Age and Visual Contribution Effects on Postural Control Assessed by Principal Component Analysis of Kinematic Marker Data.

Postural control, the ability to control the body's position in space, is considered a critical aspect of health outcomes. This current study aimed to investigate the effects of age and visual contribution on postural control. To this end, principal component analysis (PCA) was applied to extract movement components/synergies (i.e., principal movements, PMs) from kinematic marker data of bipedal balancing on stable and unstable surfaces with eyes closed and open, pooled from 17 older adults (67.8 ± 6.6 years) and 17 young adults (26.6 ± 3.3 years), one PCA-analysis for each surface condition. Then, three PCA-based variables were computed for each PM: the relative explained variance of PM-position (PP_rVAR) and of PM-acceleration (PA_rVAR) for measuring the composition of postural movements and of postural accelerations, respectively, and the root mean square of PM-acceleration (PA_RMS) for measuring the magnitude of neuromuscular control. The results show the age and visual contribution effects observed in PM 1 , resembling the anteroposterior ankle sway in both surface conditions. Specifically, only the greater PA 1 _rVAR and PA 1 _RMS are observed in older adults ( p ≤ 0.004) and in closed-eye conditions ( p < 0.001), reflecting their greater need for neuromuscular control of PM 1 than in young adults and in open-eye conditions.