P1.1 Muscles of the abdomen and core stability Simone Crocker 9 th January 2010

Aims The aims of this talk/presentation are to: ｷ Name the CORE muscles of the abdomen ｷ Explain their insertions ｷ Explain their actions ｷ Explain their relationship to other muscles of the abdomen ｷ Explain the term ‘ core stability ’ and core stabilizing mechanisms ｷ Debunk some abdominal training myths

Objectives By the end of the presentation, trainee yoga teachers should: ｷ Be able to name critical muscles of the abdomen, understand their actions and role in core stabilizing. ｷ Understand and be able to explain the term ‘ core stability ’. ｷ Be aware of some common misunderstandings about abdominal training.

PART ONE - FUNCTIONAL ANATOMY OF THE ABDOMINAL WALL The following muscles form the fundaments of the CORE & abdominal wall: ｷ External Oblique ｷ Internal Oblique ｷ Rectus Abdominis ｷ Transverse Abdominis ｷ Psoas ｷ Quadratus Lumborum

EXTERNAL OBLIQUE INSERTIONS: by interdigitating it slips from the external surfaces of lower 8 ribs into the anterior half of the outer lip of the iliac crest and the wide aponeurosis of the anterior abdominal wall.

ACTIONS ｷ Flexion of trunk through bilateral stimulation ｷ Critically influences lumbar spine by tilting pelvis posteriorly. Through this action the external obliques are considered lower abdominals. ｷ Produces ipsilateral side flexion and contralateral trunk rotation through unilateral stimulation. ｷ Stabilizer on the contralateral side. ｷ Increases intra-abdominal pressure & assists in forced respiration. THE EXTERNAL OBLIQUE IS THE LARGEST ABDOMINAL MUSCLE

INTERNAL OBLIQUE INSERTIONS: at lumbar fascia, anterior two thirds of iliac crest & lateral two thirds of inguinal ligament, ends ribs 9-12 and linea alba.

ACTIONS ｷ Flexion of trunk through bilateral (both sides) stimulation. ｷ Lateral flexion of the trunk and rotation toward the ipsilateral side through unilateral (one sided) stimulation. ｷ During lateral flexion the ipsilateral (same side) external oblique and internal oblique co-operate. In right rotation the right internal oblique is synergistic to the left external oblique (and vice versa). ｷ Ipsilateral rotator when pelvis is anchored. ｷ Contra lateral rotator when trunk is anchored.

RECTUS ABDOMINIS INSERTIONS: Pubic symphysis and crest of pubis joining onto costal cartilages of ribs 5-7 and the xyphoid process.

ACTIONS ｷ Flexes the trunk (like in a sit up) if the pelvis is fixed ｷ Lifts and posteriorly rotates pelvis if trunk is fixed. ｷ Flexes the trunk ipsilaterally when stimulated unilaterally (minimally). ｷ Acts as stabilizer on the contralateral side under dynamic conditions or under heavy load. ｷ Increases intra-abdominal pressure and assists in forced respiration.

TRANSVERSE ABDOMINIS INSERTIONS: internal surfaces of ribs 7-12, thoraco- lumbar fascia adjoining iliac crest.

ACTIONS ｷ Increases intra-abdominal pressure by applying lateral traction to the middle layer of the lumbo-dorsal fascia creating an extension force in the flexed position (as in when lifting something). ｷ Major stabilizer of the lumbar spine. INNERVATION – TVA, MULTIFIDUS AND PELVIC FLOOR SHARE SAME NEUROLOGICAL LOOP. THIS MEANS IF TVA IS NOT WORKING PROPERLY NEITHER WILL THE OTHER MUCLES

PSOAS INSERTIONS: ventral surfaces of transverse processes of all lumbar vertebrae, sides of bodies and corresponding intervertebral discs of the last thoracic and all lumbar vertebrae and membranous arches that extend over the arches of the lumbar vertebrae, adjoining onto the lesser trochanter of the femur.

ACTIONS ｷ Flexes the trunk when the feet are anchored. ｷ Flexes the hip when the trunk is anchored. ｷ Unilateral contraction causes lumbar lateral flexion. ｷ If unchecked by lower abs then hypertrophy or hypertonicity of psoas causes anterior pelvic tilt. ｷ Minor spinal stabilizer when in rotation.

QUADRATUS LUMBORUM INSERTIONS: at the iliac crest to twelfth rib and transverse processes of lumbar vertebrae.

ACTIONS ｷ Assists the erector spinae in trunk extension from a neutral standing or sitting posture through bilateral stimulation. ｷ Bilateral stimulation also assists the abs with flexion movements from a fully flexed posture. ｷ Flexes the trunk in co-operation with the ipsilateral internal and external obliques through unilateral stimulation. WHEN THE PSOAS BECOMES SHORTENED SO DOES THE QL

PART TWO – CORE STABILITY AND CORE STABILISING MECHANISMS

What does ‘core stability’ mean? The muscles of the abdomen do not exclusive to stabilize the core. The core is a kinetic chain of energy beginning from the xyphoid process to symphysis pubis. The correct engagement of muscles of the lumbar spine and abdominal wall provide a solid platform from which dynamic and static movement can be supported.

Faulty recruitment, atrophy or hyper- tonicity of any of the muscles responsible for stabilizing the core can result in loss of optimal strength or more seriously, injury. Having core stability means that not only do you recruit the muscles involved, but you ALSO do so in the correct sequence.

THE MUSCLES OF THE CORE

The deep trunk muscles, transversus abdominis (TA), multifidus (MF), internal oblique (IO), paraspinal, pelvic floor, are key to active support of the lumbar spine. The co-contraction of these muscles produce forces via "theracolumbar fascia" (TLF) and "intra-abdominal pressure" (IAP) mechanism which stabilise the lumbar spine, and paraspinal and MF muscles act directly to resist forces acting on the lumbar spine.

Thoracolumbar fascia

THE AIM OF CORE STABILTY It is not just recruitment of deep-trunk muscles, but how they are recruited that is important. Hodges and Richardson (1996) showed that co- contraction of the TA and MF muscles occurred prior to movement of the limbs. This suggests that these muscles anticipate dynamic forces that may act on the lumbar spine and stabilise the area prior to any movement. Timing of co-ordination of these muscles is very significant.

The aim of core stability training is to CORRECTLY recruit the trunk musculature and then learn to control the position of the lumbar spine during dynamic movements.This prevents injury and provides optimum stability. Lack of core stability is like trying to perform EVERY movement as though on a canoe.

An example of anterior head carriage & kyphotic spine Yoga & core IN yoga the core is also referred to as ‘bandha’. There are two bandha’s that ebgage core musculature: Moola bandha - lifting the perineum or anus Uddiyana bandha - drawing the abdomen strongly inwards and upwards with the breath expelled from the body

MAD CORE MYTHS Having a ‘six pack’ equates to good core stability Core stability can be achieved by doing abdominal crunches Once you have achieved a strong core you can stop exercising consistently Core stability is only important for pregnancy & injury Dysfuntion and pain of any part of the axial or appendicular skeleton is unlikely to be connected to poor core strength Overweight people will naturally have poor core stability Every pilates & yoga teacher will have good core stability