The Effects of a 16-week Physical Activity Intervention on Physical Activity Levels in Children

Purpose This study investigated the effect of a 16-week physical activity intervention on physical activity levels in children.

Methods Forty-one boys and girls (mean age = 9.6 ± 1.0 years) were randomized to either a control (n=17) or intervention (n=24) group. Children randomized to the intervention group exercised for one hour at least 3 days/week for 16 weeks. The intensity goal for the exercise sessions was a heart rate of ≥140 beats per minute. The exercises completed were free play activities in either a one-on-one setting or within small groups. Physical activity levels were measured by an ActiGraph accelerometer and pedometer for 5 days at baseline and post-intervention. A series of 2 x 2 (group x time) repeated measures ANOVAs examined the effects of the intervention on time spent in sedentary behavior as well as in light, moderate, and vigorous physical activity. The interaction effect of group and time on the physical activity levels was also examined. Statistical significance was set at p<.05.

Results A significant time effect was observed for sedentary behavior, as well as light and moderate physical activity (p<.05). Over the 16 weeks, in both groups sedentary time increased (control: 825.7 vs. 904.1 min; intervention: 895.3 vs. 994.7 min) and minutes of light physical activity decreased (control: 207.3 vs. 167.9 min; intervention: 181.6 vs. 161.3 min). Group effects were not present for these physical activity levels. A group by time interaction was present for moderate physical activity. Over 16 weeks, minutes of moderate physical activity decreased in the controls (pre:35.4 min; post: 24.0 min), but remained the same among those in the interventiongroup (pre: 28.4 min; post: 28.6 min). Neither time nor group effects were observed for vigorous physical activity and pedometer steps.

Conclusions physical activity intervention did not influence time spent in sedentary behavior or light physical activity. Further, this intervention was able to maintain the time children spend in moderate physical activity. Physical activity interventions may help slow the decline in preadolescent children’s moderate physical activity levels.

Supported by NIH Grant RO1DK07108-02