Yaspelkis B B, Patterson J G, Anderla P A, Ding Z, Ivy J L
Department of Kinesiology, University of Texas at Austin 78712.
J Appl Physiol (1985). 1993 Oct;75(4):1477-85. doi: 10.1152/jappl.1993.75.4.1477.
Effects of carbohydrate (CHO) supplementation on muscle glycogen utilization and endurance were evaluated in seven well-trained male cyclists during continuous cycling exercise that varied between low [45% maximal O2 uptake (VO2 max)] and moderate intensity (75% VO2 max). During each exercise bout the subjects received either artificially flavored placebo (P), 10% liquid CHO supplement (L; 3 x 18 g CHO/h), or solid CHO supplement (S; 2 x 25 g CHO/h). Muscle biopsies were taken from vastus lateralis during P and L trials immediately before exercise and after first (124 min) and second set (190 min) of intervals. Subjects then rode to fatigue at 80% VO2 max. Plasma glucose and insulin responses during L treatment reached levels of 6.7 +/- 0.7 mM and 70.6 +/- 17.2 microU/ml, respectively, and were significantly greater than those of P treatment (4.4 +/- 0.1 mM and 17.7 +/- 1.6 microU/ml) throughout the exercise bout. Plasma glucose and insulin responses of S treatment were intermediate to those of L and P treatments. Times to fatigue for S (223.9 +/- 3.5 min) and L (233.4 +/- 7.5 min) treatments did not differ but were significantly greater than that of P treatment (202.4 +/- 9.8 min). After the first 190 min of exercise, muscle glycogen was significantly greater during L (79 +/- 3.5 mumol/g wet wt) than during P treatment (58.5 +/- 7.2 mumol/g wet wt). Furthermore, differences in muscle glycogen concentrations between L and P treatments after 190 min of exercise and in time to fatigue for these treatments were positively related (r = 0.76, P < 0.05). These results suggest that CHO supplementation can enhance prolonged continuous variable-intensity exercise by reducing dependency on muscle glycogen as a fuel source.
在七名训练有素的男性自行车运动员进行持续骑行运动期间，评估了碳水化合物（CHO）补充剂对肌肉糖原利用和耐力的影响。该运动强度在低强度[最大摄氧量（VO2 max）的45%]和中等强度（VO2 max的75%）之间变化。在每次运动期间，受试者分别接受人工调味的安慰剂（P）、10%的液体CHO补充剂（L；每小时3×18克CHO）或固体CHO补充剂（S；每小时2×25克CHO）。在P和L试验期间，于运动前、第一组（124分钟）和第二组（190分钟）间歇后立即从股外侧肌取肌肉活检样本。然后受试者以VO2 max的80%强度骑行至疲劳。L治疗期间血浆葡萄糖和胰岛素反应分别达到6.7±0.7 mM和70.6±17.2 μU/ml的水平，并且在整个运动期间显著高于P治疗（4.4±0.1 mM和17.7±1.6 μU/ml）。S治疗的血浆葡萄糖和胰岛素反应介于L和P治疗之间。S（223.9±3.5分钟）和L（233.4±7.5分钟）治疗的疲劳时间没有差异，但显著长于P治疗（202.4±9.8分钟）。运动190分钟后，L治疗期间的肌肉糖原（79±3.5 μmol/g湿重）显著高于P治疗（58.5±7.2 μmol/g湿重）。此外，运动190分钟后L和P治疗之间的肌肉糖原浓度差异以及这些治疗的疲劳时间呈正相关（r = 0.76，P < 0.05）。这些结果表明，CHO补充剂可以通过减少对肌肉糖原作为燃料来源的依赖来增强长时间持续的可变强度运动。
