Sarcomere length organization as a design for cooperative function amongst all lumbar spine muscles

Zwambag, Derek P.; Ricketts, T. Alexander; Brown, Stephen H.M.

doi:10.1016/j.jbiomech.2014.06.030

Cited by 14 publications

(8 citation statements)

References 28 publications

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“…SMA MNs exhibit selective vulnerability depending on the muscles they innervate, with proximal muscles more affected than distal muscles in mice 14 and humans 15 . We previously reported that SMA MNs in the first lumbar segment (L1) exhibit an increase in input resistance early in the disease 13 .…”

Section: Resultsmentioning

confidence: 99%

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Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

et al. 2017

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Behavioral deficits in neurodegenerative diseases are often attributed to the selective dysfunction of vulnerable neurons via cell-autonomous mechanisms. Although vulnerable neurons are embedded in neuronal circuits, the contribution of their synaptic partners to the disease process is largely unknown. Here, we show that in a mouse model of spinal muscular atrophy (SMA), a reduction in proprioceptive synaptic drive leads to motor neuron dysfunction and motor behavior impairments. In SMA mice or after the blockade of proprioceptive synaptic transmission we observed a decrease in the motor neuron firing which could be explained by the reduction in the expression of the potassium channel Kv2.1 at the surface of motor neurons. Increasing neuronal activity pharmacologically by chronic exposure in vivo led to a normalization of Kv2.1 expression and an improvement in motor function. Our results demonstrate a key role of excitatory synaptic drive in shaping the function of motor neurons during development and the contribution of its disruption to a neurodegenerative disease.

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Section: Resultsmentioning

confidence: 99%

“…To study vulnerable MNs, we focused on those that innervate the iliopsoas (IL) and quadratus lumborum (QL) muscles 13,14 . These muscles are involved in maintaining posture and locomotion 15 and are involved in the righting reflex which is impaired in SMA mouse models 13 . The IL/QL MNs reside within the L1 to L3 spinal segments 16 .…”

Section: Resultsmentioning

confidence: 99%

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

et al. 2017

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“…Multifidus (measured from both surgical patient biopsies 48 and cadavers 52 ), as well as erector spinae 52 have short sarcomere lengths (ie, significantly below optimal force generating length), and thus a limited ability to generate force, when in the neutral spine posture. As the spine flexes, the muscles (and thus sarcomeres) lengthen and are able to generate maximum forces in mid‐flexed to fully flexed spine positions 48,52 . Comparing passive mechanical properties of the multifidus and erector spinae in patients undergoing spine surgery has revealed that multifidus fiber bundles (muscle fibers ensheathed in their connective tissue matrix), but not individual fibers, have a significantly higher elastic modulus (higher stiffness) 53 .…”

Section: Introductionmentioning

confidence: 99%

Paraspinal muscle pathophysiology associated with low back pain and spine degenerative disorders

Noonan

Brown

2021

JOR Spine

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Low back pain disorders affect more than 80% of adults in their lifetime and are the leading cause of global disability. The muscles attaching to the spine (ie, paraspinal muscles) are critical for proper spine health and play a crucial role in the functioning of the spine and whole body; however, reports of muscle dysfunction and insufficiency in chronic LBP (CLBP) patients are common. This article presents a review of the current understanding of the relationship between paraspinal muscle pathophysiology and spine‐related disorders. Human literature demonstrates a clear association between altered muscle structure/function, most notably fatty infiltration and fibrosis, and low back pain disorders; other associations, including muscle cell atrophy and fiber type changes, are less clear. Animal literature then provides some mechanistic insight into the complex relationships, including initiating factors and time courses, between the spine and spine muscles under pathological conditions. It is apparent that spine pathology can directly lead to changes in the paraspinal muscle structure, function, and biology. It also appears that changes to the muscle structure and function can directly lead to changes in the spine (eg, deformity); however, this relationship is less well studied. Future work must focus on providing insight into possible mechanisms that regulate spine and paraspinal muscle health, as well as probing how muscle degeneration/dysfunction might be an initiating factor in the progression of spine pathology.

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“…1, 29 In moderately flexed postures, improved length-tension relationships of these muscles allow improved neuromuscular efficiency and the multifidus to resist shear forces. 5,7,38,48,51 When designing low back exercises, erector spinae muscle endurance should be considered. Erector spinae and multifidus muscles have a high percentage of type I fibres, and following low back injury there is often an increase in the percentage of type II fibres.…”

Section: Discussionmentioning

confidence: 99%

“…3). 51 Although elongation of the erector spinae in flexed lumbar postures may improve the ability to generate force and neuromuscular efficiency (ratio of EM output to muscle activation), a potential downside of the muscle lengthening is a significant reduction in inter-compartmental muscle volume at all lumbar levels. 55 This is of concern when the lumbar spine remains in flexion for prolonged periods of time, as human and animal studies have shown an increase in intramuscular pressure and a reduction in intramuscular blood flow and elevated levels of neuropeptides when lumbar muscle volume reduces.…”

Section: Fibre Type Of the Erector Spinae And Multifidusmentioning

confidence: 99%

Lumbar posture biomechanics and its influence on the functional anatomy of the erector spinae and multifidus

Mawston

Boocock

2015

Physical Therapy Reviews

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Background: Lumbar posture has a significant impact on the functional biomechanics of the erector spinae and multifidus muscles, which has implications for the loads placed on the tissues of the lumbar spine. Objectives: The objective of this review is to discuss the effects of lumbar posture on the functional biomechanics of the different divisions of the erector spinae and the multifidus muscle and its importance when developing clinical interventions.Methods: This review used the search engines PubMed, EBSCO, CINAHL and SCOPUS to identify studies investigating erector spinae and multifidus muscle architecture and the influence of lumbar posture on the biomechanical properties of these muscles and the resulting impact on spinal loading. Results: Changes in lumbar curvature alter muscle fascicle obliquity, lever arm distances, the length-tension relationships and muscle volume of the different divisions of erector spinae and multifidus, which impact on the spine's ability to resist moments and shear forces. Conclusion: Changes in lumbar posture influence the functional biomechanics of the different divisions of erector spinae and the multifidus muscles. Therapists should develop low back interventions that avoid end range of lumbar postures and optimise the functional biomechanics of the erector spinae and multifidus muscles and minimise loading on the lumbar spine.

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Sarcomere length organization as a design for cooperative function amongst all lumbar spine muscles

Cited by 14 publications

References 28 publications

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

Reduced sensory synaptic excitation impairs motor neuron function via Kv2.1 in spinal muscular atrophy

Paraspinal muscle pathophysiology associated with low back pain and spine degenerative disorders

Lumbar posture biomechanics and its influence on the functional anatomy of the erector spinae and multifidus

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