Smartphone videos of the sit-to-stand test predict osteoarthritis and health outcomes in a nationwide study

Abstract

Physical function decline due to aging or disease can be assessed with quantitative motion analysis, but this currently requires expensive laboratory equipment. We introduce a self-guided quantitative motion analysis of the widely used five-repetition sit-to-stand test using a smartphone. Across 35 US states, 405 participants recorded a video performing the test in their homes. We found novel relationships not detectable in a clinical implementation of this test. Trunk angle during the sit-to-stand transition was greater in individuals with osteoarthritis and differed across ethnicities. In individuals 50 years of age or older, those with greater trunk angular acceleration had a higher mental health score. We also detected known associations between longer time to complete the five repetitions and lower physical health scores, higher BMI, and older age. Our findings demonstrate that at-home movement analysis goes beyond established clinical metrics to provide objective and inexpensive digital outcome metrics for nationwide studies.