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.