Metabolic Effect of Breaking Up Prolonged Sitting With Stair Climbing Exercise Snacks

Hossein Rafiei; Kosar Omidian; Étienne Myette-Côté; Jonathan Peter Little

Disclosures

Med Sci Sports Exerc. 2021;53(1):150-158. 

In This Article

Abstract and Introduction

Abstract

Purpose: Prolonged sitting is associated with cardiometabolic complications. The study purpose was to investigate whether breaking up prolonged sitting with brief stair climbing exercise "snacks" could lower postprandial insulin, glucose, and free fatty acids responses.

Methods: In two separate randomized crossover studies, 12 young healthy-weight men (study 1) and 11 adults with overweight/obesity (OW; study 2) completed two experimental conditions: i) sedentary (SED; 9-h sitting) and ii) stair climbing snacks (SS; 8 × 15–30 s once per hour). The same high-glycemic index meals were consumed at 0, 3, and 6 h at each condition. The primary outcome was total insulin area under the curve (AUC) across 9 h.

Results: In healthy-weight men, there were no significant differences between SS and SED for total (9-h) insulin AUC (P = 0.24, d = 0.4), total glucose AUC (P = 0.17, d = 0.48), total nonesterified fatty acid (NEFA) AUC (P = 0.22, d = 0.4), or total triglyceride AUC (P = 0.72). In adults with OW, total insulin AUC (−16.5%, P = 0.036, d = 0.94) and total NEFA AUC (−21%, P = 0.016, d = 1.2) were significantly lower in SS versus SED. No differences were found for total glucose and triglyceride AUC (all, P > 0.31) in participants with OW.

Conclusions: Breaking up 9 h of prolonged sitting with hourly brief stair climbing exercise snacks lowered postprandial insulin and NEFA levels in adults with overweight/obesity.

Introduction

Representing the lowest end of the physical activity spectrum, sedentary behavior is formally defined as any waking behavior with an energy expenditure of ≤1.5 metabolic equivalents during sitting or reclining posture.[1] Sedentary behavior is associated with impaired metabolism and increased cardiometabolic-related morbidity and mortality (reviewed in reference.[2] Sedentary lifestyle is a known risk factor for comorbidities and mortality irrespective of physical activity level.[3] In young healthy people, sedentary behaviors have been shown to cause a substantial increase in the amount of insulin required to clear infused glucose.[4] Postprandial glucose,[5] insulin,[6] and triglycerides (TG)[7] are linked to risk of cardiovascular disease (CVD) morbidity and mortality. Such evidence warrants investigating novel interventions for interrupting prolonged sitting and targeting postprandial insulinemic, glycemic, and lipidemic responses that could decrease CVD risk. Studies report that reducing sedentary time and breaking up prolonged sitting improve markers of cardiometabolic health (reviewed in reference.[8] For example, breaking up prolonged sitting every 20–30 min with 2- to 5-min light-moderate walks[9,10] decreases postprandial glycemia and insulin. The health benefits of such interventions are particularly attractive for individuals who are overweight or obese who often display insulin resistance and are at higher risk of developing type 2 diabetes (T2D).[11]

Accumulating evidence suggests that vigorous-intensity exercise may be particularly effective to promote health by improving cardiorespiratory fitness,[12] increasing fat loss, and reducing cardiometabolic risk.[13] Low-volume sprint interval training, involving repeated short (10–30 s) "all-out" exercise bouts interspersed by periods of recovery, is often regarded as the most time-efficient alternative for traditional endurance exercise.[14,15] Studies report that as few as two to three, 20-s cycling sprints performed as part of a 10-min workout, three times a week over 6–12 wk, can improve fitness, insulin sensitivity, and glucose control.[16,17] Recently, the concept of "sprint snacks" —whereby brief isolated bursts of exercise lasting ~20 s are performed with hours of rest in between—has emerged. Sprint snacks performed as three individual 20-s cycling sprints[18] or ~20-s stair climbing efforts[19] with 1- to 4-h rest in between has been shown to be effective at increasing cardiorespiratory fitness in inactive adults. Whether breaking up prolonged sitting with sprint exercise snacks can improve postprandial metabolism and reduce markers of cardiometabolic disease risk is unknown.

Given the metabolic benefits of breaking up prolonged sitting with short activity breaks[9,10] and the potential fitness benefits of sprint snacks,[18,19] this study was designed to determine if breaking up prolonged sitting with short (15–30 s) stair climbing exercise "snacks" could improve postprandial metabolic control across the day. If efficacious, this type of intervention could be an attractive strategy to negate the acute detrimental effects of sedentary behavior while improving fitness. To this end, we conducted two separate studies with a randomized crossover design in which young healthy weight men (study 1) or adults with overweight/obesity (study 2) remained sedentary for 9 h while consuming three identical meals, or interrupted this sedentary period with 15- to 30-s stair climbing "snacks" every hour. High-glycemic index meals were provided to study participants given that such diet is commonly consumed in Western society and has been associated with increased risk of obesity, T2D, and CVD.[20] We hypothesized that, when compared with a 9-h period of being sedentary, breaking up prolonged sitting with hourly short stair climbing snacks would lower postprandial glucose and insulin responses and reduce free fatty acid levels across the day. Given that breaking up prolonged sitting with light- or moderate-intensity activity seems to benefit metabolism across a range of populations by improving insulin sensitivity,[10,21] insulin area under the curve (AUC; a proxy for insulin sensitivity) was chosen as the primary outcome.

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