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An improved multi-joint EMG-assisted optimization approach to estimate joint and muscle forces in a musculoskeletal model of the lumbar spine

Gagnon, D ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1016/j.jbiomech.2011.03.002
  3. Abstract:
  4. Muscle force partitioning methods and musculoskeletal system simplifications are key modeling issues that can alter outcomes, and thus change conclusions and recommendations addressed to health and safety professionals. A critical modeling concern is the use of single-joint equilibrium to estimate muscle forces and joint loads in a multi-joint system, an unjustified simplification made by most lumbar spine biomechanical models. In the context of common occupational tasks, an EMG-assisted optimization method (EMGAO) is modified in this study to simultaneously account for the equilibrium at all lumbar joints (M-EMGAO). The results of this improved approach were compared to those of its conventional single-joint equivalent (S-EMGAO) counterpart, the latter method being applied to the same lumbar joints but one at a time. Despite identical geometrical configurations and passive contributions used in both models, computed outcomes clearly differed between single- and multi-joint methods, especially at larger trunk flexed postures and during asymmetric lifting. Moreover, muscle forces predicted by L5-S1 single-joint analyses do not maintain mechanical equilibrium at other spine joints crossed by the same muscles. Assuming that the central nervous system does not attempt to balance the external moments one joint at a time and that a given muscle cannot exert different forces at different joints, the proposed multi-joint method represents a substantial improvement over its single-joint counterpart. This improved approach, hence, resolves trunk muscle forces with biological integrity but without compromising mechanical equilibrium at the lumbar joints
  5. Keywords:
  6. Compression and shear ; Dynamics ; EMG ; Optimization ; Spine ; Trunk muscle forces ; Biological integrity ; Biomechanical model ; Central nervous systems ; External moment ; Geometrical configurations ; Health and safety ; Joint analysis ; Joint loads ; Key modeling ; Lumbar joints ; Lumbar spines ; Mechanical equilibrium ; Multi-joint ; Muscle force ; Musculoskeletal model ; Occupational tasks ; Optimization approach ; Optimization method ; Partitioning methods ; Spine ; Trunk muscle ; Muscle ; Adult ; Analytic method ; Body posture ; Controlled study ; Geometry ; Human ; Human experiment ; Intermethod comparison ; Joint function ; Lifting effort ; Lumbar spine ; Lumbosacral spine ; Male ; Mathematical model ; Multi joint electromyography assisted optimization method ; Normal human ; Prediction ; Priority journal ; Single joint electromyography assisted optimization method ; Algorithms ; Central Nervous System ; Compressive Strength ; Electromyography ; Humans ; Lumbar Vertebrae ; Middle Aged ; Models, Anatomic ; Models, Statistical ; Muscle Contraction ; Muscle, Skeletal ; Stress, Mechanical ; Weight-Bearing
  7. Source: Journal of Biomechanics ; Volume 44, Issue 8 , 2011 , Pages 1521-1529 ; 00219290 (ISSN)
  8. URL: http://www.jbiomech.com/article/S0021-9290%2811%2900233-8/abstract