Physical activity sessions at public parks led by a Serenity Behavioral Health Certified Peer Specialist

Participants will continue their usual care in the PEERS program. They will be offered the intervention after they have completed posttest measures.

Physical activity sessions will take place 3x/week over six weeks and will take between 45 and 60 minutes for each session. The sessions will be led by a Serenity Behavioral Health CPS as part of the PEERS program and will be supervised by research staff. Sessions will occur at public parks. Transportation to the park will be provided by Serenity Behavioral Health. Structured activities will include a warm-up, a mix of simple exercises requiring minimal supplies (such as walking, basic aerobic movements, and body weight resistance exercises), and cool-down. Sessions will be held in green park environments with shade, restrooms, and level walking paths.

Feasibility will be assessed by attendance to park PA sessions (0-100%). Higher attendance indicates greater engagement with the intervention.

Acceptability will be assessed via participant satisfaction, measured using an abbreviated version of the Physical Activity Class Satisfaction Questionnaire (PACSQ). PACSQ is a valid measure for capturing client satisfaction within exercise classes in the following nine dimensions: mastery experiences, cognitive development, teaching, normative success, interaction with others, fun and enjoyment, improvement of health and fitness, diversionary experiences, and relaxation. Each of the dimensions of satisfaction is measured using an 8-point Likert scale, with responses ranging from 1="No satisfaction" to 8="Very satisfying". PACSQ has shown acceptable reliability in each of its subscales (all α's ≥ .85), and survey items are highly correlated with participants' intentions to attend a similar course in the future.

Fitbit min/week moderate to vigorous physical activity. Greater min/week physical activity is better.

The Structured Assessment of FEeasibility (SAFE) standardized measure will be used to determine overall intervention feasibility. The SAFE measure specifically evaluates interventions within a mental health services framework and includes 16 items that capture information in three categories: intervention, resource consequences, and evaluation. The PI in collaboration with CPSs will complete the SAFE measure. The SAFE measure has demonstrated excellent inter-rater and test-retest reliability (0.84, 95% confidence interval (CI) 0.79-0.89; 0.89, 95% CI 0.85-0.93 respectively). Rather than using a summary score, the individual items should be considered (e.g., yes, partial, no, unable to rate).