The clinical study aims to develop and test a gamified mobile health app called PuzzleWalk (PW) to promote physical activity (PA) and reduce sedentary behavior (SB) in autistic adults, including those with mild intellectual disabilities (ID). The study addresses the need for tailored interventions in this population, who are at higher risk for lifestyle-related chronic health conditions due to lower PA and higher SB. The upgraded version of PuzzleWalk integrates behavior change techniques and gamification strategies, such as translating step counts into puzzle game playtime, to encourage regular PA and reduce SB. The study will evaluate the app's effectiveness on preventive health behavior changes in real-world settings. The ultimate goal is to create an effective, sustainable, and scientifically validated mobile health tool to improve the health and well-being of autistic adults.

The specific aim of this study is to evaluate the feasibility and acceptability of the upgraded PW in increasing PA and reducing SB in autistic adults with and without mild ID. For this field deployment study, we will employ a pre-/post-test design to examine any changes in participants' objective levels of PA and sedentary time before, during, and after the 6-week intervention. The working hypothesis is that the 6-week PW intervention will yield significant increases in accelerometer-measured daily step counts and moderate-to-vigorous PA (MVPA) (up to 5% increases from baseline) and decreases in sedentary time (up to 10% decreases from baseline). High levels of user engagement with PW app during the intervention period will be significantly associated with sustained positive behavior changes in daily step counts, MVPA, and sedentary time among participants.

We will conduct screening interviews with an emphasis on history of diagnosis and level of intellectual functioning to verify the eligibility of prospective participants. After they consent to participate in the study, we will provide them with study materials, including an accelerometer (i.e., wristwatch), a cable charger, and study instruction sheets, via shipping or in-person meetings. Prior to baseline data collection, we will use a rubric to assess participant comfort and knowledge of study procedures. After an initial 2-3-day accelerometer familiarization period, we will start the data collection, including demographics, technology and medication use, and accelerometer-derived PA and sedentary time. From week 3, participants will start to freely use the upgraded PW app after receiving visualized step-by-step user instructions and will continue to use the app until the end of week 8 (total 6-week intervention), supported by periodic reminders and reinforcement messages based on Behavior Change Techniques. PA and sedentary time measures will be collected during four time periods: Week 1 (baseline), Week 3 (intervention start), Week 5 (mid-intervention), and Week 8 (intervention end).

Inclusion Criteria:

• adults aged 18 to 55 years
• individuals diagnosed with an autism spectrum disroder by a medical professional or self-identify as neurodivergent
• individuals who have regular access to a supported smartphone (iOS 13+ operating system)

Exclusion Criteria:

• individuals with a moderate-to-profound intellectual disability
• individuals with orthopedic conditions that significantly interfere with independent ambulation (e.g., using a wheelchair or crutches)

IPD will not be shared publicly as it will be used for refereed publications.