The magnitude of errors associated in measuring the loads applied on an assistive device while walking

Measurement of the loads exerted on the limb is a fundamental part of designing of an assistive device, which has been done by using strain gauges or a transducer. Although calculation of loads applied on an orthosis coefficients achieved from calibration is a standard way, most of researchers determined the loads based on available equations. Therefore, the aim of this research is finding the accuracy of this method with respect to calibration. Some strain gauges were attached on the lateral bar of a reciprocal gait orthosis. It was calibrated for axial force and the anteroposterior and mediolateral moments. The outputs of strain gauge were changed to force, and moments based on the coefficients were achieved from calibration using available equations, while 5 normal subjects were walking with the orthosis. There was a significant difference between the force and moments exerted on the orthosis during walking based on the two methods (mostly extension moment and compression force). The results of this research indicated that the output of strain gauge varies based on the methods of calculation. As calibration the gauge is a standard method, it is recommended to calibrate it before use.