Current guidelines recommend vigorous physical activity for at least 20 minutes three days per week, and accumulation of at least 30 minutes of moderate physical activity most days of the week. Guidelines specifically developed for youth recommend the accumulation of 60 minutes of activity of moderate or greater intensity on most days of the week. These guidelines were developed to encourage healthy habits in adolescents that will provide immediate and long-term benefits. Despite the benefits of these recommendations, significant numbers of adolescents do not meet the minimal vigorous or moderate physical activity guidelines. Adolescents receive much of their health information from their physicians and parents. Physicians can provide counseling about the benefits of physical activity but must, of necessity, be brief. Prochaska and colleagues worked to develop a reliable and valid physical activity screening measure for use in the primary care setting.

Subjects were recruited from two high school classes and two middle school classes. The project consisted of three different studies. The first two studies evaluated the test-retest reliability and validity of nine measures of physical activity. The physical activity tests were validated using electronic accelerometers to measure levels of activity minute by minute. The third study used a modified assessment strategy based on the findings from the first two studies to better match the types and patterns of youth physical activity.

The results of the first study found no consistent trend with individual items but increased reliability with the use of composite scores. In the second study, six of the nine screening measures correlated significantly with data from the accelerometer, but subjects had difficulty distinguishing between moderate and vigorous physical activity levels. Based on the results of the first two studies, the authors developed the final measure. The screening measure was reliable and valid.

The authors developed a single measure to assess the accumulation of moderate to vigorous physical activity (MVPA) that is consistent with current recommendations for youth physical activity. The authors recommend the use of a two-question, 60-minute MVPA screening measure (see accompanying figure) for clinical practice assessment of adolescent physical activity that was incorporated into the PACE+ computer-mediated physical activity program for teenagers in primary care. The measure is brief, easy to use, yields clinically meaningful scores, and will assist physicians in identifying adolescents who would benefit from counseling about their physical activity habits.