Four weeks of high-intensity interval training (HIIT) improve the cardiometabolic risk profile of overweight patients with type 1 diabetes mellitus (T1DM).

This study investigated the effects of a four-week HIIT intervention on the cardiometabolic risk profile, liver fat content, insulin requirement, hypoglycaemia, physical fitness, and health-related quality of life in patients with T1DM. A supervised exercise intervention with baseline to follow-up comparison between overweight (BMI = 28.6 ± 2.1 kg/m2) and normal weight (BMI = 23.2 ± 1.40 kg/m2) T1DM patients was performed. Eleven overweight (age = 40.7 ± 14.3 years) and 11 normal weight (age = 42.2 ± 15.5 years) T1DM patients performed a four-week, low-volume, all-out cycling HIIT (4-6 bouts, work/relief ratio 1:1) twice weekly. HIIT lowered low-density lipoprotein and uric acid levels in overweight patients by up to 10.5% (vs. normal weight, p≤0.0312). HbA1c, high-density lipoprotein, and triglyceride levels did not change in any of the groups. Participants' maximal exercise capacity and power output at individual anaerobic lactate threshold increased to an equal extend of up to 10% (p≤0.0002) in both groups. During the intervention, participants used fewer daily bolus insulin (-5.22 ± 12.80%) and less total units of insulin (-4.42 ± 10.20%, p≤0.023) compared to the pre-intervention period with no between-group difference. Overall, the average daily number of hypoglycaemias increased from 0.90 ± 0.56-1.08 ± 0.63 during the intervention (p = 0.033). SF-36 subscales showed higher scores after the intervention, with a significant improvement of "role limitations due to physical problems" (p<0.05) for both groups. We conclude that in T1DM, HIIT may exert beneficial effects on physical fitness, insulin requirement and health-related quality of life. Of note, beneficial HIIT effects on the cardiometabolic risk profile in T1DM may be larger in overweight T1DM patients.