Valid when valued: A community-engaged framework and toolkit to improve identification of autistic people's motor difficulties in research and practice.

Many autistic people experience clinically-significant motor differences that pose lifelong physical health risks including physical inactivity, cardiometabolic disease, falls and injuries, and chronic pain. These differences amplify existing cognitive and social-emotional features of autism and limit daily living skills, which in turn negatively impacts mental health and participation. Yet, professionals often overlook or mischaracterize autistic people's motor difficulties, in part because non-motor factors can affect assessment outcomes. Most standardized motor assessments presume typical communication, sensory processing, regulation, and tolerance of unfamiliar testing environments, leading to construct-irrelevant variance and potential misinterpretation of results. This risk increases when examiners lack autism-specific experience or use rigid administration practices without appropriate adaptation. Adopting a neurodiversity-affirming framework improves validity, equity, and uptake of motor assessment across research, education, and clinical contexts. Here, we present an Adapted Motor Assessment Toolkit for Autism with implementation examples grounded in the Movement Assessment Battery for Children-Third Edition. An interdisciplinary team of clinicians and researchers developed and refined the toolkit in partnership with autistic people and parents of autistic children. The toolkit enables preservation of core task demands and scoring while adapting assessment practices to support accessibility and improve validity of results. Adaptations span five domains: pre-assessment preparation, sensory supports, procedural adaptations, communication supports, and motivation/engagement. The toolkit helps examiners to identify support needs, implementing adaptations, interpreting results, and determining whether normative comparisons remain appropriate. Neurodiversity-affirming assessment practices enable earlier identification of motor differences, inclusion of more diverse participants in research, and tailored intervention and prevention planning to advance physical health equity across the lifespan.