Disturbance and recovery of trunk stiffness and reflexive muscle responses following prolonged trunk flexion: influences of flexion angle and duration

Details

• Personal Author:
  Bazrgari B ; Hendershot B ; Madigan ML ; Muslim K ; Nussbaum MA ; Toosizadeh N
• Description:
  Background: Experimental studies suggest that flexed working postures reduce passive support of the spine, which could represent a significant risk factor for the development of occupational low back disorders. Neuromuscular compensations to reduced passive stiffness include increases in baseline activity or reflexive activation of trunk muscles. Yet, alterations and recovery of the synergy between active and passive tissues following prolonged flexion in humans are currently unknown. Methods: Twelve healthy participants were exposed to all combinations of two trunk flexion durations (2 and 16 min) and three flexion angles (33, 66, and 100% of individual flexion-relaxation angle). Load relaxation was recorded throughout exposures, whereas trunk stiffness and reflexive behaviors of the lumbar extensor muscles were investigated during dynamic responses to sudden perturbations. Findings: The magnitude of load relaxation increased with increasing flexion angle. Trunk stiffness decreased and reflex gains increased following flexion exposures; for both outcomes, acute changes were larger following exposure to increasing flexion angle. Reflex gains remained elevated one hour after exposure to maximum flexion. Interpretation: Exposure to prolonged trunk flexion changed trunk stiffness and reflex behavior in patterns consistent with epidemiological evidence linking such exposure with the risk of occupational low back disorders. Observed increases in reflex gains, at least among healthy individuals, may be a compensation for decreases in passive trunk stiffness following acute exposure to flexed postures. It remains to be determined whether the neuromuscular system can similarly respond to accumulated disturbances in passive structures following exposure to repeated flexion tasks. [Description provided by NIOSH]
• Subjects:
  Biomechanical Phenomena Ergonomics Musculoskeletal Diseases Musculoskeletal System Nervous System Occupational Exposure Occupational Health Risk Assessment Risk Factors Safety
• Keywords:
  Author Keywords: Low Back Pain Back-injuries Biodynamics Biomechanical-modeling Biomechanics Body-burden Body-mechanics Load Relaxation Lumbar Spine Mathematical-models Musculoskeletal-system Musculoskeletal-system-disorders Neuromuscular-function Neuromuscular-system Occupational-hazards Physiological-response Physiological-stress Physiology Posture Prolonged Flexion Reflex Repetitive-work Risk-analysis Risk-factors Stiffness

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• ISSN:
  0268-0033
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 3 ; Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  250-256
• Volume:
  26
• Issue:
  3
• NIOSHTIC Number:
  nn:20039332
• Citation:
  Clin Biomech 2011 Mar; 26(3):250-256
• Contact Point Address:
  Maury A. Nussbaum, Wake Forest School of Biomedical Engineering and Sciences, Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA 24061
• Email:
  nussbaum@vt.edu
• Federal Fiscal Year:
  2011
• Performing Organization:
  Virginia Polytechnic Institute and State University
• Peer Reviewed:
  True
• Start Date:
  20060801
• Source Full Name:
  Clinical Biomechanics
• End Date:
  20120731
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:877b6d3a33d4a57541d40d244ab8d8e76325e78d70e29d35158b6e506344b63647ee3f6ecf782c6e26a74b35c8f1d37444bbd033a9e5ef330b53af0dbdffc5ff
• Download URL:
  https://stacks.cdc.gov/view/cdc/192674/cdc_192674_DS1.pdf
• File Type:
  [PDF - 438.70 KB ]