Validation of portable muscle tone measurement device based on a motor-driven system

As a component of upper motor neuron syndrome, assessment of abnormality in muscle tone, including spasticity and rigidity, is a routine clinical examination. The aim of this study is to extend a sophisticated motor-driven measurement system, developed in our previous research, as a validation platform for developing a portable muscle tone measurement system. The main features of hand-held muscle tone measurement device are small angular-rate sensor for recording stretch velocity and light air-bag cuff for measuring the pressure difference at two sides of the wrist. To test the validity, the measurements recorded from the portable device shows good correlation with that recorded from the motor-driven system after removing the gravitational effect. To differentiate the normal from abnormal muscle tone, the slope of stretch resistance versus position was used to differentiate the normal muscle tone from that of a parkinsonism. However, there several factors, including the application of air-bag, the air-filled pressure, and the stretch velocity, could affect the accuracy in using the hand-held device for muscle tone assessment.