The Effects of Time following Acute Growth Hormone Administration on Metabolic and Power Output Measures during Acute Exercise

We examined the effects of GH infusion on metabolism and performance measures during acute exercise. Nine males [(X ± sem): age 23.7 ± 1.9 yr, height 182.6 ± 1.6 cm, weight 77.3 ± 2.6 kg, percent fat 17.7 ± 1.9%, peak oxygen consumption 37.9 ± 2.9 ml/kg·min] completed six 30-min randomly assigned bicycle ergometer exercise trials at a power output midway between the lactate threshold and peak oxygen consumption. In five of the six trials, the subjects received a recombinant human GH infusion (10 μg/kg, 6-min square wave pulse) at 0800 h, followed by a 30-min exercise trial initiated at one of the following times: 0845, 0930, 1015, 1100, or 1145 h. During one of the six trials, the subject received a saline infusion followed by a 30-min exercise trial initiated at 0845 h. Mixed-effect, repeated-measures ANOVA analyses corrected for multiple comparisons revealed that there were no significant condition effects for total work, caloric expenditure, heart rate response, the blood lactate response, or ratings o...