The relationship between electrical stimulus and viscoelastic parameters of the denervated anterior thigh muscles

As a part of the EU-project ldquoRISErdquo a pendulum test was applied to evaluate the effect of functional electrical stimulation (FES) on denervated degenerated anterior thigh muscles. A sensor-actuator system was connected to the lower leg via an adjustable lever to hold the subject's knee joint align with the pivot of the test device. The motor of the pendulum system allowed to compensate static torques due to electrical stimulation and gravity. The tests were performed at two initial positions (knee angle of 90deg and 120deg). First passive measurements were taken and secondly FES was applied up to plusmn60V. A second-order dynamical model was applied to extract stiffness and viscous parameters 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. Therefore, the pendulum test is a useful clinical tool to assess muscle performance in denervated paraplegics.