Effect of High-Intensity Interval Training on Glycemic Control in Adults With Type 1 Diabetes and Overweight or Obesity: A Randomized Controlled Trial With Partial Crossover

OBJECTIVE: To study the effect of 12 weeks of high-intensity interval training (HIIT) on glycemic control in adults with type 1 diabetes and overweight or obesity. RESEARCH DESIGN AND METHODS: Thirty inactive adults with type 1 diabetes who had BMI ≥25 kg/m(2) and HbA(1c) ≥7.5% were randomized to 12 weeks of either HIIT exercise intervention consisting of 4 × 4-min HIIT (85–95% peak heart rate) performed thrice weekly or usual care control. In a partial crossover design, the control group subsequently performed the 12-week HIIT intervention. The primary end point was the change in HbA(1c) from baseline to 12 weeks. Glycemic and cardiometabolic outcomes were measured at 0, 12, and 24 weeks. RESULTS: Participants were aged 44 ± 10 years with diabetes duration 19 ± 11 years and BMI 30.1 ± 3.1 kg/m(2). HbA(1c) decreased from 8.63 ± 0.66% at baseline to 8.10 ± 1.04% at 12 weeks in the HIIT intervention group (P = 0.01); however, this change was not significantly different from the control group (HIIT −0.53 ± 0.61%, control −0.14 ± 0.48%, P = 0.08). In participants who undertook at least 50% of the prescribed HIIT intervention, the HbA(1c) reduction was significantly greater than control (HIIT −0.64 ± 0.64% [n = 9], control −0.14 ± 0.48% [n = 15], P = 0.04). There were no differences in insulin dose, hypoglycemia on continuous glucose monitoring, blood pressure, blood lipids, body weight, or body composition between groups. CONCLUSIONS: Overall, there was no significant reduction in HbA(1c) with a 12-week HIIT intervention in adults with type 1 diabetes. However, glycemic control may improve for people who undertake HIIT with greater adherence.