Isokinetic Leg Muscle Strength in Older Americans and Its Relationship to a Standardized Walk Test: Data from the National Health and Nutrition Examination Survey 1999–2000

OBJECTIVES: To describe isokinetic knee extensor muscle strength in older U.S. men and women by age and race/ethnicity and to ascertain its relationship to a standard, timed walking-speed test. SETTING: The U.S. National Health and Nutrition Examination Survey (NHANES) 1999-2000. DESIGN: A cross-sectional nationally representative health examination survey. PARTICIPANTS: All surveyed persons aged 50 and older (N=1,499) who performed muscle strength and timed walk examinations in the NHANES mobile examination center. MEASUREMENTS: Concentric peak torque (strength) of the knee extensors at 1.05 rads/ s(-1) velocity and a 6-m walk timed in seconds. RESULTS: Knee extensor strength was inversely associated with age (P<.01), and women had less knee extensor muscle strength than men (P<.01). After adjustment for standing height, no significant difference in muscle strength was found across the three race/ethnicity groups (Mexican Americans, non-Hispanic blacks, and non-Hispanic whites) for men or women. After adjustment for age, race/ethnicity, weight, and height, increasing knee extensor strength was associated with significant increases in meters walked per second (P<.01). CONCLUSION: Knee extensor muscle strength is affected by age and sex but not by race/ethnicity and it is significantly associated with timed walk.