Effects of low dose caffeinated coffee consumption on energy system contributions and repeated sprint indices in combat sports athletes

Caffeine research has mostly examined anhydrous capsules between 3 and 13 mg·kg − 1 , doses of 3 mg·kg − 1 and above generally have ergogenic effects. Little is known about doses of 3 mg·kg − 1 or below given as coffee, the form athletes usually consume. Therefore, the present study compared two low doses within the same form; the acute effects of 1.5 and 3 mg·kg − 1 of caffeine as regular coffee against a decaffeinated coffee as placebo on repeated sprint performance and energy system contributions. No anhydrous caffeine form was included, so this was not a coffee vs. capsule comparison. Fifteen national level male combat sports athletes (age 20.4 ± 1.6 years; height 176.3 ± 4.1 cm; body mass 68.1 ± 5.9 kg) completed three sessions with 48 h interval in a double-blind, placebo-controlled, randomized crossover design. Repeated sprint test was conducted on a cycle ergometer one hour after supplementation; peak and mean power, fatigue index, perceived exertion, delta lactate, peak heart rate and estimated energy system contributions were measured. No statistically significant differences detected between the conditions in any performance related variable (all p > 0.05) or in estimated energy system contributions. The effect sizes were consistently small (η 2 p ≤ 0.01) for performance metrics; however, effect sizes were medium to large for estimated energy system contributions. However, the results of model-based estimation did not show any statistically significant difference between the conditions. No statistically significant changes were detected between the placebo, 1.5 and 3 mg·kg − 1 conditions for any performance, physiological or energy system variables. Future research should aim to evaluate possible effects with a larger sample, including both male and female athletes across different age groups and training levels. Registration of Clinical Trial : The randomized controlled trial registration with the ID: NCT07596511.