Plasma insulin, growth hormone, and blood sugar during exercise in man

Alterations in plasma immunoreactive insulin (IRI), human growth hormone (hGH) and blood glucose were studied in five male volunteers undergoing exercise for 20 min on a bicycle ergometer at 750 kpm/min. Plasma IRI and hGH levels before exercise were 4.42 +/- 1.35 micro U/ml (mean +/- SE) and 1.94 +/- 0.88 ng/ml respectively. A significant decrease (p less than 0.01) in plasma IRI was observed at 20 min postexercise and remained at lower levels upto 80 min of observations. hGH levels showed significant increase (p less than 0.05) to a mean value of 7.46 +/- 0.71 ng/ml at 20 min of exercise with a peak value of 16.0 +/- 5.04 ng/ml at 20 min postexercise. Sixty min after termination of exercise, hGH levels returned to pre-exercise values. Blood glucose rose progressively with the increase in the duration of exercise and peak levels were recorded at 20 min of exercise. Sixty min after termination of exercise, blood glucose levels returned to pre-exercise values. These observations suggest that exercise stress can lead to a physiological situation in which circulating insulin and glucose are not exclusively dependent on each other.