Citation

Kim S, Nussbaum MA. Proc. Hum. Factors Ergon. Soc. Annu. Meet. 2007; 51(15): 899-903.

Copyright

(Copyright © 2007, Human Factors and Ergonomics Society, Publisher SAGE Publishing)

DOI

10.1177/154193120705101507

PMID

unavailable

Abstract

Local dynamic stability was investigated during quiet upright stance with respect to age and altered sensory conditions. From center of pressure (COP) trajectories, the largest Lyapunov exponent (Λmax) was extracted to directly parameterize local dynamic stability, and the reliability of Λmax was assessed using the intra-class correlation coefficient (ICC). Thirty two participants volunteered for upright quiet stance trials. Vision and somatosenstaion were experimentally altered: vision was modified by eye closure, and somatosensation by using both a hard surface (HS) and a soft surface (SS). Age and vision had main effects on Λma, and the age x vision and vision x surface interaction effects were also significant. In general, older participants were less stable (i.e., higher Λmax) than younger, and altered sensory information resulted in a decrease in stability. Reliability was higher for older versus younger participants. Use of Λmax enabled a direct assessment of age-related differences in local dynamic stability and effects of altered sensory conditions. Such non-linear measures can provide additional information to that available from traditional COP-based analyses.

Language: en