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Background: Caffeine has been used by some athletes to improve short-term high-intensity exercise performance; however, the literature is equivocal. Objectives: The objective of this study was to investigate the effects of caffeine on plasma potassium and catecholamine concentrations, pain and fatigue perception, to determine whether potassium ion handling and altered perception related to the central nervous system are associated with enhanced performance during a 1 km cycling time trial.  Methods: Thirteen well trained men with a mean age of 27 ± 6 yrs (body mass: 76.4 ± 6.4 kg, height: 180 ± 7 cm, and max: 57.5 ± 4.6 ml·kg -1 ·min -1 ) were recruited.  Participants were randomized to a caffeine (5 mg·kg -1 ) or a placebo condition using a double blind, cross over design.  Results: Caffeine had no significant effects on the 1 km time-trial performance indicators of time (82.1 ± 2.4 vs. 81.9 ± 3.9s), peak (633.0 ± 83.6 vs. 638.7 ± 110.1 watts) or average power (466.0 ± 37.3 vs. 467.5 ± 59.9 watts; caffeine and placebo conditions respectively).  In addition, caffeine had no significant effect on oxygen consumption () (4.11 ± 0.24 vs 4.06 ± 0.29 L),the perception of pain (5.6 ± 2.4 vs. 5.5 ± 2.6) or fatigue (7.1 ± 1.8 vs.7.1 ± 1.8: caffeine and placebo conditions respectively).  There was a significantly greater increase in post-exercise blood lactate (p<0.05) and catecholamines (p<0.05) as well as a lower pre-exercise blood potassium concentration (p<0.05) in the caffeine condition. Conclusions: The results suggest that caffeine can enhance certain metabolic parameters, but these changes were unable to augment short-distance (1km), high-intensity cycling performance. Keywords: ergogenic, anaerobic exercise, performance, oxygen consumption

Caffeine Alters Blood Potassium and Catecholamine Concentrations but not the Perception of Pain and Fatigue with a 1 km Cycling Sprint