Maximum trunk flexion angle during the sit to stand is not determined by knee or trunk-hip extension strength in healthy older adults

When rising from a chair, older adults have been reported to use a strategy in which me trunk is flexed to a greater extent than young adults, a strat egy attributed by some to concerns with the postural stability demands of t he task. This study determined the extent to which maximum trunk flexion an gle during a self-paced sit-to-stand from a standardized initial position w as influenced by the maximum isometric strength of the knee and trunk/hip e xtensor muscles in older adults. The hypothesis was mat the larger maximum trunk flexion angle attained by older adults when rising from a chair is re lated to the maximum isometric strength of the knee and trunk-hip extensor muscles. To test this hypothesis, maximum voluntary isometric strength of t he trunk extensor and knee extensor muscles of 28 older men and women were measured. Trunk motion during the sit-to-stand by these adults was then ass essed using motion analysis. Multiple regression was used to characterize t he relationship between the maximum trunk flexion angle and maximum isometr ic knee extensor and trunk extensor muscle strength. The derived relationsh ip was neither statistically significant nor biomechanically meaningful. Th is result suggests that the trunk flexion angle attained by healthy older a dults when rising from a chair from a standardized initial position is not influenced by knee extension and trunk-hip extension strength as measured i n the present study.