The Latissimus Dorsi
Only super-cool muscles get nicknames like "lats" and "pecs." In my mind, they're like rad frat brothers who like to flex in front of mirrors. Speaking of which, I don't see too many people forgetting to work out their "lats." Possibly because, although they are on the posterior, if you learn to flex them you can get them to stand out even from the front, as you can see from my thick-headed friend.
Even for the non-meathead, these are pretty cool muscles. The image above makes them look like wings you could spread like a flying squirrel, but once you add in all the other flesh, on the average human, they hardly stand out. Functionally, very important, however, and per usual, its form will dictate that.
The muscle's origin is along the spine from the lower thoracic to the sacrum. The name "latissimus" actually means "the broadest" with "dorsi" indicating the back, and you've got a wide based muscle attaching to your lower back. The exact origin varies a bit from person to person. in general attaching to the midline of 4-8 vertebrae and out to the iliac crests. The muscle fibers then stretch up to the medial or inner surface of the humerus. With this broad, solid anchor on lower half of the back down to the hips, when the muscle fibers shorten they must bring the upper arm closer to the body.
Reach up, as high as you can overhead with your right hand. Now bend your torso to the left and you will begin to feel a stretch of the latissimus dorsi. This is the opposite motion as it's action. Grab onto a pull-up bar and you will be performing its quintessential move. You might be thinking the lat pull-down is its signature lift, but really the lat pull-down is just for people who can't pull their own body weight up. If you can't do a pull-up yet, start there, but once you can do one, don't stop. It's the ultimate lat building move.
In my mind, the only exercise you need to train lats is the pull-up, although I do a bunch of variations I learned doing P90x and having very sore lats after a back day that featured about half a dozen pull-up variations.
Admittedly, the pull-up will work more than just your latissimus dorsi muscles. Because there is a lot of elbow bend, then your biceps and brachioradialis muscles will be doing a lot of work. In my experience, by placing my hands wider there is less elbow flexion and less work in my biceps. In either wide or narrow grip variations, the humerus is still being adducted from overhead to preferably at your side by getting your chin and maybe chest well above the bar.
Another tip is to lean back just a bit to add shoulder extension. It is also advisable to stabilize your shoulder blades by keeping them depressed (i.e. pulling them down) throughout the exercise. This works the lower trapezius and keeps the strain off the rotator cuff in a dead hang at the bottom. I also particularly dislike kipping pull-ups because I think it is easy to relax all the muscles at the bottom putting a ton of strain on the connective tissue not just from your body weight but also your momentum. I think this is an easy way to get injured, although I'm sure there is a safe way to do the movement. (I'll try to post more on kipping and the much-sought-after muscle-up soon). A final thought on pull-ups, doing them on rings is even better! This allows you to rotate your hands out and then internally rotate your arms as you pull down which is another action of the lats.
Check out the videos above and below for more tips and exercises that work on the various planes of motion in which you engage your lats. Now that you know where your lats are located and what they do, you should be able to feel their contraction. Pausing at the top of one of your pulling exercises is a great way to add an isometric contraction to your workout and add increased time under tension that will further stress the muscle. There are many different ways to load the arm during shoulder adduction and flexion movement, but as I said, pull-ups are my favorite, and I think that any person who wants to consider themselves fit should work toward 20 strict reps.
