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

本研究旨在评价运动前30 min蛋白质摄入量对单次踏车运动（70%VO_2peak，30 min）恢复期疲劳指标的影响，如心率（HR）、R-R间期、自主活动、血乳酸浓度、色氨酸/支链氨基酸比值（Trp/BCAA）和主观疲劳。此外，我们还验证了剧烈运动后中枢疲劳程度增加的假设，并与Trp/BCAA比值增加相关，结果运动时心率增加，R-R间期显著缩短，恢复期恢复到运动前水平。在我们目前的研究中，尚不清楚膳食蛋白质摄入量如何影响心率和自主活动的运动后变量。需要进一步的研究来阐明不同水平的膳食蛋白质对HR变量的影响。无论蛋白质摄入水平如何，运动后血乳酸水平和主观疲劳都显着增加。运动后30 min乳酸水平和疲劳水平均显著降低。这些观察结果表明，外周和中枢疲劳增加的运动和变化是短暂的。另一方面，在本实验期间，低蛋白质摄入组中Trp/BCAA的比例没有变化（蛋白质能量比的7%）。另一方面，高蛋白质摄入组的Trp/BCAA比值（54%蛋白质能量比）在运动后即刻显著下降，运动后60 min仍维持较低水平，提示主观疲劳的变化与血清Trp/BCAA水平的变化不一定一致，用血清Trp/BCAA水平的变化来解释中枢疲劳理论似乎是困难的。

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.