Background: Over the last decade use of raw acceleration metrics to assess physical activity has increased. Metrics such as Euclidean Norm Minus One (ENMO), and Mean Amplitude Deviation (MAD) can be used to generate metrics which describe physical activity volume (average acceleration), intensity distribution (intensity gradient), and intensity of the most active periods (MX metrics) of the day. Presently, relatively little comparative data for these metrics exists in youth. To address this need, this study presents age- and sex-specific reference percentile values in England youth and compares physical activity volume and intensity profiles by age and sex. Methods: Wrist-worn accelerometer data from 10 studies involving youth aged 5 to 15 y were pooled. Weekday and weekend waking hours were first calculated for youth in school Years (Y) 1&2, Y4&5, Y6&7, and Y8&9 to determine waking hours durations by age-groups and day types. A valid waking hours day was defined as accelerometer wear for ≥ 600 min·d−1 and participants with ≥ 3 valid weekdays and ≥ 1 valid weekend day were included. Mean ENMO- and MAD-generated average acceleration, intensity gradient, and MX metrics were calculated and summarised as weighted week averages. Sex-specific smoothed percentile curves were generated for each metric using Generalized Additive Models for Location Scale and Shape. Linear mixed models examined age and sex differences. Results: The analytical sample included 1250 participants. Physical activity peaked between ages 6.5–10.5 y, depending on metric. For all metrics the highest activity levels occurred in less active participants (3rd-50th percentile) and girls, 0.5 to 1.5 y earlier than more active peers, and boys, respectively. Irrespective of metric, boys were more active than girls (p < .001) and physical activity was lowest in the Y8&9 group, particularly when compared to the Y1&2 group (p < .001). Conclusions: Percentile reference values for average acceleration, intensity gradient, and MX metrics have utility in describing age- and sex-specific values for physical activity volume and intensity in youth. There is a need to generate nationally-representative wrist-acceleration population-referenced norms for these metrics to further facilitate health-related physical activity research and promotion.
|Number of pages||14|
|Journal||International Journal of Behavioral Nutrition and Physical Activity|
|Early online date||25 Mar 2023|
|Publication status||E-pub ahead of print - 25 Mar 2023|
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FunderThe authors thank the participating students and schools for taking part in the contributing studies, and West Lancashire Sport Partnership and Liverpool School Sport Partnership for their assistance. Full or partial funding support for the studies from the Waterloo Foundation and Edge Hill University is gratefully acknowledged. Funding Information: Funding for selected contributing studies was provided by the Waterloo Foundation (#1669/3509), West Lancashire Sport Partnership, West Lancashire Leisure Trust, Edge Hill University, and Wigan Council. Alex Rowlands is supported by the Lifestyle Theme of the Leicester NHR Leicester Biomedical Research Centre and NIHR Applied Research Collaborations East Midlands (ARC-EM). These funders had no role in the design of the study and collection, analysis, and interpretation of data, and in writing the manuscript. Funding Information: The authors thank the participating students and schools for taking part in the contributing studies, and West Lancashire Sport Partnership and Liverpool School Sport Partnership for their assistance. Full or partial funding support for the studies from the Waterloo Foundation and Edge Hill University is gratefully acknowledged. Publisher Copyright: © 2023, The Author(s).
- Raw data
- Average acceleration
- Intensity gradient
- MX metrics