Ground Reaction Forces during Human Standing

Abstract

Foundamental characteristics of ground reaction forces measured by using a force plate during human standing were investigated. Force fluctuation levels and power spectrums of the force data for standing posture were compared with those for sitting. The force fluctuation levels in the horizontal plane and their time varying characteristics were evaluated by using an index of short time interval variance (SIV). Three curves, denoted by A, E, and G, approximating change with time of the centre of gravity of the body were calculated from the force data and traces of these curves were compared. The fluctuation levels of forces in relaxed standing were not so high as those during sitting. The value of SIV and its mid-mean value for each measured data appeared to be useful to represent the force fluctuation level in the standing posture. The curves A, E, and G were well fitted as a whole and each of them can be estimated, more or less, an approximation of the true curve of centre of gravity unless the body movement is not so vigorous.