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The 6-minute walk test in mobility-limited elders: what is being measured?
Jonathan F Bean1, Dan K Kiely, Suzanne G Leveille
1Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, Massachusetts, USA. bean@mail.hrca.harvard.edu
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.