Why are physical activity breaks more effective than a single session of isoenergetic exercise in reducing...

Previous studies revealed that interrupting sitting time with short, frequent physical activity (PA) breaks were more effective than a single session of isoenergetic exercise in reducing postprandial glucose. However, in those studies, the expected glucose-lowering effects of single-session exercises were diminished or even eliminated by exercise-induced glucose counterregulation as evidenced by the higher glucose levels during or after exercise compared to uninterrupted sitting. This study was aimed to investigate whether glucose counterregulation is a potential explanation of PA breaks being more effective than a single session of isoenergetic exercise in reducing postprandial glucose. We meta-analysed the standardized mean differences (SMD) of glucose incremental area under the curve (iAUC). PA breaks were more effective than single-session exercise in reducing glucose iAUC (5 studies, SMD = -0.581; 95% confidence interval [CI], -0.777 to -0.385; P < 0.0001) when exercise-induced glucose counterregulation occurred. There was no significant difference in glucose iAUC between PA breaks and single-session exercises (2 studies, SMD = 0.302; 95% CI, -0.107 to 0.711; P = 0.451) when glucose counterregulation did not occur. We concluded that the exercise-induced glucose counterregulation was a potential explanation of PA breaks being more effective than a single session of isoenergetic exercise in reducing postprandial glucose responses. (PROSPERO ID: CRD42020175737).