Riddell M C, Bar-Or O, Schwarcz H P, Heigenhauser G J
Children's Exercise and Nutrition Centre, McMaster University, Chedoke Hospital Division, Hamilton, Ontario, Canada.
Eur J Appl Physiol. 2000 Nov;83(4 -5):441-8. doi: 10.1007/s004210000259.
The influence of glucose ingestion on substrate utilization during prolonged exercise in children and adolescents is currently unknown. In the present study we determined the effect of intermittent exogenous glucose (GLUexo) ingestion on substrate utilization during prolonged exercise, in adolescent boys ages 13 17 years. Healthy untrained volunteers performed four 30-min exercise bouts on a cycle ergometer, separated by 5-min rest periods (approximately equal to 60% maximum O2 consumption), on two occasions spaced 1-4 weeks apart. Two trials were performed, a control trial (CT), in which subjects ingested water intermittently during the exercise, and a glucose trial (GT), in which subjects ingested a 13C-enriched GLUexo drink (approximately egual to glucose kg body mass(-1)), also intermittently during the exercise. Total free fatty acids (FATtotal), glucose (GLUtotal) and carbohydrate (CHOtotal) oxidation was determined from indirect calorimetry, while GLUexo oxidation was calculated from the 13C/12C ratio in expired air after 5-10 min and 25-30 min of exercise in each bout. Heart rate and rating of perceived exertion (RPE) were determined at the same time intervals. The oxidation of CHOtotal was 169.1 (12.9) g x 120 min(-1) and 203.1 (15.9) g x 120 min(-1) (P < 0.01) and that of FATtotal was 31.0 (4.2) g x 120 min(-1) and 17.1 (2.5) g x 120 min(-1) (P < 0.01) in CT and GT, respectively. GLUexo oxidation in GT was 57.8 (4.3) g x 120 min(-1), or 34.2 (2.2)% of that ingested. Endogenous glucose oxidation was 169.1 (12.9) g x 120 min(-1) and 145.3 (11.9) g x 120 min(-1) (P < 0.01) in CT and GT, respectively. Insulin and glucose concentrations were higher in GT than in CT by 226% and 37%, respectively (both P < 0.05). Free fatty acids and glycerol concentrations were lower in GT than in CT, by 27% and 79%, respectively (both P < 0.05). Heart rate was similar between trials, but RPE was lower in GT vs CT at both 115 and 135 min. Thus, under these experimental conditions, GLUexo intake spares endogenous carbohydrate and fat by 16% and 45%, respectively, contributes to approximately 25% of the total energy demand of exercise, and lowers the RPE.
目前尚不清楚在儿童和青少年长时间运动期间摄入葡萄糖对底物利用的影响。在本研究中，我们测定了间歇性摄入外源性葡萄糖（GLUexo）对13至17岁青春期男孩长时间运动期间底物利用的影响。健康的未经训练的志愿者在功率自行车上进行了四次30分钟的运动，每次运动之间间隔5分钟的休息时间（约为最大耗氧量的60%），分两次进行，两次间隔1至4周。进行了两项试验，一项是对照试验（CT），受试者在运动期间间歇性摄入水；另一项是葡萄糖试验（GT），受试者在运动期间也间歇性摄入富含13C的GLUexo饮料（约为每千克体重摄入葡萄糖的量）。通过间接测热法测定总游离脂肪酸（FATtotal）、葡萄糖（GLUtotal）和碳水化合物（CHOtotal）的氧化，而GLUexo的氧化则根据每次运动5至10分钟和25至30分钟后呼出气体中的13C/12C比值计算得出。同时测定心率和主观用力程度（RPE）。CT组和GT组中CHOtotal的氧化分别为169.1（12.9）克×120分钟-1和203.1（15.9）克×120分钟-1（P<0.01），FATtotal的氧化分别为31.0（4.2）克×120分钟-1和17.1（2.5）克×120分钟-1（P<0.01）。GT组中GLUexo的氧化为57.8（4.3）克×120分钟-1，占摄入总量的34.2（2.2）%。CT组和GT组中内源性葡萄糖氧化分别为169.1（12.9）克×120分钟-1和145.3（11.9）克×120分钟-1（P<0.01）。GT组中的胰岛素和葡萄糖浓度分别比CT组高226%和37%（均P<0.05）。GT组中的游离脂肪酸和甘油浓度分别比CT组低27%和79%（均P<0.05）。两次试验之间心率相似，但在115分钟和135分钟时，GT组的RPE低于CT组。因此，在这些实验条件下，摄入GLUexo分别使内源性碳水化合物和脂肪节省了16%和45%，约占运动总能量需求的25%，并降低了RPE。
