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.

Fitness Is Independently Associated with Central Hemodynamics in Metabolic Syndrome.

PURPOSE: Fit individuals with metabolic syndrome (MetS) have lower mortality risk compared with less fit counterparts, despite the presence of obesity as a component of the syndrome. To understand the importance of fitness in treating this condition, we examined the association of fitness and fatness with central hemodynamic indices that are known independent predictors of cardiovascular events. METHODS: Sixty-eight individuals with MetS participated in this cross-sectional study. Central hemodynamics is calculated from radial applanation tonometry and comprised aortic reservoir pressure, backward pressure wave (Pb), reflection magnitude (RM), and augmentation index at 75 bpm (AIx75). Cardiorespiratory fitness (CRF) and body fat percentage (BF%) were determined via indirect calorimetry during maximal exercise testing and dual-energy x-ray absorptiometry, respectively. RESULTS: CRF was inversely associated with aortic reservoir pressure (r = -0.29, P = 0.02), Pb (r = -0.42, P < 0.001), RM (r = -0.48, P < 0.001), and AIx75 (r = -0.65, P < 0.001). BF% was also correlated with AIx75 (r = 0.37, P < 0.05) and RM (r = 0.36, P < 0.005) but at a weaker association compared with CRF. Multiple regression analysis revealed CRF as a predictor of aortic reservoir pressure (ß = -0.52, P = <0.01), Pb (ß = -0.41, P < 0.03), and AIx75 (ß = -0.45, P = 0.01), independent of BF% and other confounding factors. CONCLUSIONS: CRF predicts central hemodynamics independent of BF% and other confounding factors. This suggests that CRF improvement may be a higher priority when compared with fat loss for lowering the risk of cardiovascular mortality in MetS individuals.

12 min/week of high-intensity interval training reduces aortic reservoir pressure in individuals with metabolic syndrome: a randomized trial.

OBJECTIVE: Decreased aortic reservoir function leads to a rise in aortic reservoir pressure that is an independent predictor of cardiovascular events. Although there is evidence that high-intensity interval training (HIIT) would be useful to improve aortic reservoir pressure, the optimal dose of high-intensity exercise to improve aortic reservoir function has yet to be investigated. Therefore, this study compared the effect of different volumes of HIIT and moderate-intensity continuous training (MICT) on aortic reservoir pressure in participants with the metabolic syndrome (MetS). METHODS: Fifty individuals with MetS were randomized into one of the following 16-week training programs: MICT [n = 17, 30 min at 60-70% peak heart rate (HRpeak), five times/week]; 4 × 4-min high-intensity interval training (4HIIT) (n = 15, 4 × 4 min bouts at 85-95% HRpeak, interspersed with 3 min of active recovery at 50-70% HRpeak, three times/week); and 1 × 4-min high-intensity interval training (1HIIT) (n = 18, 1 × 4 min bout at 85-95% HRpeak, three times/week). Aortic reservoir pressure was calculated from radial applanation tonometry. RESULTS: Although not statistically significant, there was a trend for a small-to-medium group × time interaction effect on aortic reservoir pressure, indicating a positive adaptation following 1HIIT compared with 4HIIT and MICT [F (2,46) = 2.9, P = 0.07, η = 0.06]. This is supported by our within-group analysis wherein only 1HIIT significantly decreased aortic reservoir pressure from pre to postintervention (pre-post: 1HIIT 33 ±â€Š16 to 31 ±â€Š13, P = 0.03; MICT 29 ±â€Š9-28 ±â€Š8, P = 0.78; 4HIIT 28 ±â€Š10-30 ±â€Š9 mmHg, P = 0.10). CONCLUSION: Three sessions of 4 min of high-intensity exercise per week (12 min/week) was sufficient to improve aortic reservoir pressure, and thus may be a time-efficient exercise modality for reducing cardiovascular risk in individuals with MetS.