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 HbA _1c 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.