Fig. 1. An overview of our web application to collect and analyze movement data.

a Participants perform the five-repetition sit-to-stand test while an untrained individual records the test using only a smartphone or tablet from a 45-degree angle to capture a combined sagittal and frontal view. b The video is uploaded to the cloud and a computer vision algorithm, OpenPose¹², computes body keypoints throughout the movement. c Our tool computes the key transitions in each STS cycle (i.e., as the participant rises from the chair and returns to sitting). d Our algorithms compute the total time to complete the test and several important biomechanical parameters, like trunk angle (see Methods for details). Note: the photograph in (b) is an actor, not a study participant, who consented for their photo to be used in the publication.