Simulated movement termination for balance recovery: can movement strategies be sought to maintain stability in the presence of slipping or forced sliding?

Slipping during various kinds of movement often leads to potentially danger ous incidents of falling. The purpose of this study was to determine whethe r there was evidence to support the theory that movement strategies could b e used by individuals to regain stability during an episode of slipping and whether forced sliding from a moving platform accurately simulated the eff ect of slipping on stability and balance. A single-link-plus-foot biomechan ical model was used to mathematically simulate base of support (BOS) transl ation and body segment rotation during movement termination in sagittal pla ne. An optimization routine was used to determine region of stability [defi ned at given COM locations as the feasible range of horizontal velocities o f the center of mass (COM) of human subject that can be reduced to zero wit h respect to the BOS while still allowing the COM to traverse within the BO S limits]. We found some 30% overlap in the region of stability for slippin g and non-slipping conditions. This finding supports the theory that moveme nt strategies can be sought for restoring stability and balance even if sli pping unexpectedly occurs. We also found that forced sliding produces effec ts on stability that are similar to those of slipping, indicated by over 50 % overlap in the regions of stability for the two conditions. In addition, forced sliding has distinctive effects on stability, including a "shift" of the region of stability extended beyond the BOS in the direction of slidin g. These findings may provide quantifiable guidance for balance training ai med at reducing fall incidents under uncertain floor surface conditions. (C ) 1999 Elsevier Science Ltd. All rights reserved.