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.

Effect of high-intensity interval training in patients with type 1 diabetes on physical fitness and retinal microvascular perfusion determined by optical coherence tomography angiography.

OBJECTIVE: Physical activity may protect from ocular complications of diabetic retinopathy (DR). We investigated exercise training effects on the retinal microvasculature using optical coherence tomography angiography (OCTA) in type 1 diabetes (T1D). METHODS: Twenty T1D patients without clinical signs of DR performed four weeks of high-intensity interval training (HIIT). Cycle ergometry was used for determination of physical fitness. OCTA of the macula and optic nerve head was applied to analyze effects on the foveal avascular zone area, vessel density, vessel diameter index and fractal dimension of the superficial plexus, deep plexus and radial peripapillary capillaries. RESULTS: Large effects for improvement of physical fitness in terms of power output at the individual lactate threshold (+10.7 ± 11.3%, p < .001, ES = 0.95) and maximal power output (+8.2 ± 6.4%, p < .001, ES = 1.4) were detected. Participants presented a reduced increase in heart rate (HR) and lactate (LA) at given exercise intensities at follow-up (p ≤ .0176). Baseline OCTA revealed that HbA1c levels were associated with vessel density in the radial peripapillary capillary and the parafoveal superficial region (p ≤ .014). None of the analyzed microvascular parameters changed in response to the intervention. CONCLUSION: Despite favorable effects of HIIT on physical fitness of T1D patients, disease-specific training protocols may be needed to overcome potentially impaired retinal microvascular adaptations.