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Frequency of cyclic lumbar loading is a risk factor for cumulative trauma disorder.

Authors
Lu-D; Le-P; Davidson-B; Zhou-BH; Lu-Y; Patel-V; Solomonow-M
Source
Muscle Nerve 2008 Jul; 38(1):867-874
NIOSHTIC No.
20034400
Abstract
Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulative trauma disorder (CTD), and the frequency or velocity of the movement is one of the risk factors. Experimental neurophysiological evidence to confirm the epidemiology is not available. The response of the multifidus muscles to cyclic loading in anterior lumbar flexion-extension was assessed to test the hypothesis that high-frequency loading may induce an acute neuromuscular disorder leading to CTD. Two groups of feline preparations were subjected to cyclic loading with a peak of 20 N: one at 0.25 HZ and the second at 0.5 HZ, with an equal number of cycles. Electromyogram (EMG), lumbar displacement and load were recorded throughout the loading periods and during single-cycle tests over a 7-hour rest period following the load-rest sessions. A model was developed to quantify the creep and neuromuscular responses, and analysis of variance (ANOVA) was applied to assess significance of the results. The group exposed to 0.5 HZ exhibited spontaneous spasms followed by sustained spasms during the loading periods. During the 7-hour recovery period, a significant (P < 0.001) delayed hyperexcitability as well as sustained spasms of the multifidi were present in the last 5 hours, confirming a significant (P < 0.024 to P < 0.042) acute neuromuscular disorder. High-frequency cyclic loading of the lumbar spine may trigger a severe acute neuromuscular disorder, as evidenced by the sustained spasms and delayed hyperexcitability, and should be considered as a risk factor. We suggest that workers avoid high-frequency exposure to cyclic activity in order to prevent the development of cumulative trauma disorder.
Keywords
Biomechanics; Cumulative-trauma-disorders; Neuromuscular-system-disorders; Rest-periods; Epidemiology; Back-injuries; Animal-studies; Laboratory-animals; Laboratory-testing; Musculoskeletal-system-disorders; Physiological-fatigue; Physiological-effects; Physiological-factors; Physiological-measurements; Physiological-response; Risk-factors; Statistical-analysis; Mathematical-models
Contact
Moshe Solomonow, Musculoskeletal Disorders Research Laboratory, Bioengineering Division, Department of Orthopedics, University of Colorado at Denver and Health Sciences Center, Aurora, CO 80045
CODEN
MUNEDE
Publication Date
20080701
Document Type
Journal Article
Email Address
moshe.solomonow@uchsc.edu
Funding Amount
695194
Funding Type
Grant
Fiscal Year
2008
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-007622
Issue of Publication
1
ISSN
0148-639X
Source Name
Muscle & Nerve
State
LA; CO
Performing Organization
Louisiana State University, Health Sciences Center, New Orleans, Louisiana
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