Use of inclinometers for measuring postures and movements in order to predict muscle activity

Abstract:
In order to get to know the loads on bone and other tissues there is a need to measure motion.

So far, the best way of measuring human locomotion is done in a gait laboratory. But since the equipment is quite expensive and it isn’t mobile, it cannot be used for measuring on people during their daily activities. There is a great interest of finding easier ways to capture the motion in daily situations.



Inclinometers, comprising tri-axial accelerometers, were used to measure the orientation of up to four body-segments during different test motions. The activity in some selected muscles was also measured during the motions using surface electromyography (EMG). Using the data from the inclinometers the angle between the actual body segment and the global vertical line was derived. This data was used as input for the AnyBody Modeling System which is a complete system for simulation of human movements. Selected parts of, or a complete model of the musculo-skeletal system was used in the Anybody System and the activity in different muscles was calculated.



The study shows that it is possible to get a good accordance between predicted and measured muscle activities when the motion is quite slow. When the dynamic effects grow it is harder to get good results. This might be due to angular errors introduced in the inclinometer measures from dynamic effects, and/or incompleteness in the numerical model.