Ambulatory joint mobility and muscle strength assessment during rehabilitation using a single wearable inertial sensor

Aim: Monitoring injured athlete's condition and the response to a therapeutic treatment allows doctors and therapists to understand whether the rehabilitation program is heading to the right direction, eventually making modifications to injury management techniques in response to therapy's outcomes. The present study aims at exploring the feasibility of using inertial sensors for a quantitative assessment of joint mobility and muscle strength in ambulatory settings during the rehabilitation program of injured athletes. Methods: A wireless inertial sensor with a dedicated software was used for the assessment of joint mobility and muscle strength during the rehabilitation program of an elite rescue swimmer after a SLAP tear surgery. Joint function of the injured shoulder was assessed in terms of range of motion and movement fluidity with respect to the healthy joint during selected standardized joint mobility tests (sensor fixed to the arm). Strength of the injured shoulder was assessed in terms of mechanical force and power with respect to the healthy joint during isoinertial-resistance exercises performed at a vertical pulley (sensor was fixed to the weight stack). Tests were performed once a week. Strength tests started when joint mobility was fully recovered. Results: Results of joint mobility tests showed that progresses in the recovery of joint mobility can be effectively monitored over the period of the therapy, and the complete recovery was objectively established after 9 weeks from the beginning of active joint movements. With regard to the assessment of muscle strength, measuring the force impressed to the external resistance allowed the identification of the correct training loads which were not determined using fixed tables but customized with respect to actual muscle strength residuals. Training load was, thus, safely increased as force was fully recovered. With the present methodology, the complete recovery of joint function was objectively established, whereas strength recovery was carried out by first identifying the exact training load that was subsequently administered in a controlled manner using a real time biofeedback. Conclusion: This case study showed how an inertial sensor can be used for an ambulatory and time-effective assessment of joint mobility and muscle strength during the rehabilitation program of injured athletes, assisting doctors in evaluating the efficacy of the therapy and providing evidence to clinical decision making.