Center of mass approximation during walking as a function of trunk and swing leg acceleration.

The 3D center of body mass (COM) trajectory provides us with a measure of movement performance and level of stability while walking. As an alternative to directly calculating the COM from motion trajectories and anthropometric data, we propose developing models to estimate the COM trajectory during walking on irregular surfaces. The inputs to the models were acquired via two accelerometers, one representing the trunk segment placed on T2 and the second representing the swing leg placed on the lateral malleolus. The subjects walked on a fixed surface and encountered an uneven, irregular surface, causing instability in the balance system. The results were encouraging, providing an estimate of the COM trajectory with a low error of 4.17 +/- 1.94%. The reasonable accuracy, portability, ease of use and low cost (compared with video motion analysis systems) of the accelerometers increases the range of clinical applications of the proposed method.