Effect of high-intensity interval training on glycemic control in adults with type 1 diabetes with overweight or obesity: a randomized controlled trial with partial cross-over

Objective: To study the effect of 12 weeks of high-intensity interval training (HIIT) on glycemic control in adults with type 1 diabetes with overweight or obesity.

Research Design and Methods: Thirty inactive adults with type 1 diabetes who had BMI≥25kg/m² and HbA1c≥7.5% were randomized to 12 weeks of either: HIIT exercise intervention consisting of 4x4 minutes HIIT (85-95% HRpeak) performed thrice weekly, or usual care control. In a partial cross-over design, the control group subsequently performed the 12-week HIIT intervention. The primary endpoint was the change in HbA1c 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/m². HbA1c 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 to 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 HbA1c 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 HbA1c with a 12-week HIIT intervention in adults with type 1 diabetes. However glycaemic control may improve for people who undertake HIIT with greater adherence.