BIOMECHANICS OF LUMBAR CORE MUSCLES

By: Khushali JoganiThe Sarvajanik College Of Physiotherapy

Rampura,Surat

Contents

What is core Models for spinal stabilization Muscles of core Biomechanics of core muscles References

What is core? CORE is defined as a clinical manifestation in

which a delicate balance of movement and stability occurs simultaneously.

The “core” has been described as a box with the abdominals in the front, paraspinals and gluteals in the back, the diaphragm as the roof, and the pelvic floor and hip girdle musculature as the bottom.

Attention to core is important because it serves as a muscular corset that works as a unit to stabilize the body and spine, with and without limb movement.

In short, the core serves as the center of the functional kinetic chain.

Stabilization of lumbar spine is provided by the passive support of the osseoligamentous structures, the support of the muscle system, and control of the muscle system by the central nervous system.

Interrelated parameters of spinal stability need to be considered due to the multisegmental nature of the lumbar spine.

Control of spinal orientation, which relates to the maintenance of the overall posture of the spine against imposed forces and compressive loading.

Control of the intersegmental relationship at the local level (i.e.lumbar segmental control), irrespective of changes in the overall orientation of the spine.

Control of lumbopelvic orientation

The main function of lumbopelvic hip region is to transfer the loads generated by the body weight and gravity during standing, walking and sitting.

Panjabi introduced an innovative model for the spinal stabilization system(effective load transfer) which serves as an appropriate model for understanding the entity of spinal stability and instability.

It included passive, active and neural control systems and all these three systems produce approximation of joint surfaces which is essential if stability is to be insured.

The amount of approximation required is variable and and difficult to quantify as it depends on individual’s structure and forces they need to control.

The integrated model of function is been proposed for managing impaired function.

It has four components:-form closure-force closure-motor control-emotional

1. Form closure - It was coined by Vleeming and snijders.- All joints have variable amount of form

closure.- Depending on individual’s anatomy –

decides the force closure.- Form of lumbar spine, pelvis &hip are

included.

The Lumbar region-compression-torsion or rotation-posteroanterior translation

The pelvic girdle

The hip

2. Force Closure If the articular surfaces of the lumbar spine,

pelvic girdle, and hip were constantly and completely compressed, mobility would not be possible. However, compression during loading is variable and therefore motion is possible and stabilization required.

This is achieved by increasing compression across

the joint surface at the moment of loading

The amount of force closure required depends on the individual's form closure and the magnitude of the load. The anatomical structures responsible for force closure are the ligaments,muscles, and fascia.

3. Motor control

4. Emotions

By active subsystem of panjabi model, muscles provides the mechanism by which control system may modulate the stability of spine.

Stability of spine is important because movement is important for optimal spinal health.

Movement is required to assist in dissipation of forces and to minimize the energy expenditure.

Core muscles

Lumbopelvic stability is provided by the core muscles.

Bergmark has categorised the trunk muscles into local and global muscle system.

Local muscle system stabilises the spinal segment whereas global muscle system act as guy ropes to support the vertebrae

Biomechanical contribution to lumbopelvic control

Anterolateral abominal paraspinal wall and abdominal muscles of cavity lumbar

region posterior abdominal wall

Anterolateral abominal wall and abdominal cavity

Global muscles(obliquus internus abdominis, obliquus externus abdominis, rectus abdominis

Transversus abdominis Diaphragm and pelvic floor

Global muscles-Four slings of muscle system stabilizes the

pelvis regionally.-posterior, anterior, longitudinal, lateral slings-Individual muscles are important for regional

stabilization and mobility and it is necessary to understand how they connect and function togather.

-Muscle contraction-production of forces-transfer of forces-transfer of load-increases the stiffness of SIJ

-Global muscle-integrated sling system.-participation of muscle in more than one sling-

overlap & interconnect-depending on task

-obliquus externus abdominis make a powerful contribution to control of buckling forces

-contribution to lumbopelvic movement and stabilization is based on moment arm and direction of forces.

-if high loads are unpredictable, muscles on both sides are coactivated to stiffen the trunk.

Transversus abdominis- Due to transverse orientation of muscle it

has limited ability to flex, extend or laterally flex the spine.

- Limited moment arm to contribute to rotatory torque.

- Contribution through spinal buckling.- Though contribution is small,it produces

very efficient effect.- Modulation via intra-abdominal

pressure(IAP), fascial tension and compression of sacaroiliac joint

Intra-abdominal pressure-IAP in daily activities-abdominal cavity as ‘pressurized balloon’-production of extension torque and offset of

flexion moment by abdominal muscle-TrA is the most active of abdominal muscles

in extension efforts.-concurrent flexion and extension moments

may increase spinal stiffness like co-contraction.

-IAP increase spinal stiffness

Fascial tension-thoracolumbar fascia and contribution to

spinal stiffness-TrA muscle and its attachment to

thoracolumbar fascia.-Mechanics of thoracolumbar fascia-control of intersegmental motion via lateral

tension in thoracolumbar fascia.-stabilization of lumbar spine in coronal

plane via tension in middle layer of thoracolumbar fascia.

Pelvic stability-mechanism of stability of sacro-iliac joint is

dependent on compression between ilium and sacrum.

Diaphragm and pelvic floor-contribution through IAP and restriction of

movement of abdominal viscera for spinal stability

Posterior abdominal wall Psoas-it has tendency to overactivity and

tightness -two separate muscles and contribution of

posterior fibres for control of intervertebral motion.

Quadratus lumborum-its medial fibres through the attachment to

lumbar vertebral transverse processes is capable of providing segmental stability via its segmental attchment

Paraspinal muscles of lumbar region

Intersegmental muscles-intertransversarii-interspinales Lumbar muscles-lumbar multifidus-longissimus thoracis-iliocostalis lumborum

Biomechanical factors-control of neutral zone-control of lordosis-tensioning the thoracolumbar fascia-control of shear forces

Control of neutral zone-lumbar muscles increase the spinal

segmental stiffness and control of neutral zone

-increased combined muscle activation-muscle forces decrease the sagittal plane

displacement ,anterior rotation and anteroposterior translation

-load bearing surface of zygoapophyseal joints

-intersegmental nature of multifidus

Control of lordosis-spinal curves efficient to deal with force of

gravity-role of mulitifidus-local and global muscles increase the

capacity of spine to withstand the compressive forces without buckling.

Tensioning the thoracolumbar fascia-muscle enhance the spinal stability by

increasing stiffness of spinal segment-thoracolumbar fascia contributes to lumbar

stabilization by increasing the bending stiffness of spine.

Control of shear forces-shear forces are those that cause the

vertebrae to slide with respect to one another

-control of anterior shear forces-Provided by passive elements as well as

muscles-lumbar extensor muscles helps in

controlling

References

Carolyn Richardson,Paul Hodges,Julie Hides Therapeutic exercise for lumbopelvic stabilization. second edition.

Diane Lee,Paul Hodges,The pelvic Girdle,an approch to the examination and treatment of the lumbopelvic-hip region.Third edition.

Carolyn Richardson,Gwendolen Jull, Julie Hides,Paul Hodges. Therapeutic exercise for spinal segmental stabilization in low back pain