Guidelines for T1D suggest reducing basal insulin delivery 60 to 90 min before aerobic exercise. In this study, participants with T1D on CSII (Omnipod®, Insulet) (n=13) were randomized in a crossover design to three basal rate reduction strategies pre-exercise. All participants completed three 60 min aerobic exercise sessions (walking, ∼50% VO2max). Basal insulin delivery was reduced by; a) -80%, 90 min pre-exercise; b) -50%, 90 min pre-exercise or; c) -100% at exercise onset. Basal rates were resumed post exercise and participants then took 75% of usual bolus with a standardized meal. Pre-exercise blood glucose (BG) was similar in all conditions (9.5 ± 2.8 mmol/L). The mean BG drop during exercise was greater (p<0.05) in the -100% (-4.2 ± 3.3 mmol/L) compared to the -50% and -80% conditions (-3.3 ± 2.4 vs. -2.0 ± 2.1 mmol/L), respectively. In the -100% condition, seven (54%) participants had hypoglycemia (hypo), whereas in the other two conditions only one hypo event occurred (8%, p<0.001). Meal related BG responses after exercise were similar among all conditions.

In summary, reducing basal insulin delivery by 50-80% 90 min before aerobic exercise better mitigates hypo risk vs. basal suspension or disconnection at exercise onset. Basal rate reductions well in advance of exercise do not cause pre-exercise hyperglycemia or meal related rebound hyperglycemia.

D. Zaharieva: Speaker's Bureau; Self; Medtronic, Ascensia Diabetes Care. S.M. McGaugh: None. R. Pooni: None. T. Vienneau: Employee; Self; Insulet Corporation. Stock/Shareholder; Self; Insulet Corporation, GlaxoSmithKline plc. T.T. Ly: Employee; Self; Insulet Corporation. M. Riddell: Speaker's Bureau; Self; Medtronic. Consultant; Self; Eli Lilly and Company, JAEB Center For Health Research, Xeris Pharmaceuticals, Inc.. Research Support; Self; Insulet Corporation. Speaker's Bureau; Self; Insulet Corporation. Advisory Panel; Self; Sanofi. Speaker's Bureau; Self; Ascensia Diabetes Care. Stock/Shareholder; Self; Zucara Theraputics. Other Relationship; Self; JDRF.

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