The Effect of Caffeine on Enhancing Muscle Activity After Fatigue in Explosive Exercises: A Study on Sports Performance with an Electromyographic Approach

Background and Objective: Exhaustive exercise induces fatigue that can compromise muscle performance, particularly in explosive movements such as the Sargent jump, which requires maximal power output. Caffeine, widely recognized as an ergogenic aid, may mitigate fatigue-related declines in neuromuscular function. This study aimed to evaluate the effect of caffeine consumption following exhaustive exercise on the electromyographic (EMG) activity amplitude of lower limb muscles during the Sargent jump in male students, hypothesizing that caffeine would enhance muscle activation post- fatigue.

Methods: A randomized, double-blind, placebo-controlled trial was conducted with 30 healthy male students aged 19–25 years, randomly allocated to an experimental group (n=15) and a control group (n=15). Both groups underwent an identical exhaustive exercise protocol, consisting of high-intensity aerobic cycling until volitional exhaustion, designed to induce significant neuromuscular fatigue. Post-exercise, the experimental group received 6 mg of caffeine per kilogram of body weight, while the control group received a placebo (a tasteless, caffeine-free solution). Electromyographic activity was recorded from eight lower limb muscles—medial gastrocnemius, rectus femoris, biceps femoris, semitendinosus, semimembranosus, vastus medialis, vastus lateralis, and gluteus maximus — during the Sargent jump in two phases: pre-test (before the exhaustive exercise) and post-test (after caffeine/placebo administration). EMG signals were captured using surface electrodes, normalized to maximum voluntary contraction, and analyzed for amplitude changes. Data were processed using two-way repeated-measures ANOVA in SPSS version 24, with a significance threshold of 0.05.

Results: Statistical analysis revealed a significant time effect on the EMG activity amplitude of the medial gastrocnemius during the Sargent jump (P=0.039, d=0.258), with post-test amplitudes significantly lower than pre-test values, indicating fatigue-induced reductions. A significant group effect was observed for the rectus femoris (P=0.013, d=0.483) and biceps femoris (P=0.041, d=0.374), where the caffeine group exhibited significantly higher EMG amplitudes compared to the placebo group in the post-test. No significant differences were noted for the other muscles, suggesting selective effects of caffeine on specific muscle groups.

Conclusion: Caffeine consumption post-exhaustive exercise significantly enhances the EMG activity amplitude of the rectus femoris and biceps femoris during the Sargent jump, likely due to its stimulatory effects on the central nervous system and reduction of neuromuscular fatigue. These findings highlight caffeine’s potential as an ergogenic aid for improving explosive power performance in fatigued states. Future research should investigate optimal caffeine dosages, timing of administration, and its effects across varied exercise modalities to further elucidate its ergogenic benefits.

Keywords: Electromyography, Muscle fatigue, Rehabilitation, Performance-Enhancing Substances.