How Much Activity Do Youth Get? A Quantitative Review of Heart-Rate Measured Activity Leonard H. Epstein, PhD*; Rocco A. Paluch, MS*; Lisa E. Kalakanis, PhD*; Gary S. Goldfield, PhD‡; Frank J. Cerny, PhD§; and James N. Roemmich, PhD* ABSTRACT. Objective. Recommendations for adult physical activity have shifted from 20 to 60 minutes of continuous vigorous activity 3 to 5 times a week to accu- mulation of 30 minutes of moderate to vigorous physical activity most days of the week. Variations of these guide- lines also have been suggested for children, based on the idea of accumulating moderate to vigorous physical ac- tivity throughout the day, rather than attaining vigorous physical activity in continuous blocks. The goal of this study was to assess accumulated amounts 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 mea- sure physical activity in children to determine accumu- lated daily activity. Included were studies that provided time being active for at least 2 heart rate intensities at or above 120 beats/minute. Descriptive characteristics of the study groups were determined, and the influence of age, gender, and hours and days of observation on the slope 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 14.7  6.0 minutes/day between 20% to 40%, 40% to 50%, 50% to 60%, and greater than 60% HRR, respectively. Age was a significant predictor of the inter- cept and slope of the physical activity and %HRR rela- tionship. Conclusion. Youth of all ages attain >60 minutes/day of low-intensity physical activity and approximately 30 minutes/day of activity at traditional cardiovascular fit- ness training levels of 50% or more of HRR. Recommen- dations for youth activity are discussed. Pediatrics 2001; 108(3). URL: http://www.pediatrics.org/cgi/content/full/ 108/3/e44; activity, heart rate, exercise intensity, exercise duration. ABBREVIATIONS. ACSM, American College of Sports Medicine; CDC, Centers for Disease Control and Prevention; HRR, heart rate reserve; bpm, heart beats per minute; VO 2max , maximal oxygen consumption; METS, metabolic equivalents; MVPA, moderate to vigorous physical activity. T he importance of a physically active lifestyle for reducing the risk of morbidity and mortal- ity is well documented. 1,2 To encourage adop- tion of active lifestyles, the American College of Sports Medicine (ACSM) developed guidelines for the amount of physical activity required to produce health benefits. The original guidelines for youth and adults recommended attainment of 3 to 5 sessions of 20 to 60 minutes of continuous, high-intensity phys- ical activity per week. 3 On the basis of epidemiologic and controlled research in adults on the health ben- efits of lower-intensity, less-structured physical ac- tivity 4,5 and the small percentage of the population who met original guidelines 6 and because modest increases in physical activity were most beneficial for those who were most sedentary, 4,5 the ACSM and the Centers for Disease Control and Prevention (CDC) revised the physical activity guidelines. The current recommendation is that adults and children who are older than 2 years accumulate 30 minutes of at least moderate-intensity physical activity on most but preferably all days of the week. 7 For youth, the shift in recommendations from continuous sessions of higher-intensity activity to allowing moderate-in- tensity activity to be accumulated over shorter bouts means that activities such as walking to school, play- ground activities, and some chores (eg, raking leaves) that would not meet the original duration or intensity standards for aerobic activity may count toward daily physical activity under the new stan- dards. This may mean that more youth will meet the revised guidelines. Weyer et al 8 found that 17.4% of a sample of 109 obese adults met the previous activ- ity guidelines as based on self-reported activity, but 33.9% of the participants met the revised guidelines. Pediatric scientists have used the new recommen- dations to argue that physical activity rather than fitness should be encouraged. 9 Blair et al 10 provided models for ways in which physical activity can im- prove the health of youth. Physical activity can im- prove health directly by reducing body weight, 11 improving blood lipid concentrations, and reducing insulin sensitivity. 12 Activity during childhood also could produce changes that alter health later in life. For example, an active lifestyle could defer the de- velopment of obesity during adolescence, which pre- dicts adult mortality, independent of adult weight. 13 Finally, developing an active lifestyle during child- hood and adolescence may be predictive of being physically active in adulthood, 14,15 when significant From the *Departments of Pediatrics, State University of New York at Buffalo, Buffalo, New York; ‡Children’s Hospital of Eastern Ontario Re- search Institute, Ontario, Canada; and §Department of Physical Therapy, Nutrition and Exercise Sciences, State University of New York at Buffalo, Buffalo, New York. Received for publication Oct 30, 2000; accepted Apr 11, 2001. Reprint requests to (L.H.E.) Department of Pediatrics, School of Medicine and Biomedical Sciences, Farber Hall, University at Buffalo, Buffalo, NY 14214. E-mail: lhenet@acsu.buffalo.edu. PEDIATRICS (ISSN 0031 4005). 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