Knee extensor isometric unsteadiness does not predict functional limitation in older adults.

Abstract

To determine how knee extensor steadiness is related to age and difficulty performing everyday tasks. In this cross-sectional study performed at a research laboratory, 50 older adults (age range, (56-95 yrs) performed steadiness testing at 50% of maximum strength and were timed and rated on four tasks of daily living: chair rise, stair ascent and descent, and walk. The independent variables of age, steadiness, and strength-to-weight ratio were entered into regression models with the ratings and time to complete the four everyday tasks as dependent variables. The strength-to-weight ratio was the only significant predictor in the multiple regression models, explaining 29%, 33%, 14%, and 14% of the variance in gait speed and time to complete a chair rise, stair ascent, and stair descent, respectively. Similar results were seen with task ratings. Age was not correlated with steadiness (r = 0.25, P = 0.07). This study suggests that knee extensor isometric steadiness performance does not carry over to tasks of everyday living, and older subjects, regardless of age, have similar steadiness values. Because the strength-to-weight ratio predicted the most variance in functional performance, it is recommended that muscle strength be improved to increase function in older adults.