Real-Time Digitized Visual Feedback in Exercise Therapy for Lower Extremity Functional Deficits: Qualitative Study of Usability Factors During Prototype Testing
Authors: Widhalm Klaus , Maul Lukas , Durstberger Sebastian , Putz Peter , Klupper Carissa , Werner Franz 
Published: December 2024

Background
Osteoarthritis is one of the most common degenerative diseases of the musculoskeletal system and can ultimately lead to the need for surgery, such as total knee or hip arthroplasty. Functional movement deficits can be a prognostic factor for osteoarthritis in the lower extremities. Thus, training physiological movement patterns may help in the treatment of such functional deficits. Motivation to exercise frequently is of utmost importance and can be promoted by using digital real-time feedback.

Objective
This qualitative study aims to gather user recommendations for prototype feedback visualizations in a real-time exercise-feedback system called homeSETT for the treatment of functional deficits. The system provides real-time feedback to participants while performing exercises that focus on functional deficits, such as lateral trunk lean, pelvic drop, and valgus thrust. The findings of this study should help to optimize the prototype feedback visualizations. Thus, the main research questions were how patients, physiotherapists, and physicians evaluate the presented, current state of prototype feedback visualizations for selected functional exercises, and what improvements and variations would be recommended.

Methods
Testing of the prototype feedback visualizations took place at a movement laboratory using a 3D optoelectronic movement analysis system. Data on usability factors were acquired using the thinking aloud method during and semistructured interviews after prototype testing. Transcribed audio recordings of semistructured interviews as well as scribing logs of the thinking aloud method were examined using qualitative content analysis.

Results
Data were analyzed from 9 participants, comprising 2 (22%) patients, 2 (22%) physicians, and 5 (56%) physiotherapists. The mean age of the participants was 45 (SD 9) years and the mean work experience among the participating physiotherapists and physicians was 22 (SD 5) years. Each participant tested 11 different exercise-feedback combinations. Overall, results indicated that participants enjoyed the prototype feedback visualizations and believed that they could be used in therapeutic settings. Participants appreciated the simplicity, clarity, and self-explanatory nature of the feedback visualizations. While most participants quickly familiarized themselves, some struggled to recognize the feedback goals and connect the visualizations to their movements. Recommendations for improvement included optimizing color schemes, sensitivity, and difficulty adjustments. Adding instructional information and game design elements, such as repetition counting and reward systems, was deemed useful. The main study limitations were the small sample size and the use of feedback on performance as the sole feedback modality.

Conclusions
The prototype feedback visualizations were positively perceived by the participants and were considered applicable in therapy settings. Insights were gathered on improving the color scheme, sensitivity, and recognizability of the feedback visualizations. The implementation of additional gamification and instructional elements was emphasized. Future work will optimize the prototype feedback visualizations based on study results and evaluate the homeSETT system’s efficacy in eligible patient populations.