title: Step-rate cut-points for physical activity intensity in patients with multiple sclerosis: The effect of disability status.
abstract: BACKGROUND
  Evaluating the relationship between step-rate and rate of oxygen uptake (VO2) may allow for practical physical activity assessment in patients with multiple sclerosis (MS) of differing disability levels.
  
  
  OBJECTIVE
  To examine whether the VO2 to step-rate relationship during over-ground walking differs across varying disability levels among patients with MS and to develop step-rate thresholds for moderate- and vigorous-intensity physical activity.
  
  
  METHODS
  Adults with MS (N=58; age: 51 ± 9 years; 48 women) completed one over-ground walking trial at comfortable speed, one at 0.22 m · s(-1) slower, and one at 0.22 m · s(-1) faster. Each trial lasted 6 min. VO2 was measured with portable spirometry and steps with hand-tally. Disability status was classified as mild, moderate, or severe based on Expanded Disability Status Scale scores.
  
  
  RESULTS
  Multi-level regression indicated that step-rate, disability status, and height significantly predicted VO2 (p<0.05). Based on this model, we developed step-rate thresholds for activity intensity that vary by disability status and height. A separate regression without height allowed for development of step-rate thresholds that vary only by disability status.
  
  
  CONCLUSIONS
  The VO2 during over-ground walking differs among ambulatory patients with MS based on disability level and height, yielding different step-rate thresholds for physical activity intensity.
authors.affiliation: Department of Kinesiology, Mississippi State University, 240 McCarthy Gym, P.O. Box 6186, Mississippi State, MS 39762, US. Electronic address: sagiovlasitis@colled.msstate.edu.
authors.forename: Stamatis
authors.initials: S
authors.lastname: Agiovlasitis
authors.affiliation: Kessler Foundation, 300 Executive Drive, Suite 70, West Orange, NJ 07052, US.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Sandroff
authors.affiliation: Department of Kinesiology & Community Health, University of Illinois at Urbana-Champaign, 233 Freer Hall, 906 S Goodwin Ave., Urbana, IL 61801, US.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Motl
mesh_terms: D000328:Adult; D004185:Disability Evaluation; D006233:Persons with Disabilities; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D009103:Multiple Sclerosis / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000502:physiology; D016138:Walking / Q000502:physiology*
keywords: Measurement; Neurological disability; Over-ground walking; Physical activity