Does the six-minute walk test measure walking performance or physical fitness in persons with multiple sclerosis?

BACKGROUND:There is psychometric evidence that supports the six-minutewalk (6MW) as a measure ofwalking performance, whereas other psychometric data support it as a submaximal measure of physical fitness in persons with MS. OBJECTIVE: The current cross-sectional study compared measures ofwalking performance and physical fitness as head-to-head predictors of 6MW distance in a sample of persons with MS across the disability spectrum. METHODS: All participants completed the 6MW test, as well as other measures of walking performance (i.e., timed-25 foot walk, gait velocity captured by a GaitRite™ electronic walkway) and physical fitness (i.e., peak aerobic capacity, lower limb muscular strength). RESULTS: 6MW distance was strongly associated with measures of walking performance and physical fitness, though the correlations were significantly stronger for measures of walking performance than physical fitness (z > 4.04, p < 0.01). Walking performance explained a large portion of variance in6MWdistance (R² > 0.85), and measures of physical fitness explained minimal variance in 6MW distance over-and-above that of measures of walking performance (ΔR² < 0.06). CONCLUSIONS: The current results suggest that 6MW distance is primarily a measure of walking performance rather than aerobic and muscular fitness in MS.