The Effects of High Doses of Caffeine on Maximal Strength and Muscular Endurance in Athletes Habituated to Caffeine

Abstract

Background: The main goal of this study was to assess the acute effects of the intake of 9 and 11 mg/kg/ body mass (b.m.) of caffeine (CAF) on maximal strength and muscle endurance in athletes habituated to caffeine. Methods: The study included 16 healthy strength-trained male athletes (age = 24.2 ± 4.2 years, body mass = 79.5 ± 8.5 kg, body mass index (BMI) = 24.5 ± 1.9, bench press 1RM = 118.3 ± 14.5 kg). All participants were habitual caffeine consumers (4.9 ± 1.1 mg/kg/b.m., 411 ± 136 mg of caffeine per day). This study had a randomized, crossover, double-blind design, where each participant performed three experimental sessions after ingesting either a placebo (PLAC) or 9 mg/kg/b.m. (CAF-9) and 11 mg/kg/b.m. (CAF-11) of caffeine. In each experimental session, participants underwent a 1RM strength test and a muscle endurance test in the bench press exercise at 50% 1RM while power output and bar velocity were measured in each test. Results: A one-way repeated measures ANOVA revealed a significant difference between PLAC, CAF-9, and CAF-11 groups in peak velocity (PV) (p = 0.04). Post-hoc tests showed a significant decrease for PV (p = 0.04) in the CAF-11 compared to the PLAC group. No other changes were found in the 1RM or muscle endurance tests with the ingestion of caffeine. Conclusion: The results of the present study indicate that high acute doses of CAF (9 and 11 mg/kg/b.m.) did not improve muscle strength nor muscle endurance in athletes habituated to this substance.

The effects of different doses of caffeine on maximal strength and strength-endurance in women habituated to caffeine

“…on mean power output and mean bar velocity during the bench press throw in athletes habituated to CAF, and performance enhancements were obtained even when the dose of CAF did not exceed the value of habitual consumption. It should be noted that results presented by Wilk et al [1,2,25] apply only to males habituated to CAF and there are no such analysis in women habituated to CAF.…”

“…The acute intake of caffeine (CAF) has been found effective in enhancing exercise performance in a wide range of resistance-based exercises based on strength-endurance [1][2][3], and strength-power exercise modalities [4,5]. The ergogenic effect of CAF has been found when consumed at doses ranging from 3 to 13 mg/kg body mass (b.m.)…”

“…Hence, to date, it is unknown if the ergogenic effects of CAF related to resistance exercise performance observed in male subjects [1][2][3]5] apply to female athletes, and it is unfeasible to determine if the magnitude of caffeine's ergogenic effect on resistance exercise is similar in athletes of both sexes.…”

“…may be necessary to obtain minor effects of acute CAF uptake on maximal muscle strength [1,2]. Pickering et al [38] suggested that the reduction in the ergogenic effects of CAF in habitual users can be modi ed using doses greater than the daily habitual intake, however a study by Wilk et al [1,2] showed no bene ts (except in maximal strength) from acute ingestion of CAF when the doses of CAF were above their habitual intake. In another study, Wilk et al [39] found a positive effect of CAF (3 and 6 mg/kg/b.m.)…”

Inconsistency in the Ergogenic Effect of Caffeine in Athletes Who Regularly Consume Caffeine: Is It Due to the Disparity in the Criteria That Defines Habitual Caffeine Intake?

“…The threshold used to classify individuals as high caffeine consumers varied from 190 mg/day [19] to more than 600 mg/day [20]. In addition, only three studies estimated daily caffeine intake in relation to body mass [21][22][23]. In those investigations that used absolute values to assess the level of habituation to caffeine, the findings could lead to incorrect conclusions because the same absolute amount of caffeine (in mg/day) would have a different impact on subjects with different body mass.…”