Skeletal muscle substrate utilization during submaximal exercise in man: effect of endurance training.

作者：Bente Kiens, Birgitta Essén-Gustavsson, N. J. Christensen, Bengt Saltin · 发表于：The Journal of Physiology · 年份：1993 · DOI：10.1113/jphysiol.1993.sp019823 · 被引用次数：443 · 研究领域：Muscle metabolism and nutrition、Sports Performance and Training、Cardiovascular and exercise physiology

1. The influence of training-induced adaptations in skeletal muscle tissue on the choice between carbohydrates (CHO) and lipids as well as the extra- vs. intracellular substrate utilization was investigated in seven healthy male subjects performing one-legged knee-extension exercise. In each subject one of the knee extensors was endurance trained for eight weeks, whereafter the trained (T) and non-trained (NT) thighs were investigated a week apart. 2. The activity of beta-hydroxy-acyl-coenzyme A dehydrogenase (HAD) and capillary density in the knee extensors were significantly larger in T than in NT. 3. During dynamic knee-extension exercise, performed at the same absolute intensity for 2 h, femoral venous blood flow was lower in T than in NT (P < 0.05), but oxygen uptake was similar. 4. Respiratory quotient (RQ) values over the exercising thigh, averaging 0.81 (T) vs. 0.91 (NT; P < 0.05) indicated that a shift towards a larger fat combustion occurred with endurance training. 5. Both free fatty acids (FFA) and serum triacylglycerol contributed to the utilization of fat in NT and T muscles with no significant contribution from muscle fibre triacylglycerol. 6. At high plasma FFA concentrations net uptake of FFA plateaued in NT but not in T muscles. 7. The findings suggest that FFA uptake in exercising muscle is a saturable process and that the transport capacity is enhanced by training. The lower CHO utilization in the T leg was mainly a function of the glycogenolysis of the mu...