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Lower torso muscle activation patterns for high-magnitude static exertions: gender differences and the effects of twisting.

Authors
Perez-MA; Nussbaum-MA
Source
Spine 2002 Jun; 27(12):1326-1335
NIOSHTIC No.
20031285
Abstract
Surface electromyographic signals were collected from 14 lower torso muscles while participants resisted high-magnitude static trunk moments applied in a variety of directions. To obtain a description of muscle activations in response to large moment magnitudes and axial twisting, including levels of agonistic and antagonistic muscle cocontraction. To assess differences in lower torso muscle activation patterns associated with gender and trial repetition. Back pain is associated with mechanical loads in the back. Biomechanical modeling of these loads is facilitated by knowledge of typical muscle activation patterns. Previous efforts in obtaining such data have often limited their scope to low-magnitude exertions or relatively simple scenarios. Eight male and eight female participants, matched by height and mass, performed static exertions in an apparatus that immobilized their lower body while the activation levels of seven bilateral torso muscles were measured using surface electromyography. Activation patterns were analyzed to assess differences resulting from a variety of factors. No significant differences in activation patterns were found between genders or repetitions, but moment magnitude and direction elicited substantial differential responses. Good repeatability was found between trial repetitions, as indicated by intraclass correlation coefficients (>0.65). Significant synergistic muscle coactivation, large intersubject variability (mean coefficient of variation 82.2%), and consistent levels of antagonism ranging from 10% to 30% maximum voluntary exertions were observed. Individuals of different genders, but similar anthropometry, have comparable muscular reactions to complex torso loads, suggesting similar motor control strategies. Future spine models should consider that the variability in muscle recruitment patterns is larger between subjects than within subjects. High-magnitude exertions, especially those with moment loads in more than one plane, require most muscles to be active (>5%) and moderate levels of antagonism.
Keywords
Muscles; Demographic-characteristics; Sex-factors; Muscle-tension; Muscle-contraction; Repetitive-work; Back-injuries; Injuries; Biomechanics; Anthropometry
CODEN
SPINDD
Publication Date
20020615
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
2002
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-T01-OH-008613
Issue of Publication
12
ISSN
0362-2436
Source Name
Spine
State
VA
Performing Organization
Department of Industrial and Systems Engineering, Virginia Tech University, Blacksburg, Virginia
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