Resumen de Caffeine's Ergogenic Effects on Cycling: Neuromuscular and Perceptual Factors.

Christopher D. Black, Dwight E. Waddell, Alexander R. Gonglach

• AB Caffeine improves endurance exercise performance, but its ergogenic mechanism(s) remain unclear. Purpose: This investigation sought to examine the effects of caffeine on perceptual and physiological responses to endurance exercise. Methods: Two experiments were performed. In study A, 14 participants were tested. Maximal voluntary strength (MVC) and motor-unit recruitment (%ACT) of the knee extensors and elbow flexors were tested before and 60 min after ingestion of a 5-mg[middle dot]kg-1 dose of caffeine or placebo and after completion of 40 min of exercise (30 min of submaximal leg or arm cycling followed by a 10-min time-trial performance). Muscle pain, RPE, and cardiorespiratory variables were assessed throughout. To determine the effects of caffeine on muscle pain and RPE during high-intensity exercise, a second study (study B) was performed. Twelve participants exercised at 95% of their gas exchange threshold (GET) and at 70% of the difference between their GET and V[spacing dot above]O2peak (70%[DELTA]) after caffeine and placebo ingestion. Results: Compared to placebo, caffeine improved MVC (6.3%, P = 0.014) and %ACT (5.5%, P = 0.013) in the knee extensors, but not the elbow flexors, and reduced muscle pain (P < 0.05) and RPE (P < 0.05) during both submaximal cycling modalities. Caffeine ingestion improved time-trial performance during leg cycling (4.9% +/- 6.5%, P = 0.03), but not arm crank cycling (2.1% +/- 8.2%, P = 0.28), but the effect on pain and RPE was eliminated. Caffeine ingestion had no effect on pain or RPE during cycling at 95% GET and 70%[DELTA]. Conclusions: Our results suggest that augmented strength and motor-unit recruitment, rather than reductions in pain and effort, may underlie caffeine's ergogenic effect on endurance exercise