The six-minute walk test had been used to assessment the cardiopulmonary parameter in patients with lung and heart disease. And it has good reliability and validity. It has been used extensively in research into the aerobic capacity in patients of peripheral vascular disease, neural system disease, and even the muscular-skeletal system disease, such as osteoarthritis, total hip or knee arthroplasty. There were studies investigate the predictors based on cardiopulmonary factors, neuromuscular and skeletal factors of the six-minute walk distance. But the last is the neuromuscular and skeletal factors.

The purpose of this study is to investigate the correlations between the six-minute walk distance and neuromuscular parameters: muscle function (including muscle endurance, muscle strength and muscle power), knee proprioception, and standing balance. For that it could be more useful for evaluation and treatment patients in clinic.

The study was planed to select 100 subjects, they are older than 65 years old with independent walking and without any diagnosis or symptoms about cardiopulmonary or neural disease. The evaluation are including knee proprioception (closed chain, active-active test), six-minute walk test, one leg standing balance test (open and close eyes for 30 seconds), quadriceps muscle strength at velocities of 600/s,1200/s and 1800/s, quadriceps muscle power at 1800/s, and quadriceps muscle endurance.

To investigate the correlations between the six-minute walk distance and characteristics of subjects, the correlations between six-minute walk distance and neuromuscular parameters, including quadriceps muscle function (strength, endurance and power), knee proprioception, and one leg standing balance. And to analyze what's the most contribution to the six-minute walk distance.

Inclusion Criteria:

• older than 65 years old
• independent walking

Exclusion Criteria:

• diagnosis or symptoms about cardiopulmonary or neural disease
• depression