Description of Sporadic Physical Activity and the Relationship between Non-Bouted Physical Activity and the Metabolic Syndrome in American Adults

Abstract

Less than 15% of North American adults currently met the physical activity guidelines. These guidelines recommend that adults accumulate at least 150 minutes per week of moderate-to-vigorous physical activity (MVPA) in bouts of 10 minutes or more. Emerging evidence suggests that accumulating sporadic MVPA (i.e. physical activity performed in periods of less than 10 consecutive minutes) also has health benefits. Little is known about how much sporadic physical activity (SPA) adults get. Furthermore, it is not known if SPA needs to be of at least moderate intensity to convey health benefits. The purpose of this thesis was twofold: 1) to describe SPA levels and intensity patterns in adults, and 2) to investigate the relationship between various intensities of SPA and the metabolic syndrome. The metabolic syndrome is a clustering of risk factors for cardiovascular disease and diabetes. Data for the thesis research came from the National Health and Nutrition Examination Survey, a representative cross-sectional sample of adults from the United States. Physical activity was measured over 7 days using accelerometers, which are small electronic sensors worn on the hip. The metabolic syndrome was determined from direct body measurements and blood samples. Results of this thesis indicate that the typical American adult accumulates 103 minutes/day of SPA, which represented 27% of their total daily physical activity. Of these 103 minutes/day, only 2 minutes/day were of moderate-to-vigorous intensity. However, adults accumulated 16 minutes/day of MVPA that was embedded within bouts of primarily light intensity activity – this activity did not meet the MVPA bout criteria but it was not truly sporadic since it occurred within bouts of primarily light intensity activity. Accumulation of this iii embedded MVPA was as strongly related to the MetS as bouted MVPA. Conversely, sporadic light intensity physical activity was weakly associated with the metabolic syndrome. Together, these results suggest MVPA is commonly accumulated outside of the current recommended bout length and that this type of activity is strongly associated with the metabolic syndrome.