Lats

Big back muscles are often a goal of many gym-goers. Those muscles are numerous, but one that gets particular attention is latissimus dorsi, abbreviated simply as lats. Traditionally they extend, internally rotate and adduct the arms, however that is a one-dimensional representation of their actions and typically one observed in what is called open chain. In a closed chain scenario where the hand is fixed to an object, like during a pull-up, the action can change and primarily influence the shape of the spine.

Lats attach on your arm, slightly to the lower aspect of your shoulder blade and along your spine with fascial connections to your glutes as well. While there is truth in how they move your arms, the often-ignored aspect of spinal movement is coupled with arm motion. Imagine the pull-up situation again, because the arm is relatively fixed it will not move as readily as the spine. I think most likely the arm is moving, but the spine is predominant in this circumstance. As the lats squeeze to move our body toward the bar, the spine compresses and moves forward faster than the arm. We see this often in someone who is going for those last few repetitions, they look to arch their back and complete the motion. That is the spine moving forward and compressing in order for the body to move upward toward the bar.

This exercise will certainly develop a tremendous amount of strength; however it tends to reduce mobility in places like the shoulder and spine. That may be due to the amount of compression in the lower thorax limiting the arm from elevating fully. Once we train the lats to be not only more active, but also larger, they inhibit arm motion. The rib cage is highly influential on arm motion, if we train it to be rigid via lat work at the gym, movement capabilities of the arm change.

Lats are often one of the primary targets when performing back work at the gym and for understandable reasons, they look great in the mirror. Just like with almost anything else, training yourself to do something comes at the expense of something. In this scenario, larger and more active lat muscles reduce motion at the thorax and the arms due to greater trained stiffness. One of the really interesting things that happens is the effect pull-ups have on hip stiffness, but that may be for another post.

Austin Ulrich, Physical Therapist