Nonlinear mathematics detect subtle changes in center of pressure measures

Falls are one of the most significant health concerns for elderly individuals and 30% of individuals over the age of 65 experience at least one fall per year. It is estimated that falls account for one third of the total cost of medical treatment for all injuries. Because maintaining the center of mass over the base of support is required for balance, it is safe to assume that impaired postural control could lead to falls. In biological signals it is theorized that there exists an optimal amount and structure of variability that is indicative of a healthy system, and there are techniques of nonlinear mathematics that allow us to investigate this healthy variability. The purpose of this research is to measure center of pressure, which is a reflection of center of mass movement, to investigate the structure of variability that is present, and to see how that changes with aging.Ten healthy young subjects and seven healthy older subjects were collected. Ninety-second trials of standing posture were recorded on a force platform while the different sensory systems responsible for balance were challenged. The center of pressure data was analyzed with a variety of linear and nonlinear measures. It was found that when the visual and somatosensory systems were challenged there were significant differences in nonlinear measures of posture. Instead, typical linear measures failed to show a difference. This indicates that the systems responsible for balance may start to decline before standard balance measures show a difference