Identification of Aging Effects on the Control of Upright Stance Using a Local Maximum Wavelet Transform Method

Abstract

The purpose of this study was to investigate aging effects on the mechanisms of postural control during upright stance, and specifically the use of proprioceptive feedback on this control. Thirty-two healthy individuals participated, equally divided among younger (19–22 years) and older groups (54–68 years) and genders. Experimental trials involved several sessions of quiet stance on a firm surface with eyes closed. Center of pressure (COP) data were obtained from a force platform and processed using a new local maximum wavelet transform method. The critical time interval (CTI) derived from this method was proposed to describe the activation period of proprioceptive function, which is mainly influenced by the proprioceptive feedback loop. A reduced CTI was assumed to indicate poorer control based on proprioceptive input. Results showed that younger participants' CTI significantly increased from the first experimental session to consecutive experimental sessions in both the mediolateral (ML) and anteroposteriorer (AP) directions. However, older participates' CTI did not exhibit significant differences between the first and the consequent experimental sessions in either direction. This result suggests that the adaptability of proprioceptive function was impaired with age. Younger adults' CTIs were significantly larger than those of older adults in both ML and AP directions, indicating that among older adults stance control based on proprioceptive function was significantly impaired due to aging.