A Randomized Crossover Trial Comparing Glucose Control During Moderate-Intensity, High-Intensity, and Resistance Exercise With Hybrid Closed-Loop Insulin Delivery While Profiling Potential Additional Signals in Adults With Type 1 Diabetes

Objective: To compare glucose control with hybrid closed loop (HCL) when challenged by moderate-intensity exercise (MIE), high-intensity intermittent exercise (HIE) and resistance exercise (RE) while profiling counter-regulatory hormones, lactate, ketones, and kinetic data in adults with type 1 diabetes. Methods: Open-label multisite randomized crossover trial. Adults with type 1 diabetes undertook 40 min of HIE, MIE, and RE in random order while using HCL (Medtronic 670G) with a temporary target set 2 hours prior to and during exercise and 15g carbohydrates if pre-exercise glucose was Primary outcome was median (IQR) continuous glucose monitoring (CGM) time-in-range (TIR, 70-180 mg/dL) for 14 hours post-exercise commencement. Accelerometer data and venous glucose, ketones, lactate, and counter-regulatory hormones were measured for 280 min post-exercise commencement. Results: Median TIR was 81% [67, 93]%, 91% [80, 94]%, and 80% [73, 89]% for 0-14 hours post-exercise commencement for HIE, MIE and RE, respectively (n=30), with no difference between exercise types (MIE v HIE; p=0.11, MIE v RE p=0.11, HIE v RE p=0.90). Time-below-range was 0% for all exercise bouts. For HIE and RE compared with MIE, there were greater increases respectively in noradrenaline (p=0.01, p=0.004), cortisol (p Conclusions: Under controlled conditions, HCL provided satisfactory glucose control with no difference between exercise type. Lactate, counter-regulatory hormones, and kinetic data differentiate type and intensity of exercise, and their measurement may help inform insulin needs during exercise. However, their potential utility as modulators of insulin dosing will be limited by the pharmacokinetics of subcutaneous insulin delivery.