| Abstract: | The metabolic and hormonal responses to exhaustive short-term supramaximal exercise were studied in 10 male physical education students. The exercise task was a single bout of running on the treadmill at 22 km X h-1 and 7.5% slope. It was performed with single oral doses of 100 mg Bupranolol (non-selective beta-blockade), 100 mg Metoprolol (beta-1-selective blockade), and placebo. Arterialized capillary and venous blood were sampled until 30 min post exercise. Time to exhaustion was 52.0 +/- 2.6, 47.6 +/- 2.0, and 46.0 +/- 1.9 s in the control, Metroprolol, and Bupranolol experiments. At cessation of exercise, adrenaline and noradrenaline were grossly elevated in all three conditions. Lactate and glucose increased markedly, this being accompanied by increasing insulin in the control and Metoprolol, but not the Bupranolol trials. Glycerol increased moderately, while FFA were depressed. Growth hormone showed a delayed increase at 15 and 30 min post exercise. Cortisol was unaffected by exercise. beta-blockade reduced the increases of lactate, glucose, glycerol, insulin, and growth hormone, exaggerated the depression of FFA and had no effect on cortisol. The results demonstrate that the strong sympatho-adrenal response to exercise of this nature is a major determinant of the increase of glucose at cessation of exercise. The hyperglycemia in concert with beta-2-adrenergic stimulation leads to elevation of insulin. Furthermore, lipolysis is controlled by beta-adrenergic stimulation. The delayed increase of growth hormone seems to be triggered by the declining glucose level during recovery. |
