Balance during movement
To evaluate human balance, the relative positions of the whole body center of mass and the center of pressure are essential. When the body is moving, the velocity of the center of mass should be taken into account as well. This can conveniently be done by defining the ‘extrapolated center of mass’: the position of the center of mass plus its weighted velocity. On the basis of this concept simple control laws suggest themselves.
We will show that these control laws can indeed be verified in a number of experiments. Special attention will be given to walking with a prosthesis and with unexpected disturbances. In these cases two balance strategies are important, the stepping strategy and the ankle strategy. As is seems, balance reactions during walking are to a large extent caused by medium- and long latency reflexes in functionally relevant muscles.