DEPARTURES FROM LINEARITY IN THE RELATIONSHIP BETWEEN MEASURES OF MUSCULAR STRENGTH AND PHYSICAL PERFORMANCE OF THE LOWER-EXTREMITIES - THEWOMENS HEALTH AND AGING STUDY

Background. Sarcopenia, an age-related reduction in muscular mass and strength, may cause a decline in physical functioning and subsequent l oss of autonomy. It has been suggested that strength is associated wit h lower extremity function mainly in the lower portion of the range of strength. Identifying the threshold under which strength is most crit ical to function may help in targeting groups who may benefit most fi: om exercise interventions. Methods, The study uses data from the Women 's Health and Aging Study. The study population, recruited by screenin g a population-based sample aged 65 years and older, comprised 1,002 w omen who represent the one-third most disabled women without severe co gnitive impairment living in the community. Knee extensor and hip flex or strength were assessed using a hand-held dynamometer. Lower extremi ty performance was evaluated using rests of walking, standing balance, and rising from a chair. Results. Among women tested for strength (n = 892), those who could walk (97%), do the side-by-side stand (87%), o r complete 5 chair stands (74%) had significantly greater strength. Wa lking speed was linearly associated with knee extensor strength over t he entire range of strength, but its association with hip strength was limited to values below 15 kg. Time for five chair stands was associa ted with knee extensor and hip flexor strength below 10 and 15 kg, res pectively, and no significant association was detected above these val ues. Stronger women were more likely to hold balance for 10 sec in the side-by-side, semi-tandem, and tandem positions. The percentage of th e variance in performance explained by strength alone was always lower than 20%. Conclusions, In this population, which does not include the strongest older women, there is a departure from linearity in the rel ationship between muscular strength and some measures of lower extremi ty performance.