How much activity do youth get? A quantitative review of heart-rate measured activity

Objective. Recommendations for adult physical activity have shifted from 20 to 60 minutes of continuous vigorous activity 3 to 5 times a week to accum ulation of 30 minutes of moderate to vigorous physical activity most days o f the week. Variations of these guidelines also have been suggested for chi ldren, based on the idea of accumulating moderate to vigorous physical acti vity throughout the day, rather than attaining vigorous physical activity i n continuous blocks. The goal of this study was to assess accumulated amoun ts of physical activity at different intensities in children. Methods. We reviewed 26 studies (n = 1883) in youth aged 3 to 17 years that used heart-rate recording to measure physical activity in children to dete rmine accumulated daily activity. Included were studies that provided time being active for at least 2 heart rate intensities at or above 120 beats/mi nute. Descriptive characteristics of the study groups were determined, and the influence of age, gender, and hours and days of observation on the slop e of activity time as a function of percentage of heart rate reserve (HRR) was determined using hierarchical linear regression. Results. Youth attained 128.0 +/- 45.6, 47.1 +/- 14.9, 29.3 +/- 13.7, and 1 4.7 +/- 6.0 minutes/day between 20% to 40%, 40% to 50%, 50% to 60%, and gre ater than 60% HRR, respectively. Age was a significant predictor of the int ercept and slope of the physical activity and %HRR relationship. Conclusion. Youth of all ages attain >60 minutes/day of low-intensity physi cal activity and approximately 30 minutes/day of activity at traditional ca rdiovascular fitness training levels of 50% or more of HRR. Recommendations for youth activity are discussed.