{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T22:05:31Z","timestamp":1789423531815,"version":"build-2803163510"},"reference-count":66,"publisher":"JMIR Publications Inc.","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JMIR Serious Games"],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>People with multiple sclerosis (MS) are at high risk of falls, with approximately half experiencing at least 1 fall within 6 months. Multidirectional step training has shown potential for fall prevention, but evidence in people with MS remains inconsistent. Mixed reality (MR) offers adaptive and home-based rehabilitation opportunities. However, successful implementation of MR-based serious games requires structured co-design processes integrating patient, clinician, and technical perspectives.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>This qualitative study describes the co-design and prototyping of a home-based MR serious game called Head Your Limits for volitional step training in people with MS, aiming to identify patient-, clinician-, and technology-driven design requirements and translate them into an MR rehabilitation application.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We implemented a cross-sectional qualitative user-centered co-design process. Phase 1 involved 2 online focus groups with people with MS to identify experiential and design preferences related to MR-based training. Phase 2 included a focus group with 4 clinicians and 1 engineer to define clinical and technical requirements. Phase 3 consisted of in-person hands-on testing of 2 MR prototypes (\u201cclock\u201d and \u201cgrapes\u201d), developed in Unity and deployed on Meta Quest 3. Twenty people with MS were purposively screened from among individuals referred for motor rehabilitation; 14 participated in the online focus groups and 9 in in-person prototype testing (mean age 56.2, SD 7.0 years; mean Expanded Disability Status Scale score 5.1, SD 1.3; 6\/9, 66.7% female). Iterative refinement followed each phase, translating stakeholder-derived requirements into architectural modifications of the MR application. Focus group recordings and moderator notes were reviewed to identify themes and design requirements guiding iterative prototype refinement.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Five primary patient-derived requirements emerged: multisensory feedback, gamification, progress tracking, visual accessibility, and ergonomic comfort. Clinicians emphasized adaptive difficulty, cognitive-motor integration, biomechanical validity, and caregiver compatibility. Prototype comparison showed that floor-level targets induced cervical discomfort and postural compensation, whereas auditory guidance reduced head flexion. The final application repositioned targets at eye level and implemented head-mounted display tracking to ensure appropriate center-of-mass displacement, preserve proprioceptive engagement, enable caregiver proximity, and integrate gamified feedback and performance reporting.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Iterative stakeholder engagement resolved key design tensions related to ergonomics, sensory reliance, biomechanical validity, and motivation. The transition to eye-level, head-mediated interaction emerged as a core solution integrating therapeutic and user-experience goals. Through a rigorous user-centered co-design process, aligned with contemporary human-centered development models, we developed an MR serious game for volitional step training in people with MS. This study contributes to the field by providing a transparent methodological framework integrating biomechanical validity, usability, and engagement. Although clinical effectiveness remains to be tested, these findings may inform the design of accessible, personalized home-based rehabilitation for people with MS and other neurological populations.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.2196\/94312","type":"journal-article","created":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T21:45:06Z","timestamp":1789422306000},"page":"e94312","source":"Crossref","is-referenced-by-count":0,"title":["Development of a Mixed-Reality Application for Volitional Step Training in People With Multiple Sclerosis: Cross-Sectional Qualitative User-Centered Co-Design Study"],"prefix":"10.2196","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-6854-4028","authenticated-orcid":false,"given":"Gabriele","family":"Perachiotti","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9414-9759","authenticated-orcid":false,"given":"Isolde 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