H. Tanaka et al., CHANGES IN PLASMA TRYPTOPHAN BRANCHED-CHAIN AMINO-ACID RATIO IN RESPONSES TO TRAINING VOLUME VARIATION, International journal of sports medicine, 18(4), 1997, pp. 270-275
The major symptoms of overtraining including decreased exercise perfor
mance, altered mood states, and depleted muscle glycogen stores closel
y resemble the effects of brain serotonin, the level of which is depen
dent on the plasma ratio of tryptophan to branched-chain amino acids (
BCAA). To examine the relation between plasma amino acids and overtrai
ning, ten highly-trained endurance runners underwent two weeks of base
training (normal training) before increasing their training volume by
40 % for two weeks to achieve a state of short-term overtraining (or
overreaching). The overtraining period was followed by two weeks of re
covery in which training volume was reduced by 41 % of the base traini
ng. For the whole group, no significant changes were observed in runni
ng economy and maximum oxygen uptake. There were no changes in resting
heart rate, blood pressure, resting metabolic rate, and serum cortiso
l level in response to the changes in training volume. The runners exp
erienced a significant increase (p < 0.05) in fatigue score for the pr
ofile of mood states when the training volume was increased. The eleva
ted fatigue score returned to baseline when the training volume was re
duced. Plasma free or total tryptophan, BCAA, and the tryptophan/BCAA
ratio were not significantly altered throughout the course of this stu
dy. We concluded that proposed physiological markers of overtraining,
including plasma tryptophan and BCAA levels, were unchanged despite a
40 % increase in training volume.