Soft-tissue vibrations in the quadriceps measured with skin mounted transducers

The purpose of this study was to develop a method to characterize the frequ ency and damping of vibrations in the soft tissues of the leg. Vibrations w ere measured from a surface-mounted accelerometer attached to the skin over lying the quadriceps muscles. The free vibrations in this soft tissue were recorded after impact whilst the muscle was performing isometric contractio ns at 0, 50, and 100% maximum voluntary force and with the knee held at 20, 40, and 60 degrees angles of flexion. The acceleration signals indicated t hat the soft tissue oscillated as under-damped vibrations. The frequency an d damping coefficients for these vibrations were estimated from a model of sinusoidal oscillations with an exponential decay. This technique resolved the vibration coefficients to 2 and 7% of the mean values for frequency and damping, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.