title: Stooping, crouching, and standing - Characterizing balance control strategies across postures.
abstract: While stooping and crouching postures are critical for many activities of daily living, little is known about the balance control mechanisms employed during these postures. Accordingly, the purpose of this study was to characterize the mechanisms driving net center of pressure (COPNet) movement across three postures (standing, stooping, and crouching) and to investigate if control in each posture was influenced by time.
  
  
  
  Ten young adults performed the three postures for 60s each. Kinetic signals were collected via a force platform under each foot. To quantify mechanisms of control, correlations (CorrelLR) were calculated between the left and right COP trajectories in the anterior-posterior (AP) and medio-lateral (ML) directions. To examine the potential effects of time on balance control strategies, outcomes during the first 30s were compared to the last 30s.
  
  
  
  CorrelLRvalues did not differ across postures (AP: p = 0.395; ML: p = 0.647). Further, there were no main effects of time on CorrelLR(AP: p = 0.976; ML: p = 0.105). A significant posture-time interaction was observed in the ML direction (p = 0.045) characterized by 35% decreases in CorrelLRover time for stooping (p = 0.022).
  
  
  
  The dominant controllers of sway (i.e., AP: ankle plantar/dorsi flexors; ML: hip load/unload mechanism) are similar across quiet stance stooping, and crouching. Changes in ML control strategies over time suggests that fatigue could affect prolonged stooping more so than crouching or standing.
authors.affiliation: Injury Biomechanics and Aging Laboratory, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada.
authors.forename: Tyler B
authors.initials: TB
authors.lastname: Weaver
authors.affiliation: Injury Biomechanics and Aging Laboratory, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada.
authors.forename: Michal N
authors.initials: MN
authors.lastname: Glinka
authors.affiliation: Injury Biomechanics and Aging Laboratory, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada. Electronic address: actlaing@uwaterloo.ca.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Laing
mesh_terms: D000203:Activities of Daily Living; D000843:Ankle Joint / Q000502:physiology; D005260:Female; D005528:Foot / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008297:Male; D009068:Movement; D004856:Postural Balance / Q000502:physiology*; D011187:Posture; D011312:Pressure; D055815:Young Adult
keywords: Bending; Center of pressure; Force plates; Postural sway; Squatting