ABSTRACT
The importance of support In physical terms, whether someone – or something – falls over or not is entirely a matter of the vertical projection of his centre of gravity relative to their supports. If this line
of projection (X) lies within the area defined by the points of contact with the ground (the support area), then all is well – small disturbances will result in a turning couple tending to restore the status quo. If X lies outside this critical area, then the system is unstable, and any further tilting will cause an ever-increasing rotational force that will make them fall over. Because the support area is much smaller in Man than in four-footed animals, maintaining an upright posture is correspondingly more difficult: a tilt of only a few degrees is suffi cient to cause instability. Thus proper standing is not, as is often implied, just a matter of keeping upright: this man clearly has an excellent upright posture, but is equally clearly about to experience a postural disaster, because the vertical projection of his centre of gravity lies outside his region of contact with
a g
g
a g
g
his support. Support is in every sense fundamental to posture, which must be controlled either by moving the centre of gravity relative to the feet, or moving the feet relative to the centre of gravity.
