title: Ground reaction forces during stair locomotion in pregnant fallers and non-fallers.
abstract: BACKGROUND
  More than 27% of pregnant women fall. Approximately 40% of falls occur during staircase locomotion. The purpose of this study was to examine ground reaction forces in pregnant fallers, pregnant non-fallers, and non-pregnant controls to determine if pregnant fallers display alterations to ground reaction forces that increase their risk of falling on stairs.
  
  
  METHODS
  Fifteen pregnant fallers and 14 pregnant non-fallers participated during their second and third trimesters. Forty non-pregnant women served as controls. Subjects ascended and descended a four-step staircase. A force plate in the second stair collected ground reaction forces. Ascent and descent velocities were assessed. In the statistics, group (pregnant faller, pregnant non-faller, control) and subject were independent variables. Stance time and ascent/descent velocity were analyzed with an ANOVA. Mediolateral center of pressure excursion was analyzed with an analysis of covariance. Ground reaction forces were categorized into anterioposterior, mediolateral, and vertical forces and normalized to the subject's bodyweight. A multivariate analysis of covariance was used to compare between groups and subjects for each force category, with velocity as the covariate (α = 0.05).
  
  
  RESULTS
  Pregnant fallers had an increased anterioposterior braking impulse (P < 0.01), medial impulse (P = 0.02), and minimum between vertical peaks (P = <0.01) during ascent. During descent, pregnant fallers demonstrated a smaller anterioposterior propulsive peak and propulsive impulse (P = 0.03) and a greater minimum between vertical peaks (P<0.01).
  
  
  CONCLUSIONS
  These alterations are likely related to a strategy used by pregnant fallers to increase stability during staircase locomotion.
authors.affiliation: Division of Exercise Physiology, Department of Human Performance and Applied Exercise Science, West Virginia University, Morgantown, WV, USA; Department of Health and Physical Activity, University of Pittsburgh, Pittsburgh, PA, USA. Electronic address: jlmccrory@hsc.wvu.edu.
authors.forename: Jean L
authors.initials: JL
authors.lastname: McCrory
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: April J
authors.initials: AJ
authors.lastname: Chambers
authors.affiliation: Obstetrics, Gynecology, and Reproductive Services, West Penn Allegheny Health System, Pittsburgh, PA, USA.
authors.forename: Ashi
authors.initials: A
authors.lastname: Daftary
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Redfern
mesh_terms: D000058:Accidental Falls; D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena / Q000502:physiology; D016022:Case-Control Studies; D005260:Female; D017276:Friction / Q000502:physiology; D005684:Gait; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D055595:Mechanical Phenomena; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology; D011247:Pregnancy
keywords: Center of pressure; Falls; Ground reaction forces; Pregnancy; Stairs