No disadvantage to insulin pump off versus pump on during intermittent high-intensity exercise in adults with type 1 diabetes

Abstract Objectives Evidence suggests that patients with type 1 diabetes (T1D) performing aerobic exercise with their insulin pump connected ( pump on ) vs. pump disconnected ( pump off ) have an increased risk of hypoglycemia. Whether this risk remains during high-intensity exercise has not been examined. This study compared the effects of pump on (50% basal insulin at exercise onset) vs. pump off (0% basal insulin at exercise onset) on glucose concentrations during intermittent high-intensity exercise in adults with T1D and on patients’ own perspective of their glycemia. Methods Twelve adults with T1D using insulin pump therapy completed two 40-min intermittent high-intensity exercise bouts. Insulin adjustments included 1) pump set to 50% of usual basal rate (pump on) or 2) pump suspended (pump off) during exercise, in random order. Blood glucose was recorded every 10-min during exercise and, after providing subjects with an initial reference glucose value pre-exercise, participants were asked to estimate their glucose during exercise. Results Glucose levels were higher in pump off (8.1±1.3mmol/L) vs. pump on (7.4±2.1mmol/L) at exercise start ( P P =0.9). During exercise, hypoglycemia incidence did not differ between conditions (1/12 for both). However, percent time in hypoglycemia 12h post-exercise was 5±8% vs. 1±2% in pump on vs. pump off, respectively ( P =0.3). Participants were better able to estimate their own glucose during pump on vs. pump off (r 2 =0.46 vs. r 2 =0.11). Conclusions Pump on vs. pump off at exercise onset showed no significant differences in blood glucose concentrations during 40-min intermittent high-intensity exercise.