Association between Bout Duration of Physical Activity and Health: Systematic Review.

PURPOSE: This study aimed to conduct a systematic literature review to determine whether physical activity episodes of <10 min in duration have health-related benefits or, alternatively, if the benefits are only realized when the duration of physical activity episodes is ≥10 min. METHODS: The primary literature search was conducted for the 2018 Physical Activity Guidelines Advisory Committee Report and encompassed literature through June 2017, with an additional literature search conducted to include literature published through March 2018 for inclusion in this systematic review. RESULTS: The literature review identified 29 articles that were pertinent to the research question that used either cross-sectional, prospective cohort, or randomized designs. One prospective cohort study (N = 4840) reported similar associations between moderate to vigorous physical activity (MVPA) and all-cause mortality when examined as total MVPA, MVPA in bouts ≥5 min in duration, or MVPA in bouts ≥10 min in duration. Additional evidence was identified from cross-sectional and prospective studies to support that bouts of physical activity <10 min in duration are associated with a variety of health outcomes. Randomized studies only examined bouts of physical activity ≥10 min in duration. CONCLUSIONS: The current evidence, from cross-sectional and prospective cohort studies, supports that physical activity of any bout duration is associated with improved health outcomes, which includes all-cause mortality. This may suggest the need for a contemporary paradigm shift in public health recommendations for physical activity, which supports total MVPA as an important lifestyle behavior regardless of the bout duration.

Physical Activity and the Prevention of Weight Gain in Adults: A Systematic Review.

PURPOSE: To conduct a systematic literature review to determine if physical activity is associated with prevention of weight gain in adults. METHODS: The primary literature search was conducted for the 2018 Physical Activity Guidelines Advisory Committee and encompassed literature through June 2017, with an additional literature search conducted to include literature published through March 2018 for inclusion in this systematic review. RESULTS: The literature review identified 40 articles pertinent to the research question. There is strong evidence of an association between physical activity and prevention of weight gain in adults, with the majority of the evidence from prospective cohort studies. Based on limited evidence in adults, however, there is a dose-response relationship and the prevention of weight gain is most pronounced when moderate-to-vigorous intensity physical activity (≥3 METs) is above 150 min·wk. Although there is strong evidence to demonstrate that the relationship between greater time spent in physical activity and attenuated weight gain in adults is observed with moderate-to-vigorous intensity physical activity, there is insufficient evidence available to determine if there is an association between light-intensity activity (<3 METs) and attenuated weight gain in adults. CONCLUSIONS: The scientific evidence supports that physical activity can be an effective lifestyle behavior to prevent or minimize weight gain in adults. Therefore, public health initiatives to prevent weight gain, overweight, and obesity should include physical activity as an important lifestyle behavior.