GH secretion in acute exercise may result in post-exercise lipolysis

Exercise is a potent stimulator of growth hormone (GH) secretion. We hypothesised that after a short bout of intense exercise GH may increase lipolysis during recovery. In 7 moderately trained young male subjects (21.8 +/- 0.5 years) and 7 moderately trained older male subjects (56.0 +/- 1.0 years) [H-2(5)] glycerol was infused for 370 min to measure glycerol production rate (R-a) a measure of lipolysis. At 130 min subjects exercised on a cycle ergonometer for 20 min at 70% V-O2 max, followed by rest for 220 min. On a separate occasion the study was repeated in the young subjects with a 1 h GH infusion (4 mu g kg(-1) h(-1)) at 130 min instead of exercise. In response to exercise, catecholamines (p <0.02) and glycerol R-a (p <0.0 1) increased, peaking during exercise. GH concentration increased in response to exercise (p <0.01), peaking after exercise (150-160 min) in both groups with no significant difference in peak response between groups. A post-exercise rise in glycerol R-a was demonstrated in both groups peaking at 265-295 min in the older group (p <0.002, peak vs. basal) and continuing to rise until 370 min in the young group (p <0.01, peak vs. basal). The timing and magnitude of this was reproduced with the GH infusion. There was a significant correlation between the peak GH response to exercise and the post-exercise rise in glycerol R-a Measured as area under the curve (r = 0.57, p <0.04). In conclusion, this study provides evidence that the GH response to acute exercise may increase lipolysis during recovery. (c) 2005 Elsevier Ltd. All rights reserved