Objective: To evaluate and validate appropriate premeal insulin dose reductions for postprandial exercises of different intensities and durations to minimize the risk of exercise-induced hypoglycemia in type 1 diabetic subjects.
Research design and methods: Eight male type 1 diabetic patients on a basal-bolus insulin regimen of ultralente (UL) as basal insulin and lispro (LP) as premeal insulin were tested in a randomized, crossover fashion during postprandial exercise at 25% VO2max for 60 min, 50% VO2max for 30 and 60 min, and 75% VOmax for 30 min starting 90 min after a standardized mixed breakfast (600 kcal, 75 g carbohydrates). Each subject served as his own control and was rested after a full dose of insulin LP (LP 100%) and/or 50% (LP 50%) and/or 25% (LP 25%) of the current dose.
Results: At all intensities, the full premeal insulin dose was associated with an increased risk of hypoglycemia. At 25% VO2max for 60 min, a 50% reduction in the premeal insulin dose resulted in plasma glucose of -0.62 mmol/l compared with baseline at the end of exercise. At 50% VO2max for 30 and 60 min, 50 and 75% reductions of the premeal insulin dose were associated with plasma glucose of -0.39 and +0.49 mmol/l, respectively, at the end of the exercise. At 75% VO2max, a 75% reduction of the premeal insulin dose was required to achieve appropriate postexercise plasma glucose (+0.71 mmol/l). Such reductions in the premeal insulin dose resulted in a 75% decrease in the incidence of exercise-induced hypoglycemia. CONCLUSIONS In well-controlled type 1 diabetic subjects on intensive insulin therapy with the basal-bolus (UL-LP) insulin regimen, risk of hypoglycemia can be minimized during postprandial exercises of different intensities and different durations by appropriate reduction of premeal insulin LP.