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.