The Relationship of Strength to Function in the Older Adult

Reduced lower extremity strength has been associated with reductions in gait speed, balance, stair-climbing ability, and getting up from a seated position. The relationship of lower extremity strength and the ability to accomplish selected functional activities was examined in 16 healthy but frail older adults ranging in age from 75 to 88 years (x = 80.9 years). The following measures were obtained for each subject: preferred gait speed under laboratory and free walking conditions, 5 timed chair stand-ups, and time to complete an obstacle course. Strength measures of the hip extensors, hip abductors, knee extensors, planter flexors, and dorsifiexor muscle groups were obtained using a handheld dynamometer. The relationship between the time to complete the functional activities and each of the strength variables was determined using Pearson product moment correlations. In addition, performance was examined in relation to various combinations of strength measures (e.g., hip and knee extension). Weak, nonsignificant hip, knee and ankle strength/functional activity relationships were found for all of the variables examined. When hip extension, knee extension, and ankle plantar flexion strength values were combined and normalized to body weight, a significant strength-to-functional activity relationship was found for 14″ chair stand-ups (r = .636, p < .01). When values for quadriceps strength and gait speed for 35 adults ranging in age from 60–72 years were compared to those for 75–88 year olds, marked differences emerged. A more significant relationship between knee extension force and gait speed was observed for the younger adults (r = .528 vs r = .353). While it would appear that lower extremity strength is a factor in the successful completion of activities of daily living, other variables appear to contribute substantially to normal daily function. Potential barriers to the successful completion of functional tasks for the older adult may be inadequate sensation, pain, joint impairment, poor balance, and fear. It is clear that the role of factors other than muscle strength needs to be identified and investigated.