Abstract
OBJECTIVES: This study aimed to evaluate the effects of a novel, low-volume combined high-intensity interval training (HIIT) and progressive resistance training (PRT) in overweight/obese adults. METHODS: This randomised control trial compared the effect of regular supervised HIIT combined with PRT (Exercise) with an unsupervised stretching intervention (Control), in previously inactive adults with either normal glucose (NG), pre-diabetes or type 2 diabetes (T2DM) with body mass index of >25 kg/m(2). Participants were randomly allocated (1:1) to receive low-volume exercise or control by an online randomisation tool. The primary outcome was the difference in change of hepatic steatosis between Exercise and Control. A prespecified sensitivity analysis was undertaken for weight stable participants (<5% change in bodyweight from baseline). Secondary outcomes were change in hepatic steatosis within the glucose groups, glycaemic control, cardiorespiratory fitness, muscle strength and body composition. RESULTS: Between June 2018 and May 2021, 162 participants were randomly assigned (NG: 76, pre-diabetes: 60, T2DM: 26) and 144 were included in the final analysis. Mean absolute change in hepatic steatosis was -1.4% (4.9) in Exercise (n=73) and -0.1% (7.2) in Control (n=71)(p=0.25). By preplanned sensitivity analysis, the mean change in hepatic steatosis with Exercise (n=70) was -1.5% (5) compared with 0.7% (4.6) with Control (n=61) (p=0.017). Subgroup analysis within the glucose groups showed that exercise reduced hepatic steatosis in those with pre-diabetes but not NG or T2DM (pre-diabetes: -1.2% (4.4) in Exercise and 1.75% (5.7) in Control, p=0.019). CONCLUSION: These findings show that low-volume HIIT with PRT yields improvements in muscle strength and cardiorespiratory fitness and may have a small effect on hepatic steatosis. TRIAL REGISTRATION NUMBER: The trial was prospectively registered with the ANZCTR (ACTRN12617000552381).