title: Patients with Chronic Obstructive Pulmonary Disease Walk with Altered Step Time and Step Width Variability as Compared with Healthy Control Subjects.
abstract: BACKGROUND
  Compared with control subjects, patients with chronic obstructive pulmonary disease (COPD) have an increased incidence of falls and demonstrate balance deficits and alterations in mediolateral trunk acceleration while walking. Measures of gait variability have been implicated as indicators of fall risk, fear of falling, and future falls.
  
  
  OBJECTIVE
  To investigate whether alterations in gait variability are found in patients with COPD as compared with healthy control subjects.
  
  
  METHODS
  Twenty patients with COPD (16 males; mean age, 63.6 ± 9.7 yr; FEV1/FVC, 0.52 ± 0.12) and 20 control subjects (9 males; mean age, 62.5 ± 8.2 yr) walked for 3 minutes on a treadmill while their gait was recorded. The amount (SD and coefficient of variation) and structure of variability (sample entropy, a measure of regularity) were quantified for step length, time, and width at three walking speeds (self-selected and ±20% of self-selected speed). Generalized linear mixed models were used to compare dependent variables.
  
  
  RESULTS
  Patients with COPD demonstrated increased mean and SD step time across all speed conditions as compared with control subjects. They also walked with a narrower step width that increased with increasing speed, whereas the healthy control subjects walked with a wider step width that decreased as speed increased. Further, patients with COPD demonstrated less variability in step width, with decreased SD, compared with control subjects at all three speed conditions. No differences in regularity of gait patterns were found between groups.
  
  
  CONCLUSIONS
  Patients with COPD walk with increased duration of time between steps, and this timing is more variable than that of control subjects. They also walk with a narrower step width in which the variability of the step widths from step to step is decreased. Changes in these parameters have been related to increased risk of falling in aging research. This provides a mechanism that could explain the increased prevalence of falls in patients with COPD.
authors.affiliation: 1 Department of Biomechanics and.
authors.forename: Jennifer M
authors.identifier: http://orcid.org/0000-0001-6550-7759
authors.initials: JM
authors.lastname: Yentes
authors.affiliation: 2 Department of Pulmonary and Critical Care Medicine and.|3 Clinical Discovery Unit, AstraZeneca, London, United Kingdom.
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Rennard
authors.affiliation: 4 College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska; and.
authors.forename: Kendra K
authors.initials: KK
authors.lastname: Schmid
authors.affiliation: 5 School of Health, Physical Education, and Recreation, University of Nebraska at Omaha, Omaha, Nebraska.
authors.forename: Daniel
authors.initials: D
authors.lastname: Blanke
authors.affiliation: 1 Department of Biomechanics and.|4 College of Public Health, University of Nebraska Medical Center, Omaha, Nebraska; and.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Stergiou
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005684:Gait; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009329:Nebraska; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D000070857:Walk Test
keywords: biomechanics; entropy; gait; locomotion; lung disease