Aging and Posture Control: Changes in Sensory Organization and Muscular Coordination

TLDR

The study examined how older adults coordinate muscle timing and amplitude during postural perturbations and how they reorganize sensory inputs to modify postural responses under changing environmental conditions. Twelve elderly participants (61–78 y) and a younger comparison group (19–38 y) performed postural perturbations on a movable platform while leg muscle electromyography was recorded to assess coordination. Older adults showed delayed distal muscle responses, occasional reversal of proximal/distal onset timing, disrupted amplitude correlations within synergies, and impaired balance when sensory information was reduced or conflicting, with half losing balance under inappropriate visual/somatosensory cues but most maintaining stability thereafter.

Abstract

The following study examined two aspects of balance control in the older adult: 1) the coordination of the timing and the amplitude of muscle responses to postural perturbations, and 2) the ability of the participant to reorganize sensory inputs and subsequently modify postural responses as a consequence of changing environmental conditions. Coordination of muscle activity in postural responses of twelve elderly (sixty-one to seventy-eight years) participants were compared to those of young (nineteen to thirty-eight years) adults using a movable platform and recording the electromyographic activity of muscles of the legs. The following changes were noted in the timing and amplitude of muscle activity within a postural response synergy: 1) increases in the absolute latency of distal muscle responses were observed in all older adults; 2) in five of the twelve older adults temporal reversals of proximal and distal muscle response onset were observed; and 3) there was a breakdown in the correlation of the amplitude of responses within a synergy. The ability of the older adult to balance under conditions of reduced or conflicting sensory information was also impaired. When confronted with functionally inappropriate visual and/or somatosensory inputs, half of the older group lost balance. In most instances, however, the older participants were able to maintain stability during subsequent responses to conflicting stimuli.