Anatomy and Stretching 101
Anterolateral Abdominal Wall
• Although the abdominal wall is continuous, it is subdivided in the anterior wall, right and left lateral wall, and posterior wall for descriptive purposes. • Because there is no definite boundary, the term anterolateral abdominal wall is often used. Some structures, such as muscles and cutaneous nerves, are in both the anterior and lateral walls. The anterolateral abdominal wall extends from thoracic cages to the pelvis.
Anatomy • There are five (bilaterally paired) muscles in the anterolateral abdominal wall (see images below). • The two vertical muscles are the large rectus abdominis and the small pyramidalis. • The three flat muscles are the external oblique, internal oblique, and transverse abdominis. • Their attachments are listed, along with their nerve supply and main actions, in Table 1.
Table 1. Muscles of Anterlateral Abdominal Wall Muscle
External oblique (A)
External surfaces of 5th – 12th ribs
Linea alba, pubic tubercle, and anterior half of iliac crest.
Thoracoabdominal nerves (T7-T11 spinal nerves) and subcostal nerve
Flexes and rotates trunk, laterally flexes trunk
Internal oblique (B)
Thoracolumbar fascia, anterior two thirds of iliac crest, and connective tissue deep to lateral third of inguinal ligament
Inferior borders of 10th – 12th ribs, linea alba, and pecten pubis via conjoint tendon
Thoracoabdominal never (anterior rami T6-T12 spinal nerves) and first lumbar nerves
Compresses and supports abdominal viscera, flexes and rotates trunk. Laterally flexes trunk
Transverse abdominis (C)
Internal surfaces of 7th – 12th costal cartilages, thoracolumbar fascia, iliac crest, and connective tissue deep to lateral third of inguinal ligament
Linea alba with aponeurosis of internal oblique, pubic crest and pecten pubis via conjoint tendon
Rectus abdominis (D)
Pubic symphysis and pubic crest
Xiphoid process and 5th – 7th costal cartilages
Compresses and supports abdominal viscera
Thoracoabdominal nerves (anterior rami of T6-T12 spinal nerves)
Flexes trunk (lumbar vertebrae) and compresses abdominal viscera; stabilizes and controls tilt of pelvis (antilordosis)
• The muscle fibers of these three concentric muscle layers have varying orientations, with the fibers of the outer two layers (obliques) running diagonally and perpendicular to each other for the main part, and the fibers of the deep layer (TA) running transversely. • All three flat muscles are continued anteriorly and medially as strong, sheet-like aponeuroses (Flattened white fascia) • Between the midclavicular line (MCL) and the midline, the aponeuroses forms the tough, aponeurotic, tendinous rectus sheath enclosing the rectus abdominis muscle (See image A below). • The aponeuroses then interweave with their fellows of the opposite side, forming a midline raphe (G. rhaphe, suture, seam), the linea alba (L. white line), which extends form the xiphoid process to the pubic symphysis (images A below). IMAGE A
Image A. The rectus sheath, white aponeurosis and Linea Alba
External Oblique Muscle • The external oblique muscle is the largest and most superficial of the three flat anterolateral abdominal muscles (Images B, C, D). • The attachments of the external abdominal oblique are listed, along with the nerve supply, and main actions, in Table 1. In contrast to the two deeper layers, the external oblique does not originate posteriorly from the thoracolumbar fascia; its posterior-most fibers (the thickest part of the muscle) have a free edge where they span between its costal origin and the iliac crest • The fleshy part of the muscle contributes primarily to the lateral part of the abdominal wall. Its aponeurosis contributes to the anterior part of the wall. • Most of the fleshy fibers run inferomedially – in the same direction as the fingers do when the hands are in one’s side pockets – with the most anterior and superior fibers approaching a horizontal course. • Thus, the contralateral external and internal oblique muscles together form a “digastric muscle,” a two bellied muscle sharing a common central tendon that works as a unit. • For example, the right external oblique and left internal oblique work together when flexing and rotating to bring the right shoulder towards the left hip (torsional movement of trunk). See image E. • Inferiorly, the external oblique aponeurosis attaches to the pubic crest and the pubic tubercle.
Image B, C & D. External oblique
Image E. The external oblique and internal oblique work together when flexing and rotating the trunk.
