Physical activity in Ontario preschoolers: prevalence and measurement issues.

Early childhood is a critical period for the development of active living behaviours; however, very little is known about the physical activity levels of preschoolers from Canada. The objectives of this study were to (i) examine physical activity in a sample of Ontario preschoolers by using high-frequency accelerometry to determine activity and step counts; (ii) assess the relationship between step counts and physical activity; (iii) examine the influence of epoch length or sampling interval on physical activity; and (iv) compare measured physical activity to existing recommendations. Thirty 3- to 5-year-old children wore accelerometers to monitor habitual physical activity in 3-s epochs over a 7-day period. Preschoolers engaged in an average of 220 min of daily physical activity, 75 min of which were spent in moderate-to-vigorous physical activity (MVPA), and they accumulated 7529 ± 1539 steps·day(-1). Preschoolers who engaged in more MVPA also took more steps on a daily basis (r = 0.81, p < 0.001). Compared with a 3-s epoch, sampling intervals of 15, 30, and 60 s resulted in an average of 2.9, 9.0, and 16.7 missed minutes of MVPA per day, respectively. All 30 preschoolers met the National Association for Sport and Physical Education recommendation of at least 120 min of total physical activity per day for preschool-age children. Our data highlight important methodological considerations when measuring physical activity in preschoolers and the need for preschool-specific physical activity guidelines for Canadian children.