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/m2 and HbA1c >= 7.5% were randomized to 12 weeks of either HIIT exercise intervention consisting of 4 x 4-min HIIT (85 to 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 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 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 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, glycemic control may improve for people who undertake HIIT with greater adherence.
Copyright American Diabetes Association. Reprinted with permission from The American Diabetes Association.

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