Motor control of lumbar instability following exposure to various cyclic load magnitudes.
Ben-Masaud-A; Solomonow-D; Davidson-B; Zhou-BH; Lu-Y; Patel-V; Solomonow-M
Eur Spine J 2009 Jul; 18(7):1022-1034
The motor control system may compensate for lumbar instability following cyclic work with differential response to load magnitude. In vivo felines were exposed to a cumulative 1 h of cyclic work at 0.25 Hz. One group exposed to light whereas the second to heavy load while recording lumbar displacement and multifidus EMG during work and in single test cycles over 7 h rest post-work. Significant laxity and reduced reflexive EMG activity were evident immediately post-work in both groups. EMG and laxity recovered over 7 h rest in the group exposed to light load whereas in the group exposed to heavy load, motor control compensation was triggered within 1-2 h post-work. The compensation was expressed by earlier and stronger muscular activation than in baseline. It is concluded that cyclic work is deleterious to spine stability immediately after work. Work with heavy loads elicits delayed motor control compensation whereas work with light loads leaves the spine unstable and exposed to injury for several hours. Overall, prolonged cyclic or repetitive work elicits a transient instability disorder, regardless of the load handled, exposing the individual to potential injury.
Back-injuries; Biomechanics; Ergonomics; Exposure-levels; Exposure-methods; Muscle-stress; Musculoskeletal-system; Posture; Repetitive-work; Statistical-analysis;
Author Keywords: Spine; Lumbar; Stability; Muscles; EMG; Multifidus; Ergonomics; Disorder
Moshe Solomonow, Musculoskeletal Disorders Research Laboratory, Bioengineering Division, Department of Orthopedic Surgery, University of Colorado, Denver, Health Sciences Center, 12800 E 19th Ave, RC-1N, Mail Stop 8343, Box 6511, Denver, CO 80045
European Spine Journal
Virginia Polytechnic Institute and State University