Age-related changes in postural control associated with location of the center of gravity and foot pressure

The purpose of this study was to assess the limitations of the head and lumbar movements in relation to the center of gravity which is needed to maintain standing balance with aging. The subjects of the study were 22 healthy volunteers. The subjects were divided into two age categories, the young group (mean 21.7 +/- 2.9 years, 7 males and 6 females); and the elderly group (mean 71.3 +/-2.6 years, 3 males and 4 females). The instruments for measuring lumbar and head movements and the center of pressure (COP) were a three-dimensional motion analysis system and a force plate. In addition, the peak foot pressure was measured during standing using the F-Scan system. The subjects were first asked to stand relaxed for 10 s. They then shifted from the starting position to the four directions (sways); anterior, posterior, right, and left. They tried to maintain standing balance at the maximal possible distance position for each sway for 10 seconds. Analyzing parameters were performed by measuring the average maximal linear displacement (cm) of the head and lumbar markers, the COP (cm), and the peak foot pressure (percent of body weight per squared centimeters; BW%/cm2) in each subject. The data of the young group for lumbar maximal displacement were greater than those of the elderly group in the anterior, posterior, and lateral sways. A significant difference between the young and elderly data was found in the posterior sway. According to the data of the head's maximal displacement, the elderly group was greater than the young group in all sways except for the anterior side. For the data of peak foot pressure in the posterior sway, the elderly group's data was greater than the young group's data. The forefoot area data of the young group was significantly greater than that of the elderly group and the heel area data of the elderly was significantly greater than that of the young group in the right sway. The results suggest that evaluating the maximal displacement of head and lumbar positions and toe's activity in the forefoot are all important factors associated with the center of gravity in healthy adults.