The Lats While Benching

There is a misconception that the latissimus dorsi — commonly referred to as “the lats” — aid in the upward movement of the bar when benching. This has bothered me for a long time, so I have broken this down anatomically to explain why it isn’t the case. We will then learn what the lats actually do during a bench press to be so important.

The Lat
First, we must understand where the lat attaches as this will dictate everything it does. The attachment sites of a muscle obviously don’t change, and the muscle will contract to bring these bones together. It’s pretty easy to discern what actions that muscle causes after knowing the attachment sites (and why you learn bone anatomy prior to muscles, because the markers on the bones are where the muscle’s tendons attach).

The lat attaches onto the spine from the sacrum all the way up to the mid-thoracic spine (the lower it goes the more of an aponeurosis there is, but don’t worry about that right now). The fibers of the muscle angle upward and diagonal from the spine to the humerus (upper arm bone). The fibers cross behind and under the humerus and wrap around it to attach near the crest of the greater tubercle (a name for a mark on the bone). If you want to see the proximal attacchment, then this picture is an anterior (front) view of the humerus, and the lat will wrap around the left side of the picture (where it says ‘surgical neck’) to attach in the area indicated. For those who are kind of confused, just look at the picture below.

Muscle Actions
Now that we know the attachment sites, we can see what will happen to the shoulder if the muscle contracts. The lat has “five movement roles at the shoulder, some more important than others: extension, adduction, horizontal abduction, flexion from an extended position, and internal rotation” (2). If you are confused on some of those movements, then watch this video (will jump to shoulder section). The lat’s primary function is extension, yet it’s interesting attachment site allows it do some other things. We’ll see them crop up in the analysis below.

Since the lat is a shoulder extensor and medial abductor (pulling the humerus away from the mid-line — like a row), it obviously cannot flex the shoulder or medially adduct — the two primary movements that occur on the ascent of the bench.

The Lat While Benching
However, because the lat wraps around the under-side of the humerus, it is an internal rotator. Internal rotation in the shoulder when bench pressing, pressing, or doing push-ups is when the elbows flare out (closer to 90 degrees away from the torso). It inherently looks bad, but in the bench it prevents the force application from effectively being distributed throughout the anterior shoulder girdle. Furthermore, since the shoulder internally rotates, the external rotators are stretched and strained, resulting in injuries after chronically internally rotating (i.e. “I blew out my rotator cuff benching, bro”). Remember, when one muscle group contracts, the antagonist stretches (e.g. the triceps stretch when the biceps contract). Yet internal rotation when benching or pressing isn’t caused by the lats, but it’s an error made by the lifter that often results in injuries.

Instead, the shoulder should be in some degree of external rotation when benching (closer to a 45 degree angle) so that a) the external rotators are not stretched like they were in the last paragraph, b) it effectively distributes the load through the anterior shoulder girdle, and c) it stretches the internal rotators. This last point is the most relevant to our discussion.

In a mechanically efficient bench, the shoulders are pinched, the thoracic spine is extended to lift the chest, a big breath of air helps lift the chest even more, and the elbows are kept in external rotation while the forearms are vertical. This entire set up facilitates tightness — the shoulder girdle requires tension and tightness to perform optimally since it’s a joint that doesn’t have a lot of stability. This kind of set up allows the feet to drive the pinched upper back into the bench to solidify the articulation between the body and the bench. The more solid the body is on the bench AND the tighter the tension around the shoulder joint, then more force can be applied to the bar. If there was less tightness or stability, some arbitrary amount of force application would be lost due to instability (the same reason you can’t squat your 1RM on a Bosu ball or water bed).

We know that the attachment of the lat makes it an internal rotator. When the shoulder externally rotates, the internal rotators (the lats) are stretched. Throughout the descent of a bench, the lats shorten since the shoulder is experiencing extension and slight horizontal abduction. During the ascent, the lats are stretched a bit when the movement is reversed — this shows that they aren’t contracting during the ascent to “help the bar up”. However, since the shoulder maintains external rotation, the lats maintain a steady stretch, or constant tension, throughout the descent and ascent. When the lat maintains it’s tension it reinforces the shoulder and makes it incredibly more stable. Tension and stability equals more force application in the bench. Voila.

This concept of the lats maintaining tension is analogous to the hamstrings maintaining their tension in a squat or deadlift; the tensed muscle may not be applying force at a particular moment but is incredibly important to the execution of the lift.

Recap
To put it more simply, the lats don’t help apply force to the bar to make it go up, yet they are incredibly important for maintaining tensile force to make the shoulder joint stronger. Strong lats are required in good benches and will augment the ability to do all of this (which is why rowing and weighted pull-ups can help the bench).

Astute readers or skeptics will say, “Hey, but what about the ‘flexion from an extended position’ that was detailed in the muscle action list? This is pretty easy to show why this isn’t the case in the bench, but I’ll save it for another post. This post probably has plenty for people to digest.

Sources:
1. Biel, Andrew. Trail Guide to the Body, 3rd Ed. Boulder, CO: Books of Discovery, 2005. Print.
2. Kilgore, Lon. Anatomy Without A Scalpel. Iowa Park, TX: Killustrated Books, 2010. Print.