Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation

Objective: To investigate the influence of habitual caffeine intake on exercise performance to acute caffeine supplementation. Methods: A double-blind, crossover, counterbalanced study was performed. Forty endurance-trained cyclists were allocated into tertiles according to their daily caffeine intake: low (58 ± 29 mg^.d^-1), moderate (143 ± 25 mg^.d^-1), and high consumers (351 ± 139 mg^.d^-1). Participants completed three trials in which they performed simulated cycling time-trials in the fastest time possible following ingestion of: caffeine (CAF: 6 mg^.kg^-1 BM), placebo (PLA), and no supplement (CON). Results: Mixed-model analysis revealed time-trial performance was significantly improved in CAF compared to PLA and CON (29.92±2.18 min vs 30.81±2.67 and 31.14±2.71 min; P = <0.0002). ANCOVA revealed no influence of habitual caffeine intake as a covariate on exercise performance (P=0.47). Time-trial performance was not significantly different between tertiles (P=0.75). No correlation was observed between habitual caffeine intake and absolute changes (CAF - CON) in time-trial 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. A Fisher's Exact Test did not show any significant differences in the number of individuals who improved in CAF between the tertiles (P>0.05). Blood lactate and ratings of perceived exertion were not different between trials and tertiles (P>0.05). Conclusion: Performance effects of acute caffeine supplementation during a ~30 min cycling TT performance were not influenced by the level of habitual caffeine consumption.

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