Bridging the Gap: Implementing BRIDGES

Patient Health Questionnaire-9 modified for Adolescents (PHQ-A) The PHQ-A is a brief instrument modified to adolescents used to assess the severity of depression (41). It contains 9 items that are on a scale from 0 to 3, with the total score ranging from 0 to 27.

Physical Activity Vital Sign (PAVS) The PAVS is a screening tool used to assess patients' physical activity levels (37). It consists of two questions: (a) on average, how many days per week do you engage in moderate to vigorous physical activity, and (b) on those days, how many minutes do you typically spend participating in moderate to vigorous physical activity? The product of these responses (days × minutes) provides an estimate of the patient's average weekly minutes of physical activity in moderate to vigorous physical activity.

Beck Depression Index (BDI II) The BDI-II captures specific behavioral manifestations of depression. It is a 21-item self-report inventory, with each item scored from 0 to 3 based on four statements reflecting symptom severity, yielding a total score ranging from 0 to 63.

The Multidimensional Scale of Perceived Social Support (MSPSS) is a widely used self-report instrument designed to assess an individual's perception of social support from different sources (49). The scale comprises 12 items, each rated on a 7-point Likert scale ranging from a score of 7 to 84.

Exercise self-efficacy (SEE) is a key determinant of intention formation and engagement in physical activity. In the original SEE, respondents rate their confidence in exercising three times per week for 20 minutes. For the present study, the scale was adapted so that the target behavior reflects an individualized exercise goal defined by each adolescent, that is, the type of physical activity they wish to perform.

Astrand Rhyming test (ART) ART is a single-stage cycle ergometer test, to measure the CRF fitness levels (assessed as an estimation of VO2 max)

Waist-to-height ratio (WHtR) WHtR is calculated as waist circumference (cm) divided by height (cm). Waist circumference will be measured in standing position, midway between the lowest border of the rib cage and the superior border of the iliac crest, at the end of a normal expiration.

Fidelity to motivational interviewing (MI) will be assessed using a combination of observer- and participant-reported measures. First, adherence to MI principles will be evaluated using the Independent Tape Rater Scale (ITRS), which is recommended for effectiveness studies

the Client Perception of Motivational Interviewing (CPMI) scale captures participants' experiences of MI-consistent communication during sessions. This combined approach enables assessment of both the technical and relational components of MI fidelity while remaining feasible within the constraints of a pilot implementation study.

Adolescents will complete the Health Care Climate Questionnaire (HCCQ) (61) to evaluate perceived autonomy support provided by the physiotherapist. In addition, brief post-session feedback forms will invite participants to rate the extent to which they felt understood, empowered, and supported in setting their own goals-key indicators of SDT-congruent delivery.

the physiotherapist will fill out a logbook with their participation describing their presence, the context, the mechanisms at work, and clinical observations on the adolescents and their participation in physical activities

For the implementation assessment, PRISM will provide the overarching conceptual structure to examine organizational, individual, and system-level factors that influence delivery, uptake, and sustainability of the intervention (26). Within this framework, the RE-AIM dimensions (Reach, Effectiveness, Adoption, Implementation, and Maintenance) will be systematically applied (27). Reach will assess the proportion and representativeness of adolescents. Effectiveness will evaluate changes in physical activity, depressive symptoms, and secondary outcomes. Adoption will explore barriers and facilitators to participation and delivery from the perspectives of adolescents, clinicians, and community partners. Implementation will monitor fidelity to motivational interviewing and self-determination theory principles. Maintenance will evaluate the potential for long-term integration of the intervention. Semi-structured interviews guided by PRISM domains will complement quantitative measures.