The 6-minute walk test in mobility-limited elders: What is being measured?

Background. The 6-minute walk (6mw) is a well-established measure of aerobic capacity in elders with cardiorespiratory and peripheral vascular disease and may be an accurate measure of functional performance in healthy elders. In mobility-limited elders, a population at risk for disability, impairments in strength and power are predictive of performance-based measures of function. Though commonly utilized as an outcome measure among otherwise healthy mobility-limited elders, it is not clear whether the 6mw best represents a measure of functional limitation, aerobic capacity, or both. Methods. We hypothesized that the 6mw would be strongly representative of performance-based measures of function being determined by impairments in muscle strength and power. We performed a cross-sectional analysis of 45 community-dwelling elders with mild to moderate mobility limitations. Results. The 6mw was strongly associated with established functional measures (r = .61-83; p < .001), but was poorly associated with indirect measures of aerobic capacity (r < .25; p > .05). Multivariate linear regression models demonstrated that impairments in leg strength and power, especially those at the knee and ankle, were predictive of 6mw performance. Conclusions. These findings emphasize the 6mw as a measure of functional limitation among mobility-limited elders without cardiorespiratory or peripheral vascular disease.