity-based differences were found.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eSixteen weeks of ACT produces beneficial effects on functional fitness (represented by muscle strength and cardiorespiratory fitness), BDNF, IGF-1, and cognitive function among older women, irrespective of training intensity. Improvements in muscular strength and neurotrophic factors were influenced by exercise intensity, whereas cognitive gains were independent of intensity. These findings indicate that ACT is an effective and safe intervention for enhancing physical fitness and promote neuroplasticity, thereby contributing to improved cognitive function among older women.\u003c/p\u003e\u003ch2\u003eTrial registration\u003c/h2\u003e \u003cp\u003eClinical Research Information Service (CRIS), KCT0011903. Registered 27 April 2026 (Retrospectively registered).\u003c/p\u003e","manuscriptTitle":"Impact of Intensity-Specific Aquatic Cycling Training on Muscle Strength, Cardiorespiratory Fitness, Neurotrophic Factors, and Cognitive Function Among Older Women","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-14 17:42:18","doi":"10.21203/rs.3.rs-9285643/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"163401072222661834506781748144616249071","date":"2026-05-18T10:33:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"184578941998229409071875153011310728885","date":"2026-05-17T09:15:28+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-15T16:00:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"219660726646455960476477573527108060935","date":"2026-05-06T12:31:48+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-06T03:32:33+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-29T09:49:34+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-29T09:05:37+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-28T06:34:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Sports Science, Medicine and Rehabilitation","date":"2026-04-28T06:21:53+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":"9b3c745c-7594-4f50-ab8b-843582370765","owner":[],"postedDate":"May 14th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"163401072222661834506781748144616249071","date":"2026-05-18T10:33:07+00:00","index":61,"fulltext":""},{"type":"reviewerAgreed","content":"184578941998229409071875153011310728885","date":"2026-05-17T09:15:28+00:00","index":59,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-15T16:00:07+00:00","index":43,"fulltext":""},{"type":"reviewerAgreed","content":"219660726646455960476477573527108060935","date":"2026-05-06T12:31:48+00:00","index":42,"fulltext":""},{"type":"reviewersInvited","content":"23","date":"2026-05-06T03:32:33+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-29T09:49:34+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-29T09:05:37+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-14T17:42:19+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-14 17:42:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9285643","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9285643","identity":"rs-9285643","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}