The purpose of this study was to determine the effect of exercise intensity on the proportion and rate of carbohydrate oxidation and glucoregulatory hormone responses during recovery from exercise. Six physically active participants completed 1 hr of low-intensity (LI; 50% lactate threshold) or moderate-intensity (MI; 100% lactate threshold) exercise on separate days following a randomized counterbalanced design. During exercise and for 6 hr of recovery, samples of expired air were collected to determine oxygen consumption, respiratory exchange ratio, energy expenditure, and substrate oxidation rates. Blood samples were also collected to measure glucoregulatory hormones (catecholamines, GH) and metabolites (glucose, free fatty acids, lactate, pH, and bicarbonate). During exercise, respiratory exchange ratio, energy expenditure, and the proportion and rate of carbohydrate (CHO) oxidation were higher during MI compared with LI. However, during recovery from MI, respiratory exchange ratio and the proportion and rate of CHO oxidation were lower than preexercise levels and corresponding LI. During exercise and early recovery, catecholamines and growth hormone were higher in MI than LI, and there was a trend for higher levels of free fatty acids in the early recovery from MI compared with LI. In summary, CHO oxidation during exercise increases with exercise intensity but there is a preference for CHO sparing (and fat oxidation) during recovery from MI exercise compared with LI exercise. This exercise intensity-dependent shift in substrate oxidation during recovery is explained, in part, by the pattern of change of key glucoregulatory hormones including catecholamines and growth hormone and plasma fatty acid concentrations.

本研究的目的是确定运动强度对运动恢复过程中碳水化合物氧化和葡萄糖调节激素反应的比例和速率的影响。六名身体活跃的参与者按照随机平衡设计，在不同的日子完成了 1 小时的低强度（LI；50% 乳酸阈值）或中等强度（MI；100% 乳酸阈值）运动。在运动期间和 6 小时的恢复期间，收集呼出空气样本以确定耗氧量、呼吸交换率、能量消耗和底物氧化率。还收集血样来测量葡萄糖调节激素（儿茶酚胺，GH）和代谢物（葡萄糖、游离脂肪酸、乳酸、pH 值和碳酸氢盐）。运动过程中，MI期间的呼吸交换率、能量消耗以及碳水化合物（CHO）氧化的比例和速率均高于LI。然而，在MI恢复过程中，呼吸交换率以及CHO氧化的比例和速率低于运动前水平和相应的LI。在运动和早期恢复期间，MI中的儿茶酚胺和生长激素比LI中更高，并且与LI相比，MI早期恢复中游离脂肪酸水平有较高的趋势。总之，运动期间的 CHO 氧化随着运动强度的增加而增加，但与 LI 运动相比，在 MI 运动恢复期间更倾向于保留 CHO（和脂肪氧化）。恢复过程中底物氧化的这种运动强度依赖性变化部分可以通过关键葡萄糖调节激素（包括儿茶酚胺和生长激素）以及血浆脂肪酸浓度的变化模式来解释。