Aleksandra Filip-Stachnik, Michal Wilk, Michal Krzysztofik, Ewelina Lulińska, James J Tufano, Adam Zajac, Petr Stastny, Juan Del Coso
Journal: Journal of the International Society of Sports Nutrition 2021;18(1):25
PMID: 33781269
Athletes commonly consume caffeinated drinks or supplements containing caffeine due to its ergogenic effect on performance. However, very few studies have investigated the effect of acute intake of caffeine on muscular performance in strength-trained women. This randomised, double-blinded, crossover trial examines the effect of acute intake of caffeine on maximal strength and local strength-endurance during the bench press exercise in women habituated to acute intake of caffeine. In this study, twenty-one healthy and strength-trained women were randomised to take 3 and 6 mg/kg/body mass acute caffeine intake. While both doses showed positive effects, this study also observed a dose-dependent (6 mg/kg body mass) significant increase in the response of acute intake of caffeine on maximal strength in women habituated to caffeine. The acute intake of caffeine at 6 mg/kg/body mass also increased the number of repetitions and time under tension during the bench press. The results of the study must be interpreted with caution due to a wide variation in caffeine habituation, resistance training levels, and strength exercise practices across the general population. Future robust studies are required to investigate this further. This study may help healthcare practitioners better understand the ergogenic effects of caffeine consumption in strength-trained habituated women.
PURPOSE
The main goal of this study was to assess the acute effects of 3 and 6 mg of caffeine intake per kg of body mass (b.m.) on maximal strength and strength-endurance in women habituated to caffeine.
METHODS
Twenty-one healthy resistance-trained female students (23.0 ± 0.9 years, body mass: 59.0 ± 6.6 kg), with a daily caffeine intake of 5.8 ± 2.6 mg/kg/b.m. participated in a randomized, crossover, double-blind design. Each participant performed three experimental sessions after ingesting either a placebo (PLAC) or 3 mg/kg/b.m. (CAF-3) and 6 mg/kg/b.m. (CAF-6) of caffeine. In each experimental session, the participants underwent a 1RM test and a strength-endurance test at 50 %1RM in the bench press exercise. Maximal load was measured in the 1RM test and the time under tension, number of preformed repetitions, power output and bar velocity were registered in the strength-endurance test.
RESULTS
The one-way ANOVA showed a main effect of caffeine on 1RM bench press performance (F = 14.74; p < 0.01). In comparison to the PLAC (40.48 ± 9.21 kg), CAF-3 (41.68 ± 8.98 kg; p = 0.01) and CAF-6 (42.98 ± 8.79 kg; p < 0.01) increased 1RM bench press test results. There was also a significant increase in 1RM for CAF-6 when compared to CAF-3 (p < 0.01). There was a main effect of caffeine on time under tension during the strength-endurance test (F = 13.09; p < 0.01). In comparison to the PLAC (53.52 ± 11.44 s), CAF-6 (61.76 ± 15.39 s; p < 0.01) significantly increased the time under tension during the maximal strength-endurance test.
CONCLUSION
An acute dose of 3-to-6 mg/kg/b.m. of caffeine improves maximum strength. However, these doses of caffeine had minimal ergogenic effect on strength-endurance performance in women habituated to caffeine.
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