Abstract
The performance of strenuous physical exercise is associated with discomfort and pain,
the tolerance forthat being modulated by the activity of the endogenous opioid systems.
As 5-hydroxy-tryptamine (5-HT) affects nociception through its effects on the enkephalin-endorphin
system, we have analyzed the effects of a moderate supplementation with L-tryptophan,
the immediate precursor of 5-HT, on endurance and sensation of effort.
Twelve healthy sportsmen were subjected to a work load corresponding to 80% of their
maximal oxygen uptake on two separate trials, after receiving a placebo and after
receiving the same amount of L-tryptophan. The subjects ran on a treadmill until exhaustion.
Total exercise time, perceived exertion rate, maximum heart rate, peak oxygen consumption,
pulse recovery rate, and excess post-exercise oxygen consumption were determined during
the two trials.
The total exercise time was 49.4% greater after receiving L-tryptophan than after
receiving the placebo. A lower rate of perceived exertion was exhibited by the group
while on tryptophan although the differences from the control group were not statistically
significant. No differences were observed in the other parameters between the two
trials.
The longer exercise time als well at the total work load performed could be due to
an increased pain tolerance as a result of L-tryptophan ingestion.
Key words
L-tryptophan - fatigue - nociception - total exercise time
