THE ANKLE STRATEGY FOR POSTURAL CONTROL - A COMPARISON BETWEEN A MODEL-BASED AND A MARKER-BASED METHOD

When analysing postural control statistical characteristics of the cen tre of pressure or the ground reaction force are often used. A complem ent would be to analyse movement strategies as well. The purpose of th is Study was to determine to what extent the ankle strategy is used to maintain the balance in standing. One important question is if it is sufficient to use only force plate data in this determination, or if m arkers have to be used. To answer this question we studied two differe nt methods-a marker-based method and a model-based method. The latter needs force plate data only as input to an inverted pendulum model. Di fferent measures were calculated and used to draw conclusions of to wh at extent the ankle strategy was used. Experiments demonstrated that t he data from the two methods provided the same general conclusions, al though there were some differences in the-estimated measures. By using the model-based method instead of tracking markers we can increase th e clinical effectiveness considerably, get a lesser amount of data, an d still get results comparable to the marker-based method. (C) 1997 El sevier Science Ireland Ltd.