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

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Abstract
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.