Design of the Trial of Activity in Adolescent Girls (TAAG)

June Stevens, David M. Murray, Diane J. Catellier, Peter J Hannan, Leslie A. Lytele, John P. Elder, Deborah R. Young, Denise G. Simons-Morton, Larry S. Webber

Research output: Contribution to journalArticlepeer-review

132 Scopus citations

Abstract

The primary aim of the Trial of Activity in Adolescent Girls (TAAG) is to test an intervention to reduce by half the age-related decline in moderate to vigorous physical activity (MVPA) in middle school girls. The intervention will be evaluated using a group-randomized trial involving 36 middle schools. The primary endpoint is the mean difference in intensity-weighted minutes (i.e., MET-minutes) of MVPA between intervention and comparison schools assessed using accelerometry. The TAAG study design calls for two cross-sectional samples, one drawn from 6th graders at the beginning of the study and the second drawn from 8th graders at the end of the study following the 2-year implementation of the intervention. An important strength of this design over a cohort design is the consistency with the goals of TAAG, which focus on environmental-level rather than individual-level interventions to produce change. The study design specifies a recruitment rate of 80% and a smaller sample of girls at baseline (n=48 per school) than at follow-up (n=96 per school). A two-stage model will be used to test the primary hypothesis. In the first stage, MET-weighted minutes of MVPA will be regressed on school, time (baseline or follow-up), their interaction, ethnicity and week of data collection. The second stage analysis will be conducted on the 72 adjusted means from the first stage. In the main-effects model, we will regress the follow-up school mean MET-weighted minutes of MVPA on study condition, adjusting for the baseline school mean. The TAAG study addresses an important health behavior, and also advances the field of group-randomized trials through the use of a study design and analysis plan tailored to serve the main study hypothesis.

Original languageEnglish (US)
Pages (from-to)223-233
Number of pages11
JournalContemporary Clinical Trials
Volume26
Issue number2
DOIs
StatePublished - Apr 2005

Bibliographical note

Funding Information:
The National Heart, Lung, and Blood Institute (NHLBI) is participating in and sponsoring this project, which is funded under cooperative agreements. Six universities were awarded funds to establish field centers in the vicinities of Washington, D.C. and Baltimore, Maryland (University of Maryland); Columbia, South Carolina (University of South Carolina); Minneapolis, Minnesota (University of Minnesota); New Orleans, Louisiana (Tulane University); Tucson, Arizona (University of Arizona); and San Diego, California (San Diego State University). The Coordinating Center is at the University of North Carolina, Chapel Hill.

Keywords

  • Accelerometry
  • Cross-sectional design
  • Group-randomized trial
  • Intervention
  • Middle School
  • Physical activity

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