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Randomized Controlled Trial
. 2015 Jun;47(6):1145-58.
doi: 10.1249/MSS.0000000000000513.

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

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Randomized Controlled Trial

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

Christopher D Black et al. Med Sci Sports Exerc. .

Abstract

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·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 VO(2peak) (70%Δ) 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%Δ.

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.

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