Gorostiaga E M, Czerwinski S M, Hickson R C
Department of Physical Education, University of Illinois, Chicago 60680.
J Appl Physiol (1985). 1988 Mar;64(3):1098-106. doi: 10.1152/jappl.1988.64.3.1098.
This study was undertaken to determine the effects of increased substrate availability (glycogen + plasma fatty acids) by glucocorticoids on energy metabolism during exercise to exhaustion. Female rats received a single subcutaneous injection of cortisol acetate (CA) (100 mg.kg body wt-1) 21 h before treadmill running (30.8 m/min). At the start of exercise in the CA-treated rats, plasma fatty acids and liver glycogen were increased by 40%. Glycogen levels were also increased by CA treatment in slow-twitch soleus (61%), fast-twitch white vastus (38%), and fast-twitch red vastus lateralis (85%) muscles. Exercise time to exhaustion was increased by CA treatment (114 +/- 5 vs. 95 +/- 6 min, P less than 0.05). During the exercise, total glycogen depletion was greater in the CA-treated than in the control animals, whereas estimated relative rates of carbohydrate utilization (R = 0.90) were similar. However, while running the CA-treated group consumed 11% more O2 than the controls (P less than 0.05). These results show that a single injection of glucocorticoids is capable of improving endurance. Yet the increased O2 uptake during exercise may have minimized the impact of the initial increased availability of carbohydrates and fatty acids in prolonging exercise capacity. This decreased running economy by the CA-treated runners may be secondary to alterations in energy production or utilization.
本研究旨在确定糖皮质激素增加底物可用性（糖原 + 血浆脂肪酸）对运动至疲劳期间能量代谢的影响。雌性大鼠在跑步机跑步（30.8米/分钟）前21小时接受一次醋酸皮质醇（CA）皮下注射（100毫克·千克体重-1）。在接受CA治疗的大鼠开始运动时，血浆脂肪酸和肝糖原增加了40%。CA治疗还使慢肌比目鱼肌（61%）、快肌白色股四头肌（38%）和快肌红色股外侧肌（85%）的糖原水平升高。CA治疗使运动至疲劳的时间增加（114±5分钟对95±6分钟，P<0.05）。在运动过程中，CA治疗组的总糖原消耗比对照动物更大，而估计的碳水化合物利用相对速率（R = 0.90）相似。然而，在跑步过程中，CA治疗组比对照组多消耗11%的氧气（P<0.05）。这些结果表明，单次注射糖皮质激素能够提高耐力。然而，运动期间增加的氧气摄取可能在延长运动能力方面最小化了最初增加的碳水化合物和脂肪酸可用性的影响。CA治疗的跑步者降低的跑步经济性可能继发于能量产生或利用的改变。
