5American Academy of Pediatrics, American Public Health As- sociation,National Resource Center for Health and Safety in Child Care and Early Education. 2011. Caring for Our Children: National Health and Safety Performance Standards; Guidelines for Early Care and Education Programs[M]. Elk GroveVillage, IL: American Academy of Pediatrics; Washington, DC: Ameri can Public Health Association, 2011 : 90-91.
6BIDDLE S J, PEARSON N, ROSS G M, et a l. Tracking of sed- entary behaviors of young people: a systematic review[J]. Pre Med, 2010,51 (5) : 345-351.
7BOCARRO J N, FLOYD M F, SMITH W R, et al. Social and environmental factors related to boys' and girls" park-based physical activity[J ]. Prev Chronic Dis, 2015,12 (6) : 140532.
8BONVIN A, BARRAL J, KAKEBEEKE T H, et al. Weight status and gender-related differences in motor skills and in child care - based physical activity in young children[J]. BMC Pediatr, 2012,12(3) : 23.
9BURDETTE H L,WHITAKER R C,DANIELS S R. Parental report of outdoor playtime as a measure of physical activity in preschool aged children[J]. Arch Pediatr Adolesc Med, 2004, 158(4) :353-357.
10DOLINSKY D H, NAMENEK BROUWER R J, et al. Corre- lates of sedentary time and physical activity among preschool- aged children[J]. Prev Chronic Dis, 2011,8 (6) : 1-14.
