Specific aims are:

1. Evaluate the feasibility of the intervention related to (1) girls' participation; (2) adherence to protocols; and (3) user and provider (nurse and PA Club instructors) satisfaction.
2. Explore if participants in the intervention group, compared to those in the control group, show improvement in the primary outcome of minutes of moderate to vigorous physical activity (MVPA; measured by accelerometer), and also secondary outcomes of self-report of MVPA, cardiovascular fitness, body mass index, percent body fat, and waist circumference at 6 months.
3. Explore if the primary outcome is mediated by cognitive (perceived benefits of PA, perceived barriers to PA,PA self-efficacy, social support, norms, models) and affective (enjoyment of PA) variables.
4. Explore if participants in the intervention group, compared to those in the control group, have greater minutes of MVPA at 7 months.

The purpose of this study is to test the feasibility of and obtain preliminary evidence of efficacy for a 6-month "Girls on the Move" intervention (guided by the Health Promotion Model and Social Cognitive Theory). The intervention involves motivational, individually tailored counseling plus after-school physical activity (PA) to increase moderate to vigorous physical activity (MVPA) and cardiovascular (CV) fitness, as well as improve body composition and cognition and affective responses related to MVPA among 6th-grade girls. Specifically, it consists of a 90-minute after-school PA Club that includes MVPA and 6 one-on-one monthly motivational, individually tailored counseling sessions with a registered (school) nurse during the school day to support each girl's continued MVPA. Applying the motivational interviewing communication style, the school nurse will individually tailor the counseling based upon each girl's key responses gleaned from computerized questionnaires assessing cognitive and affective variables related to MVPA. One middle school will be randomly assigned to receive the intervention and another to serve as attention control.

Inclusion Criteria:

(1) 6th-grade girls (ages 10-12) (7th-graders if needed; up to and including age 14) who report not meeting national MVPA recommendations; (2) available and willing to participate 6 mos.; and (3) able to read, understand, and speak English (e.g., school nurse checks that girl is reading at grade level or enrolled in remedial course).

Exclusion criteria:

(1) Involved in school or community sports or other organized PAs or lessons, such as dance, martial arts, gymnastics, or tennis, that involve MVPA and require participation 3 or more days/wk. during every season of the school year; and (2) a health condition limiting or precluding safe MVPA.