Effects of high intensity interval training and its different protocols in VO2max and HbA1c in type 2 diabetes: a metanalysis

High intensity interval training (HIIT) has been used as an efficient strategy in patients with type 2 diabetes (T2D) and the choice of the most appropriate HIIT protocol for physiological responses. The aim of this study was to systematically review the effects of HIIT and its different protocols, compared to continuous training of moderate intensity (MICT) and control, in VO2max and HbA1c in patients with T2D. A search was conducted in the PubMed / MEDLINE, EMBASE, Cochrane CENTRAL, Sport Discus and Web of Science databases, including randomized controlled trials that compared HIIT with MICT or control, in adults with T2D. The meta-analysis was performed using the random effect model and the data were presented by weighted mean difference (WMD), together with the 95% confidence intervals (CI). Of the 726 records found, 20 studies were included. The meta-analysis showed that HIIT promoted a significant increase in VO2max from 5.092 mL / kg / min (95% CI 2.994 to 7.190) compared to the control and from 1.896 mL/kg/min (95% CI 0.810 to 2.982) in comparison to MICT. In HbA1c, HIIT promoted a significant reduction of -0.776% (95% CI -1.060 to -0.493) in relation to the control, however there was no significant difference when compared to the MICT. When compared to the control, the moderate interval, high volume and long period caused a significantly greater increase in VO2max. However, long intervals, moderate volumes and periods showed greater increases in VO2max compared to MICT. In HbA1c, a short interval, moderate volume and period caused greater reductions compared to the control. In conclusion, HIIT provides greater benefits to functional capacity in T2D, but induces similar effects to MICT in HbA1c. The protocols of moderate to long interval, moderate to high volume and period of moderate to long training can represent effective and efficient strategies to improve the effects of HIIT on VO2max and HbA1c in patients with T2D.