The relation between age-related changes in neuromusculoskeletal system and dynamic postural responses to balance disturbance.

BACKGROUND: The purpose of this study was to identify some critical factors whose functional changes with age in the neuromusculoskeletal systems would potentially relate to the maintenance of standing balance.
METHODS: A total of 38 healthy subjects were tested (age range, 21-77 years). A postural disturbance at the foot was provided, and the range of movement of the head, trunk, thigh, shank, and foot was examined. Three supporting surfaces were tested: hard, soft, and reduced. The functions evaluated in each subject included general health, touch, and cutaneous vibratory perception threshold at four different locations, ankle strength, and range of motion. The functions were then correlated with the maximum magnitude of the body movement.
RESULTS: There were significant age-related changes in cutaneous vibratory perception threshold at all four locations of the foot, in plantarflexor strength, and in touch sensation at the heel region. Age had a positive correlation with head movement regardless of the supporting surface and the movement direction of the platform. Plantarflexor strength was also correlated with head movement but only when the platform moved in the backward direction. When standing on a large supporting base the change in cutaneous vibratory perception threshold at the 5th metatarsal head with respect to age showed a larger, although weak, effect on the head movement than the cutaneous vibratory perception threshold at other regions.
CONCLUSIONS: The stabilization of an upright balance, especially the head, was related to age, plantarflexor strength, and vibratory perception at the foot. The laboratory test in this study identified such correlations.