Plain language summary
Caffeine is a common ingredient in tea, coffee, chocolate, soft drinks and multi-ingredient pre-workout supplements. It is believed to elicit an ergogenic effect that enhances athletic performance. However, only very few studies have examined the effect of caffeine on women who take contraceptive pills. The aim of this double-blind, randomised, counterbalanced, crossover trial was to investigate the ergogenic effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females taking contraceptives. Fourteen women were randomised to consume doses of 3 and 6 mg·kg−1 body mass of caffeine supplement or placebo thirty minutes prior to the exercise. Caffeine supplementation at 3 and 6 mg·kg−1 body mass significantly improved muscular endurance and total strength. No significant difference was observed between the higher and lower doses of caffeine in improving performance, indicating that the lower dose can potentially provide the same benefit without the adverse effect of the higher dose. The low dose had a similar caffeine content to that of a large coffee latte from a coffee shop, suggesting beneficial effects could be achieved through coffee/latte consumption. Caution should be applied when extrapolating the findings for eumenorrheic females with different training statuses. Healthcare practitioners can, however, use the results of this study to understand the potential benefits of caffeine for strength-trained women using hormone contraception.
Abstract
Caffeine supplementation has shown to be an effective ergogenic aid enhancing athletic performance, although limited research within female populations exists. Therefore, the aim of the investigation was to assess the effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females. In a double-blind, randomised, counterbalanced design, fourteen strength-trained females using hormonal contraception consumed either 3 or 6 mg·kg-1 BM of caffeine or placebo (PLA). Following supplementation, participants performed a one-repetition maximum (1RM) leg press and repetitions to failure (RF) at 60% of their 1RM. During the RF test, rating of perceived exertion (RPE) was recorded every five repetitions and total volume (TV) lifted was calculated. Repeated measures ANOVA revealed that RF (p = 0.010) and TV (p = 0.012) attained significance, with pairwise comparisons indicating a significant difference between 3 mg·kg-1 BM and placebo for RF (p = 0.014), with an effect size of 0.56, and for 6 mg·kg-1 BM (p = 0.036) compared to the placebo, with an effect size of 0.65. No further significance was observed for 1RM or for RPE, and no difference was observed between caffeine trials. Although no impact on lower body muscular strength was observed, doses of 3 and 6 mg·kg-1 BM of caffeine improved lower body muscular endurance in resistance-trained females, which may have a practical application for enhancing resistance training stimuli and improving competitive performance.
Methodological quality
Jadad score
:
2
Allocation concealment
:
No
