Metabolic effects of physical exercise in insulin-dependent diabetics controlled by continuous subcutaneous insulin infusion or conventional injection therapy

Abstract

The metabolic and hormonal response to moderately severe exercise 2 h after breakfast was assessed in 8 insulin-dependent diabetics during conventional insulin injection therapy and after 3 weeks of continuous sc insulin infusion. Blood glucose fell from 12.1 to 4.4 mmol/l on injection therapy; this was accompanied by a significant rise (P less than 0.05) in free insulin to 57 mU/l. On infusion therapy plasma glucose fell and stabilised at 3.6 mmol/l from pre-exercise levels of 7.1 mmol/l, while free insulin level was unchanged at the end of the exercise period (31 mU/l). The fall in blood glucose on injection therapy was accompanied by an exaggerated growth hormone response to exercise that was normalised by 3 weeks of infusion therapy. Basal and post-prandial levels of intermediary metabolites, catecholamines and glucagon were comparable on the two insulin regimens. Responses during exercise were generally similar and no different from those of normal subjects, with the exception of plasma NEFA levels which became abnormally suppressed. Good metabolic control of diabetes is thus accompanied by nearly normal hormonal and metabolic response to moderately severe exercise.