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This study examined average daily physical activity and discrete activity intensities in 102 adolescents (age M = 15 yr). Dependent physical activity variables were constructed from minute-by-minute movement counts measured during 4 consecutive days of accelerometry. Independent variables included gender, sexual maturation, TV viewing, and video playing. The stability of 4 days of activity measures ranged from R = .66 to 30. Video game playing was inversely associated with average daily movement for boys (r = −.38) and girls (r = −.55). Boys at all levels of sexual maturation had higher levels of activity than girls. Late and postpubertal boys and girls were more sedentary, had lower levels of vigorous activity, and lower levels of average daily movement than boys and girls in midpuberty.
K.F. Janz is with the Department of Sport, Health, and Leisure Studies at the University of Iowa, 102 FH, Iowa City, IA 52242. L.T. Mahoney is with the Department of Preventive Medicine and Environmental Health and the Department of Pediatrics, Divison of Pediatric Cardiology at the University of Iowa, Iowa City, IA 52242.