Abstract

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 x 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.