This study focuses on the usability testing of the PhysViz system prototype, designed for individuals with Achilles Tendinopathy (AT). The aim is to evaluate how users interact with the prototype, assessing ease of use and overall user experience. By employing a low-cost rapid usability testing approach and involving people with AT as well as physical therapists who manage AT, the study seeks to refine the PhysViz system based on valuable user feedback. Through measures like the System Usability Scale and Mobile Application Rating Scale, the research aims to create a user-friendly tool for subsequent pilot testing, specifically in the context of therapeutic exercise for AT. The study involves iterative refinement with input from patient and clinician partners, ultimately striving for a feasible and effective solution. Please refer to the 'README' file as a place to start.