Abstract
To determine whether the amount of television (TV) watched by participants enrolled in a physical activity intervention mediates or moderates program effectiveness. Nine-month, controlled, school-based physical activity intervention. Public high school. One hundred twenty-two sedentary adolescent females (mean +/- standard deviation age = 15.04 +/- 0.79 years). Supervised in-class exercise, health education, and internet-based self-monitoring. Physical activity by 3-day physical activity recall; TV viewing by self-reports; cardiovascular fitness by cycle ergometer. T-tests were conducted to examine between-group differences. Linear regression equations tested the mediating or moderating role of TV watching relative to the intervention. TV viewing moderated the intervention's effect on vigorous activity; the intervention significantly predicted change in physical activity among high (beta = -.45; p < .001), but not among low (p > .05), TV watchers. TV viewing did not mediate the intervention effect. Consistent with displacement theory, adolescents who watched more TV prior to the intervention showed postintervention increases in vigorous physical activity and concomitant decreases in TV viewing, whereas those who watched less TV showed no change in physical activity or TV viewing.
Highlights
Comparisons were made for age, VO2max, and Body mass index (BMI), but this data is not included in Table 1, as there were no significant differences between any of the groups for these variables
There were no significant differences between high-TV viewers at the intervention and the comparison schools
Moderation was evidenced, in that adolescents who were above the median in TV viewing at baseline showed postintervention increases in vigorous Physical activity (PA) and simultaneous decreases in TV viewing, whereas those who were below the median for TV viewing showed no change in vigorous PA or in TV viewing
Summary
A 9-month, controlled, school-based PA intervention was conducted at two Southern California high schools. Sample Participants were sedentary adolescent females (N 5 122; mean 6 standard deviation (SD) age 5 15.04 6 .79 years) who were recruited via flyers at two public high schools. Intervention Participants attended supervised exercise sessions 4 days per week throughout the school year (approximately 40 minutes of PA per session). The intervention effectively increased average levels of PA and cardiovascular fitness among the participants.. Ences (i.e., age, ethnicity, VO2max, BMI, TV viewing time, and amount of vigorous activity) between groups (i.e., high- and lowTV groups overall, intervention and comparison groups overall, and high- and lowTV groups within the intervention and comparison groups) at baseline. Paired t-tests examined the changes in vigorous activity and TV viewing over time within each of the four subgroups: high-TV intervention, low-TV intervention, high-TV comparison, and low-TV comparison
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