Age-associated increase in postural variability relate to greater low-frequency center of pressure oscillations

BACKGROUND: Postural control is impaired in older adults, as evidenced from greater variability of the center of pressure (COP) during postural tasks. Although COP variability associates with low-frequency COP oscillations (<1 Hz) in young adults, it remains unknown if the age-associated increase in COP variability relates to greater low-frequency COP oscillations. RESEARCH QUESTION: Do low-frequency oscillations contribute to greater postural sway (center of pressure (COP) variability) in older adults when attempting to voluntarily maintain posture in a forward leaning position compared to young adults? METHODS: Seven young (25.7 ± 4.8) and seven older (71.0 ± 7.0) adults performed a postural lean forward task and attempted to match a COP target in the anterior-posterior direction as steady as possible. We quantified the COP variability as the standard deviation (SD) of COP displacements in the anterior-posterior and medial-lateral directions and quantified the frequency modulation of COP as the power in COP displacement spectra from 0-1 Hz. RESULTS: We found that older adults had significantly greater anterior-posterior SD of COP (p = 0.027) and power below 0.5 Hz (p = 0.048) than young adults, but power from 0.5-1 Hz was similar (p = 0.083). In contrast, the medial-lateral SD of COP (p = 0.5) and power from 0-1 Hz (p = 0.228) was similar for the two age groups. For both the anterior-posterior and medial-lateral direction, the SD of COP was related to low frequency oscillations below 0.5 Hz. SIGNIFICANCE: For the first time, we show that the age-associated increase in postural variability relates to greater COP oscillations below 0.5 Hz.