Estimation of grip strength using monocular camera for home-based hand rehabilitation

Grip strength exercises are commonly used rehabilitation methods for recovery of hand function. They are easy to perform even without the direct support of a healthcare professional. However, without objective feedback, the patient may not be fully engaged in the rehabilitation process. To solve this problem, we developed a system for measuring grip strength in real time using a soft ball and a monocular camera. The system estimates the grip strength using the modelled relationship between the finger joint angles extracted from the camera image and the person's grip strength. A patient can get the feedback as numbers or movements displayed on the screen. Experimental results showed that there is a correlation between the finger joint angles and the air pressure of a ball when squeezed. The average estimation error was 16.1 hPa, and the average measurement range was 100–230 hPa. The estimation error was about 12% of the measurement range. They also showed that there is a correlation between the air pressure of a ball and the applied force. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.