Age and gender differences in objectively measured physical activity in youth.
OBJECTIVE
The purpose of this study was to evaluate age and gender differences in objectively measured physical activity (PA) in a population-based sample of students in grades 1-12.


METHODS
Participants (185 male, 190 female) wore a CSA 7164 accelerometer for 7 consecutive days. To examine age-related trends, students were grouped as follows: grades 1-3 (N = 90), grades 4-6 (N = 91), grades 7-9 (N = 96), and grades 10-12 (N = 92). Bouts of PA and minutes spent in moderate-to-vigorous PA (MVPA) and vigorous PA (VPA) were examined.


RESULTS
Daily MVPA and VPA exhibited a significant inverse relationship with grade level, with the largest differences occurring between grades 1-3 and 4-6. Boys were more active than girls; however, for overall PA, the magnitudes of the gender differences were modest. Participation in continuous 20-min bouts of PA was low to nonexistent.


CONCLUSIONS
Our results support the notion that PA declines rapidly during childhood and adolescence and that accelerometers are feasible alternatives to self-report methods in moderately sized population-level surveillance studies.
Trost
Stewart G
SG
School of Human Movement Studies, University of Queensland, Brisbane, Australia. strost@hms.uq.edu.au
Pate
Russell R
RR
Sallis
James F
JF
Freedson
Patty S
PS
Taylor
Wendell C
WC
Dowda
Marsha
M
Sirard
John
J
D000203:Activities of Daily Living; D000293:Adolescent; D017677:Age Distribution; D002648:Child; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D012574:Schools; D017678:Sex Distribution; D013177:Sports / Q000706:statistics & numerical data; D013334:Students / Q000706:statistics & numerical data*