Improvements in glycaemic control after acute moderate-intensity continuous or high-intensity interval exercise are greater in South Asians than white Europeans with nondiabetic hyperglycaemia: a randomised crossover study

Objective: To examine whether circulating metabolic responses to low-volume high-intensity interval (LV-HIIE) or continuous moderate-intensity aerobic (CME) exercise differ between white Europeans and South Asians with nondiabetic hyperglycaemia (NDH). Research Design and Methods: 13 white Europeans and 10 South Asians (combined median (IQR) age 67 (60–68) years, HbA1c 5.9 (5.8–6.1)% [41.0 (39.9–43.2) mmol·mol-1]) completed three 6-hour conditions (sedentary control [CON], LV-HIIE, CME) in a randomised order. Exercise conditions contained a single bout of LV-HIIE and CME respectively (each ending at 2h), with meals provided at 0 and 3h. Circulating glucose (primary outcome), insulin, insulin resistance index (IRI), triglyceride and non-esterified fatty acids were measured at 0, 0.5, 1, 2, 3, 3.5, 4, 5 and 6h. Data were analysed as post-exercise time-averaged area under the curve (AUC), adjusted for age, sex and pre-exercise AUC. Results: Glucose was similar in each condition and ethnicity, with no condition-by-ethnicity interaction (P≥0.28). However, insulin was lower in LV-HIIE (mean [95% CI]: -44.4 [-23.7, -65.1] mU·L-1) and CME (-33.8 [-13.7, -53.9] mU·L-1) compared to CON. Insulin responses were greater in South Asians (interaction P=0.03) such that values were similar in each ethnicity during exercise conditions, despite being 33% higher in South Asians during CON. IRI followed a similar pattern to insulin. Lipids were unaffected by exercise. Conclusions: Reductions in insulin and insulin resistance after acute LV-HIIE and CME are greater in South Asians than white Europeans with NDH. Further trials are required to examine longer-term impact of LV-HIIE and CME on cardiometabolic health.