Serum insulin and glucose response to graded exercise in adults. Part I: the influence of fitness status.

The effect of acute exercise upon serum immunoreactive insulin levels (IRI) and serum glucose concentrations (GC) was studied in groups of middle-aged men of contrasting physical fitness status. Two groups of subjects, one active and one sedentary (both N = 11, mean age 44 years), performed a graded cycle ergometer exercise test in the post-absorptive state. Venous blood samples were taken at rest, during low and high work intensities, and after recovery. The response of serum IRI to exercise was similar in both groups of subjects with significant increases observed during exercise followed by a return to resting values during recovery. However, the magnitude of serum IRI response was lower in the active group. In contrast, the sedentary group demonstrated little or no change in serum GC during exercise, whereas significant increases in serum GC were observed during exercise in the active group.