Estimation of the center of body mass during forward stepping using body acceleration.

The center of body mass (COM) calculation is a key factor in analyzing human postural control. In recent years there have been attempts to estimate the COM by body acceleration during standing. In this study, a parabolic model is used to estimate the COM trajectory during forward stepping, using the body segments' accelerations, which were measured by inexpensive and portable accelerometers placed on the trunk and swing leg. Paced and voluntary forward stepping was performed on different support surfaces and with different speeds of stepping. Forward steps were extracted by analyzing the ankle marker position in vertical direction. The model was calibrated by genetic algorithm and tested on forward stepping data using the leave one out method. The results are encouraging for the use of the proposed model as a mean to estimate the COM trajectory during forward stepping.