Abstract
High-intensity interval training (HIIT) has gained attention as a potentially effective alternative to traditional exercise modalities for individuals with type 2 diabetes mellitus (T2DM). Previous studies have evaluated this exercise strategy with various regimens, comparator groups and outcomes, limiting the generalisability of findings. We performed a novel umbrella review to generate an up-to-date synthesis of the available evidence regarding the effect of HIIT on glycaemic control and other clinically relevant cardiometabolic health outcomes in individuals with T2DM, as compared with traditional moderate-intensity continuous training (MICT) and/or non-exercise control (CON). This umbrella review followed the Preferred Reporting Items for Overviews of Reviews guideline. Seven databases were searched until August 2024. Systematic reviews with meta-analyses comparing HIIT with MICT and/or CON were included. Literature search, data extraction and methodological quality assessment (A MeaSurement Tool to Assess systematic Reviews 2 [AMSTAR-2]) were conducted independently by two reviewers. Ten systematic reviews with meta-analyses, encompassing 76 primary studies and 2954 unique participants, met the inclusion criteria. The data indicated that HIIT significantly improves glycosylated haemoglobin and cardiorespiratory fitness compared with CON (weighted mean difference [WMD]: -0.83% to -0.39% and 3.35-6.38 mL/kg/min) and MICT (WMD: -0.37% to -0.07% and 1.68-4.12 mL/kg/min) in individuals with T2DM. HIIT is also effective in improving other glycaemic parameters, including fasting blood glucose, fasting blood insulin and HOMA-IR. Improvement in body composition, lipid profiles and blood pressure has also been observed following HIIT. Most systematic reviews received moderate to low AMSTAR-2 score. This umbrella review supports HIIT as an efficacious exercise strategy for improving glycaemic control and certain relevant cardiometabolic health outcomes in individuals with T2DM. Our findings offer a comprehensive basis that may potentially contribute to informing physical activity recommendations for incorporating HIIT into T2DM management strategies.