Young adults often engage in high amounts of sedentary behavior (SB),1 which is defined as “any waking behavior characterized by an energy expenditure of ≤1.5 metabolic equivalents while in a sitting or reclining posture.”2 Although the findings among the studies are inconsistent, there appears to be a potential association between SB and cardiovascular disease risk factors (eg, triglycerides [TG], non-high-density lipoprotein cholesterol [non-HDL-C], HDL-C, and glucose) in young adults.3 Replacing SB with physical activity (PA) of any intensity, including light intensity, has been associated with improved cardio-metabolic health in this group.4

Postprandial hyperglycemia5 and hyperlipidemia,6 described as postprandial dysmetabolism, are risk factors for atherosclerotic cardiovascular disease. Besides these risk factors, a meta-analysis revealed that fasting serum total cholesterol (TC) (hazard ratio: 1.27) and low-density lipoprotein cholesterol (LDL-C) (hazard ratio: 1.25) are associated with increased cardiovascular disease mortality.7 In contrast, HDL-C (hazard ratio: 0.56) is inversely associated with cardiovascular death.7 Given that most young adults are predominantly in the postprandial state and have high amounts of SB during the day, it is crucial to address reducing sedentary time and improving postprandial hyperlipidemia and hyperglycemia to enhance cardio-metabolic health. It has been well-known that exercise reduces postprandial glucose8 and TG9 levels. Furthermore, studies have reported that PA breaks are more effective in lowering postprandial glucose than a single session of isoenergetic exercise when blood glucose levels do not increase during or after exercise as a counter-regulatory response.10 Indeed, spreading exercise throughout the day may be more effective in improving postprandial glycemia than completing a single bout of continuous exercise.11 Interrupting prolonged sitting with regular light or moderate-intensity PA breaks has been shown to decrease blood glucose, insulin, and TG levels.11 Both exercise and interruption of SB appear to have acute beneficial effects on postprandial glucose and TG levels. On the other hand, activity breaks have no acute effect on the postprandial TC, LDL-C, and HDL-C levels in young, healthy adults.12, 13, 14, 15 However, individuals who exercise may be under the misconception that they can sit for prolonged periods afterward. SB has been shown to affect various cardiovascular disease risk factors, including vascular stiffness, endothelial dysfunction, insulin resistance, and elevated blood lipids16; thus, prolonged sitting after exercise may diminish or even reverse the acute beneficial effects of aerobic exercise on postprandial glucose, TG, and cholesterol. Therefore, it is very important to determine whether interrrupting sitting after exercise is superior to prolonged sitting after exercise to improve postprandial glucose, TG, and cholesterol. We aimed to investigate the effects of volume- and intensity-matched light-intensity walking breaks from sitting after aerobic exercise on the postprandial glucose, TG, and cholesterol compared to exercising prior to prolonged sitting. Additionally, we sought to determine the optimal frequency of activity breaks following aerobic exercise to improve postprandial glucose, TG, and cholesterol if activity breaks after aerobic exercise are effective.