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

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., METminutes) 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 grouprandomized trials through the use of a study design and analysis plan tailored to serve the main study hypothesis.

Correlates of Physical Activity Guideline Compliance for Adolescents in 100 U.S. Cities

“…As expected, there were large sex differences, with 57% of males versus 40% of females meeting guidelines. This is a large difference, indicating that many more males than females are being physically active enough to gain health benefits and that more interventions are needed to target adolescent females [26]. Following the collection of our data, the first report was published that provided national data for adolescent physical activity guideline compliance.…”

Promoting Physical Activity in Middle School Girls

“…The approximate doubling of the number of girls measured in each 8th-grade survey compared to the 6th-grade survey was purposeful and based on our determination that the smaller 6th-grade sample would have little adverse effect on power. 20 The study population was diverse with the largest percentage of African-American girls in Louisiana and South Carolina and the largest percentage of Hispanic girls in California and Arizona (Table 1).…”

Comparing Perceived and Objectively Measured Access to Recreational Facilities as Predictors of Physical Activity in Adolescent Girls

“…16 TAAG has six field centers in metropolitan areas (at the Universities of Arizona, Maryland, Minnesota, and South Carolina; San Diego State University; and Tulane University), a Coordinating Center (at the University of North Carolina, Chapel Hill) and a Project Office at the National Heart Lung and Blood Institute. Each center_s Human Subjects Institutional Review Board approved the study protocol.…”

“…The probability of having one or more incomplete days of accelerometer data was not associated with race, age, or average activity based on completely observed days. 16 We converted counts above 1,500 per half minute into METs using a regression equation developed from a pilot study for TAAG. 20 One MET-minute represents the metabolic equivalent of energy expended sitting at rest for 1 minute.…”