EFFECTS OF ACUTE CAFFEINE SUPPLEMENTATION ON ISOKINETIC STRENGTH AND FATIGUE IN RESISTANCE-TRAINED VERSUS UNTRAINED INDIVIDUALS

The purpose of this study was to examine the acute effects of two doses of caffeine on measures of maximal strength, fatigue, and neuromuscular activity between trained and untrained individuals. Fifteen lower-body resistance-trained and fifteen non-resistance-trained male volunteers (mean ± SD, age: 22.13 ± 3.18 years; height: 173.33 ± 6.62 cm; body mass: 79.50 ± 13.03 kg; body fat: 21.65 ± 10.67%) visited the laboratory four times. The first visit was a familiarization visit where participants tested their body composition. During the remaining three visits, participants ingested a randomly assigned drink containing either a placebo, a moderate dose, or a high dose of caffeine (0, 4, and 8 mg·kg−1 of body mass, respectively) sixty minutes before testing. Participants performed three maximal voluntary isometric contractions of the knee extensors, followed by three maximal isokinetic contractions at three separate velocities (60, 180, and 300°·s-1) using isokinetic dynamometry, and then finished by performing fifty isokinetic contractions to assess fatigue. Peak isokinetic torque, torque decline, electromyographic and mechanomyographic amplitude and mean power frequency were measured for the right knee extensors. The results indicated that caffeine did not significantly affect maximal strength, fatigue, or any measure of neuromuscular activity (p > 0.05) when compared to the placebo. These findings suggest that neither a moderate nor a high dose of caffeine provides performance enhancements during isokinetic knee extensions.