[Influence of the movable support under one leg on human vertical posture during standing with asymmetric load on...

The posture in standing subjects was studied when the legs were placed on supports of different degrees of mobility, as well as, when a part of body weight was voluntary transferred to one leg. The aim of these experiments was to explore how the mobility of support under the feet affects the balance and how this influence could be changed by the load distribution between the legs during standing. When both legs were on rigid immovable supports, the posture maintaining was accomplished by control of center of pressure (CP) of both legs. When the subject transferred the weight on one foot the posture was maintained mainly due to the control of CP of loaded leg. When the legs were on the supports of different mobility, the balance was maintained by the control of CP of the leg on the immovable support. This result was observed both when the subject stood with symmetric load on the legs and when the load was transferred to one leg. Even when the leg was unloaded but was placed on immovable support its CP moved more in comparison with the CP of loaded leg on movable support. The results show that the support mobility under the legs is a factor that determines the mechanisms of the posture maintenance, and this factor is more significant than the load distribution between the legs. So, we can conclude that the upright posture is maintained accounting the physical properties of the supports under the feet.