One of the most frequent questions coming from beginners is:
"What's better pull-ups or chin-ups?"
Short answer: Chin-ups.
Many people consider pull-ups a better exercise than chin-ups for the simple fact that they can do less pull-ups than chin-ups. This is wrong for several reasons. First, the fact that you can do less reps on a particular exercise does not always mean that it's harder, especially in this case. The reason that your number of pull-ups is less than you chin-ups is because there is less muscle mass involved when you use overhand grip (knuckles facing you) not because the chin-up is an easier exercise.
When you grip the bar in a pull-up fashion the biceps which are the main elbow flexors are placed in large disadvantage and cannot provide a really strong contraction during the movement. They still have to work relatively hard but not that much compared to a chin-up. That makes the chin-up more complete pulling exercise because the biceps are also worked hard and they are an important part of the pulling musculature.
“But pull-ups work your lats harder.”
The participation of your lats during a pull-up or a chin-up does not depend so much on your grip. Your lats still have the same function during both movements - pull the humerus (upper arm) close to your body. When you use an overhand grip (pull-up) you take the biceps out of the movement and the small elbow flexors (brachialis and brachioradialis) become the main elbow flexors. Since they are smaller and weaker than your biceps you end up doing less pull-ups.
Of course it would be very stupid to ignore the fact that the biceps may act as bullies during the chin-up. In other words you may end up doing more work with them than your back. You see it all the time - guys with big biceps and no back. However the problem is not the chin-up. Your biceps and small elbow flexors can still be the same mean and nasty bullies when you perform pull-ups. It's all about mind muscle connection when it comes to lat activation. If you don't have it doing pull-ups won't fix the problem.
If during pull-ups or chins you are focused only on getting up and not so much on how to get-up it's very likely that your body will find the easiest way to lift your ass up. You don't want that if your goal is to develop your lats. You have to force your body to focus mainly on the lat contraction than on just getting up.
“Fuck. I never feel my lats during pull-ups and chin-ups. What am I doing wrong?”
“Activating” you lats is not that hard as some gurus would like you to believe. I remember reading in one famous book that developing the mind muscle connection with your lats can take years. What?
Not the case.
My favorite drill for teaching beginners how to “feel” their lats are the scapular pull-ups. The form of the scapular pull-ups is very simple and the movement itself is quite useful for getting used to full range pull-ups and chin-ups.
Step1: Find a pull-up bar, tree branch, gymnastic rings...etc and assume the so called dead hang position - just hang from the bar and relax completely. Keep your shoulders relaxed and your elbows straight.
Step 2: While keeping your elbows as straight as you can bring your shoulder down. In other words perform the opposite movement of a shrug. Chances are you will finally learn where you lats are and you won't have to run for the anatomy book again.
The reason why this is such a great drill for “activating” your lats is the simple fact that you can't perform that movement with any other muscle than your lats. It's virtually impossible. You will feel them fire right from the lower back to the armpit.
Note: Consult the video at the end of the article for visual demonstration of scapular pull-ups.
Remember that every pull-up or chin-up should start with a scapular pull-up. That's first part of the movement. Then you keep pulling while arching your back (sticking your chest out) as much as you can. Your lat cannot contract unless you arch your back. Keep it arched if you want to grow some lats.
Conclusion: The chin-up is more complete exercise than the pull-up due to added biceps work which allows you to reach higher stimulation of your back despite what many "functional" fitness gurus believe. The biceps is placed in a stronger position and this will allow your back to work more before your arms fail while limiting the potential work that can be done by your back which is a much stronger and harder to "cook" muscle group.
Open you chest like Franco when doing chin-ups or pull-ups for maximum lat contraction
The fact that you can do less pull-ups has nothing to do with more back work. It's due to the minimized biceps work and the increased participation of the small elbow flexors such as the brachialis and brachioradialis.
However I prefer the ring pull-up over both exercises. I explain why in the article:
If your form is correct the lats still get plenty of stimulation during chin-ups. In fact the chin-up works your lower lats harder than pull-ups and since the biceps is placed at its strongest position you can perform more total reps before your arms reach failure. In other words your lats have the chance to receive more work because the biceps are tougher than the small elbow flexors used during a pull-up.