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    Acute effect of different doses of caffeinated chewing gum on exercise performance in caffeine-habituated male soccer players
    (Frontiers Media Sa, 2023) Yildirim, Ulas Can; Akcay, Neslihan; Alexe, Dan Iulian; Esen, Ozcan; Gulu, Mehmet; Cirtita-Buzoianu, Cristina; Cinarli, Fahri Safa
    The ergogenic benefits of caffeine have been well established, but there is scarce research on its chewing gum form. The present research aimed to examine the effects of different doses (100 and 200 mg) of caffeinated chewing gum on muscle strength, vertical jump performance, and ball-kicking speed in trained male soccer players. In a double-blind, randomized counterbalanced, and crossover research design, 14 male soccer players (age = 22 +/- 2 y; body mass = 74.2 +/- 7.1 kg; height = 180.0 +/- 6.8 cm; habitual caffeine intake = 358.9 +/- 292.4 mg/day) participated in three experimental trials. In each trial, participants performed isometric handgrip strength, quadriceps and hamstring strength, ball-kicking speed, and 15 s countermovement jump test 10 min after chewing 100 mg (LCAF) or 200 mg (MCAF) of caffeinated gum or placebo (PLA). MCAF improved quadriceps strength (53.77 +/- 5.77 kg) compared to LCAF (49.62 +/- 8.81 kg, p = 0.048) and PLA (49.20 +/- 7.20 kg, p = 0.032). However, neither LCAF nor MCAF had a significant effect on the isometric handgrip and hamstring strength, ball-kicking speed, and 15 s countermovement jump test (all p > 0.05). These findings support chewing gum as an alternative mode of caffeine administration which can be used as a nutritional ergogenic aid for trained soccer players, at least for quadriceps strength.
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    Biochemical Effects of Long-Term Exercise on Oxidative Stress and Antioxidant Markers in Adolescent Female Athletes
    (Mdpi, 2025) Bilici, Omer Faruk; Erkan, Dilara; Alexe, Dan Iulian; Tohanean, Dragos Ioan; Demir, Canan; Alexe, Cristina Ioana; Voiculescu, Virgil Ene
    Background: Adolescence is a critical period where exercise-induced oxidative stress is modulated by both training adaptations and hormonal changes, particularly the antioxidant effects of estrogen in females. However, data on how adolescent female athletes respond to long-term exercise remain limited. The aim of this study was to examine oxidative stress levels and some antioxidant defense parameters in adolescent female athletes who train regularly. Methods: The study included 20 adolescent female basketball players (16.65 +/- 0.67 years; 165.50 +/- 0.06 cm; 59.75 +/- 5.50 kg) with at least three years of training experience and 20 non-athlete adolescent female participants (16.80 +/- 0.69 years; 159.95 +/- 0.04 cm; 60.15 +/- 4.23 kg). Malondialdehyde (MDA), glutathione (GSH), and catalase (CAT) levels were analyzed by a spectrophotometric method using a UV/VIS spectrophotometer in blood samples taken from all participants, and the data were compared between the groups. Results: The results showed that MDA levels were significantly lower in the athlete group (p < 0.01; d = 4.78). In addition, CAT activity was significantly higher in athletes compared to non-athletes (p < 0.01; d = 7.81). However, no significant difference was observed in GSH levels between the groups (p > 0.05; d = 0.15). A strong negative correlation was found between MDA and CAT (r = -0.900). Conclusions: These findings suggest that prolonged exercise reduces oxidative stress and enhances catalase-mediated antioxidant defense in adolescent women. Increased CAT activity and decreased MDA levels support this effect, while stable GSH levels point to the role of compensatory mechanisms.
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    Caffeine Improves Sprint Time in Simulated Freestyle Swimming Competition but Not the Vertical Jump in Female Swimmers
    (Mdpi, 2024) Acar, Kuersat; Mor, Ahmet; Mor, Hakki; Kargin, Zehra; Alexe, Dan Iulian; Abdioglu, Mekki; Karayigit, Raci
    Caffeine (CAF) has been shown to be an effective ergogenic aid in enhancing sports performance, including vertical jump (VJ), sprint, balance, agility, and freestyle swimming performance (FSP). However, whether acute CAF supplementation improves FSP in moderately trained female swimmers has not been well documented. Therefore, this study aimed to investigate the effects of CAF intake on vertical jump, balance, auditory reaction time (ART), and swimming performance in female swimmers. In a double-blind, cross-over design, eight moderately trained female swimmers (age: 21.3 +/- 1.4 years, height: 161.2 +/- 7.1 cm, body mass: 56.3 +/- 6.7 kg, body mass index (BMI): 21.9 +/- 1.3 kg/m(2), and habitual CAF intake: 246.4 +/- 111.4 mg/day) ingested caffeine (CAF) (6 mg/kg) or a placebo (PLA) 60 min before completing VJ, balance, ART, and 25/50 m FSP. CAF supplementation resulted in a significantly lower time both in 25m (p = 0.032) and 50m (p = 0.033) FSP. However, CAF resulted in no significant difference in VJ, ART, and RPE (p > 0.05). Balance test results showed a non-significant moderate main effect (d = 0.58). In conclusion, CAF seems to reduce time in short-distance swimming performances, which could be the determinant of success considering the total time of the race. Thus, we recommend coaches and practitioners incorporate CAF into swimmers' nutrition plans before competitions, which may meet the high performance demands.