The inguinal ligament • You may be able to palpate your inguinal ligament by pressing deeply into the center of the crease between the thigh and trunk while moving the fingertips up and down. • Inferiorly the inguinal ligament is continuous with the deep fascia of the thigh. The inguinal ligament is therefore not a freestanding structure, although – as a useful landmark – it is frequently depicted as such. Image F. • It serves as a retinaculum (retaining band) for the muscular and neurovascular structures passing deep to it to enter the thigh.
Image F. The inguinal ligament
Internal Oblique Muscle • The intermediate of the three flat abdominal muscles, the internal oblique is a thin muscular sheet that fans out anteromedially (G, H, I). • Except for its lowermost fibers, which arise from the lateral half of the inguinal ligament, its fleshy fibers run perpendicular to those of the external oblique, running superomedially (like your fingers when the hand is placed over your chest). • Its fibers also become aponeurotic at the MCL and participate in the formation of the rectus sheath. • The attachments of the internal oblique are and listed, along with the nerve supply and main actions, in Table1.
Image G. Anterior IO
Image H. Lateral IO
Image I. Posterior IO
Transverse Abdominis Muscle • The fibers of the transverse abdominis, the innermost of the three flat abdominal muscles run more or less transversally, except for the inferior ones, which run parallel to those of the internal oblique. See images J, K, L. • This transverse, circumferential orientation is ideal for compressing the abdominal contents, increasing intra-abdominal pressure. • The fibers of the transversus abdominis muscle also end in an aponeurosis, which contributes to the formation of the rectus sheath (Image M). • The attachments of the transversus abdominis are demonstrated and listed, along with the nerve supply and main actions, in Table 1.
Image J. Anterior
Image K. Lateral
Image L. Posterior transversus abdominus
Image M. Fibers of the transversus abdominis muscle also end in an aponeurosis, which contributes to the formation of the rectus sheath, enveloping the rectus abdominussee left side of image.
• The transversus abdominis is also known as the “corset muscle,” reflecting its role in compressing the abdomen as well as stabilizing the lower back through attachments into the thoracolumbar fascia. • The TA also stabilizes the attachment sites for the other lateral abdominal muscles. Because of its horizontal disposition the transversus abdominis creates a circumferential splinting effect across the entire low back region, including the sacroiliac joints. By acting primarily in the transverse direction, the transversus abdominis can increase intra-abdominal pressure without creating a concurrent flexion torque or an increase in vertical compression force on the lumbar spine. • Transferred through the thoracolumbar fascia, this is thought to provide an additional element of stabilization to the region, particularly effective during lifting.
Rectus Abdominis Muscle • A long, broad strap-like muscle, the rectus abdominis (L. rectus, straight) is the principal vertical muscle of the anterior abdominal wall. Image P. • The attachments of the rectus abdominis are listed, along with the nerve supply and main actions, in Table 1. • The paired rectus muscles, separated by the linea alba (Image A), lie close together inferiorly. • The rectus abdominis is three times as wide superiorly as inferiorly; it is broad and thin superiorly and narrow and thick inferiorly. • Most of the rectus abdominis is enclosed in the rectus sheath. The rectus muscle is anchored transversely by attachment to the anterior layer of the rectus sheath at three or more tendinous intersections (Images N,O). When tensed in muscular people, the areas of muscle between the tendinous intersections bulge outward. Image N. Anterior Rectus Abdominus
Image O. Lateral rectus abdominus
Quadratus lumbrorum • The Quadratus lumborum lies in the posterior abdominal wall. • It is stretched however, with many of the stretches in this chapter, and therefore included here • The quadrilateral quadratus lumborum forms a thick muscular sheet in the posterior abdominal wall (images Q, R). • It lies adjacent to the lumbar transverse processes and is broader inferiorly. • Contracting bilaterally, the quadratus lumborum is an extensor of the lumbar region. Its action is based on the line of force passing about 3.5 cm posterior to the medial-lateral axis of rotation at L3.
• Contracting unilaterally, the quadratus lumborum has very favorable leverage as a lateral flexor of the lumbar region. The axial rotation potential of the quadratus lumborum, however, is minimal. • Clinically, the quadratus lumborum is often called a “hip hiker” when its role in walking is being described, especially for persons with paraplegia at or below the L 1 neurologic level. By elevating (hiking) one side of the pelvis, the quadratus lumborum raises the lower limb to clear the foot from the ground during the swing phase of brace-assisted ambulation.
