1 Cyberpsychology Laboratory and Department of Psychoeducation and Psychology, Université du Québec en Outaouais (UQO|Campus de Saint-Jerôme), Saint-Jérôme, Canada.
2 Substantive-Methodological Synergy Research Laboratory, Department of Psychology, Concordia University, Montreal, Canada.
3 School of Education, Translational Health Research Institute, Western Sydney University, Sydney, Australia.
4 Department of Psychoeducation and Psychology, Université du Québec en Outaouais (UQO|Campus de Saint-Jérôme), Saint-Jérôme, Canada.
5 Institute for Positive Psychology and Education, Australian Catholic University, Sydney, Australia.

Purpose: To validate a version of the Motives for Physical Activity Measure (MPAM) adapted for youth with intellectual disabilities (ID).

Materials and methods: A sample of 359 youth with mild to moderate ID from Australia and Canada respectively completed English and French versions of the MPAM-ID.

Results: Exploratory structural equation models supported the validity and reliability of the five-factor structure of the MPAM-ID, as well as the weak, latent variance-covariance, and latent mean invariance across linguistic versions. Additional results supported the partial strong and strict invariance of most MPAM-ID items across linguistic versions. The results also supported the complete measurement invariance of the MPAM-ID over time and revealed a lack of differential item functioning (DIF) as a function of youth's age, body-mass index (BMI), ID level, and frequency of sport involvement (FSI). However, partial DIF was found as a function of youth's sex. Additionally, latent mean differences in MPAM-ID's factors were found as a function of youth's ID level, sex, and FSI. Finally, results supported the convergent validity of the MPAM-ID factors with a measure of perceived physical abilities.

Conclusion: The MPAM-ID can be used among English- and French-speaking youth with ID irrespective of their age, BMI, ID level, sex, and FSI.IMPLICATIONS FOR REHABILITATIONWe propose English and French adaptations of the Motives for Physical Activity Measure for Youth with Intellectual Disabilities (MPAM-ID).The MPAM-ID was able to identify the same motives as the original measure.The MPAM-ID will facilitate the assessment of motives for physical Activity in cross-sectional and longitudinal studies.The MPAM-ID will facilitate the assessment of motives for physical Activity among English- and French-speaking youth with ID.The MPAM-ID could be used to compare youth motives for physical Activity as a function of their age, body-mass index, ID level, and frequency of sport involvement.