Physical activity among adolescents in New South Wales (Australia): 1997 and 2004.

PURPOSE To examine secular trends, seasonal and socioeconomic differences in physical activity participation among Australian adolescents in 1997 and 2004. METHODS Repeat cross-sectional school survey, conducted in 1997 and 2004. School students were randomly selected from grades 8 and 10 in New South Wales Australia (1997, N = 2026; 2004 N = 1771). Time spent in moderate-to-vigorous physical activity (MVPA) was assessed by self-reported participation in organized and nonorganized physical activity separately for summer and winter by sex, grade, and socioeconomic status (SES). RESULTS Between survey periods, the proportion of students reporting > or = 60 min.d(-1) of MVPA increased, except among grade 10 boys during winter. MVPA (min.d(-1)) increased among all groups during summer school terms, during winter school terms, MVPA was relatively stable between surveys for grade 8 students but inconsistent among grade 10 students. Organized MVPA increased among all groups in both summer (19-49 min.d(-1)) and winter (7-21 min.d(-1)) school terms. Participation in nonorganized MVPA increased only during summer school terms (4-32 min.d(-1)) and decreased during winter school terms (7-17 min.d(-1)). MVPA increased consistently among students in the high-SES group compared with other SES groups, independent of season, and in some cases MVPA decreased in low-SES groups during winter school terms. CONCLUSION Overall, the patterns of change were similar for boys and girls, with substantial increases in summer school terms and insubstantial changes during winter school terms (with the exception of a decrease among grade 10 boys). There was a direct association between change in participation in MVPA and SES, indicating that interventions are required to focus on the needs of less-advantaged students.