A Review of US Adults Weekly Physical Activity Time as Measured by Accelerometry

Abstract

PURPOSE: To analyze the weekly moderate-to-vigorous physical activity times (MVPAt) measured by accelerometry reported in previous studies for US adults. METHODS: Computer-based searches (MEDLINE and Web of Science) and manual searches were conducted in the English language literature from 2001 to 2010. Key words used for the computer searches were physical activity, accelerometer, accelerometry. Inclusion criteria were as follows: (a) subjects were residents of US, apparently healthy, and in the age range of 18-65 yr; (b) subjects were recruited without bias of their previous physical activity level; (c) the independent variable was the 7-day minute-by-minute MVPAt assessed by accelerometry. Research reports were excluded if there was any control of physical activity. For studies sharing the same database, only one was used for the present analysis. As population physical activity patterns might change in time, only reports for the last decade were used. The reported MVPAt (mean ± sd) and 95% confidential level were calculated. A two-sample t-test and an F-test were performed to determine the effect of sample size on reported physical activity times. RESULTS: The average reported MVPAt was 249.48 ± 83.95 min·wk-1, and the 95% confidential interval was (211.73, 287.22 min·wk-1). The sample sizes of these studies ranged from 6 to 639 subjects, with two significant clusters (n < 300 vs. n > 500). Using n=300 as the cut-off point of the sample size, MVPAt of the small sample size reports (n=11) was not significantly different from MVPAt of the large sample size reports (n=8) (277.80 ± 93.28 vs. 210.53 ± 51.93 min·wk-1, p=.06, power=.47); and the variances between the small and large sample size groups were not significantly different (F10,7 = 3.23, p=.13). CONCLUSIONS: ACSM recommends at least 150 min·wk-1 moderate physical activity to maintain and promote health. This study suggests as for those reports using accelerometry, the US adults as a group appear to meet this recommendation. Similar analyses using other methods of estimation of MVPAt are needed.