Coyle E F, Coggan A R, Hemmert M K, Lowe R C, Walters T J
J Appl Physiol (1985). 1985 Aug;59(2):429-33. doi: 10.1152/jappl.1985.59.2.429.
The effect of a high-carbohydrate meal 4 h before 105 min of exercise at 70% of maximal O2 uptake was determined in seven endurance-trained cyclists and compared with exercise following a 16-h fast. The preexercise meal produced a transient elevation of plasma insulin and blood glucose, which returned to fasting basal levels prior to the initiation of exercise. The meal also resulted in a 42% elevation (P less than 0.05) of glycogen within the vastus lateralis at the beginning of exercise. The 1st h of exercise when subjects were fed was characterized by a 13-25% decline (P less than 0.05) in blood glucose concentration, a suppression of the normal increase in plasma free fatty acids and blood glycerol, and a 45% (P less than 0.05) greater rate of carbohydrate oxidation compared with exercise when subjects were fasted. After 105 min of exercise, there were no significant differences when subjects were fed or fasted regarding blood glucose levels, rate of carbohydrate oxidation, or muscle glycogen concentration. The greater muscle glycogen utilization (97 +/- 18 vs. 64 +/- 8 mmol glucosyl units X kg-1; P less than 0.05) and carbohydrate oxidation when subjects were fed appeared to be derived from the glycogen synthesized following the meal. These results indicate that preexercise feedings alter substrate availability despite a return of plasma insulin to fasting levels prior to exercise and that these effects persist until the 2nd h of exercise.
在7名耐力训练的自行车运动员中，测定了在以最大摄氧量的70%进行105分钟运动前4小时摄入高碳水化合物餐的效果，并与16小时禁食后运动的情况进行了比较。运动前餐导致血浆胰岛素和血糖短暂升高，在运动开始前恢复到空腹基础水平。该餐还导致运动开始时股外侧肌内糖原升高42%（P<0.05）。在进食的受试者运动的第1小时，血糖浓度下降13%-25%（P<0.05），正常的血浆游离脂肪酸和血液甘油增加受到抑制，与禁食的受试者运动时相比，碳水化合物氧化速率提高45%（P<0.05）。运动105分钟后，进食或禁食的受试者在血糖水平、碳水化合物氧化速率或肌肉糖原浓度方面没有显著差异。进食的受试者更大的肌肉糖原利用率（97±18对64±8 mmol葡萄糖基单位×kg-1；P<0.05）和碳水化合物氧化似乎源自餐后合成的糖原。这些结果表明，尽管运动前血浆胰岛素恢复到空腹水平，但运动前进食会改变底物可用性，并且这些影响持续到运动的第2小时。
