INTRODUCTION Exercise with low carbohydrate availability increases protein degradation, which may reduce subsequent performance considerably. The present study aimed to investigate the effect of carbohydrate ingestion during standardized exercise with and without exhaustion on protein degradation and next-day performance. METHODS Seven trained male cyclists (V̇O 2max 66.8 ± 1.9 mL·kg -1 ·min -1 ; mean ± SEM) cycled to exhaustion (~2.5 h) at a power output eliciting 68% of V̇O 2max (W 68% ). This was followed by repeating 1-min work/1-min recovery intervals at 90% of V̇O 2max (W 90% ) until exhaustion. During W 68% , cyclists consumed a placebo water drink (PLA) the first time and a carbohydrate drink (CHO), 1 g carbohydrate·kg -1 ·h -1 , the second time. The participants performed the same amount of work under the two conditions, separated by at least 1 wk. A standardized diet was provided to the participants so that the two conditions were isoenergetic. To test the impact of carbohydrates on recovery, participants completed a time trial (TT) the next day. RESULTS Carbohydrate ingestion maintained carbohydrate availability during W 68% and W 90% : total carbohydrate oxidation was significantly higher in CHO ( P = 0.022), and plasma glucose concentration was maintained compared with PLA ( P = 0.025). Next-day performance during TT was better after CHO ingestion (CHO, 41:49 ± 1:38 min; PLA, 42:50 ± 1:46 min; P = 0.020; effect size d = 0.23, small), as was gross efficiency (CHO, 18.6% ± 0.3%; PLA, 17.9% ± 0.3%; P = 0.019). Urinary nitrogen excretion ( P = 0.897) and urinary 3-methylhistidine excretion ( P = 0.673) did not significantly differ during the study period. Finally, tyrosine and phenylalanine plasma concentrations increased in PLA but not in CHO ( P = 0.018). CONCLUSIONS Carbohydrate ingestion during exhaustive exercise reduced deterioration in next-day performance through reduced metabolic stress and development of fatigue. In addition, some parameters point toward less protein degradation, which would preserve muscle function.

中文翻译：

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长时间骑行期间摄入碳水化合物可提高第二天计时赛的表现并改变氨基酸浓度。

简介 碳水化合物含量低的运动会增加蛋白质降解，这可能会大大降低随后的表现。本研究旨在调查在有或没有疲惫的标准化运动中碳水化合物的摄入对蛋白质降解和第二天表现的影响。方法 七名训练有素的男性自行车手（V̇O 2max 66.8 ± 1.9 mL·kg -1 ·min -1 ；平均值±SEM）以产生 V̇O 2max (W 68% ) 68% 的功率输出骑行至力竭（~2.5 小时）。随后以 90% V̇O 2max (W 90% ) 重复 1 分钟工作/1 分钟恢复间隔，直至精疲力竭。在W 68% 期间，骑行者第一次饮用安慰剂水饮料(PLA)，第二次饮用碳水化合物饮料(CHO)，1 g 碳水化合物·kg -1 ·h -1 。参与者在两种条件下执行相同量的工作，且间隔至少 1 周。为参与者提供了标准化饮食，以便两种条件下的能量相等。为了测试碳水化合物对恢复的影响，参与者第二天完成了计时赛 (TT)。结果 碳水化合物摄入在第 68% 和第 90% 期间维持了碳水化合物的利用率：与 PLA 相比，CHO 中的总碳水化合物氧化显着较高（P = 0.022），并且血浆葡萄糖浓度得以维持（P = 0.025）。摄入 CHO 后，TT 期间的第二天表现更好（CHO，41:49 ± 1:38 分钟；PLA，42:50 ± 1:46 分钟；P = 0.020；效应值 d = 0.23，小），与总体表现一样效率（CHO，18.6% ± 0.3%；PLA，17.9% ± 0.3%；P = 0.019）。研究期间尿氮排泄量（P = 0.897）和尿3-甲基组氨酸排泄量（P = 0.673）没有显着差异。最后，PLA 中酪氨酸和苯丙氨酸血浆浓度增加，但 CHO 中没有增加（P = 0.018）。结论 在力竭运动期间摄入碳水化合物可以通过减少代谢压力和疲劳的发生来减少第二天表现的恶化。此外，一些参数表明蛋白质降解较少，这将保持肌肉功能。