Title page for ETD etd-01062005-170155

Type of Document Master's Thesis
Author Lee, Patrick James
Author's Email Address palee2@vt.edu
URN etd-01062005-170155
Title Low Back Biomechanical Analysis of Isometric Pushing and Pulling Tasks
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Granata, Kevin P. Committee Chair
Duma, Stefan M. Committee Member
Madigan, Michael L. Committee Member
  • stiffness
  • spine
  • low-back
  • co-contraction
  • push
  • stability
Date of Defense 2005-01-03
Availability unrestricted
Few studies have investigated the neuromuscular recruitment and stabilizing control of the spine during pushing and pulling exertions. Past theoretical investigation suggest that co-contraction of the of the paraspinal muscles is necessary to stabilize the spine during pushing exertions. We hypothesized greater levels of co-contraction during pushing exertions. Co-contraction of trunk musculature was quantified during isometric pushing and pulling tasks. The mean value of co-contraction during pushing was two-fold greater (p < 0.01) than during extension.

Co-contraction has been shown to increase the stiffness of the ankle but this effect has not been demonstrated in the trunk. Trunk stiffness was measured as a function of co-activation during extension exertions. Results demonstrate trunk stiffness was significantly (p < 0.01) greater with co-activation.

Trunk stiffness was calculated during isometric pushing and pulling exertions. We hypothesized trunk stiffness would be greater during pushing tasks due to increased levels of co-contraction to maintain stability of the spine. Results demonstrate trunk stiffness was significantly (p < 0.05) greater during pushing compared to pulling exertions.

Results suggest that trunk isometric pushing tasks require more co-contraction than pulling tasks enable to maintain spinal stability. Greater levels of co-contraction during pushing exertions caused trunk stiffness to be greater during pushing compared to pulling tasks. Results may indicate greater risk of spinal instability from motor control error during pushing tasks than pulling exertions. Future studies need to consider co-contraction and neuromuscular control of spinal stability when evaluating the biomechanical risks of pushing and pulling tasks.

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