Functional performance levels of strength and power needed for independence in 80-year-old individuals

Background: The ability to climb stairs (ascending and descending stair without using a handrail) and rise from a chair (rising from chairs without using an elbow rest) are among the most important measures of physical function for ADL evaluation for the independent living, and assessed by the questioners on many epidemiological studies in elderly. But little is known about the relationship between the self-reported performance level of the tasks and lower leg strength and power in very elderly people. The purpose of this study was to ascertain the relationship between the self-reported performance level of two tasks and the lower leg function in communitydwelling 80-year-old population. Methods: Out of 994 persons who were 80 years old living in Morioka City, Iwate Prefecture, Japan, 607 individuals (236 men and 371 women) underwent a physical fitness test that included measurements of leg extensor power and knee extensor strength. The ability to climb up stair and to rise from a chair was assessed by selfreported questionnaire which was ranked in three levels. The area under the receiver-operating characteristic (ROC) curve (AUC) was used to evaluate the measurements. Results: The cut-off points for the leg extensor power of subjects who could completely perform the stair-climbing and chair-rising functions were determined to be approximately 8.6 watt/kg body mass for men and 5.6 watt/kg body mass for women. In addition, the cut-off points for the knee extensor strength of subjects who could completely perform the stair-climbing and chair-rising functions were determined to be approximately 0.97 kg/kg body mass for men and 0.84 kg/kg body mass for women. Conclusions: From a practical viewpoint, the present study suggested that the cut-off points of leg extensor power and knee extensor strength can be used as targets in simple self-reported questionnaires to help in screening for mobility in 80-year-old population