Youth with physical disabilities experience greater limitations to participation in community- based activities than do their average-developing peers, which can result in poor health outcomes. Emerging treatment approaches aimed at improving activity and participation have shifted from focusing only on impaired body functions towards the performance of functionally meaningful activities within the youth's natural environment. It is unclear; however, whether targeting intervention at the activity/participation level can simultaneously result in improvement of personal functional skills (e.g., reaching) and body functions (e.g., range of motion, balance) - components known to worsen with age and, thus, important to address and maintain within the rehabilitation process. Our team has partnered with key community-based stakeholders including youth, clinicians and policy-makers, and together we plan to examine whether engaging in an 8-week self-chosen community-based activity (e.g., sledge hockey, boccia) can lead to a significant improvement in three key body functions: motor, cognitive and affective. Thirty youth with physical disabilities will take part in the study and engage in an activity program of their choice. Changes in their body functions (e.g., movement, attention, mood) will be measured multiple times before, during and after engagement in the chosen activity/program. Findings of this study can guide clinicians, families and policy-makers to select effective approaches that not only promote participation but also facilitate additional motor and mental benefits from one single intervention. Such treatment approaches may also reduce the burden on the healthcare system as well as on the youth and families. Moreover, findings can advance our understanding of methods for testing complex and unique 'real-life' individual-based interventions that are highly relevant to practice.

Youth with physical disabilities experience restrictions to participation in community-based activities, leading to poor health outcomes. Personalized participation-based treatment approaches, implemented in the individual's natural environment, are considered recommended practice. However, it is unclear whether enhancing participation (e.g., engaging in sledge hockey) can simultaneously improve both body functions (e.g., grip, trunk control) and activity performance - two key outcomes in pediatric rehabilitation. Specifically, the impact of participation in a self-chosen real-life activity, that is meaningful to the youth, on a range of functions (motor, cognitive and affective) has not been established. Supported by Canadian Institutes of Health Research (CIHR), we first proved the effectiveness of the Pathways and Resources for Engagement and Participation (PREP) intervention in promoting youth's community participation; then, through Strategy for Patient-Oriented Research (SPOR), we successfully pilot- tested an innovative pragmatic clinical trial to improve body functions through participation, informing the design of this proposed larger study. Using the PREP, we aim to examine the impact of youth engagement in an 8-week community-based activity program (e.g., drawing, swimming) on underlying body functions or impairments (e.g., movement, attention, mood), as well as on performance of the selected activity. Specifically, change in 3 relevant body functions will be examined: motor (using the Functional Reach Test, Trunk Impairment Scale, and dynamometer), cognitive and affective (using the Behavior Assessment System for Children), and activity performance (via the Canadian Occupational Performance Measure). A 22-week interrupted time series design with multiple baselines systematically replicated across 30 youth with physical disabilities (e.g., cerebral palsy, spina bifida) aged 15 to 24 will be employed. Each activity, individually selected by the youth, will be analyzed using the task analysis approach to identify underlying body functions. These functions will be measured multiple times throughout the entire study, resulting in 90 trajectories of change in body functions (30 youth X 3 functions) and 30 trajectories representing change in activity performance. A linear model will be fit for each of the 120 trajectories. Motor-related scores will be standardized to allow comparison across different outcomes and mixed-effects models will be used to estimate an intervention effect across participants. Our interdisciplinary team includes researchers in the field of childhood disability, including occupational therapy, physical therapy and pediatric medicine. Partnered with the Centre of Integrated University Health and Social Services (CIUSSS) West-Central Montreal and CanChild Centre for Childhood Disability, as well as key local and national stakeholders, the team will collaborate throughout the research process. This novel patient-oriented study will support a paradigm shift in clinical practice and build knowledge that can guide clinicians, families and policy-makers in appraising the benefits of participation- based therapies on improving both functional capacities and performance in meaningful life activities. Describing the multiple benefits generated by one single intervention can facilitate efficient youth-engaging therapies, contributing to the provision of pediatric rehabilitation services. Findings can also enhance knowledge of pragmatic clinical trials for testing complex individual-based interventions highly applicable to practice.

Inclusion Criteria:

• have a physical disability (e.g., cerebral palsy, spina bifida, musculoskeletal disorders)
• restricted mobility, such as an inability to navigate all surfaces and stairs independently and safely without the use of aids, physical assistance or external support

Exclusion Criteria:

Youth who are recovering within the first year following a severe brain injury or an orthopedic surgery or botulinum toxin treatment 6 months prior or anticipated during the study period or those with degenerative disorders will be excluded.

Youth with significant intellectual delay will be excluded due to the demands required for completing self-reported assessments.

Youth with co-occurrence of an untreated mental health condition will also be excluded.

Assessors will be blinded to the time point in which the intervention begins and to the chosen activity