No effect of caffeine on exercise performance in high ambient temperature.

Eur J Appl Physiol 111(12):3089-95 (2011) PMID 21461761

Caffeine, an adenosine receptor antagonist, has shown to improve performance in normal ambient temperature, presumably via an effect on dopaminergic neurotransmission through the antagonism of adenosine receptors. However, there is very limited evidence from studies that administered caffeine and examined its effects on exercise in the heat. Therefore, we wanted to study the effects of caffeine on performance and thermoregulation in high ambient temperature. Eight healthy trained male cyclists completed two experimental trials (in 30°C) in a double-blind-randomized crossover design. Subjects ingested either placebo (6 mg/kg) or caffeine (6 mg/kg) 1 h prior to exercise. Subjects cycled for 60 min at 55% W (max), immediately followed by a time trial to measure performance. The significance level was set at p