The latissimus dorsi and teres major are paired together because they work in synergy with each other. Specifically the teres major is a synergist muscle to the latissimus dorsi, helping to increase the actions of the latter. For this reason, the teres major is sometimes called “Lat’s little helper”. Together the 2 muscles are also sometimes called the “handcuff muscles” because they collectively enable the arms to be placed into the arresting position for handcuffs!
Where are they?
The latissimus dorsi is the broadest muscle of the back. It’s attachments are:
Origin: the inferior angle of the scapula (shoulder blade), the spinious processes of the thoracic spinal vertebrae T7-T12, the lower 3 or 4 ribs, the thoracolumbar aponeurosis and the posterior iliac crest (hip bone).
Insertion: The intertubercular groove of the humerus (arm bone)
The teres major is attached to the scapular but is the only muscle so located and not part of the rotator cuff group of muscles. It’s attachments are:
Origin: Inferior angle and lower third of the lateral border of the scapular.
Insertion: Crest of the less tubercle of the humerus.
What do they do?
Because of the synergist relationship of the 2 muscles, they both have the same actions to:
- Extend the glenohumeral shoulder joint (G/H Joint). ie when you extend your arm behind you
- Adduct the G/H shoulder Joint. ie when you take your arm horizontally out to the side, away from your body
- Medially rotate the G/H shoulder Joint. ie when you rotate your arms inwardly (towards your ribs)
Although the latissimus dorsi acts on your shoulder joint to move your arm, because of it’s location on your back, it also affects your trunk and spine. It, therefore, assists in laterally flexing your trunk to the side. When the arm is fixed, it will help to extend the spine.
If you take part in activities such as swimming (ie front crawl), gymnastics (ie parrallel bars), climbing or rowing, you will be using these 2 muscles a lot.
Strengthening exercises for latissimus dorsi and teres major
Always seek professional or medical advice before commencing any sort of exercise to ensure it is suitable for you.
Seated Rowing: This strengthens the back. It is essential that a good technique is followed, especially if any weights or gym equipment are used (seek professional advice for this). This example doesn’t rely on any weights but uses a dina band for resistance. Secure the dina band around a stable and heavy object that can stay secure (ie a dining room table leg). In a seated position on the floor with knees bent in front of you so that your feet are braced. Ensure that you are in a stabilise and secure position with your arms extended in front and you back is neutral. Holding the dina band in each hand draw your elbows back as far as possible, keeping spine in neutral and body upright. Return to starting position.
Pulley shoulder adduction: Secure a dina band to a stable object that is above shoulder height so that it hangs down by your side. Taking the dina band in the hand closest to it so that your arm is extended to the side, pull the dina bank down diagonally across the body. Return to start.
14 July 2016