The Effect of Caffeine Supplementation on Muscular Endurance in Recreationally Active College Age Males

Objective: Caffeine is a drug consumed regularly by approximately 90% of adults worldwide, primarily due to its ability to reduce fatigue and increase wakefulness. The benefit of caffeine consumption on athletic performance in large doses (3-9 mg/kg body weight or BW) is frequently documented in aerobic athletes. The benefits of caffeine supplementation in resistance training variables, such as muscular endurance, has shown mixed results, partially due to the inconsistency of testing variables. Furthermore, while caffeine supplementation shows promising ergogenic effects in muscular endurance in elite athletes, it is unknown if this effect translates to the recreational athlete. Therefore, the purpose of this study is to observe the potential ergogenic effect caffeine supplementation may have in recreational athletes and to consider how caffeine habituation may influence individuals’ response to a high dosage of 7 mg/kg BW. Design: This study used a randomized, double-blind crossover design. Subjects performed bench press and Smith machine squat repetitions to failure using 60% of their respective one repetition maximum (1RM), vertical jump, and isometric squat tests. Subjects consumed either caffeine equivalent to 7 mg/kg BW or placebo 60 minutes prior to testing. Test sessions were separated by 7 days. Number of complete bench press and Smith machine squat repetitions, vertical jump height, and isometric power were evaluated. Rating of perceived exertion (RPE) was also recorded and assessed. A repeated measures analysis of variance (ANOVA) was used to determine differences between treatments. Subjects: Subjects were healthy college age males with at least 6 months of prior strength training experience (n=23, 22.0±2.2 years). Results: There was no effect of treatment order. There was a significant increase in bench press repetitions to failure between caffeine (18.9±3.7) and placebo (17.3±3.7, p=0.002). There was a significant increase in Smith machine squat repetitions to failure between caffeine (17.2±4.7) and placebo (15.3±4.5, p=0.018). No significant difference was found in vertical jump or isometric force plate tests between treatments. RPE was not statistically different between treatments. Conclusions: This study suggests that acute caffeine supplementation equivalent to 7 mg/kg BW has an ergogenic effect in recreationally trained males in resistance training exercises. RPE was not statistically different between treatments, indicating that caffeine supplementation may also reduce perception of exertion relative to the amount of work performed immediately following a bout of high-intensity resistance exercise to failure.