The Effects of Breaking up Prolonged Sitting Time: A Review of Experimental Studies.

INTRODUCTION: Prolonged time spent in sedentary behaviors (i.e., activities performed while sitting or reclining) has been consistently shown as an independent risk factor for increased cardiometabolic risk and all-cause mortality, whereas breaking up sedentary time is associated with improved cardiometabolic profile. However, there is still great controversy with the respect to what would be the optimal or minimum type, intensity, and frequency of physical activity necessary to revenue such positive outcomes in different populations.

OBJECTIVE: In this review, we aimed to discuss the available evidence from prospective experimental studies regarding the beneficial effects of breaking up prolonged sitting time on cardiometabolic risk factors, and the influence of intensity, frequency, and volume of the physical activity replacing sitting.

METHODS: A structured computer-based search on the electronic databases PUBMED and SCOPUS was independently conducted by two researchers. Only prospective intervention studies (controlled and uncontrolled) evaluating the effects of explicitly replacing sitting time with physical activity (including standing) on metabolic parameters as outcomes were included.

RESULTS: Seventeen studies were included in the review.

DISCUSSION: The currently available prospective experimental studies do advocate that breaking up sitting time and replacing it with light-intensity ambulatory physical activity and standing may be a stimulus sufficient enough to induce acute favorable changes in the postprandial metabolic parameters in physically inactive and type 2 diabetic subjects, whereas a higher intensity or volume seems to be more effective in rendering such positive outcomes in young habitually physically active subjects.

CONCLUSION: Prospective experimental studies provide considerable evidence of the positive effects of breaking up prolonged time spent sitting on metabolic outcomes. However, it seems that the type, intensity, and frequency of physical activity necessary to effectively counteract the detrimental effects of prolonged sitting may differ according to the subjects' characteristics, especially with respect to the subjects' habitual physical activity level.