Image Q. Anterior view of QL
Image R. Posterior view of QL
Functions and actions of anterolateral abdominal muscles The muscles of the anterolateral abdominal wall: • Form a strong expandable support for the anterolateral abdominal wall. • Support the abdominal viscera and protect them from most injuries. • Compress the abdominal contents to maintain or increase the intra-abdominal pressure and, in so doing, oppose the diaphragm (increased intra-abdominal pressure facilitates expulsion). • Move the trunk and help to maintain posture.
Part B: Stretching To stretch the lateral and posterior parts of the abdominal wall, try any of the stretches below.
The Posterior Stretch • Standard: Beginner • Spring Tension: Light - Medium • Muscle Emphasis: All spinal extensors from superficial to deep, hamstrings, calves, adductor magnus, gluteus maximus, latissimus dorsi A
A & B. How to stretch Sit with feet on lower position. Align feet with sit bones. Slowly try to straighten legs to POT. Take chin toward chest.
B. How to contract Press feet down into reformer.
C. How to restretch Straighten legs further.
What to watch out for: • Moving carriage out too fast. • Not taking chin to chest. • Too much flexion in thoracic
spine and legs still bent.
The Posterior Stretch 2.0 • Standard: Beginner • Spring Tension: Light - Medium • Muscle Emphasis: All spinal extensors from superficial to deep, hamstrings, calves, adductor magnus, gluteus maximus, latissimus dorsi
A & B. How to stretch Sit with hands and balls of feet on foot bar. Align feet with sit bones. Slowly try to straighten legs to POT. Take chin toward chest.
B. How to contract Press feet down into foot bar. Try to lift chest to straighten spine.
C. How to restretch Straighten legs fully if possible.
What to watch out for: • Moving carriage out too fast. • Not taking chin to chest. • Too much flexion in thorax
and legs still bent.
The Dangler • Standard: Any • Spring Tension: Heavy • Muscle Emphasis: Entire posterior spinal muscles, posterior disks, posterior portion of internal obliques, transversus abdominus, quadratus lumborum
A. How to stretch
Clasp carriage and then shoulder rests as pictured. Allow legs to hang or dangle. Hold for 90 seconds.
How to breathe
Take deep abdominal breaths to expand abdominal region.
What to watch out for: • Lifting head or feet, which engages spinal muscles. • Shallow breathing. • Coming out of the stretch too quickly.
The Dangler FLEXION HOW TO STRETCH: Photo A - Lie over box with pubic bone off the edge - Allow head and knees to drop completely - Take deep abdominal breaths
HOW TO CONTRACT: Photo B - Imagine pressing legs and head/upper back to ceiling
PARTNER VARIATION: Photo D - Allow legs and upper body to dangle - Contract by pushing pelvis/chest up into partner resistance - Restretch by hanging further - Deep abdominal breaths are important
HOW TO RESTRETCH: Photo B - Let hips and head drop down to floor - Allow legs to float as much as possible
Major muscles stretched Erector spinae Rhomboids
Photo C - Stronger versions with less floor contact - Instructions as above
Hamstring Spine Combo FLEXION
HOW TO STRETCH: Photo A - Bend one knee and drop it out to the side - Clasp opposite foot slide leg away to POT - Partner to press on pelvis towards neutral position
HOW TO CONTRACT: Photo B - Press heel of foot into floor - Press ball of foot into hand
Major muscles stretched Hamstrings Calves Erector spinae Gluteus maximus
HOW TO RESTRETCH: Photo C - Straighten leg if possible - Partner to roll pelvis forwards as much as possible - Lower chest and head onto leg
BOSU Back Bend EXTENSION HOW TO STRETCH: Photo A - Clasp stick and lie back over BOSU with head supported - Partner to pull lightly on stick, both backwards and downwards - Other partner to press lightly onto upper thighs - Allow pelvis to sink into floor
HOW TO CONTRACT: Photo B - Press arms and thighs towards ceiling for five seconds - Pull stick towards head for another five seconds HOW TO RESTRETCH: Photo B - Allow pelvis to relax into floor - Pull arms backwards and downwards
ALTERNATIVE ARM POSITION: Photo C - Clasp hands together and bend elbows - Pull elbows back and downwards - Try if A creates shoulder joint discomfort
VARIATION: Photo D - Pull one side of the stick in horizontal plane for lat focus
Major muscles stretched Abdominals Pectorals Latissimus dorsi Teres major
The Cobra EXTENSION HOW TO STRETCH: Photo A - Relax lower back and gluteal muscles - Draw elbows towards body and lift chest HOW TO CONTRACT: Photo A - Press arms and feet into floor
