The latissimus dorsi muscle is known to be the largest in the entire trunk. It is located on the back of the arm and is trained to give a much more robust and strong appearance to the sides of the back, as well as to provide more force when lifting heavy weights.
The great difficulty of training this area is to improve the muscle growth of the latissimus dorsi , and to do so you have to take into account several factors that you must implement during your training; for example: how the latissimus dorsi works, knowing its anatomy, regional anatomy and the length of the internal moment arm, among others.
Find out how to train the latissimus dorsi muscle with the help of this guide.
Latissimus dorsi training
1. Anatomy of the latissimus dorsi muscle
This muscle originates from the superior posterior aspect of the ilium of the pelvis, the posterior sacrum, the spinous processes of the 6 lower thoracic and lumbar vertebrae, and the posterior surfaces of the 3 lowest ribs. At the same time it is inserted into the upper part of the medial humerus.
The muscle is fan-shaped, being narrower as it gets closer to the arm, but wider as it gets closer to the spine. These characteristics make the latissimus dorsi a pair of fan-shaped muscles, which cover the mid-lower back.
By raising the arm, the latissimus dorsi muscle lengthens naturally. The arm lift occurs each time the shoulder is abducted (side arm lift) or flexed (the arm is raised in front of the body).
When the arm is placed in front of the face from the sides of the body, the latissimus dorsi also lengthens, although to a lesser degree. Finally, due to the location of the insertion on the medial side of the humerus, the muscle lengthens when the shoulder externally rotates (Gerling and Brown, 2013).
2. Involvement of the latissimus dorsi muscle during exercises
When training, the latissimus dorsi is a large muscle that performs a wide range of movements for the shoulder and spine. Simply put, by training it, you will have a huge impact on the size of your back muscles.
You can use a large number of exercises to train the muscle, but shoulder exercises (adduction and extension) are likely to be much more effective than back exercises (lateral flexion or extension).
3. Regional anatomy of the latissimus dorsi
Anatomical studies performed on the latissimus dorsi have divided it into thoracic and lumbopelvic regions. The thoracic region includes fascicles that originate only from the 6 lower thoracic vertebrae. On the other hand, the limbopelvic region includes fascicles that originate from the three lower ribs, the lumbar vertebrae, the sacral vertebrae, and the pelvis (Gerling and Brown, 2013).
These investigations determined that the lumbopelvic region has almost twice the physiological cross-sectional area of the thoracic region (3.6 vs 2 cm³) and that the lengths of the muscle bundles are longer in the lumbopelvic region than in the thoracic region. Therefore, it seems logical to infer that the lumbopelvic region is larger in volume than the thoracic region (Gerling and Brown, 2013).
However, since studies of arm length at the medial moment have subdivided the lumbopelvic region into lumbar and pelvic regions based on muscle function, this larger region is actually made up of two smaller regions (Ackland et al. ., 2008).
The arm length of the latissimus dorsi medial moment has been divided into the thoracic, lumbar, and pelvic regions, which are commonly referred to as the upper, middle, and lower regions based on their relative anatomy. Each of these regions differs slightly in terms of their contributions to shoulder adduction and extension.
In general, the upper (thoracic) region contributes less to shoulder adduction than the mid (lumbar) and lower (pelvic) regions, but more to shoulder extension.
4. Length of the internal moment arm
The latissimus dorsi muscle causes shoulder adduction when lowering your arms to the sides of your body, when you extend your shoulders by lowering your arms in front of you, during horizontal shoulder extension by moving your arms to the sides and away from the front of the body. body, and, finally, during internal rotation of the shoulder, which is also involved in lateral flexion and spinal extension (Hik and Ackland, 2018).
However, the latissimus dorsi is not a prime mover during horizontal shoulder extension or internal shoulder rotation, as the rotator cuff muscles are more important.
4.1 Shoulder extension
Taking all three regions together, the latissimus dorsi shoulder extensor moment arm changes the shoulder elevation angle, although it should be noted that its curve is quite flat. At low degrees of shoulder elevation (arms at the sides), the arm length of the shoulder extensor moment is quite short (Hik and Ackland., 2018).
A wide level is reached at 45 degrees of shoulder elevation, then as the shoulder is raised to more than 60 degrees, the arm of the shoulder extensor moment, decreases linearly. On the other hand, surprisingly, the latissimus dorsi does not influence shoulder extension once the arm is raised above 120 degrees.
4.2 Shoulder adduction
Again, taking all three regions together, the latissimus dorsi shoulder adduction moment arm changes with the shoulder elevation angle, reaching a maximum of 70 degrees of shoulder elevation. When it is above or below this level, the arm of the shoulder adduction moment is much shorter, but at the same time it is present (Hik and Ackland., 2018).
5. Length of working sarcomere
The lengths of the working sarcomere of the latissimus dorsi have been investigated, and differ between movements involving spinal movement and the shoulder and, at the same time, between the thoracic and lumbopelvic regions of the muscle. Similarly, when standing anatomically, the sarcomere lengths of both regions are close to your optimal length, resting in the plateau region (Garner and Pandy, 2003).
Investigations carried out indicate that the thoracic and lumbopelvic regions of the latissimus dorsi work in the final part of the ascending limb and the plateau region of the length-tension region, during extension and axial rotation of the spine. However, they work through the ascending limb, the plateau, and the descending limb in lateral flexion (Gerling and Brown, 2013). On the other hand, the role of the latissimus dorsi during lateral spine flexion is quite small.
conclusion
The latissimus dorsi muscle covers a large part of the back region (the side area). In order to exercise it you have to perform different exercises, the most effective being those used to train the shoulders. The latissimus dorsi is subdivided into the upper (thoracic), middle (lumbar) and lower (pelvic) region, therefore, it is very likely that different exercises are needed to cause maximum hypertrophy for this muscle.
References
- Ackland, D., Pak, P., Richardson, M. and Pandy, M. (2008). Moment arms of the muscles crossing the anatomical shoulder. Journal of Anatomy. doi: 10.1111 / j.1469-7580.2008.00965.x
- Garner, B. and Pandy, M. (2003). Estimation of musculotendon properties in the human upper limb. Annals of Biomedical Engineering. doi: 10.1114 / 1.1540105
- Gerling, M. and Brown, S. (2013). Architectural analysis and predicted functional capability of the human latissimus dorsi muscle. Journal of Anatomy. doi: 10.1111 / joa.12074
- Hik, F. and Ackland, D. (2018). The moment arms of the muscles spanning the glenohumeral joint: a systematic review. Journal of Anatomy . doi: 10.1111 / joa.12903
