ELSEVIER Gait & Posture 4 (1996) 112-121 Spectral characteristics of aging postural control Bruce A. McClenaghan* ‘,, Harriet G. Williamsb, John DickersonC, Marsha Dowdaa, Lori Thombsd, Paul Eleazere ‘Moror Rehabikalion Laborarory, Department of Exercive Science, Universily of South Carolina, Columbia, SC 29208, USA bMotor Conrrol Luboralory. Department of Exercise Science, Universi?y of South Carolina, Columbia, SC 29208, USA cDeparlment of Civil Engineering, Universiry of South Carolina, Columbia, SC 29208, USA dDepartmenr of Statisrics, University of Sourh Carolina, Columbia. SC 29208, USA =Department of Geriatrics, University of South Carolina, Columbia, SC 2920% USA Received 14 April 1994; accepted 30 September 1994 Abstract The purpose of this study wasto apply techniques of spectral analysis to the study of postural control and determine if aging results in changes to spectralparameters obtained from postural forces. Subjects were young adults and elderly who live in- dependently and hadno difficulty performing tasks of daily living. Ground reactionforces were obtained from a measurement plat- form during repeated trials of static standing. Forces were analyzedusing spectralanalysis and selected parameters (central tendency and dispersion) wereextracted from averaged spectral data. Significant differences wereobserved between agegroups in all parameters extractedfrom spectra obtainedfrom medial-lateral postural forces.Similar results were not obtained for data in the anterior-posterior direction. Results suggest that aging affectsthe spectral characteristics of postural forces used to maintain stability in the m-l direction. Keywords: Posture, spectral analysis; Medial-lateral postural forces;Anterior-posterior posturalforces;Falling; Aging 1. Introduction Fall-related injuries represent a major threat to func- tional ability and quality of life of the elderly [l]. The incidence of falls increases with age, and in any given year approximately one-third of individuals aged 65 and older experience a fall [2]. Although most falls do not result in mortality, nearly 32% of all deaths resulting from fall-related injuries occur in individuals 85 years and older [3]. It is widely accepted that most falls are the result of both extrinsic and intrinsic factors [4,5] and are not caused by any single factor, rather they are often the result of several factors which occur simultaneously [6]. Age-related declines in physiological functioning result in slowness in executing the rapid adjustments necessary to maintain stability following minor perturbations to balance that commonly occur when an individual is engaged in activities of daily living [7,8]. This often l Corresponding author. Tel.: +I 803 7776583. 0966-6362/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0966-6362(95)01040-G results in individuals who can function adequately in the more restricted home environment, but who have dif- ficulty maneuvering in unfamiliar situations where un- predictable and unexpected perturbations to postural stability may occur [9]. The belief that some impairments to the human motor system can be detected prior to the observation of clini- cal signs and that rehabilitation or slowing of a func- tional loss can be facilitated by early detection has stimulated interest in establishing ‘biomarkers’ of diminished motor control [lo]. An initial step in im- plementing interventions to reduce falls is to identify measures that are sensitive to age-related changes that occur in postural control. Postural adjustments underlying the maintenance of equilibrium are a result of the interaction between sen- sory and motor systems, which ultimately produce pos- tural forces that result in movement of the center of pressure to maintain balance or posture. A variety of techniques have been used for clinical assessment of