Effect of low-volume combined aerobic and resistance high-intensity interval training on vascular health in people with type 2 diabetes: a randomised controlled trial

Purpose: We compared the effects of low-volume combined aerobic and resistance high-intensity interval training (C-HIIT), combined moderate-intensity continuous training (C-MICT) and waitlist control (CON) on vascular health after 8-weeks of supervised training, and an additional 10-months of self-directed training, in adults with type 2 diabetes (T2D). Methods: Sixty-nine low active adults with T2D were randomised to 8-weeks of supervised C-HIIT (3 times/week, 78-min/week), C-MICT (current exercise guidelines, 4 times/week, 210-min/week) or CON. CON underwent usual care for 8-weeks before being re-randomised to C-HIIT or C-MICT. This was followed by 10-months of self-directed training for participants in C-HIIT and C-MICT. Vascular outcomes were evaluated at baseline, 8-weeks, and 12-months. Results: After 8-weeks, supervised C-HIIT significantly improved relative flow-mediated dilation (FMD) compared with CON (mean difference [MD] 0.8% [0.1, 1.4], p = 0.025). Although not significantly different from CON, the magnitude of change in relative FMD following 8-weeks of supervised C-MICT was similar (MD 0.8% [–0.1, 1.7], p = 0.080). There were no differences in haemodynamic indices, carotid-femoral pulse wave velocity (cfPWV), or aortic reservoir pressure between groups at 8-weeks. After 12-months, there was a significant reduction in haemodynamic indices (time effect, p < 0.05) for both C-HIIT and C-MICT, with no between-group difference. The reduction in cfPWV over 12-months was significantly greater in C-MICT than C-HIIT (group × time effect, p = 0.018). There was no difference in FMD over time or between groups at 12-months. Conclusions: Short-term supervised C-HIIT and C-MICT both increased brachial artery FMD compared with CON. Long-term C-HIIT and C-MICT were beneficial for improving haemodynamic indices, but not brachial artery FMD. C-MICT was superior to C-HIIT for improving cfPWV at 12-months. Trial Registration: Australian New Zealand Clinical Trials Registry Identifier ACTRN12615000475549.