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.
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.