Accommodating Planned Exercise in Type I Diabetic Patients on Intensive Treatment

Abstract

To achieve optimal metabolic control in type I diabetic patients treated with continuous subcutaneous insulin infusion (CSII) and multiple subcutaneous injections of insulin (MSI) appropriate adjustments of the insulin prescription should be made for exercise, which is a normal component of everyday life. The present study describes the responses of seven type I diabetic adolescents treated with CSII and six patients treated with MSI to specific insulin dose changes in anticipation of postprandial exercise. The effect of 45 min of cycle ergometer exercise at 55% VO2 on glucose regulation was studied 2 h after morning insulin and a breakfast meal. To quantify the potential benefit of modifying the insulin dose before exercise, the subjects were studied on five different days in a random order: (1) resting control day, (2) postprandial exercise preceded by the usual dose of insulin, (3) postprandial exercise preceded by one-half of the usual dose of insulin, (4) postprandial exercise preceded by two-thirds of the usual dose of insulin, and (5) postprandial exercise without the usual dose of insulin. In all cases insulin was injected or infused subcutaneously in the anterior abdominal wall. When exercise was performed without changing the usual insulin dose, there was a significant fall in glycemia in both groups, with the nadir occurring after 45 min. In the CSII group, the ± SEM plasma glucose was 57 ± 5 mg/dl (P < 0.05 versus rest) with hypoglycemia occurring in four patients. In the MSI group, the mean ± SEM plasma glucose fell to 65 ± 10 mg/dl (P < 0.05 versus rest) and hypoglycemia occurred in three patients. This was corrected with the administration of approximately 25 g of glucose by mouth. When exercise was performed after one-half and two-thirds of the usual insulin dose, the plasma glucose profile observed during exercise in both groups was not statistically different from that observed during the rest day. Postprandial exercise without prior insulin resulted in significant hyperglycemia in both groups (P < 0.01). Plasma free insulin levels remained unchanged throughout the exercise period in all protocols. A 50–66% reduction of the insulin dose in anticipation of postprandial exercise of moderate intensity resulted in near-normal glycemic values and prevented hypoglycemia. Alternatively, in the case of unplanned postprandial exercise of 45 min duration, the intake of 25–30 g of glucose may prevent hypoglycemia in the CSII- and MSI-treated type I diabetic patients.