A moderate caffeine dose increases strength performance in resistance-trained females

INTRODUCTION:
The effects of caffeine on strength performance have mainly been studied in male participants with caffeine doses of 5 and 6 mg·kg-1. Therefore, the aim of this study was to investigate the acute effects of 4 mg·kg-1 caffeine ingestion on markers of strength and power in resistance-trained females.
METHODS:
In a randomized, double-blind, placebo-controlled, crossover design, 15 highly resistance-trained females (30.0±4.0 years, 63.8±5.5 kg) consumed a moderate caffeine dose (4 mg·kg-1) or placebo 60 minutes before completing a test battery. Both trials were completed during the early follicular phase. All participants completed the trials separated by 3 days and following two familiarisations to the test battery. One repetition maximum (1RM) and repetitions to failure at 60% of 1RM were assessed in the back squat and in the bench press. Maximal voluntary contraction and rate of force development were assessed in 90-degree isometric knee-extensions, while utilising the interpolated twitch technique to measure voluntary muscular activation. Their maximal power and jump height were assessed during countermovement jumps performed on a force plate. Blood samples were taken at 60 and 210 minutes after ingestion of either treatment to measure plasma caffeine concentration.
RESULTS:
Caffeine significantly improved squat (+4.5±1.9%) and bench press (+3.3±1.4%) 1RM compared to placebo. Number of repetitions to failure performed in the squat (+15.9±17.9%) and in the bench press (+9.8±13.6%) were also significantly increased. Furthermore, maximal isometric strength, jump height and jump power were all improved (p<0.05). There were no significant differences in rate of force development and muscle activation. The plasma caffeine concentration did not change significantly from 60 minutes to 210 minutes following caffeine consumption.
CONCLUSION:
This study demonstrates that a 4 mg·kg-1 dose of caffeine enhances maximal strength, power and muscular endurance in resistance-trained females. Female strength and power athletes may consider using a moderate caffeine dose before competition. This in turn may reduce the negative side effects that have been described previously with higher doses (Goldstein et al., 2010).

Abstract-ID: 2377