Caffeine Increases Peripheral Fatigue in Low- but not in High-Performing Cyclists.

The influence of cyclist's performance level on caffeine-induced increases in neuromuscular fatigue after a 4-km cycling TT was investigated. Nineteen cyclists performed a 4-km cycling TT one hour after ingesting caffeine (5 mg‧kg-1) or placebo (cellulose). Changes from baseline to post-exercise in voluntary activation (VA) and potentiated 1 Hz force twitch (Qtw,pot) were used as markers of central and peripheral fatigue, respectively. Participants were classified as "high-performing" (HP, n=8) or "low-performing" (LP, n=8) in accordance with their performance in placebo trial. Compared with placebo, caffeine increased the power, the anaerobic mechanical power and the anaerobic work, reducing the time to complete the trial for both groups (p<0.05). There was a group vs. supplement and group vs. supplement vs. trial interaction for Qtw,pot, where the post-exercise reduction was higher after caffeine compared with placebo in LP (Qtw,pot=-34±17 vs. -21±11%, p=0.02) but not in HP (Qtw,pot=-22±8 vs. -23±10%, p=0.64). There was no effect of caffeine on VA, but there was a group vs. trial interaction with lower post-exercise values in LP than in HP (p=0.03). Caffeine-induced improvement on 4-km cycling TT performance seems to be at the expense of greater locomotor muscle fatigue in low- but not in high-performing cyclists. BULLET POINTS -Caffeine improves exercise performance at the expense of a greater end-exercise peripheral fatigue in low-performing athletes. -Caffeine-induced improvement on exercise performance does not affect end-exercise peripheral fatigue in high-performing athletes. -High-performing athletes seems to have augmented tolerance to central fatigue during a high-intensity time-trial.