Impulse technique for dynamic measurements of muscular structures in biomechanical applications

Abstract

Impulse techniques (using modern low-impedance quartz transducers and minicomputers) greatly simplify the dynamic testing of mechanical structures. The impact method involves striking the test object with a hammer, measuring the impact force and resultant motion (acceleration, velocity or displacement) at points of interest, then automatically computing and plotting the transfer characteristic, compliance (XIF) or impedance (F/V) as a function of frequency. Results show resonance, vibration mode shapes and dynamic stiffness, which relate displacement to the force causing it. In this system, a force transducer instrumented hammer conveniently generates a force impulse when striking the test object. This impulse approach saves considerable time over the more conventional and laborious sweep frequency methods. In advanced research measurements and in biomechanical applications such as on limbs a long measurement time is not acceptable because of the variability of the muscle structure. The paper describes the proposed technique applied to the muscular structures and reports clinical results on hemiplegic patients during a rehabilitative treatment with functional electrical stimulation.