Browsing by Author "Eyuboglu, Ender"

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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; Yildirim, Ulas 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.
Citation - WoS: 12
Citation - Scopus: 10
Impact of Detraining Process Experienced During the Covid-19 Pandemic on the Selected Physical and Motor Features of Football Players
(Mattioli 1885, 2020) Korkmaz, Sezgin; Aslan, Cem Sinan; Eyuboglu, Ender; Celebi, Murat; Kir, Ridvan; Karakulak, Izzet; Geri, Serdar
Study Objectives: The purpose of this study was to examine the changes in the selected physical and physiological properties of football players in the long-term detraining stage during the pandemic period. Methods: In this study, 14 semi-professional football players (mean age: 22.21 +/- 3.29 years old and mean height: 177.86 +/- 5.35 cm) took part voluntarily. The participants had remained in detraining in the home environment for 89 days until the final measurements, following the decision of cessation of the leagues made by the Turkish Football Federation, except soft and irregular exercises they did with theirbody weight. The participants' body composition characteristics, anaerobic performance, flexibility, and speed performance were measured. The descriptive statistics for numeric variables were expressed as mean standard deviation. Since parametric test assumptions were provided as a result of examining the data acquired from the experimental subjects via the Shapiro-Wilk test, the repetitive measurements were evaluated using the "Paired-Sample t-test". In addition, the mathematical differences between the two measurements were indicated with percentage. The results were evaluated at the confidence interval of 95% and the value p <0.05 was accepted to be significant. Results: Comparing the pretest-posttest results of the participants; the difference between the two measurements was statistically insignificant in terms of body weight, BMI, 30 m speed, and fatigue index properties, while the difference in terms of body muscle mass, fat mass, fat ratio, waist-hip ratio, peak power, average power, minimum power and flexibility properties was significant. Conclusion: A long-term detraining process significantly damages the physical and motor performance of football players.
Citation - WoS: 6
Citation - Scopus: 9
Is There Any Effect of Non-Suitable Pull Technique in Back & Leg Dynamometers on the Leg Strength Test Results
(Carbone Editore, 2019) Aslan, Cem Sinan; Karakulak, Izzet; Sahin, Fatma Nese; Eyuboglu, Ender
Introduction: Dynamometers are valid and reliable test instruments that have been used for many years to measure strength. However, there are excessive differences in leg strength scores in different studies with similar groups. This situation suggests a non-conformity to testing procedures occurred during the practice of the tests. The purpose of this study was to determine the effect of non-suitable pulling technique on the leg strength test results. Materials and methods: A total of 127 healthy subjects (24 female athletes and 41 male athletes, 22 sedentary females and 40 sedentary males) were included in the study. A back & leg Dynamometer was used to determine the leg strength of the participants. The participants pulled up the dynamometer's grab handle with and without contact with their upper leg. Results: The results showed that there was a significant difference (p=0.000) between contacted and non-contact pulling trials of all participants. The percentage difference of leg strength between contacted and non-contact pull was 51.69% (43.25 kg) for female athletes, 54.78 (73.46 kg) for male athletes, 5631% (37.52 kg) for sedentary females, and 50.69% (65.55 kg) for sedentary males. Conclusion: There were significant differences between contacted and non-contact pull trials. It was determined that during the pulling phase if the dynamometer's grab-handle contacted the upper leg of a subject, the strength measurement's score increased considerably. In this case, it can be said that non-suitable pulling technique in the "back & leg dynamometers" affects the leg strength test scores.
Kültüre Özgü Mükemmeliyetçilik Örüntüleri: Çocuk Sporcular, Ebeveynleri ve Antrenörleri
(2025) Karakulak, İzzet; Tez, Özge Yavaş; Eyuboglu, Ender; Erkan, Dilara
Araştırmada, Türk kültürüne özgü spora ilişkin mükemmeliyetçilik örüntüleriyle ilişki olarak rekreasyonel amaçlı çeşitli sporlarla uğraşan çocuk sporcuların spora ilişkin mükemmeliyetçilik düzeylerinin demografik değişkenler açısından incelenmesi amaçlanmıştır. Kolayda örnekleme yöntemi gerçekleştirilen araştırmaya Türkiye’de çeşitli illerdeki spor kulüpleri altında yer alan rekreasyonel amaçlı çeşitli sporlarla (voleybol, futbol, yüzme, tenis, cimnastik ve basketbol) ilgilenen 394 çocuk sporcudan veriler toplanmıştır. Veri toplama aracı olarak “Sporda Mükemmel Performans Ölçeği (Çocuk Formu)” kullanılmıştır. Verilerin analizinde tanımlayıcı istatistikler, T-testi, Anova, Post-Hoc analizleri kullanılmıştır. T-testi analizi sonuçları, cinsiyet ve yaş değişkenleri ile cinsiyet, ebeveyn baskısı ve antrenör baskısı değişkenlerinin performans mükemmeliyetçiliği ile anlamlı bir ilişkisi olduğunu göstermiştir (p