Support for a linear length-tension relation of the torso extensor muscles: An investigation of the length and velocity EMG-force relationships

Raschke, Ulrich

doi:10.1016/0021-9290(96)00044-9

Cited by 8 publications

(10 citation statements)

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“…Specifically, previous experiments typically permit gravitational contributions to trunk moment to increase with flexion angle whereas the current protocol was designed such that flexion angle was achieved without changes in trunk flexion moment. The decline in baseline EMG activity may also be influenced by the length-force relationship of the extensor muscles, i.e., monotonic increase in passive muscle stiffness provide greater force per unit of activation as muscle length increases with flexed postures (Hawkins and Bey, 1997;Raschke and Chaffin, 1996). Measurement sensitivity may also contribute to the observed effects.…”

Section: Discussionmentioning

confidence: 90%

Torso flexion modulates stiffness and reflex response

Granata

Rogers

2007

Journal of Electromyography and Kinesiology

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Section: Discussionmentioning

confidence: 90%

Torso flexion modulates stiffness and reflex response

Granata

Rogers

2007

Journal of Electromyography and Kinesiology

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“…The activations in the global system depend on the T1 sagittal position, muscle forces increasing linearly [34] with the distance from the initial T1 position. The recruitment pattern of the global muscles shows coactivation [19] (Fig.…”

Section: Discussionmentioning

confidence: 99%

Synergy of the human spine in neutral postures

Kiefer

Shirazi‐Adl

Parnianpour

1998

European Spine Journal

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IntroductionAn understanding of mechanisms for the load-resisting capacity of the human spine and load sharing between the passive ligamentous spine and the active muscle tissues in neutral posture is essential for investigation of spinal functioning in normal and pathologic conditions. Several approaches have been taken in previous numerical models for static analysis of the lumbar spine: maximum moment-generating capacity models [7,38], transverse section equilibrium models [36], and stability criterion models [5,10,16]. Experimental measurements of, for instance, electromyographic activities in spinal muscles and Abstract The neutral position of the spine is the posture most commonly sustained throughout daily activities. Previous investigations of the spine focused mainly on maximal exertions in various symmetric and asymmetric postures. This report proposes a new synergetic approach for analysis of the spine in neutral postures and evaluates its performance. The model consists of passive components, the osteoligamentous spine, and active components, the spinal muscles. The muscle architecture includes 60 muscles inserting onto both the rib cage and lumbar vertebral bodies. The passive spine is simulated by a finite element model, while kinematic constraints and optimization are used for resolution of a redundant muscle recruitment problem. Although the passive spine alone exhibits little resistance to a vertical load, its load-bearing capacity in neutral posture is significantly enhanced by the muscles, i.e., the passive spine and its muscles must be considered as a synergetic system. The proposed method is used to investigate the response of the spine when the T1 vertebra displaces 40 mm anteriorly and 20 mm posteriorly from its initial position. The sacrum is fixed at all times and the T1 displacements are achieved by the action of muscles. The results suggest that relatively small muscle activations are sufficient to stabilize the spine in neutral posture under the body weight. The results also indicate that muscles attaching onto the rib cage are important for control of the overall spinal posture and maintenance of equilibrium. The muscles inserting onto the lumbar vertebrae are found mainly to enhance the stability of the spine. The proposed method also predicts forces and moments carried by the passive system. Flexion moments ranging from 8000 Nmm to 15,000 Nmm, corresponding to decreases in lordosis of 6°and 7.5°respectively, are found to be carried by the passive spine at the thoracolumbar junction when the T1 vertebra is 40 mm anterior to its initial position.

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“…Using these new anatomic estimates, the length-strength and force-velocity relations were developed for men and women using techniques previously reported in literature. 12,23,57 Thus, the current alterations to the EMG-assisted model improved on the previously published EMG-assisted model by acquiring more accurate representations of the muscle anatomy.…”

mentioning

confidence: 95%

Spine Loading as a Function of Gender

Marras

Davis²,

Jorgensen³

2002

Spine

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Study Design. In vivo laboratory studies were conducted to investigate the spine loads imposed on men and women during a series of lifting tasks that varied in the degree of lifting control required by the subject.Objective. To identify and understand differences in spine loading and musculoskeletal control strategies between men and women performing lifts of varying task complexity.Summary of Background Data. Few studies have examined differences in spine loading as a function of individual factors such as subject gender. Furthermore, no biomechanical studies have attempted to quantify and understand how differences in anthropometry between genders might influence muscle recruitment and subsequent spine loads. Because the modern workplace seldom discriminates between genders in job assignments, it is important to understand how differences in spine loading and potential low back disorder risk might be associated with gender differences.Methods. For this study, 140 subjects participated in two separate experiments requiring different degrees of musculoskeletal motion control during sagittal plane lifting. The two experiments consisted of 35 men and 35 women performing lifts in which motion was isolated to the torso and 35 men and 35 women completing wholebody free-dynamic whole body lifts. An electromyography-assisted model was used to evaluate spine loading under these conditions.Results. Absolute spine compression generally was greater for the men. Under the highly controlled (isolated torso) conditions, most differences were attributed solely to differences in body mass. Under a whole-body freedynamic condition, significant differences in muscle coactivations resulted in greater relative compression and anterior-posterior shear spine loading for the women.Conclusions. Differences in spine loadings as a function of gender under the more controlled lifting conditions were primarily a function of different body masses. However, loading pattern differences existed between the genders under whole-body free-dynamic conditions as a result of kinematic compensations and increases in muscle cocontraction, with women generally experiencing greater relative loads. When spine tolerance differences are considered, one would expect that females would be at greater risk of musculoskeletal overload during lifting tasks. [Key words: electromyography, gender kinematics, lifting, low back pain, spine loads] Spine 2002;27:2514 -2520 Recent reviews of low back disorder (LBD) causality have indicated that factors inherent to the individual, workplace, physical factors, and organization factors all can contribute to biomechanical loading and LBD risk. 53Whereas numerous studies have evaluated biomechanical responses to workplace physical factors 10,17,19,23,24,36,43,48,56 and psychosocial factors, 11,37 few have assessed the contribution of individual factors such as gender to risk.Work exposure has changed for women recently. Over the past several decades, women have increasingly undertaken physically demanding jobs that tradition...

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Support for a linear length-tension relation of the torso extensor muscles: An investigation of the length and velocity EMG-force relationships

Cited by 8 publications

References 0 publications

Torso flexion modulates stiffness and reflex response

Torso flexion modulates stiffness and reflex response

Synergy of the human spine in neutral postures

Spine Loading as a Function of Gender

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