Disability, physical activity, and muscle strength in older women: The women's health and aging study

Objective: To study associations of motor disability, physical activity, an d muscle strength in older women, in particular to investigate whether mode l of spiraling decrease is expressed in the data. Design: Cross-sectional analysis using data from the baseline measurements of The Women's Health and Aging Study (WHAS). Setting: Participants' homes. Participants: A total of 1,002 disabled women aged 65 years and older livin g in the community. Outcome Measures: Motor disability was measured by the number of self-repor ted difficulties in grasping, lifting 101b, walking across a small room, wa lking 1/4 mile, climbing 10 steps, and doing heavy housework. Level of phys ical activity was determined from response to a series of questions on the frequency and amount of common activities and physical exercise. Hand grip and knee extension forces were measured using portable hand-held dynamomete rs. Results: Disability and physical activity were inversely associated, with i nactivity being most common among the most disabled women. Those with poore r strength reported more difficulties in motor activities. Greater strength was found among the physically more active. in stratified analyses, the po sitive association of physical activity on knee extension strength was cons istent across disability levels. Multiple regression analysis showed that b oth physical activity and muscle strength were significant predictors for s everity of disability. Structural equation model (LISREL) showed that muscl e strength had a mediating role between physical activity and disability; d isability was associated with physical inactivity, which correlated with lo wer muscle strength, which was associated with,greater degree of disability . Conclusion: Even though causality cannot be confirmed in this cross-section al analysis, our findings suggested a spiraling model of decline in which m uscle strength has a significant role, (C) 1999 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.