运动前进食不同血糖指数食物对长跑能力的影响

目的 :探讨运动前进食不同血糖指数食物对长跑能力的影响。方法 :实验设计采用平衡重复测试法 ,8名男子耐力长跑运动员在间隔期不少于 7天内 ,在隔夜空腹情况下分别进食含相等热量的低血糖指数 [Glycemicindex (GI) ](GI =37)或高GI(GI =77)的碳水化合物 (CHO)食物 (CHO∶1 5g/kg体重 )。 2小时后 ,受试者在水平跑台上进行 2 1km的长跑能力测试。首 5km中 ,受试者以其 70 %VO2 max的速度跑步 ,而其后的 16km ,则可随意选择速度以最短时间完成。结果 :与高GI试验相比 ,所有受试者在进食低GI食物后的跑步时间明显缩短 (98 7± 2 0vs 10 1 5± 2 1min ,P<0 0 1)。整个跑步全程中 ,低GI试验的血糖及血清游离脂肪酸 (FFA)的水平较高GI试验为高。虽然进食高GI食物后两小时的血清胰岛素较高 ,但在运动过程中 ,血清胰岛素、皮质醇、血乳酸水平与低GI试验相比均无显著差异。与高GI试验相比 ,低GI试验中CHO氧化在能量供应上的依赖低 9 5 % ,而脂肪氧化则高 17 9%。结论 :在运动前 2小时进食低血糖指数的CHO食物 ,比提供同等热量的高血糖指数食物能更有效地提高长跑运动的能力。

Influence of Pre-exercise Consumption of Low and High Glycemic Index Food on Endurance Performance

Purpose This study examined the effect of pre-exercise low and high glycemic index (GI) carbohydrate (CHO) meals on running performance. Methods Eight endurance-trained male runners completed two trials that were separated by at least seven days in a counterbalanced design. Two hours before the run and after an overnight fast, each subject consumed an isocaloric meal containing either low (GI = 37, LGI) or high (GI = 77, HGI) GI CHO foods that provided 1.5 g CHO(kg -1 body mass in random order. Each trial consisted of a 21km performance run on a level treadmill. The subjects were required to run at 70% VO 2max during the first 5km of the run. They then completed the remaining 16km as fast as possible. Results All of the subjects achieved a faster performance time after the consumption of the LGI meal (LGI vs HGI: 98 7± 2 min vs 101 5±2 min, P <0 01). Blood glucose and serum free fatty acids concentrations were higher throughout the performance run in the LGI trial. Serum insulin concentrations were higher in the HGI trial during the postprandial resting period. However, there were no differences between the trials in serum insulin, serum cortisol, and blood lactate concentrations throughout the exercise. Compared with the HGI trial, CHO oxidation was 9 5% lower and fat oxidation was 17 9% higher during exercise in the LGI trial. Conclusion Consumption of a LGI meal 2 hours before a 21km performance run is more effective in improving the run time when compared to an isocaloric HGI meal.