L-Tryptophan Supplementation Does Not Improve Running Performance

Abstract

In 1988 Segura and Ventura (14) reported that 1.2g of L-Tryptophan (L-TRY) supplementation increased total exercise time by 49.4% when the subjects were running at 80% of maximal oxygen uptake (V̇O₂max). In human performance research, acute improvements of that category are rather uncommon. Both for this reason and because ingestion of purified L-TRY may have adverse effects, it seemed pertinent to repeat the investigation of Segura and Ventura. Forty-nine well-trained male runners, aged 18-44, with an average maximal aerobic power of 66 (57-78) ml·kg^-1·min^-1, participated in a randomized double blind placebo (P) study. Each subject underwent four trials on the treadmill. The first two served as learning experience, including measurement of V̇O₂max and anaerobic threshold. During the last two trials the subjects ran until exhaustion at a speed corresponding to 100% of their V̇O₂max - first an initial trial and then after receiving a total of 1.2 g L-TRY or p over a 24 hour period prior to the run. No significant difference between the improvements in the L-TRY and p group could be demonstrated. It is concluded that oral L-TRY supplementation does not enhance running performance.

Key words

L-Tryptophan - running performance - fatigue - pain threshold - all-out run - dietary supplementation