Research article
Promoting Physical Activity in Middle School Girls: Trial of Activity for Adolescent Girls

https://doi.org/10.1016/j.amepre.2007.11.018Get rights and content

Background

Physical activity is important for weight control and good health; however, activity levels decline in the adolescent years, particularly in girls.

Setting/participants

Middle school girls with English-speaking skills and no conditions to prevent participation in physical activity in 36 schools in six geographically diverse areas of the United States. Random, cross-sectional samples were drawn within schools: 6th graders in 2003 (n=1721) and 8th graders in 2005 (n=3504) and 2006 (n=3502).

Intervention

A 2-year study-directed intervention (fall 2003 to spring 2005) targeted schools, community agencies, and girls to increase opportunities, support, and incentives for increased physical activity. Components included programs linking schools and community agencies, physical education, health education, and social marketing. A third-year intervention used school and community personnel to direct intervention activities.

Main outcome measures

The primary outcome, daily MET-weighted minutes of moderate-to-vigorous physical activity (MET-weighted MVPA), was assessed using accelerometry. Percent body fat was assessed using anthropometry.

Results

After the staff-directed intervention (pre-stated primary outcome), there were no differences (mean=−0.4, 95% CI=−8.2 to 7.4) in adjusted MET-weighted MVPA between 8th-grade girls in schools assigned to intervention or control. Following the Program Champion–directed intervention, girls in intervention schools were more physically active than girls in control schools (mean difference 10.9 MET-weighted minutes of MVPA, 95% CI=0.52–21.2). This difference is about 1.6 minutes of daily MVPA or 80 kcal per week. There were no differences in fitness or percent body fat at either 8th-grade timepoint.

Conclusion

A school-based, community-linked intervention modestly improved physical activity in girls.

Trial Registration

NCT00006409

Introduction

Physical inactivity is an independent risk factor for cardiovascular and other diseases and a major contributor to obesity in adults.1 The health-related sequelae of physical inactivity—type 2 diabetes, high blood pressure, dyslipidemia, obesity, and sleep disorders—have increased in children and adolescents.2 About 6% to 20% of adolescents are physically inactive3; 17% of children and adolescents are overweight4; and 26% to 75% of overweight youths become obese adults.5 Effective interventions to increase physical activity among adolescents could reduce obesity prevalence and reduce disease risk in youth and adults.6

Despite the known health benefits, physical activity declines among youth in the U.S. as they grow through adolescence.7 The decline is more prevalent in girls than in boys, suggesting that interventions targeting girls are needed.8 Interventions to promote physical activity, generally directed to both boys and girls, have been conducted in school settings,9 but have met with limited success, perhaps because only about 30 hours per year of moderate-to-vigorous physical activity (MVPA) occur in physical education in schools.10, 11

Previous intervention studies have focused primarily on school settings. The Middle School Physical Activity and Nutrition (M-SPAN) study targeted physical activity change in physical education class and other periods throughout the school day and noted an increase in observer-recorded physical activity in the intervention schools relative to control schools for boys, but not for girls.12 The Child and Adolescent Trial for Cardiovascular Health (CATCH)13 and the Sports, Play and Active Recreation for Kids (SPARK)14 studies reported increased physical activity in physical education class in intervention compared to control schools. CATCH found a concomitant increase in vigorous physical activity from self-reported assessment that was sustained over additional follow-up periods.15 The Pathways study noted intervention–control differences in physical activity measured by self-report, but not accelerometry.16 The Lifestyle Education for Activity Program (LEAP), an environmental intervention, targeted girls in South Carolina high schools and found increased vigorous physical activity in intervention compared with control schools as measured by self-report.17 In Belgium, a middle school physical activity and healthy eating intervention showed positive intervention effects on physical activity for both boys and girls18 and on BMI for girls.19

The National Heart, Lung, and Blood Institute (NHLBI) sponsored the multi-center group-randomized Trial of Activity for Adolescent Girls (TAAG) to develop, implement, and evaluate an intervention that linked schools to community organizations to reduce the age-related decline in MVPA in middle school girls.20 TAAG was designed to overcome limitations in previous intervention studies following guidelines proposed by the Centers for Disease Control and Prevention (CDC).21 Cooperative agreements funded field centers at the University of Arizona, San Diego State University, Tulane University, the University of Maryland, the University of Minnesota, and the University of South Carolina. The Coordinating Center was at the University of North Carolina, Chapel Hill. The NHLBI project office collaborated in the research. The purpose of this paper is to report the primary and secondary outcomes of TAAG.

Section snippets

Specific Objectives and Hypotheses

The primary aim of TAAG was to test an intervention to reduce by half the observed decline in MVPA experienced by adolescent girls. Based on prior data about the magnitude of decline, TAAG was powered to detect a difference of 14.5 MET-weighted minutes of MVPA, favoring girls in intervention schools compared to girls in control schools at the 8th grade.20, 22 One MET-minute represents one metabolic equivalent of energy expended for 1 minute. Secondary aims, at the individual level, were to

Study Sample

All 36 schools participated in the 6th-grade measurements during spring 2003 and in the 8th-grade measurements during spring 2005; however, only 34 schools participated in the 8th-grade measurements during spring 2006. During 2003 spring, 60 girls per school were randomly chosen. A total of 1721 (79.7%) of the 2160 eligible girls consented and participated in the measurement (Figure 2). During 2005 spring, 4123 girls were eligible for the student-level measurements, and 3504 (85.0%) consented

Discussion

Over the 3 years of TAAG, there was a modestly higher level of physical activity for girls in intervention schools compared to girls in control schools. In 6th grade, girls in control schools had about 2.2 MET-weighted minutes more per day of MVPA than did girls in intervention schools. At the end of the staff-directed intervention, there was less than 1 MET-weighted-minute-per-day difference between girls in the two sets of schools (prestated primary outcome); however, at the end of the

Conclusion

Although the TAAG intervention was intense and well-received by the middle school girls, the results, although statistically significant for the 2006 measurements, were modest. The difference in daily minutes of MVPA for girls in intervention schools compared to girls in control schools was only 1.6 minutes. Because activities at or above moderate intensity expend approximately 30 kJ/min (7.17 kcal/min) in adolescent girls,54 this would translate into 80 kcal/week or 2880 kcal/36-week of

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