ADVANCED VARIATION: Photo D - Bring hands closer to hips under shoulders - Contract leg and spinal muscles to lift knees and hips - Contract back muscles to arch spine backwards
D HOW TO RESTRETCH: Photo B - Take hands wider than mat - Relax low back muscles - Press arms straight to lift chest
Major muscles stretched
Abdominals Hip flexors SCM INTERMEDIATE VARIATION: Photo C - Lower chest and bring hands closer together onto mat - Press arms straight and lock elbows - Relax and ‘hang’ spine between shoulders - Deep abdominal breathing
Box Wheel EXTENSION
HOW TO SET UP: Photo A - Place feet onto box, thighs vertical - Place hands behind shoulders, fingers facing shoulders
HOW TO STRETCH: Photo B - Press hands and feet towards floor - Lift body up onto head - Partner to clasp shoulders
Major muscles stretched Pectorals Hip flexors Latissimus dorsi Abdominals
HOW TO STRETCH: Photo C - Press up to final position - Straighten arms - Partner to pull chest over the top of hands
The Cobra • Standard: Any • Spring Tension: Light - Medium • Muscle Emphasis: Abdominals, anterior surface of disks, hip flexors
A & B. How to stretch Place hands onto foot board. Spine in neutral position. Allow carriage to slide in very slowly. When shoulders are almost above wrists, allow hips to sink toward floor.
B. How to contract Press hands and feet downwards.
C. How to restretch Lower hips further toward carriage/ floor. Relax all muscles including shoulders and lats.Explore gently rotating to both sides.
How to breathe
Deeply, filling entire abdominal region.
What to watch out for: • Failure to allow low back
and gluteal muscles to relax.
Lying Backbend • Standard: Any • Muscle Emphasis: Psoas, rectus femoris, abdominals, pectorals, lats, anterior neck, triceps long head, rotator cuff
A & B. How to stretch Sit on back bender as pictured. Sitting lower down will give less lumbar stretch. Support head if necessary. As body relaxes straighten legs further.
B. How to contract Press hands and thighs up toward ceiling.
C. How to restretch Allow pelvis, legs and arms to drop/flop. Partner can pull arms downward and alternately pull one side more. Note alternate arm position for shoulder impingement.
What to watch out for: • Unnecessary tension in arms, neck, stomach. • Dizziness is a strong sign to stop immediately.
Foam Roller Mermaid LATERAL FLEXION HOW TO SET UP: Photo A - Straighten legs and place ankles onto roller - Balance body on hand and elbow
HOW TO STRETCH/CONTRACT: Photo B - Lift chest by pressing arm straight - Press both feet down into floor
VARIATION: Photo D - Roll top hip forward
VARIATION: Photo E - Roll top hip back
Major muscles stretched HOW TO RESTRETCH: Photo C - Further straighten both arms - Move supporting arm closer to body
Hip abductors Oblique abdominals Quadratus lumborum Multifidi
Floor Side Bend LATERAL FLEXION HOW TO STRETCH: Photo A - Abduct one leg - Bend other leg - Place elbow inside straight leg - Use arm to pull trunk towards straight leg - Roll top shoulder backwards above bottom shoulder - Reach arm overhead - Partner (if you have one) to press down on hip to keep it anchored to mat - Partner to press trunk further into side bend
HOW TO CONTRACT: Photo A - Press shoulders back into partner
VARIATION: Photo D - Roll top shoulder forwards so spine is rotated and bent sideways (lateral flexion)
HOW TO RESTRETCH: Photo B - Use bottom arm to pull trunk further laterally - Reach top arm towards foot - Partner to press hip down and shoulder/spine further sideways
Major muscles stretched
VARIATION: Photo C - Bend straight leg and place support underneath - Bend top arm at elbow
Oblique abdominals Latissimus dorsi Quadratus lumborum
Seated Side Bend LATERAL FLEXION
HOW TO STRETCH: Photo A - Sit on box and clasp box strap with hand - Lean to same side as arm holding box strap - Reach other arm overhead - Position top shoulder above bottom one - Partner to press down on hip and press spine into side bend HOW TO CONTRACT: Photo A - Press spine back towards upright position/ middle
HOW TO RESTRETCH: Photo B - Lean further to side - Partner to press down on hip and press spine into side bend
VARIATION: Photo C - Roll top shoulder backwards - Roll top shoulder forwards (see photo B)
Major muscles stretched Oblique abdominals Quadratus lumborum Latissimus dorsi Erector spinae Multifidi
The Mermaid • Standard: Beginner/Intermediate • Spring Tension: Light - Medium • Muscle Emphasis: Oblique abdominals, quadratus lumborum, intercostals, abductors
A & B. How to stretch Slide carriage out and sit in center. Place top leg/foot on top of bottom leg/foot. Align feet, hips, hand, ensure top hip above bottom hip. Slide carriage in to POT to find stretch.
