Working in flexed torso postures increases the risk of occupationally related low-back disorders. These postures apply strain to spinal tissues that cause temporary disturbances in neuromuscular control of trunk muscles. Existing evidence reveals that there are residual effects on spine biomechanics following exposure to flexed postures. Recovery from these disturbances may be incomplete upon initiation of subsequent tasks thereby causing an accumulation of neuromuscular disturbance. In other words, muscle recruitment, spinal load and spinal stability during a given flexion task is influenced by previous tasks and will influence subsequent tasks. However, the role of work-task design on these disturbances remains unknown. Neuromuscular disturbance will be recorded by quantifying changes in: 1) trunk muscle co-contraction, 2) para spinal reflex response, 3) active trunk stiffness, 4) spinal load, and 5) spinal stability. An exposure-response relationship will be characterized in Specific Aim 1 to test the hypotheses that duration of static flexion is associated with progressive increases in neuromuscular disturbance and that task load increases the disturbance rate. We will quantify changes in co-contraction, stiffness, reflex, spinal load and stability recorded before and after periods of static trunk flexion by means of established methods and models.
Specific Aim 2 will record neuromuscular behavior before and after exposure to flexion postures to test the hypothesis that flexion angle and exposure-rate influence the severity and rate of neuromuscular disturbance. Rate of recovery of neuromuscular behavior following static flexion tasks will also be recorded in Specific Aims 1 &2 to gain insight into the effects of work-rest scheduling of flexion tasks.
Specific Aims 3 and 4 will test the hypotheses that neuromuscular disturbance can accumulate across repeated static flexion tasks and repetitive dynamic lifting respectively. We will investigate how disturbance severity is influenced by flexion duration, peak flexion angle and lift rate. Finally, we will test the hypothesis that these disturbances can influence the dynamic control of spinal stability. The proposed study will investigate how workplace factors influence the severity and time-course of neuromuscular disturbance (including spinal load and stability). Results will guide future studies and/or epidemiologic investigations regarding the mechanism of cumulative risk from flexed working postures.

Agency
National Institute of Health (NIH)
Institute
National Institute for Occupational Safety and Health (NIOSH)
Type
Research Project (R01)
Project #
5R01OH008504-04
Application #
7658106
Study Section
Special Emphasis Panel (ZOH1-COR (02))
Program Officer
Frederick, Linda J
Project Start
2006-08-01
Project End
2011-07-31
Budget Start
2009-08-01
Budget End
2010-07-31
Support Year
4
Fiscal Year
2009
Total Cost
$262,913
Indirect Cost
Name
Virginia Polytechnic Institute and State University
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
003137015
City
Blacksburg
State
VA
Country
United States
Zip Code
24061
Toosizadeh, Nima; Nussbaum, Maury A (2013) Creep deformation of the human trunk in response to prolonged and repetitive flexion: measuring and modeling the effect of external moment and flexion rate. Ann Biomed Eng 41:1150-61
Toosizadeh, Nima; Bazrgari, Babak; Hendershot, Brad et al. (2013) Disturbance and recovery of trunk mechanical and neuromuscular behaviours following repetitive lifting: influences of flexion angle and lift rate on creep-induced effects. Ergonomics 56:954-63
Hendershot, Brad D; Toosizadeh, Nima; Muslim, Khoirul et al. (2013) Evidence for an exposure-response relationship between trunk flexion and impairments in trunk postural control. J Biomech 46:2554-7
Miller, Emily M; Bazrgari, Babak; Nussbaum, Maury A et al. (2013) Effects of exercise-induced low back pain on intrinsic trunk stiffness and paraspinal muscle reflexes. J Biomech 46:801-5
Muslim, Khoirul; Bazrgari, Babak; Hendershot, Brad et al. (2013) Disturbance and recovery of trunk mechanical and neuromuscular behaviors following repeated static trunk flexion: influences of duration and duty cycle on creep-induced effects. Appl Ergon 44:643-51
Toosizadeh, Nima; Nussbaum, Maury A; Bazrgari, Babak et al. (2012) Load-relaxation properties of the human trunk in response to prolonged flexion: measuring and modeling the effect of flexion angle. PLoS One 7:e48625
Bazrgari, Babak; Nussbaum, Maury A; Madigan, Michael L (2012) Estimation of trunk mechanical properties using system identification: effects of experimental setup and modelling assumptions. Comput Methods Biomech Biomed Engin 15:1001-9
Hendershot, Brad D; Bazrgari, Babak; Nussbaum, Maury A et al. (2012) Within- and between-day reliability of trunk mechanical behaviors estimated using position-controlled perturbations. J Biomech 45:2019-22
Bazrgari, Babak; Hendershot, Brad; Muslim, Khoirul et al. (2011) Disturbance and recovery of trunk mechanical and neuromuscular behaviours following prolonged trunk flexion: influences of duration and external load on creep-induced effects. Ergonomics 54:1043-52
Bazrgari, B; Nussbaum, M A; Madigan, M L et al. (2011) Soft tissue wobbling affects trunk dynamic response in sudden perturbations. J Biomech 44:547-51

Showing the most recent 10 out of 13 publications