Effects of Acute Caffeine Supplementation on Isokinetic Strength and Fatigue in Resistance-Trained vs. Nonresistance-Trained Individuals

Abstract Elies, AA, Rubin, DA, Costa, PB, and Coburn, JW. Effects of acute caffeine supplementation on isokinetic strength and fatigue in resistance-trained vs. nonresistance-trained individuals. J Strength Cond Res XX(X): 000–000, 2026—This study examined the acute effects of 2 caffeine doses on maximal strength, fatigue, and neuromuscular activity of the knee extensors between resistance-trained and nonresistance-trained individuals. Fifteen lower-body resistance-trained and 15 nonresistance-trained men (mean ± SD , age: 22.1 ± 3.2 years; height: 173.3 ± 6.6 cm; body mass: 79.5 ± 13.0 kg; body fat: 21.7 ± 10.7%) completed 4 visits. The first visit involved protocol familiarization and body composition assessment using air-displacement plethysmography. During the remaining 3 visits, subjects ingested a randomly assigned drink containing either a placebo, a moderate dose, or a high dose of caffeine (0, 4, or 8 mg·kg −1 of body mass, respectively) 60 minutes before testing. Subjects then performed a total of 9 maximal isokinetic knee extensions—3 contractions at each of 3 separate velocities (60, 180, and 300°·s −1 )—to determine muscular strength, followed by 50 maximal isokinetic contractions to assess fatigue. Peak isokinetic torque, torque decline, and electromyographic and mechanomyographic amplitude and mean power frequency were measured for the right knee extensors. The results indicated that caffeine did not differentially affect maximal strength, fatigue, or any measure of neuromuscular activity ( p > 0.05) in either group compared with the placebo. These findings suggest that neither a moderate nor a high dose of caffeine provides performance enhancements during isokinetic knee extensions.