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    Acute effects of combined and isolated caffeine and theanine supplementation on physical and cognitive performance in competitive athletes: a randomized, double-blind, placebo-controlled crossover study
    (Frontiers Media Sa, 2026) Tuncer, Selin Yildirim; Ozdenk, Serhat; Yildirim, Ulas Can; Erkan, Dilara; Sari, Cengizhan; Gundem, Mehmet Can; Sar, Halit
    Introduction Modern athletic performance is driven not only by physical capacity but also by rapid decision-making, attentional control, and visuomotor coordination. Evidence regarding the acute effects of caffeine (CAF), L-theanine (TEA), and their combination remains inconsistent, particularly with respect to their combined influence on physical and cognitive performance in athletic populations. This study examined the acute effects of isolated and combined CAF and TEA supplementation on maximal strength, intermittent aerobic endurance, and eye-hand coordination in competitive athletes. It was hypothesized that the combined ingestion of CAF and TEA would differentially affect physical performance and eye-hand coordination outcomes compared with isolated CAF or TEA intake.Methods Twenty trained athletes completed four randomized, double-blind, placebo-controlled crossover conditions: CAF (3 mgkg-1), TEA (200 mg), CAF+TEA (COM), and placebo (CON), with >= 72 h washout. Outcomes included isometric leg, back, and handgrip strength; Yo-Yo Intermittent Endurance Test Level 1 performance; and visuomotor coordination (CogniFit (R)). Data were analyzed using repeated-measures ANOVA with Bonferroni corrections (alpha = 0.05).Results Condition effects were found for leg strength (p = 0.004, eta p2 = 0.24) and back strength (p = 0.008, eta p2 = 0.19). In the COM condition, no additional or synergistic effect on maximal strength was observed. Additionally, no significant difference was found between the conditions in aerobic endurance, maximum isometric handgrip strength, and hand-eye coordination results. Caffeine ingestion did not differ from placebo for any strength outcome under the present conditions. Finally, acute ingestion of TEA was associated with reduced maximal isometric leg and back strength compared with CAF and CON.Discussion Findings challenge the prevailing assumption of CAF + TEA synergy and underscore the need for task-specific interpretation of co-supplementation strategies. Future studies should evaluate dose-response interactions, habitual caffeine intake, sex-specific responses, and broader cognitive domains beyond visuomotor control. The randomized controlled trial was registered at ClinicalTrials.gov, under the registration number NCT07268573.Clinical Trial Registration ClinicalTrials.gov, NCT07268573.
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    Psychometric properties of the Turkish coach motivation questionnaire (CMQ-TR)
    (Routledge Journals, Taylor & Francis Ltd, 2025) Atasoy, Fatih Samet; Sar, Halit; Hasan Abaci, Samet; Mallett, Clifford J.; Cankaya, Soner
    Coaches' motivation is central to coaching practices including how and why they coach; however, studies examining coach motivation across different cultural contexts remains limited. Indeed, context matters. In the present study, we aimed to conduct initial validity and reliability assessment of the Turkish version of the Coach Motivation Questionnaire (CMQ; McLean, Mallett, & Newcombe (2012). Assessing coach motivation: The development of the coach motivation questionnaire (CMQ). Journal of Sport & Exercise Psychology, 34(2), 184-207). A total of 578 currently working coaches (145 females, 433 males) aged between 22 and 70 years (M = 32.4, SD = 11.04) voluntarily participated in the study. The Turkish adaptation of the CMQ (CMQ-TR) consists of 22 items and six subscales, including External Regulation, Introjected Regulation, Identified Regulation, Integrated Regulation, Intrinsic Motivation, and Amotivation, rated on a 7-point Likert scale. Confirmatory Factor Analysis (CFA) was employed to assess construct validity, while Cronbach's alpha and Composite Reliability (CR) coefficients were used to examine internal consistency. The CFA results indicated that the factor loadings of the items ranged from 0.37 to 0.92, and the model demonstrated good and acceptable fit indices: chi(2)/df = 2.31, RMSEA = 0.048, NFI = 0.97, NNFI = 0.98, CFI = 0.98, GFI = 0.94, AGFI = 0.91. Internal consistency values for the subscales ranged between 0.691 and 0.894, indicating acceptable reliability. The findings provide preliminary evidence that the CMQ-TR is a valid and reliable tool for assessing coach motivation. However, further psychometric studies with diverse sample groups are recommended to continue to examine the scale's robustness and suitability.
