This study investigated the effects of caffeine supplementation on quadriceps muscular endurance in resistance-trained and untrained women. Caffeine is a widely consumed psychoactive substance that is a safe and effective ergogenic aid that enhances alertness, athletic performance, mood, and energy levels and reduces fatigue. Caffeine is a widely known substance used to improve muscular performance. However, very little research has looked into its ergogenic effects on women to improve muscular performance, nor has it directly compared resistance-trained and untrained women. Nine women (N=9) were recruited for the study: five trained (n=5) and four untrained (n=4). Participants completed as many repetitions as possible at 60% of one repetition maximum on the leg extension machine in three conditions (caffeine, placebo, control) in a counterbalanced manner. 200 mg of caffeine or a placebo was consumed 60 minutes before completing the trial. It was hypothesised that caffeine would increase the repetitions complete, and that trained participant’s would complete more repetitions than untrained participant’s. Results revealed a significant, large main effect for the condition (when the groups’ data were combined) (p < .001). Furthermore, there was no significant interaction between groups (p = .815), showing no statistical difference between the trained and untrained groups in repetitions complete in each condition. The results align with current literature on improving individuals’ muscular endurance performance after caffeine supplementation. However, these findings and literature produce inconsistent results when comparing trained and untrained individuals. Thus, this study suggests that caffeine supplementation should be implemented in training and competitions to improve muscular endurance performance.
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