Influence of age on dynamic position sense: evidence using a sequential movement task.

Age related changes to the nervous system are well documented. The main objectives of this study were to examine age-associated changes in dynamic position sense and relate these changes to measures of balance and physical function. Two groups of individuals (young <30 years; elderly >60 years) performed an upper extremity movement sequence triggered by a pre-determined target angle during passive rotations of the ankle joint at ten random velocities (10-90 degrees s(-1)). Balance was assessed with a series of timed standing tests. Physical function was assessed with the SF 36 questionnaire. Muscle activity was recorded from the ankle dorsiflexors and plantarflexors during the dynamic position tests. Increased error in the elderly group suggested that dynamic position sense declines with age. Moreover, this decline in dynamic position sense was associated with decreased balance and an impaired perception of physical function. The elderly also co-contracted the ankle plantarflexors and dorsiflexors during the proprioceptive testing, perhaps as a strategy to "gain up" spindle sensitivity. These findings suggest that impaired dynamic position sense of the ankle contributes to alterations in the overall physical function and balance in the elderly. Rehabilitative training methods that improve dynamic position sense of the ankles may improve physical function and balance in the elderly.