Neuromuscular response to cyclic lumbar twisting.
OBJECTIVE
To study the influence of 10 min of cyclic twisting motion on abdominal and back muscle activities.


BACKGROUND
Repetitive (cyclic) occupational activity was identified by many epidemiological reports to be a risk factor for the development of work-related musculoskeletal disorders. Biomechanical and physiological confirmation, however, is lacking.


METHODS
Trunk muscle electromyography (EMG) was recorded while participants performed a continuous 10-min maximum lumbar cyclic twisting to the left, and maximum isometric twist to the left and right sides was measured before and after the exercise.


RESULTS
Abdominal muscles contracted symmetrically, independent of twisting direction. The left posterior muscles' integrated EMG (IEMG) decreased during the exercise, whereas the IEMG of the right posterior muscle increased. Simultaneously with increased antagonist coactivity level of the right posterior muscles after the exercise, decrease in maximal isometric left twisting torque was observed. The abdominal muscles did not exhibit any significant changes during the exercise. After the exercise, the right abdominals demonstrated a significant increase in effort, which was independent of the direction of the maximal effort isometric test.


CONCLUSIONS
The change in muscle activity is attributed to neuromuscular compensation for the development of laxity and microdamage in the soft tissue (ligaments, discs, facet capsules, etc.) of the lumbar spine.


CONCLUSIONS
The results of this study increase understanding of the risk factors associated with low back disorder induced by labor-intensive occupations that involve cyclic lateral twisting.
Li
Li
L
Department of Kinesiology, Louisiana State University, Baton Rouge, Louisiana, USA.
Patel
Nirav
N
Solomonow
Deborah
D
Le
Peter
P
Hoops
Heather
H
Gerhardt
David
D
Johnson
Kyle
K
Zhou
Bing He
BH
Lu
Yun
Y
Solomonow
Moshe
M
D000328:Adult; D001415:Back / Q000502:physiology; D001696:Biomechanical Phenomena; D012090:Cumulative Trauma Disorders / Q000209:etiology* / Q000517:prevention & control; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D017116:Low Back Pain / Q000209:etiology / Q000517:prevention & control; D008161:Lumbosacral Region; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology* / Q000503:physiopathology; D009784:Occupational Diseases / Q000209:etiology / Q000517:prevention & control; D012307:Risk Factors; D019415:Torque; D014102:Torsion Abnormality / Q000503:physiopathology*