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    The effect of low dose caffeine powder supplementation on serve speed, spike speed, and speed-endurance in elite sitting volleyball players: a randomized double-blind crossover study
    (Bmc, 2025) Diedhiou, Azize Bingol; Erkan, Dilara; Guler, Melek; Sar, Halit; Karakulak, Izzet; Eyuboglu, Ender; Gundem, Mehmet Can
    BackgroundSitting volleyball relies heavily on upper-body strength and anaerobic capacity. Serve, spike, and speed-endurance are decisive skills, yet the ergogenic potential of low-dose caffeine in this Paralympic sport remains unclear.PurposeTo examine the acute effects of low-dose caffeine (3 mg/kg) supplementation on serve speed, spike speed, and speed-endurance in elite sitting volleyball players.MethodsUsing a randomized, double-blind, crossover design, 13 elite male athletes from the Turkish National Sitting Volleyball Team completed serve speed, spike speed, and speed-endurance tests under caffeine (CAF) and placebo (PLA) conditions.ResultsCaffeine intake produced a moderate improvement in serve speed (p = 0.028, d = 0.460); however, this effect did not remain statistically significant after Bonferroni correction (adjusted p = 0.084). No significant effects were observed for spike speed (p = 0.547, d = 0.166) or speed-endurance performance (p = 0.709, d = 0.111). Perceived exertion during the speed-endurance test was similarly high in both conditions.ConclusionsLow-dose caffeine may offer a trend toward improved serve performance, but the effect was not robust after statistical adjustment, and no benefits were observed for spike speed or speed-endurance. These findings highlight that caffeine's ergogenic effects are context-dependent and shaped by task complexity and sport-specific motor demands. Further research with larger and more diverse samples, genotype-based subgroups, and varied dosing strategies is warranted to clarify caffeine's role in adaptive sports.Trial registrationThe randomized controlled trial was retrospectively registered on 21/06/2025 at ClinicalTrials.gov, under the registration number NCT07056231.
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    The Effects of FIFA 11+and Harmoknee Warm-Up Protocols on Flexibility, Vertical Jump and Shooting Speed in Female Football Players: A Comparative Study
    (Mdpi, 2025) Sar, Halit; Celgin, Gurkan Selim; Arslanoglu, Cansel; Kizilors, Gizem; Arslanoglu, Erkal; Ceylan, Levent; Kucuk, Hamza
    Background/Objectives: The aim of this study was to compare the acute effects of the FIFA 11+ and Harmoknee warm-up protocols in female football players on flexibility, vertical jump, and shooting speed performance. Methods: This study involved 17 female football players who volunteered to participate, had no history of medical conditions, maintained regular menstrual cycles (28 +/- 2 days, range: 26-33 days) in the three months preceding the study, and consistently engaged in football training. The Harmoknee and FIFA 11+ neuromuscular warm-up protocols were applied to the study group on different days, 48 h apart. After the exercises, athletes were tested for flexibility, vertical jump, and shooting speed. Two trials were allowed for each test, with a 3 min break between trials. The Shapiro-Wilk test was used to check for normality, and an independent sample t-test was used to compare groups. The p-value was set at <0.05 to determine statistical significance. Results: When comparing warm-up protocols, it was established that the FIFA 11+ neuromuscular warm-up protocol positively affects athletes' vertical jump performance compared to other protocols (p < 0.05). In conclusion, the FIFA 11+ warm-up protocol resulted in better vertical jump performance in female soccer players compared to the Harmoknee warm-up routine. The FIFA 11+ protocol activates leg muscles, and balance exercises improve the neuromuscular characteristics of the warm-up compared to the Harmoknee protocol.