title: Evidence for the different physiological significance of the 6- and 2-minute walk tests in multiple sclerosis.
abstract: BACKGROUND
  Researchers have recently advocated for the 2-minute walk (2MW) as an alternative for the 6-minute walk (6MW) to assess long distance ambulation in persons with multiple sclerosis (MS). This recommendation has not been based on physiological considerations such as the rate of oxygen consumption (V·O2) over the 6MW range.
  
  
  OBJECTIVE
  This study examined the pattern of change in V·O2 over the range of the 6MW in a large sample of persons with MS who varied as a function of disability status.
  
  
  METHODS
  Ninety-five persons with clinically-definite MS underwent a neurological examination for generating an Expanded Disability Status Scale (EDSS) score, and then completion of the 6MW protocol while wearing a portable metabolic unit and an accelerometer.
  
  
  RESULTS
  There was a time main effect on V·O2 during the 6MW (p=.0001) such that V·O2 increased significantly every 30 seconds over the first 3 minutes of the 6MW, and then remained stable over the second 3 minutes of the 6MW. This occurred despite no change in cadence across the 6MW (p=.84).
  
  
  CONCLUSIONS
  The pattern of change in V·O2 indicates that there are different metabolic systems providing energy for ambulation during the 6MW in MS subjects and steady state aerobic metabolism is reached during the last 3 minutes of the 6MW. By extension, the first 3 minutes would represent a test of mixed aerobic and anaerobic work, whereas the second 3 minutes would represent a test of aerobic work during walking.
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana Champaign, 233 Freer Hall, Urbana, IL 61801, USA. robmotl@illinois.edu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Motl
authors.forename: Yoojin
authors.initials: Y
authors.lastname: Suh
authors.forename: Swathi
authors.initials: S
authors.lastname: Balantrapu
authors.forename: Brian M
authors.initials: BM
authors.lastname: Sandroff
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Sosnoff
authors.forename: John
authors.initials: J
authors.lastname: Pula
authors.forename: Myla D
authors.initials: MD
authors.lastname: Goldman
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
mesh_terms: D000328:Adult; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology*; D013997:Time Factors; D016138:Walking