Hanse, J. J., Faria, E. W., & Faria, I. W. (1999). Effect of 5-hydroxytryptophan on central fatigue. Medicine and Science in Sports and Exercise, 31(5), Supplement abstract 451.

This study investigated the effects of enhanced serotonin production during prolonged exercise using subjective and objective measures of fatigue. Male trained cyclists (N = 10) performed under experimental and placebo conditions. The serotonin precursor, 5-hydroxytryptophan (5-HTP), was administered at a dose level of 5 mg/kg. Ss cycled on an ergometer for two hours at 65% VO2max.

There were no significant differences between the conditions for time to exhaustion, rated perceived exertion, amount of work accomplished, heart rate, blood glucose, and blood lactate levels.

Implication. 5-HTP has no effect on subjective or objective measures of fatigue in prolonged cycling.

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