Physical-activity support for people with intellectual disabilities: development of a tool to measure behavioural determinants in direct support professionals

Background Physical-activity approaches for people with intellectual disabilities (ID) are more likely to be effective and sustainable if they also target direct support professionals' behaviour. However, no tools to measure the behavioural determinants for direct support professionals are available as of yet. This study aims to construct a self-report tool to measure direct support professionals' behavioural determinants in physical-activity support for people with ID and to analyse its psychometric properties. Methods The tools' sub-scales and items corresponded with a proposed conceptual model. A pilot study was carried out to investigate and improve content validity. Construct validity and measurement precision were examined using item response theory models with data from a convenience sample of 247 direct support professionals in the support of people with ID. Results Results supported the three theory-driven behaviour scales and indicated reasonable to good construct validity. The marginal reliability for the scales ranged from 0.84 to 0.87, and adequate measurement precision along the latent continua was found. Conclusions The tool appears to be promising for measuring the behavioural determinants of direct support professionals for the physical-activity support of people with ID and has potential as a tool for identifying areas to focus on for interventions and policies in the future