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The aim was to analyse the limitation of the head and lumbar movements in relation to the centre of gravity which is needed to maintain standing balance with ageing. The participants of the study were 25 healthy volunteers divided into two age categories, the young group (mean 22.4 +/- 2.7 years) and the elderly group (mean 71.2 +/- 3.6 years). The instruments for measuring the movements of the lumbar region and head and the centre of pressure (COP) were a 3-D motion analysis system and a force plate. In addition, the peak foot pressure was measured during standing using the F-Scan system. The participants were first asked to stand relaxed for 10 s. They then shifted from the starting position to the four directions of sway: anterior, posterior, right and left. They were asked to maintain standing balance at the maximal distance position for each sway as much as possible for 10 s. Analysis of parameters was performed by measuring the average maximal linear displacement (cm) of the head and lumbar markers, the COP (cm), and the peak foot pressure (% of body weight per cm2) in each participant. 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's data were greater than the young group's data 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 the maximal displacement of head and lumbar positions and the toe's muscle activity in the forefoot are important factors associated with the centre of gravity in elderly adults. It is postulated that each base of support area of the older adults in smaller than that of younger adults. These variables could be made available as a clinical test for the degree of poor balance.

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.

The purpose of this study was to examine the relationship between toe pressure and tactile sensitivity in the great toe and to describe two newly developed measurements of postural stability. The subjects of the study were 21 healthy volunteers. The subjects were divided into two age groups, the young group (mean 21.0 +/- 1.6 years, 7 males and 6 females), and the elderly group (mean 71.4 +/- 2.8 years, 4 males and 4 females). The methods and materials used for the first experiment (balance test): The instrument for measuring standing balance was a force plate. Data were analyzed to provide two main variables: 1) body sway index (SI: mm) and 2) toe pressure (%BW/cm2). The subjects were asked to stand in a relaxed posture for 20 s. The variables of body sway were measured in four conditions: normal surface with eyes open or closed, and soft surface with eyes open or closed. Second experiment (tactile sense test): This experiment utilized a new system which was developed for measuring the tactile sensation. The tactile threshold value was measured with the subject seated in a chair, the back supported, and the hips and knees flexed at 90 degrees. The contactor pulled and pushed the toe longitudinally along its axis at a constant velocity of 1 mm/s. There were significant differences between the young and elderly groups in the tactile sense of the great toe (p < .001). No significant difference between age groups was found for postural sway while the subjects stood on the normal surface with eyes open; however, when they stood on the soft surface with their eyes open and closed, the elderly showed significantly more sway (p < 0.01) than the young. Moreover, the maximal great toe pressure in the elderly group was significantly greater than that in the young group. The results suggest that the reduced tactile sense, deprivation of visual information, and toe pressure weakness are all important factors associated with postural instability.