Can caffeine alter blood potassium concentration or the perception of pain and fatigue after a 1 km cycling sprint?

Abstract

Caffeine is used by some athletes to improve endurance performance, however, the mechanism(s) by which caffeine elicits performance improvements have been unclear. The purpose of this study was to investigate the effects of caffeine on pain perception, fatigue perception, plasma catecholamine concentrations and plasma potassium concentrations to determine whether altered perception related to the central nervous system and potassium ion handling are associated with enhanced performance during a 1 km cycling time trial. A cross-over, double blind design of 13 well trained men (age: 27 ± 6 yrs, height: 180 ± 7 cm, body mass: 76.4 ± 6.4 kg, and VO2max: 57.5 ± 4.6 ml•kg-1•min-1) were randomized to a caffeine (5 mg•kg-1) or a placebo condition. Caffeine had no significant effects on the 1 km time-trial performance indicators; time, peak power, or average power. In addition, caffeine had no significant effect on the perception of pain or overall fatigue. There was a significantly greater increase in post-exercise blood lactate, post-exercise catecholamines and lower pre-exercise blood potassium concentrations when caffeine was consumed. The results suggest that although there were no differences in performance time, caffeine caused changes in metabolic markers. In conclusion, caffeine consumption prior to a 1 km simulated cycling time-trial did not improve performance and its use is not warranted.