A critical point for the onset of falls in the elderly. A pilot study.

BACKGROUND: Falls in the elderly during walking often result in very serious injuries. Gait analysts have meticulously explored the causes of these falls and reported age-related changes in gait parameters. It has not been possible to determine the level of derangement of gait parameters that is critical for falls in this population. There is the need to identify age-related interaction patterns of gait parameters. Such an interaction pattern could at least provide a mirror image of how the neural system adjusts to the age-related derangement.

OBJECTIVE: The purpose of this study was to utilize the interaction of gait parameters in the velocity field diagram (VFD) to explore the causes of falls in the elderly during walking. The VFD is a graph of the numerical values of gait parameters versus speed numbers derived by serially numbering the five speeds of walking from very slow to very fast.

METHODS: The gaits of healthy elderly persons (fallers and nonfallers) were recorded with those of healthy younger controls. The subjects walked along a 5-meter walkway in their shoes, but without walking aids. The subject walked from very slow to very fast according to what he/she considered to represent the respective speeds. Strides were counted, and the time taken to walk the distance was noted with a stopwatch. Numerical values of velocity (m/s), stride length (m), and stride frequency (strides/s) were used to construct the VFD.

RESULTS: The x-axis value of the equality point (E(1)) of the numerical values of velocity and stride frequency of the three study groups differed significantly (Anova alpha = 0.05, F = 22.94, p = 0. 001). The E(1) was formed in relation to gait efficiency. The x-axis value of the E(1) was least in controls and greatest in fallers, while the reverse was the case for gait efficiency. The E(1) of nonfallers defined a critical point for the precipitation of falls in the elderly. The value on the x-axis of the VFD of the critical point for the precipitation of a fall was 3.5 velots. A vertical line passing through E(1) and abutting on the x-axis at 3.5 velots was described as fall precipitation line.

CONCLUSION: Since the x-axis value of the critical point for the precipitation of a fall was 3.5 velots, it was suggested that elderly persons who equalize the numerical values of velocity and stride frequency at 3.5 velots should be provided with adequate preventive measures against falls.