The muscles of the posterior trunk are organized into three layers: superficial, intermediate, and deep.
Muscles in the superficial layer include the trapezius, latissimus dorsi, rhomboids, levator scapula, and serratus anterior. The trapezius and latissimus dorsi are most superficial, followed by the deeper rhomboids and levator scapula. The serratus anterior muscle is located more laterally on the thorax. In general, bilateral activation of the muscles of the superficial layer extends the adjacent region of the axial skeleton. Unilateral activation, however, laterally flexes and, in most cases, axially rotates the region. The right middle trapezius, for example, assists with right lateral flexion and left axial rotation of the upper thoracic region. Muscles within the superficial and intermediate layers of the back are often referred to as “extrinsic” because, from an embryologic perspective, they were originally associated with the front “limb buds” and only later in their development migrated dorsally to their final position on the back. Although muscles such as the levator scapula, rhomboids, and serratus anterior are located within the back, technically they belong with upper limb muscles.
The Anatomy –
Latissimus Dorsi Proximal attachments:
Posterior layer of the thoracolumbar fascia, spinous processes and supraspinous ligaments of the lower half of the thoracic vertebrae and all lumbar vertebrae, median sacral crest, posterior crest of the ilium, lower four ribs, small area near the inferior angle of the scapula, and muscular interdigitations from the obliquus external abdominis See image 1,3,4
Distal attachment: floor of the intertubercular groove of the humerus. See image 4
The latissimus dorsi means “broadest muscle of the back.” Because of its size and the large region that it spans, it has multiple actions. Well known actions of the Lats include adduction, extension and internal rotation of the arm. In addition, as noted above, it can assist with ipsilateral rotation of the trunk when the glenohumeral joint is well stabilized by other muscles, and lateral flexion. See Image 2.
As noted above, as well as attaching into the thoracolumbar fascia, the latissimus dorsi attaches into the posterior aspect of the pelvis, sacrum, and spine. See Image 3.
Based on these attachments and its relative moment arm for producing lumbar extension, the latissimus dorsi has all the attributes of an extensor of the low back.
The oblique fiber direction of the muscle as it ascends the trunk can also provide torsional stability to the axial skeleton, especially when bilaterally active. This stability may be especially useful when large loads are handled in an asymmetric fashion.
With the distal attachments of arm muscles stabilized, the sternocostal head of the pectoralis major and latissimus dorsi can assist with inspiration by elevating the sternum and lower ribs, increasing intrathoracic volume.
Because of its myriad actions, stiffness in the lats can create several potential biomechanical problems. Stiffness in the lats for example, increases internal rotation at the shoulder, affecting function at the joint, particularly during overhead activities. Tightness may inhibit the necessary upward rotation of the scapula and create impingement and dysfunction. See image 5.
The usual upward rotation pattern or “scapulohumeral rhythm” associated with overhead activities. This may be disrupted by stiffness in the lats.
Illustrates the line of pull of the lats (LD) during extension of the arm. This directional pull will affect the scapulohumeral rotation required in overhead movements displayed in image 5
Stiffness in the latissimus dorsi can cause other symptoms. They may include:
- tingling in the lower arms
- difficulty breathing
- tendonitis in the middle and lower back
Given the negative effects of the lats on posture, pain and movement, stretching make obvious sense. At StretchFit, we use several variations of the side bend to stretch and target the lats. The first is gentler and more focused on the lower part of the muscle. The sensations arise generally from the lateral and posterior abdominal regions. The locus of the stretch can be shifted depending on the position of the shoulders relative to the hips. Given the close proximity of the lats to the oblique abdominals and quadratus lumborum, and its fascial connection to the transversus abdominus, it is likely all of these muscles are affected by the stretch. See Image 7
How to Stretch –
The stretch below, from our StretchFit training manual, targets the lateral and posterior abdominal region.
The Standing Mermaid –
Standard: Any • Muscle Emphasis: Latissimus dorsi, oblique abdominals, quadratus lumbo rum, rotator cuff, log head triceps, erector spinae
The second stretch is stronger, using the arm closest to the bar to create a stronger side bend with the point of maximum bend higher up near the armpit.
The Standing Lats –
- Standard: Any
- Muscle Emphasis: Latissimus dorsi, rotator cuff, long head triceps, erector spinae unilaterally
The Latissimus Dorsi and its little helper, Teres Major, are stretched strongly as you lean away and press. Your Internal Obliques will be stretched strongly too.
One half of the erector spinae are stretched, Along with the quadratus lumborum and teres major. Underneath, or “deep” to the erector spinae, you can see the multifidus group stretching also. This muscle group stabilizes the joints of the spine.
The third stretch is less demanding. Because the top arm is open chained, i.e not fixed or attached to anything, the stretch is far gentler. Only the weight of the arm, rather than the weight of the body, is pulling and lengthening the lats.
This stretch can be a good alternative for beginners, or elderly clients for example, who don’t have the grip strength to hold themselves in the positions above. Placing a one or two kilogram weight in their hand will increase the stretch too.
The lats are large, strong and have multiple actions and attachment points. Consequently, they can have a strong affect on posture, movement and pain. If you or your clients have difficulty reaching overhead, you may well need to give them a regular stretch.
The stretches above will assist in keeping them supple and your movements free and easy. If you are like our clients, you will feel a wonderful sense of freedom after performing them too. Enjoy!
To explore a full range of stretches, please consider attending a StretchFit studio, or purchasing our equipment for your home or studio setting. For further enquires email director Anthony Lett at firstname.lastname@example.org