Trunk muscle cocontraction: The effects of moment direction and moment magnitude

This study investigated the cocontraction of eight trunk muscles during the application of asymmetric loads to the torso. External moments of 10, 20, 30, 40, and 50 Nm were applied to the torso via a harness system. The direction of the applied moment was varied by 30° increments to the subjects' right side between the sagittally symmetric orientations front and rear. Electromyographic (EMG) data from the left and right latissimus dorsi, erector spinae, external oblique, and rectus abdominus were collected from 10 subjects. The normalized EMG data were tested using multivariate and univariate analyses of variance procedures. These analyses showed significant interactions between the moment magnitude and the moment direction for seven of the eight muscles. Most of the interactions could be characterized as due to changes in muscle recruitment with changes in the direction of the external moment. Analysis of the relative activation levels, which were computed for each combination of moment magnitude and direction, indicated large changes in muscle recruitment due to asymmetry, but only small adjustments in the relative activation levels due to increased moment magnitude.

[1]  W S Marras,et al.  Trunk Strength during Asymmetric Trunk Motion , 1989, Human factors.

[2]  W S Marras,et al.  A Comprehensive Evaluation of Trunk Response to Asymmetric Trunk Motion , 1992, Spine.

[3]  Don B. Chaffin,et al.  A Biomechanical Model for Analysis of Symmetric Sagittal Plane Lifting , 1970 .

[4]  A. Schultz,et al.  Analysis of Loads on the Lumbar Spine , 1981, Spine.

[5]  M. Pope,et al.  The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes. , 1987, Journal of biomechanics.

[6]  Steven A. Lavender,et al.  Coactivation of the Trunk Muscles during Asymmetric Loading of the Torso , 1992, Human factors.

[7]  A. Schultz,et al.  The Activity of Individual Trunk Muscles During Heavy Physical Loading , 1987, Spine.

[8]  A Schultz,et al.  Use of lumbar trunk muscles in isometric performance of mechanically complex standing tasks , 1983, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[9]  G. Andersson.  Epidemiologic Aspects on Low-Back Pain in Industry , 1981, Spine.

[10]  A. Schultz,et al.  Analysis and Quantitative Myoelectric Measurements of Loads on the Lumbar Spine when Holding Weights in Standing Postures , 1982, Spine.

[11]  Z. Ladin,et al.  1989 Volvo Award in Biomechanics: Mechanical Recruitment of Low-Back Muscles: Theoretical Predictions and Experimental Validation , 1989, Spine.

[12]  W S Marras,et al.  Simulift: A Simulation Model of Human Trunk Motion , 1989, Spine.

[13]  M. Bergquist-Ullman,et al.  Acute low back pain in industry. A controlled prospective study with special reference to therapy and confounding factors. , 1977, Acta orthopaedica Scandinavica.

[14]  W S Marras,et al.  Measurements of Loads on the Lumbar Spine Under Isometric and Isokinetic Conditions , 1984, Spine.

[15]  D B Chaffin,et al.  A dynamic biomechanical evaluation of lifting maximum acceptable loads. , 1984, Journal of biomechanics.

[16]  G. Andersson,et al.  Electromyographic studies of the lumbar trunk musculature during the development of axial torques , 1986, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[17]  D G Wilder,et al.  Risk factors in low-back pain. An epidemiological survey. , 1983, The Journal of bone and joint surgery. American volume.

[18]  A B Schultz,et al.  Biomechanical model calculation of muscle contraction forces: a double linear programming method. , 1988, Journal of biomechanics.

[19]  A. Garg,et al.  Maximum acceptable weights and maximum voluntary isometric strengths for asymmetric lifting. , 1986, Ergonomics.

[20]  C J De Luca,et al.  The effects of external bending moments on lumbar muscle force distribution. , 1991, Journal of biomechanical engineering.