Coyle E F
Dept. of Kinesiology and Health, University of Texas, Austin.
Int J Sports Med. 1992 Oct;13 Suppl 1:S126-8. doi: 10.1055/s-2007-1024615.
During strenuous exercise (i.e. 70% maximal O2 consumption) there is a progressive shift from muscle glycogen to blood glucose oxidation with increasing duration of exercise. By maintaining blood glucose concentration and the rate of carbohydrate oxidation necessary to exercise strenuously, carbohydrate consumption throughout exercise delays fatigue by 30-60 min in endurance-trained subjects. This requires exogenous glucose supplementation at rates in excess of 1 gram/min (i.e., 16 mg/kg/min) as evidenced by the observation that intravenous glucose infusion at this rate is required to maintain blood glucose at 5 mM. Exogenous glucose must be infused at a rate of 2.6 gram/min (i.e., 37 mg/kg/min), which is similar to the total rate of carbohydrate oxidation, in order to maintain blood glucose at 10 mM after 2 h of exercise. However, carbohydrate supplementation during intense exercise does not spare muscle glycogen utilization in people. This suggests that over the course of 2-4 hours of exercise at 70% VO2max, muscle glycogen and blood glucose contribute equally to total carbohydrate oxidation. Furthermore, during the latter stages of prolonged exercise, exogenous blood glucose supplementation may be capable of supplying almost all of the carbohydrate requirements of exercise at intensities up to 70% VO2max.
在剧烈运动期间（即最大耗氧量的70%），随着运动时间的延长，肌肉糖原氧化逐渐向血糖氧化转变。通过维持血糖浓度以及剧烈运动所需的碳水化合物氧化速率，在耐力训练的受试者中，整个运动过程中的碳水化合物消耗可将疲劳延迟30 - 60分钟。这需要以超过1克/分钟（即16毫克/千克/分钟）的速率补充外源性葡萄糖，静脉输注葡萄糖维持血糖在5毫摩尔/升的观察结果证明了这一点。为了在运动2小时后将血糖维持在10毫摩尔/升，必须以2.6克/分钟（即37毫克/千克/分钟）的速率输注外源性葡萄糖，这与碳水化合物的总氧化速率相似。然而，在剧烈运动期间补充碳水化合物并不能节省人体肌肉糖原的利用。这表明在以70%最大摄氧量进行2 - 4小时的运动过程中，肌肉糖原和血糖对总碳水化合物氧化的贡献相同。此外，在长时间运动的后期，外源性血糖补充可能能够满足高达70%最大摄氧量强度运动时几乎所有的碳水化合物需求。
