Postural Control Adjustments with Sensory Manipulations and External Perturbations in Older Adults: Electromyographic Analysis of Lower-limb & Trunk Muscles.

OBJECTIVES: To examine the influence of vision and somatosensory information on anticipatory postural adjustments (APA) and compensatory postural adjustments (CPA) in response to an external perturbation in older adults. METHODS: Twenty healthy older adults were included in the study. Postural stability was tested under four different vision and surface support conditions using a sandbag drop while the participants were holding a tray. Electromyography (EMG) latency, amplitude amplitude - root mean square (RMS) of the erector spinae (ES) and lateral gastrocnemius (LG) muscles and centre of pressure (COP) displacement were recorded. RESULTS: Significant differences in muscle activity and COP displacements were observed across visual and somatosensory conditions. LG activity and compensatory COP displacement (CPA-COP) were significantly greater under eyes-closed and unstable surface conditions (ECUS). This indicates that the absence of visual input and altered somatosensory feedback independently and collectively amplify compensatory postural responses. Anticipatory responses were less effective under sensory- compromised conditions. CONCLUSIONS: Both vision and somatosensory inputs critically influence APA and CPA in older adults. Visual deprivation and unstable surfaces reduce the efficiency of APA and heighten CPA, reflecting the need to address both systems in balance training.