Effect of Vertical Force Sensation on Fingertips by Grasping a Balloon on Muscle Activity

Postural sway and muscle co–contraction are known to increase during upright standing with aging. A previous study demonstrated that grasping a helium–filled balloon stabilized postural. In this study, we measured the center of pressure (COP) and electromyography (EMG) of the trunk and ankle muscles in 17 healthy young adults while they grasped a balloon during standing and analyzed sway and muscle activity characteristics. The results indicated that the sway–reducing effect was observed not only with upward force sensation but also with downward force sensation. These findings suggest that sensory feedback processed at the spinal cord level primarily modulates trunk muscle activity, enhancing postural control and thereby improving stability.