运动前进食不同血糖指数和血糖负荷膳食对男子长跑运动员运动耐力和免疫机能的影响

目的:探讨运动前2小时进食不同血糖指数(glycemic index,GI)和血糖负荷(glycemic load,GL)的含碳水化合物食物对运动耐力以及免疫机能的影响。方法:8名男子长跑耐力运动员(年龄24.3±2.2岁;体重66.7±2.0公斤;最大摄氧量55.9±1.9毫升.公斤-1体重.分钟-1),采用不完全随机的平衡重复测试方法随机完成三次耐力测试,每次测试间隔不少于7天。每次运动实验前两小时,受试者需进食等热量(每公斤体重约9千卡热量)的三种配餐之一,即高血糖指数高血糖负荷(H-H)、低血糖指数低血糖负荷(L-L)和高血糖指数低血糖负荷(H-L),其碳水化合物含量、GI和GL分别为65%、79.5、82.4(H-H);65%、40.2、42.1(L-L);15%、79.5、42.1(H-L)。每次测试中,受试者先在跑台上以70%VO2max强度、跑完1小时,接着以最短时间完成随后的10公里耐力跑。分别于运动前、70%VO2max运动1小时后即刻、完成10公里跑即刻,以及恢复期第1和第2小时末取静脉血测试免疫指标。结果:进食不同配餐后受试者的耐力表现无明显差异,完成10公里跑的时间分别为52.6±2.0分钟(H-H)、51.2±2.0分钟(L-L)和52.7±2.0分钟(H-L);运动后即刻和2小时恢复期中,与H-L膳食相比,H-H和L-L两种条件下受试者的外周血中淋巴细胞及中性粒细胞均减少,且运动结束后两小时的血浆白介素6、10和皮质醇浓度较低;运动60分钟后淋巴细胞增殖反应受抑制,并于运动结束后两小时恢复至基础水平,三种实验条件之间无明显差异。结果提示:运动前2小时进食不同血糖指数和血糖负荷碳水化合物饮食对之后的运动耐力表现无明显影响;与食物的血糖指数和血糖负荷相比,运动前饮食中的碳水化合物含量可能是影响耐力运动中免疫反应的更重要因子。

Effect of Pre-exercise Dietary Carbohydrate Intake with Different Glycemic Index and Glycemic Load on Immune Responses and Endurance Running Performance

Objective This study examined the effect of a pre-exercise meal with different glycemic index(GI)and glycemic load(GL)on immune responses and running performance in long distance runners.Methods Eight endurance-trained male runners completed a 1h run at 70% VO2max on a level treadmill and then followed by a 10km performance run in three occasions,separated by at least 7 days.In each trial,one of the 3 prescribed isocaloric meals was consumed by the subjects 2h before exercise.The Carbohydrate intake(% of energy intake),GI,and GL of each meal were 65%,79.5,and 82.4(high GI and high GL(H-H)),15%,79.5,and 42.1(high GI and low GL(H-L)),65%,40.2,and 42.1(low GI and low GL(L-L))respectively.The venous blood samples were collected at pre-exercise,1h during exercise,immediately after 10km run,1h and 2h post exercise.Results The run time of the 10km was similar among the H-H,L-L,and H-L trials(52.69±2.02 vs 52.56±2.0 vs 51.17±1.97min).Pre-exercise consumption of high carbohydrate meals(H-H and L-L)resulted in less perturbation of the circulating numbers of leukocytes,neutrophils,and T lymphocyte subsets;decreased the elevation of the plasma IL-6 concentrations immediately after exercise and during the 2h recovery period as compared to the H-L trial.These responses were accompanied by an attenuated increase in plasma IL-10 and cortisol concentrations 2h post exercise.Conclusion These results suggested that compared with GI and GL,the amount of pre-exercise carbohydrate consumption might be a more important influencing factor in modifying the immunoendocrine response to prolonged exercise.