Effects of caffeine on neuromuscular fatigue and performance during high-intensity cycling exercise in moderate hypoxia.
PURPOSE
To investigate the effects of caffeine on performance, neuromuscular fatigue and perception of effort during high-intensity cycling exercise in moderate hypoxia.


METHODS
Seven adult male participants firstly underwent an incremental exercise test on a cycle ergometer in conditions of acute normobaric hypoxia (fraction inspired oxygen = 0.15) to establish peak power output (PPO). In the following two visits, they performed a time to exhaustion test (78 ± 3% PPO) in the same hypoxic conditions after caffeine ingestion (4 mg kg-1) and one after placebo ingestion in a double-blind, randomized, counterbalanced cross-over design.


RESULTS
Caffeine significantly improved time to exhaustion by 12%. A significant decrease in subjective fatigue was found after caffeine consumption. Perception of effort and surface electromyographic signal amplitude of the vastus lateralis were lower and heart rate was higher in the caffeine condition when compared to placebo. However, caffeine did not reduce the peripheral and central fatigue induced by high-intensity cycling exercise in moderate hypoxia.


CONCLUSION
The caffeine-induced improvement in time to exhaustion during high-intensity cycling exercise in moderate hypoxia seems to be mediated by a reduction in perception of effort, which occurs despite no reduction in neuromuscular fatigue.
['Smirmaul|Bruno P C|BP|', 'de Moraes|Antonio Carlos|AC|', 'Angius|Luca|L|', 'Marcora|Samuele M|SM|']
D000328:Adult D054874:Athletic Performance D002110:Caffeine D000697:Central Nervous System Stimulants D015444:Exercise D006801:Humans D000860:Hypoxia D008297:Male D018763:Muscle Fatigue D018482:Muscle, Skeletal
Perception of effort Central fatigue Altitude Exercise performance Peripheral fatigue