The Effects of Breaking up Prolonged Sitting Time

A Review of Experimental Studies

Fabiana Braga Benatti; Mathias Ried-Larsen

Disclosures

Med Sci Sports Exerc. 2015;47(10):2053-2061. 

In This Article

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, at least in physically inactive and T2D subjects.

The underlying mechanisms within the muscle responsible for these beneficial effects remain elusive. Latouche et al.[18] have shed some light into this matter using the microarray technique in a subsample of patients involved in the study of Dunstan et al..[9] The authors reported that breaking up sitting time with bouts of either light- or moderate-intensity exercise was associated with changes in the muscle expression of genes involved in cellular development, growth and proliferation, and carbohydrate metabolism. Furthermore, Peddie et al.[21] reported a slightly higher mean respiratory exchange ratio in the regular activity–break intervention when compared with prolonged sitting. This suggests an increased carbohydrate oxidation and, potentially, an increased glucose uptake with frequent breaks in the setting of prolonged sitting.

Despite the convincing evidence of the positive effects of replacing prolonged sitting with light-intensity physical activity in physically inactive subjects, a higher intensity or volume seems to be more effective in rendering such positive outcomes in young habitually, physically active subjects.[16] Moreover, there is still great controversy regarding the effectiveness of MVPA in counteracting the hazards of prolonged sitting throughout the day.

In this context, most epidemiological evidence indicates that independent of MVPA practice, a prolonged time spent sitting is still associated with a higher CVD and all-cause mortality risk.[17,19,29] Accordingly, the results of Peddie et al.[21] and Duvivier et al.[10] suggest that a bout of MVPA may not be able to counteract the detrimental effects of prolonged sitting throughout the day and further support the importance of constant interruptions of this sedentary behavior, even with light-intensity activities, at least in physically inactive subjects. In contrast, prospective studies have shown that an MVPA bout can effectively prevent the detrimental effects of prolonged sitting on glucose and lipid metabolism in T2D and physically active subjects.[16,20,28] It is likely that the different experimental designs (i.e., type, volume, and intensity of exercise), information bias in the epidemiological studies (e.g., overreporting of MVPA) and subjects' characteristics across studies may, at least partially, explain the discrepancies. Moreover, the lack of control of physical activity levels and diet intake before the trials in most of the acute studies[3,4,7,10,20–23,28] may also have introduced important bias, which warrants further randomized controlled trials.

Breaking up sitting time fundamentally implies interrupting prolonged periods of time spent sitting it in environments such as the work place (i.e., desk-bound office work) or at home (i.e., during television watching). Therefore, it is of utmost importance that strategies for "breaking up sitting" are both feasible, that is, capable of interrupting prolonged sitting without disturbing or impairing cognitive capacity, and effective in improving cardiometabolic parameters.

In this context, a recent review by Torbeyns et al.[27] reported that active work stations such as standing or treadmill workstations seemed to positively affect important health parameters while not affecting work efficiency, thus being regarded as feasible and effective vehicles to reduce sitting time in the work place. However, of the 31 studies with adults included in the aforementioned review, only three actually measured the effects of replacing sitting/sedentary time per se and concomitantly evaluated metabolic outcomes. Moreover, these studies were small and/or nonrandomized, which may have compromised both the internal and external validity of the findings and need thus to be repeated with in well-designed longer-term prospective experimental studies to confirm the feasibility and effectiveness of these strategies.

In conclusion, epidemiological and 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 subjects' characteristics, especially with respect to subjects' habitual physical activity level. Undoubtedly, there is a great need for more well-designed prospective experimental studies to elaborate on the more feasible and effective (efficient and feasible) physical activity protocol (type, volume, frequency, and intensity) to break prolonged time spent sitting across different population subsets.

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