Effect of dietary protein intakes on recovery from the central fatigue postexercise

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The aim of this study was to evaluate the effect of pre-exercise protein intakes 30min before the exercise on various indexes of fatigue in the recovery of a single bout of cycle ergometer exercise(70% VO_2peak, 30 min), such as a heart rate(HR) and R-R intervals, autonomic activity, blood lactate concentrations, ratio of tryptophan to branched chain amino acids(Trp/BCAA), and subjective fatigue. In addition, here we tested a hypothesis that central fatigue would be increased after strenuous exercise, and correlated with increased ratio of Trp/BCAA.As a result, the HR increased, R-R intervals significantly decreased during the exercise, and then those values returned to be pre-exercised levels in the recovery period. It was not clear in our present study how dietary protein intakes affect the post-exercised variables of HR and autonomic activity. Further studies are needed to clarify the effect of different levels of dietary protein on the HR variables.Levels of blood lactate and subjective fatigue increased significantly just after the exercise regardless of protein intakes levels. Both levels of lactate and fatigue decreased significantly at 30min after the exercise. These observations suggested that both peripheral and central fatigue increased by the exercise and changes were transient. On the other hand, the ratio of Trp/BCAA was unchanged in lower protein intake group during this experimental period(7% of protein energy ratio). On the other hand, the ratio of Trp/BCAA in a higher protein intake group(54% of protein energy ratio) significantly decreased just after the exercise and remained a low level until 60 min after the exercise.These observations suggested that changes in the subjective fatigue did not necessarily correspond with the changes in the serum Trp/BCAA levels, and it seems difficult to account for the central fatigue theory by the changes in serum Trp/BCAA levels.