Quadriceps muscle strength and dynamic stability in elderly persons.

Several measures of dynamic stability during two functional activities correlated to quadriceps femoris muscle strength. A total of 34 disabled elders (aged 60-88) living in the Boston area consented to maximum isometric quadriceps muscle strength testing, chair rise and gait analysis. During chair rise, quadriceps strength significantly correlated with maximum upper body vertical linear momentum, r=0.53, P<0.005, anterior posterior linear momentum, r=0. 38, P<0.05, and the time to complete the chair rise, r=-0.48, P<0.05, n=29. Stride length and gait velocity correlated (r=0.56, P<0.001 and r=0.51, P<0.002, n=34) with quadriceps muscle strength. The maximum range of whole body anteroposterior (A/P) linear momentum during gait also correlated with quadriceps strength (r=0.47, P=0. 004, n=31). Dynamic stability during chair rise and gait, at preferred speed, correlates directly with quadriceps femoris muscle strength in functionally limited elderly individuals. In our sample, elders performed one of three movement strategies to arise from a chair, and quadriceps strength did not statistically differ between the chair rise strategy groups. However, persons with the greatest quadriceps strength values were more stable regardless of which chair rise strategy they performed. Our data indicate that clinicians should not suggest that patients use compensatory momentum inducing locomotor strategies unless the patient has sufficient strength to control these induced forces.