B. How to contract Press hands and feet down into floor.
C. How to restretch Slide carriage in further. Deepen inhalations as much as possible.
What to watch out for: • Not aligning top hip with feet.
The Seated Side Bend • Standard: Beginner/Intermediate • Spring Tension: Light - Medium • Muscle Emphasis: Oblique abdominals, quadratus lumborum, intercostals, latissimus dorsi, erector spine one side, long head of triceps
A. How to stretch Push carriage out and keep both sit bones on carriage. Reach arm over and bend spine and rib cage away from footbar.
A. How to contract Imagine pressing outside shoulder away from footbar.
B & C. How to restretch Slide carriage out a little further. Deepen inhalations as much as possible. Bend spine and head to side as much as is comfortable.
The Standing Banana • Standard: Intermediate /Advanced • Spring Tension: Medium • Muscle Emphasis: Oblique abdominals, quadratus lumborum, intercostals, latissimus dorsi, abductors of hip A
A. How to stretch Push carriage away, straighten botton leg. Align hand on footbar with bottom hip and foot. Support arm at roughly 90 degrees to spine. B. Shift top foot to position shown for greater support. C. Lower hips.
C. How to contract Press hips up.
C. How to restretch Lower hips further. Deepen inhalations as much as possible.
What to watch for • Pushing carriage out too far. • Not lowering hips enough. • Not aligning body
as described above.
(A) Roll top hip forward (B) and backward to shift stretch around.
The Standing Mermaid â€˘ Standard: Any â€˘ Muscle Emphasis: Latissimus dorsi, oblique abdominals, quadratus lumbo rum, rotator cuff, log head triceps, erector spinae
B. How to contract
A. How to stretch Stand alongside ladder, inside foot in front. Outside arm over-grip, inside arm under-grip. Lean away and bend inside knee. Support bodyweight with inside arm as much as possible.
Pull on bar with top arm.
B & C. How to restretch Lean away further.
C. Variations Rotate shoulders forward and backwards with respect to fairly stable hips.
The Mermaid â€˘ Standard: Any â€˘ Muscle Emphasis: Oblique abdominals, quadratus lumborum, intercostals, abductors
A & B. How to stretch Lie over arc exploring different positions. Use top arm for support, only take top arm over if comfortable.
A & B. How to contract Imagine lifting trunk back to neutral position and pressing top leg up.
B & C. How to restretch Lean further to side, take top arm overhead. Allow top leg to drop, or press it down with bottom leg.
The Seated Rotation • Standard: Any • Muscle Emphasis: Oblique abdominals, intercostals, deep spinal rotators, spinal joints and disks
A. How to stretch Rotate trunk using arms to POT.
A. How to contract Try to twist back toward start position using abdominal muscles.
B. How to restretch Twist further into rotated position.
What to watch for • Spine flexing. • Pelvis rolling backward/posterior tilt. • Shallow breathing.
Lying Rotation ROTATION HOW TO SET UP: Photos A and C - Lie in middle of mat - Outstretch one arm with hand at head height or higher
HOW TO STRETCH: Photos B and D - Shift opposite hip to middle of mat - Rotate pelvis away from outstretched arm - Keep bottom leg straight - Allow top leg to drop towards floor HOW TO CONTRACT: Photos B and D - Press arm and shoulder up - Press hip back into partnerâ€™s hand HOW TO RESTRETCH: Photos B and D - Press arm and shoulder into floor - Allow opposite leg to drop to floor - Rotate top hip further
Major muscles stretched Pectorals Oblique abdominals Hip abductors/deep rotators
Conclusion The stretches that require no equipment can be found in my book “StretchFit: Safe Effective Stretches for Every Body,” on Amazon books. The final stretches on the Pilates reformer is from “Stretching on the Pilates Reformer: Essential Cues and Images” on Amazon books.