Locke, A., Sartin, K., Accola, D., & Burns, S. (2013). The effects of caffeine on time to exhaustion during treadmill running. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 1105.

This study determined the effect of caffeine on the running time until exhaustion in moderately active males (N = 8). Ss participated on three separate occasions, with no less than 48 hours of rest between each visit. On the first visit, Ss ran on a treadmill to determine their maximum heart rate. This was done by increasing the speed until volitional exhaustion. The final speed and heart rate were considered maximums. Ss returned two additional times and ran at 70% of maximum heart rate for 15 minutes. Immediately after the 15 minutes, treadmill speed was increased to the final speed at which exhaustion was reached during trial one. This pace was maintained until volitional exhaustion. Forty-five minutes prior to each run, Ss were given water with caffeine (5mg/kg) on one occasion and water without caffeine on the other. Ratings of Perceived Exertion were recorded every five minutes and after exhaustion. Blood lactate was sampled immediately and every minute for three minutes following each test, Heart rate was monitored throughout all tests.

Caffeine had no effect on time to exhaustion. However, there was a substantially longer time in the caffeine condition (Caffeine ~208.0 seconds; Placebo ~155.0 seconds). The non-significant difference could have resulted from a low-power statistical test due to the low numbers of Ss.

Implication. Although these results suggest that caffeine does not have an effect on time to exhaustion following submaximal running, the study needs to be repeated with a larger subject pool.

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