Association between sensorimotor function and functional and reactive balance control in the elderly.

OBJECTIVES Postural disturbances can arise from performing functional tasks and from external perturbations. Identification of sensorimotor factors associated with both types of balance control in the elderly can help us to understand better the balance problems facing older adults. DESIGN Cross-sectional. SUBJECTS Healthy young, stable older, and functionally unstable older adults with 16 participants in each group. METHODS Clinical vibration sense and muscle strength of the lower extremity, and functional balance (FB) tests were conducted. The timing and amplitude of the reactive postural muscle responses of the leg postural muscles, recorded from standing subjects following support surface backward translation, were also examined. RESULTS Young and older subjects differed significantly in the amplitude of their postural muscle responses, while the two older groups differed significantly in muscle strength and FB. When age was controlled, the strength of the ankle dorsi- and plantar-flexors was the only significant predictor for FB. For reactive postural muscle responses, none of the sensorimotor factors was significant. CONCLUSION Functional and reactive balance abilities differed in their associating factors. The difference in the patterns of association for functional and reactive balance implies the need for separate assessment for these two categories of balance control clinically.