Comparison of 10 × 1-minute high-intensity interval training (HIIT) versus 4 × 4-minute HIIT on glucose control and variability in females with type 2 diabetes.

Two high-intensity interval training (HIIT) regimens are often used in research and clinical settings. Yet there has been no direct comparison to determine if one can improve glucose control and variability to a greater extent in individuals with type 2 diabetes (T2D). Fourteen older females with T2D participated in a semi-randomized control trial where HIIT10 (10×1-minute intervals at 90% heart rate max; HRmax) and HIIT4 (4×4-minute intervals at 90% of HRmax) were compared to a control condition (CON; no exercise). Continuous glucose monitoring was used to assess glucose control and variability over 24h after each condition. Both HIIT10 (-2.1±1.1 mmol/L) and HIIT4 (-2.1±1.3 mmol/L) acutely lowered glucose compared to CON (-0.7±0.8 mmol/L; p= 0.001), with no difference between exercise conditions. This glucose-lowering effect did not persist over the 24h postexercise period, as both mean glucose (p= 0.751) and glucose variability (p= 0.168) were not significantly different among conditions. However, exploratory analyses focusing on individuals with poor glucose control (above median 24h mean glucose in the CON condition; n= 7) revealed that 24h mean glucose (7.4 [7.14-8.92] vs. 8.4 [7.5-9.9] mmol/L; p= 0.048), glucose variability (p= 0.010), and peak glucose (p=0.048) were lower following HIIT10 compared to CON, while HIIT4 reduced time spent in moderate hyperglycemia compared to CON (p=0.023). Both HIIT10 and HIIT4 acutely lower glycemia, but the effect does not persist over 24 hours. However, in individuals with worse glucose control, HIIT10 may improve mean 24-hour glucose and glycemic variability, while HIIT4 may reduce time spent in moderate hyperglycemia.