Dynamic stability requirements during gait and standing exergames on the wii fit® system in the elderly

Abstract

Background: In rehabilitation, training intensity is usually adapted to optimize the trained system to attain better performance (overload principle). However, in balance rehabilitation, the level of intensity required during training exercises to optimize improvement in balance has rarely been studied, probably due to the difficulty in quantifying the stability level during these exercises. The goal of the present study was to test whether the stabilizing/destabilizing forces model could be used to analyze how stability is challenged during several exergames, that are more and more used in balance rehabilitation, and a dynamic functional task, such as gait.

Methods: Seven healthy older adults were evaluated with three-dimensional motion analysis during gait at natural and fast speed, and during three balance exergames (50/50 Challenge, Ski Slalom and Soccer). Mean and extreme values for stabilizing force, destabilizing force and the ratio of the two forces (stability index) were computed from kinematic and kinetic data to determine the mean and least level of dynamic, postural and overall balance stability, respectively.

Results: Mean postural stability was lower (lower mean destabilizing force) during the 50/50 Challenge game than during all the other tasks, but peak postural instability moments were less challenging during this game than during any of the other tasks, as shown by the minimum destabilizing force values. Dynamic stability was progressively more challenged (higher mean and maximum stabilizing force) from the 50/50 Challenge to the Soccer and Slalom games, to the natural gait speed task and to the fast gait speed task, increasing the overall stability difficulty (mean and minimum stability index) in the same manner.

Conclusions: The stabilizing/destabilizing forces model can be used to rate the level of balance requirements during different tasks such as gait or exergames. The results of our study showed that postural stability did not differ much between the evaluated tasks (except for the 50/50 Challenge), compared to dynamic stability, which was significantly less challenged during the games than during the functional tasks. Games with greater centre of mass displacements and changes in the base of support are likely to stimulate balance control enough to see improvements in balance during dynamic functional tasks, and could be tested in pathological populations with the approach used here.

Figure 1

Mean (black squares) and minimum (grey triangles) stability index values for the group, for the five tasks. Lower stability index represents lower overall stability. Error bars represent one standard deviation (SD) of the value. The maximums of the vertical axes were chosen to show most of the values despite large scale differences, without flattening the results with lower values. However, the values for the 50/50 Challenge are missing (Min (SD): 10513.8 N (12764.6), Mean (SD): 386783.1 (4.1 x 10⁵)), as well as the SD for Slalom (SD = 2131.2).

Figure 2

Mean (black squares) and minimum (grey triangles) destabilizing force values for the group, for the five tasks (N). Lower destabilizing force represents lower postural stability. Error bars represent one standard deviation (SD) of the value.

Figure 3

Mean (black squares) and maximum (grey triangles) stabilizing force values for the group, for the five tasks. Higher stabilizing force represents lower dynamic stability. Error bars represent one standard deviation (SD) of the value. The maximum of the vertical axes was chosen to show most of the values despite large scale differences, without flattening the results with lower values. The standard deviation for the gait at fast speed is missing (SD = 17334.2 N).