Intensity of bouted and sporadic physical activity and the metabolic syndrome in adults

Background. Physical activity guidelines for adults only recognize the health benefits of accumulating bouted moderate-to-vigorous physical activity (MVPA), or MVPA occurring over at least 10 consecutive minutes. There is a lack of evidence supporting the health benefits of other patterns and intensities of activity including sporadic MVPA (i.e., MVPA occurring in periods of fewer than 10 consecutive minutes) and light intensity physical activity (LIPA). The objective of this study was to examine the health benefits associated with physical activity that does not meet the physical activity guidelines criteria for bouted MVPA. Specifically, we examined the association between sporadic MVPA and bouted and sporadic LIPA with the metabolic syndrome. Methods. We studied a representative cross-sectional sample of 1,974 adults aged 20 years and older from the 2003-2006 US National Health and Nutrition Examination Survey. Physical activity was measured over 7 days using Actigraph AM-7164 accelerometers. Each minute over the 7-day measurement period was classified as being of a sedentary, light, or moderate-to-vigorous intensity. A 10 min threshold differentiated bouted activity from sporadic activity. Average minutes/day of sporadic LIPA, sporadic MVPA, bouted LIPA, bouted MVPA, and embedded MVPA (MVPA occurring within bouts of primarily LIPA) were calculated. Metabolic syndrome status was determined using established criteria. Associations were examined using logistic regression and controlled for relevant covariates. Results. For every 30 min/day of physical activity, the odds ratio (95% confidence interval) of the metabolic syndrome was reduced by 4% (1-7%) for bouted LIPA, 64% (51-71%) for bouted MVPA, and 57% (45-67%) for embedded MVPA. Sporadic LIPA was not independently associated with the metabolic syndrome. We could not examine the association between sporadic MVPA and the metabolic syndrome because participants accumulated such a marginal amount of this type of activity (i.e., median = 2 min/day, only 11% of participants accumulated ≥5 min/day). Conclusion. The intensity of non-bouted activity is important, as embedded MVPA had a stronger association with the metabolic syndrome than sporadic LIPA and a comparable association to bouted MVPA.