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    Effects of isolated or combined carbohydrate and caffeine supplementation on tennis training performance: single-blind randomized placebo-controlled crossover session
    (Frontiers Media Sa, 2025) Abdioglu, Mekki; Mor, Ahmet; Alexe, Dan Iulian; Todor, Raul Marian; Panaet, Elena Adelina; Alexe, Cristina Ioana; Akca, Firat
    Background In long tennis matches, the number of unforced errors in groundstrokes increases. However, players need to maintain their successful strokes consistently in order to be successful in matches. To overcome this situation, tennis players utilize certain ergogenic supplements. In order to determine the most effective ergogenic supplement on players' performance, it is aimed to investigate the effects of caffeinated chewing gum (CAFGUM), carbohydrate gel (CHOGEL) and cho gel + cafe gum (CHOGEL + CAFGUM) on tennis players' basic strokes, countermovement jumps (CMJ), heart rate (HR), ratings of perceived exertion (RPE) and gastrointestinal discomfort in a training session.Method The study included 14 male tennis players (mean age: 15.93 +/- 0.83 years, height: 173.86 +/- 6.89 cm, and body mass: 60.64 +/- 2.58 kg) with experience in national and international tournaments. Players ingested CHOGEL (21.1 g) + CAFGUM (100 mg) or CHOGEL (21.1 g) + gum placebo (PLAGUM) or CAFGUM (100 mg) or PLAGUM before a high-intensity workout and at the end of each set.Results The CHOGEL + CAFGUM session performed better groundstrokes than the control (CON) (p = 0.001) and the PLAGUM sessions (p = 0.001). When total RPE values were considered in the training session, the CHOGEL + CAFGUM session had lower RPE scores than the CON (p = 0.010) and PLAGUM (p = 0.044) sessions. The CHOGEL + PLAGUM session had significantly lower RPE scores than the CON (p = 0.005) and PLAGUM (p = 0.005) sessions. The CAFGUM session had significantly lower RPE scores than the CON (p = 0.013). It was observed that no supplements significantly affected either HR (p = 0.188) or CMJ (p = 0.349) scores.Conclusions In conclusion, there was a significant difference on basic strokes and RPE scores between CHOGEL + CAFGUM supplementation used before and during training compared with the control session. At the same time, there was no significant performance outcomes between CHOGEL and CAFGUM sessions.
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    Moderate-dose caffeine enhances anaerobic performance without altering hydration status
    (Frontiers Media Sa, 2024) Mor, Ahmet; Acar, Kursat; Alexe, Dan Iulian; Mor, Hakki; Abdioglu, Mekki; Man, Maria Cristina; Karakas, Fatih
    The effects of direct nutritional supplements on athletic performance are still being investigated and arouse curiosity. Only one study in the literature was found that investigated the kicking speed performance of futsal players following low-dose caffeine supplementation (3 mg/kg); thus, the question of whether caffeine supplementation improves kicking speed as well as essential physical parameters in soccer players is still controversial. Therefore, the aim of this study was to determine the effect of caffeine supplementation on vertical jump (VJ), sprint, reaction time, balance, change of direction (COD), and ball-kicking speed in soccer players. In a double-blind, cross-over design, nine moderately trained male soccer players (21.11 +/- 2.02 years, 171.22 +/- 6.14 cm, 71.78 +/- 10.02 kg) consumed caffeine (6 mg/kg) or a placebo 60 min before completing balance, reaction time, vertical jump, agility, 30 m sprint, and ball-kicking speed tests. Greater VJ height (p = 0.01) and power (p = 0.08), and faster completion time according to the Illinois Agility Test (p = 0.08) were found following caffeine supplementation compared to placebo. Elapsed time (p = 0.01), average (p = 0.01) time, and the slowest reaction times (p = 0.016) were significantly reduced after caffeine consumption compared to placebo supplementation. Caffeine intake significantly improved VJ, agility, and reaction time (p < 0.05) but did not affect 30 m sprint, ball-kicking speed, balance, and RPE values in soccer players (p > 0.05). Although non-significant, caffeine intake also improved sprint (0.67%) and ball kicking (2.7%) performance percentages. Also, caffeine consumption did not induce dehydration, and the athletes' body hydration levels were normal. These findings support the use of caffeine supplementation as an effective nutritional ergogenic aid to enhance anaerobic performance, at least for vertical jumps, COD speed, and reaction time, in trained male soccer players.