Head movement during sudden base translations as a measure of risks for falls in the elderly.

To determine whether head movement in response to a sudden platform translation differs between healthy young subjects and healthy elderly with and without, bipedal sensory loss. A cross-sectional study with four-way comparison on subject grouping and three test conditions. Head movement has been used as a measure of balance in the elderly during voluntary movements. Studies during involuntary movement, however, are limited. Moreover, it is not clear how head movement during involuntary activities relates to postural balance and susceptibility to falls. Head movement during a sudden base translation was measured in three subject groups: 9 healthy young, 10 healthy elderly adults and 10 elderly adults with vibratory sensation loss under the feet. The surface compliance of the supporting base, the direction of the base translation and the visual condition were all varied. There were significant differences among the three groups in head range of excursion (5 degrees, 9 degrees, 13 degrees for the young, elderly, and elderly with severe vibratory sensation loss, respectively), onset time (120, 150, 180 ms), and the time from peak to peak (38, 29, 25 ms). A backward base movement increased the head movement more than a forward base movement. During sudden base translation balance tasks, head movement is significantly increased in the elderly, especially in those elderly adults who are susceptible to falls. The results suggest that an increased head movement in the elderly might be an indication of increased risks for falls.