title: Effects of seated whole-body vibration on postural control of the trunk during unstable seated balance.
abstract: BACKGROUND
  Low back disorders and their prevention is of great importance for companies and their employees. Whole-body vibration is thought to be a risk factor for low back disorders, but the neuromuscular, biomechanical, and/or physiological mechanisms responsible for this increased risk are unclear. The purpose of this study was to measure the acute effect of seated whole-body vibration on the postural control of the trunk during unstable seated balance.
  
  
  METHODS
  Twenty-one healthy subjects (age: 23 years (SD 4 years)) were tested on a wobble chair designed to measure trunk postural control. Measurements of kinematic variance and non-linear stability control were based on seat angle before and after 30 min of seated whole-body vibration (bandwidth=2-20 Hz, root-mean-squared amplitude=1.15m/s(2)).
  
  
  RESULTS
  All measures of kinematic variance of unstable seated balance increased (P<0.05) after vibration including: ellipse area (35.5%), root-mean-squared radial lean angle (17.9%), and path length (12.2%). Measures of non-linear stability control also increased (P<0.05) including Lyapunov exponent (8.78%), stability diffusion analysis (1.95%), and Hurst rescaled range analysis (5.2%).
  
  
  CONCLUSIONS
  Whole-body vibration impaired postural control of the trunk as evidenced by the increase in kinematic variance and non-linear stability control measures during unstable sitting. These findings imply an impairment in spinal stability and a mechanism by which vibration may increase low back injury risk. Future work should investigate the effects of whole-body vibration on the anatomical and neuromuscular components that contribute to spinal stability.
authors: The Kevin P. Granata Musculoskeletal Biomechanics Laboratory, Virginia Polytechnic Institute and State University, 219 Norris Hall (0219), Blacksburg, VA 24061, USA. gslota@vt.edu
authors: Gregory P
authors: GP
authors: Slota
authors: Kevin P
authors: KP
authors: Granata
authors: Michael L
authors: ML
authors: Madigan
mesh_terms: D000328:Adult; D001415:Back / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007699:Kinesthesis / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology; D014159:Transducers; D014732:Vibration / Q000009:adverse effects*