Estimating Dynamic Properties of Denervated Muscles with the Pendulum Test

Abstract

The pendulum test was applied to evaluate the effect of functional electrical stimulation (FES) on denervated degenerated anterior thigh muscles.

We performed measurements in 21 subjects affected by flaccid palsy. The actuator of the pendulum system allowed compensating the static torques of the electrical stimulated muscle and the gravity torque. The tests were performed at two initial positions - knee angle of 90° and 120°. A motor induced a deflection kick of 12° to evoke the gravity-induced oscillation. A second-order dynamical model was applied to extract viscoelastic properties of the thigh muscle from the recorded damped oscillation. The pendulum test was proved a sensitive method to detect even weak contractile capacity of long-term denervated and degenerated muscles. The results show that this system is a useful clinical tool to assess muscle performance in denervated paraplegics.