Abstract
BackgroundThe total activity volume performed is an overall measure that takes into account the frequency, intensity, and duration of activities performed. The importance of considering total activity volume is shown by recent studies indicating that light physical activity (LPA) and intermittent moderate-to-vigorous physical activity (MVPA) have health benefits. Accelerometer-derived total activity counts (TAC) per day from a waist-worn accelerometer can serve as a proxy for an individual's total activity volume. The purpose of this study was to develop age- and gender-specific percentiles for daily TAC, minutes of MVPA, and minutes of LPA in U.S. youth ages 6 – 19 y.MethodsData from the 2003 – 2006 NHANES waist-worn accelerometer component were used in this analysis. The sample was composed of youth aged 6 – 19 years with at least 4 d of ≥ 10 hours of accelerometer wear time (N = 3698). MVPA was defined using age specific cutpoints as the total number of minutes at ≥4 metabolic equivalents (METs) for youth 6 – 17 y or minutes with ≥2020 counts for youth 18 – 19 y. LPA was defined as the total number of minutes between 100 counts and the MVPA threshold. TAC/d, MVPA, and LPA were averaged across all valid days.ResultsFor males in the 50th percentile, the median activity level was 441,431 TAC/d, with 53 min/d of MVPA and 368 min/d of LPA. The median level of activity for females was 234,322 TAC/d, with 32 min/d of MVPA and 355 min/d of LPA.ConclusionPopulation referenced TAC/d percentiles for U.S. youth ages 6-19 y provide a novel means of characterizing the total activity volume performed by children and adolescents.
Highlights
Physical activity (PA) in youth is associated with a reduced risk of obesity, type 2 diabetes, and other cardiometabolic risk factors [1]
234,322 total activity counts (TAC)/d, with approximately 32 min/d spent in moderate-to-vigorous PA (MVPA) and 355 min/d of light physical activity (LPA)
An exception was seen for females in the 95th and 97th percentiles, where total activity counts per day (TAC/d) was found to be highest at age seven
Summary
Physical activity (PA) in youth is associated with a reduced risk of obesity, type 2 diabetes, and other cardiometabolic risk factors [1]. It is known that tri-axial activity counts from a wrist accelerometer predict energy expenditure better than uni-axial activity counts [4, 5, 7]. For accelerometers placed at the waist, there is less evidence that tri-axial counts per minute are superior to uni-axial. Sasaki et al [8] developed cut-points for the ActiGraph GT3X worn at the waist, and concluded that further research was needed to determine whether vector magnitude (i.e., tri-axial activity) counts yield better predictions of energy expenditure than vertical axis activity counts. Conclusion: Population referenced TAC/d percentiles for U.S youth ages 6-19 y provide a novel means of characterizing the total activity volume performed by children and adolescents
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