Brandenberger, K. (2013). Exogenous supplementation of melatonin does not affect 20-mile cycling time-trial performance. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 2395.

"While some studies suggest that melatonin may improve athletic performance in hot humid environments due to its pre-cooling effect, melatonin is consumed as a sleep aid due to its depressive effects on the central nervous system leading to the question of whether melatonin is a viable aid to performance."

This study determined whether taking a 5 mg supplement of melatonin affected performance of a laboratory simulated 20-mile cycling time-trial. Ss (N = 8) performed three 20-mile time-trials separated by a minimum of seven days on an electronically-braked cycle ergometer. During the final two trials, Ss received either a placebo or a 5 mg melatonin supplement 15 minutes prior to exercise. The experiment was a double-blind crossover design. Variables were measured at five-mile intervals.

Mean 20-mile time-trial completion times for the melatonin and placebo trials were not different. Mean time-trial power output for the melatonin and placebo conditions also were not different. Rectal temperature was not significantly affected by melatonin when compared to placebo.

Implication. A 5 mg melatonin supplement administered 15 minutes prior to exercise does not measurably impact the performance of a 20-mile time-trial.

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