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摘要
This study investigates the influence of habitual caffeine intake on aerobic exercise-performance responses to acute caffeine supplementation. A double-blind, crossover, counterbalanced study was performed. Forty male endurancetrained cyclists were allocated into tertiles, according to their daily caffeine intake: low (58 +/- 29 mg/d), moderate (143 +/- 25 mg/d), and high (351 +/- 139 mg/d) consumers. Participants completed three trials in which they performed simulated cycling time trials (TTs) in the fastest time possible following ingestion of the following: caffeine (CAF: 6 mg/kg body mass), placebo (PLA), and no supplement (CON). A mixed-model analysis revealed that TT performance was significantly improved in CAF compared with PLA and CON (29.92 +/- 2.18 vs. 30.81 +/- 2.67 and 31.14 +/- 2.71 min, respectively; P = 0.0002). Analysis of covariance revealed no influence of habitual caffeine intake as a covariate on exercise performance (P = 0.47). TT performance was not significantly different among tertiles (P = 0.75). No correlation was observed between habitual caffeine intake and absolute changes (CAF = CON) in TT performance with caffeine (P = 0.524). Individual analysis showed that eight, seven, and five individuals improved above the variation of the test in CAF in the low, moderate, and high tertiles, respectively. A Fisher's exact test did not show any significant differences in the number of individuals who improved in CAF among the tertiles (P > 0.05). Blood lactate and ratings of perceived exertion were not different between trials and tertiles (P > 0.05). Performance effects of acute caffeine supplementation during an similar to 30-min cycling TT performance were not influenced by the level of habitual caffeine consumption.
- 出版日期2017-7
