Participation in extracurricular physical activity programs at middle schools.
Powers
Holly S
HS
Community Pediatrics at the University of California San Diego, USA.
Conway
Terry L
TL
McKenzie
Thomas L
TL
Sallis
James F
JF
Marshall
Simon J
SJ
D000293:Adolescent; D002140:California; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D010806:Physical Education and Training / Q000458:organization & administration / Q000706:statistics & numerical data*