Differential effects of high intensity interval training on somatosensory and autonomic nerve function in patients with type 2 diabetes

Aims:

It remains unclear, whether exercise training has favorable effects on the development of diabetic neuropathy in patients with type 2 diabetes (T2D).

Methods:

We assessed peripheral and autonomic nerve fiber function and morphology in individuals with T2D and normal glucose tolerance (CON) before and after a high intensity interval training (HIIT) intervention program over 12 weeks. The T2D group included 20 male individuals ([median (1st;3 rd quartile)] age: 56 (53;63) years; diabetes duration: 5 (2;9) years; BMI: 31.2 (28.6;32.8)kg/m²; HbA1c: 6.9 (6.4;8.0)%). The CON group was matched for age, sex, and BMI (n = 23; age: 57 (53;60) years; BMI: 30.3 (28.4;32.2)kg/m²). Somatosensory and autonomic nerve tests included nerve conduction velocity, quantitative sensory testing, skin biopsy, cardiovascular autonomic function, and spontaneous baroreflex sensitivity (BRS).

Results:

After 12 weeks of HIIT, no improvement in somatosensory nerve tests was detected in T2D or CON. In both groups, heart rate decreased ([mean ± SEM] baseline vs. follow-up: T2D: 68.8 ± 2.3 vs. 63.4 ± 1.8 bpm; CON: 65.1 ± 1.8 vs. 60.2 ± 1.9 bpm; p ≤0.05). The change in systolic blood pressure after standing up (-13.9 ± 2.6 vs. -9.4 ± 2.2 mmHg) and three BRS sequence analysis indices (e.g. BRS-slope: 7.9 ± 1.9 vs. 12.6 ± 5.1 ms/mmHg) improved in T2D (p ≤0.05), while the standard deviation of normal RR intervals (SDNN; 36.1 ± 2.6 vs. 55.3 ± 8.8 ms) and coefficient of variation (CV; 3.8 ± 0.3 vs. 5.2 ± 0.7%) improved in CON (p ≤0.05).

Conclusions:

While cardiovascular autonomic function improved moderately after 12 weeks of HIIT in male T2D patients, a longer training period may be required to achieve favorable effects on somatosensory nerve function or morphology.