Asymmetry of erector spinae muscle activity in twisted postures and consistency of muscle activation patterns across subjects

Study Design. An experimental study involving a repeated measures design was performed. Objectives. To describe the muscle activation pattern in extending from a twisted posture; to evaluate interindividual variation of this pattern; and to study the effects of fatigue development. Summary of Background Data. Extending the trunk from a twisted posture is a risk factor for low back pain. Methods. Twelve male subjects performed contractions at 20%, 40%, 60%, and 100% of maximum in a neutral position and 15°, 30°, and 45° twisted posture. Surface electromyography of six bilateral back muscle tracts was recorded during these 5-second contractions and during sustained contractions at 0° and 30° and 40% of maximum. Results. The data show an asymmetry in muscle activation, increasing with angle of twist. Activity was higher contralateral to the direction of twisting. Linear regression analysis with angle and torque level against electromyographic amplitude yielded a significant fit in 92% of the data sets. In 75% of the subjects, the regression lines were similar. The divergence of the activation pattern in the other subjects appears to be explained by a higher co-contraction level of abdominal muscles. Fatigue caused a shift in activity to the more laterally situated muscle tracts. Conclusions. Twisting causes an asymmetry in back muscle activation. Resulting stress concentrations in spinal motion segments, and a reduced spinal stability could underlie the observed relationship between the task investigated and low back pain. Fatigue may reduce further spinal stability. Some subjects display a divergent activation pattern, which probably involves higher spinal compression forces.

[1]  J H van Dieën,et al.  Reproducibility of isometric trunk extension torque, trunk extensor endurance, and related electromyographic parameters in the context of their clinical applicability , 1996, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

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

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

[4]  B Bigland-Ritchie,et al.  Motor drive and metabolic responses during repeated submaximal contractions in humans. , 1988, Journal of applied physiology.

[5]  G Govaert,et al.  Postural load and back pain of workers in the manufacturing of prefabricated concrete elements. , 1991, Ergonomics.

[6]  G. Inbar,et al.  Relation between electromyogram and force in fatigue. , 1985, Journal of applied physiology.

[7]  M. de Looze,et al.  Validation of a dynamic linked segment model to calculate joint moments in lifting. , 1992, Clinical biomechanics.

[8]  T Moritani,et al.  Intramuscular and surface electromyogram changes during muscle fatigue. , 1986, Journal of applied physiology.

[9]  D B Chaffin,et al.  A back-propagation neural network model of lumbar muscle recruitment during moderate static exertions. , 1995, Journal of biomechanics.

[10]  I A Stokes,et al.  Lumbar spine maximum efforts and muscle recruitment patterns predicted by a model with multijoint muscles and joints with stiffness. , 1995, Journal of biomechanics.

[11]  M. Stokes,et al.  Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back pain. , 1994, Spine.

[12]  A. Schultz,et al.  Loads on the lumbar spine. Validation of a biomechanical analysis by measurements of intradiscal pressures and myoelectric signals. , 1982, The Journal of bone and joint surgery. American volume.

[13]  J. Kelsey,et al.  An epidemiologic study of lifting and twisting on the job and risk for acute prolapsed lumbar intervertebral disc , 1984, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[14]  Y. K. Liu,et al.  Mechanical response of the lumbar intervertebral joint under physiological (complex) loading. , 1978, The Journal of bone and joint surgery. American volume.

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

[16]  R. Norman,et al.  1986 Volvo Award in Biomechanics: Partitioning of the L4 - L5 Dynamic Moment into Disc, Ligamentous, and Muscular Components During Lifting , 1986, Spine.

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

[18]  Peter Vink,et al.  Specificity of surface-EMG on the intrinsic lumbar back muscles , 1989 .

[19]  N. Bogduk,et al.  1987 Volvo Award in Basic Science: The Morphology of the Lumbar Erector Spinae , 1987, Spine.

[20]  Carlo J. De Luca,et al.  Use of the surface EMG signal for performance evaluation of back muscles , 1993 .

[21]  M. Adams,et al.  Sustained Loading Generates Stress Concentrations in Lumbar Intervertebral Discs , 1996, Spine.

[22]  P Kurowski,et al.  The Relationship of Degeneration of the Intervertebral Disc to Mechanical Loading Conditions on Lumbar Vertebrae , 1986, Spine.

[23]  M. Nordin,et al.  1988 Volvo Award in Biomechanics: The Triaxial Coupling of Torque Generation of Trunk Muscles during Isometric Exertions and the Effect of Fatiguing Isoinertial Movements on the Motor Output and Movement Patterns , 1988, Spine.

[24]  G. Andersson,et al.  Intradiskal pressure, intra-abdominal pressure and myoelectric back muscle activity related to posture and loading. , 1977, Clinical orthopaedics and related research.

[25]  R. H. Rozendal,et al.  Human kinesiological electromyography: Some methodological problems , 1982 .

[26]  S. McGill,et al.  Passive stiffness of the lumbar torso in flexion, extension, lateral bending, and axial rotation. Effect of belt wearing and breath holding. , 1994, Spine.

[27]  D B Chaffin,et al.  A longitudinal study of low-back pain as associated with occupational weight lifting factors. , 1973, American Industrial Hygiene Association journal.

[28]  R. Kadefors,et al.  An electromyographic index for localized muscle fatigue. , 1977, Journal of applied physiology: respiratory, environmental and exercise physiology.

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

[30]  M K Chung,et al.  Effects of posture, weight and frequency on trunk muscular activity and fatigue during repetitive lifting tasks. , 1995, Ergonomics.

[31]  R. Norman,et al.  Comparison of muscle forces and joint load from an optimization and EMG assisted lumbar spine model: towards development of a hybrid approach. , 1995, Journal of biomechanics.

[32]  G B Andersson,et al.  Trunk muscle geometry and centroid location when twisting. , 1993, Journal of biomechanics.

[33]  K. Jørgensen,et al.  Trunk strength, back muscle endurance and low-back trouble. , 2020, Scandinavian journal of rehabilitation medicine.

[34]  W. Forrest,et al.  Muscle fibre direction of longissimus, iliocostalis and multifidus: landmark-derived reference lines. , 1989, Journal of anatomy.

[35]  J Kraemer,et al.  Water and Electrolyte Content of Human Intervertebral Discs Under Variable Load , 1985, Spine.

[36]  D G Wilder,et al.  The biomechanics of lumbar disc herniation and the effect of overload and instability. , 1988, Journal of spinal disorders.

[37]  Discharge characteristics of motor units and the surface EMG during fatiguing isometric contractions at submaximal tensions. , 1985 .

[38]  A Shirazi-Adl,et al.  Mechanical Response of a Lumbar Motion Segment in Axial Torque Alone and Combined with Compression , 1986, Spine.

[39]  M. Panjabi,et al.  Euler stability of the human ligamentous lumbar spine. Part II: Experiment. , 1992, Clinical biomechanics.

[40]  G B Andersson,et al.  Trunk muscle activation and cocontraction while resisting applied moments in a twisted posture. , 1993, Ergonomics.

[41]  A. M. Ahmed,et al.  Stress analysis of the lumbar disc-body unit in compression. A three-dimensional nonlinear finite element study. , 1984, Spine.