Muscular exercise in type I-diabetics. II. Hormonal and metabolic responses to moderate exercise.

In Type I-diabetics metabolic response to exercise is largely determined by the availability of exogenous insulin. The aim of the present study was to assess the metabolic response to moderate exercise of 24 insulin-dependent (Type I-) diabetics treated by multiple subcutaneous injections of short acting insulin. Differences in insulin availability (hypo- [trial A] or hyperinsulinemia [trial B]) resulted from the different periods of time that had elapsed since the previous insulin injection, i.e., after 3 hours (trial A), and 1 hour (trial B). Bicycle ergometer tests at intensities up to 75% VO2max, were carried out with patients and controls. Plasma glucose, FFA, glycerol, alanine, growth hormone and glucagon levels were measured during a period of 85 min. In both trials, physical exertion did not have a significant statistical effect on the glucose concentration in the blood of hypo- and hyperinsulinemics. Surprisingly, despite the different insulin availabilities FFA, glycerol, alanine and glucagon concentrations were not statistically different in either trial and appear similar to those of healthy controls. A normal metabolic response to exercise can thus also be expected in Type I-diabetics, provided adequate insulin is available. When compared to controls, growth hormone concentrations were found to have increased during exercise. These experimental data strongly suggest the great necessity of adequate insulin availability in order to obtain normal metabolic responses to exercise in insulin-dependent diabetics. Despite certain degrees of hypo- or hyperinsulinemia, moderate exercise did not cause any marked metabolic derangements. This type of moderate exercise is therefore recommended for improving metabolic control in such patients.

Muscular exercise in type I-diabetics. I. Different metabolic reactions during heavy muscular work in dependence on actual insulin availability.

The present study focussed on the impact of heavy muscular work upon metabolic homeostasis in insulin dependent (type I) diabetics in situations involving a certain degree of hyper- and hypoinsulinemia. 20 juvenile type I-diabetics were compared with 6 nondiabetic healthy subjects. The diabetics were studied in states of hypo-(trial A) and hyperinsulinemia (trial B) at the start of the exercise. Differences in insulin availability resulted from the different times that had elapsed from the last insulin injection (3 hours in trial A and 1 hour in trial B) before the ergometer test started at 7 a.m. Six diabetics out of 20 patients were studied in both trials A and B to establish the reproducibility of metabolic reactions to the exercise. Bicycle ergometer tests were carried out in the upright position at 5 graded steps of 50 W, 75 W, 100 W, 125 W and a load near to exhaustion. Rest periods of five minutes were allowed between these work periods for taking blood samples before and after each work load. Plasma glucose, FFA, glycerol, lactate, alanine, IRI and HCP concentrations were investigated. The blood pressure at rest and during exercise was measured, and the physical working capacity (PWC170) was calculated according to Wahlund on the basis of the heart rate response to exercise. The results of the exercise tests reflect clearly the different metabolic reactions to heavy muscular work despite the relatively slight differences in insulin availability at the start: --Exhausting muscular work during the hypoinsulinemic state resulted in hyperglycemia and exaggerated lipolysis. --Heavy muscular work in a hyperinsulinemic state resulted in a reduced blood glucose level and antilipolytic reactions in comparison to nondiabetics. These findings suggest the great necessity of an adequate insulin availability during heavy muscular work in juvenile type I-diabetics.