I read this article a while back in the NSCA Journal and forgot about it until I saw a post by Mike Reinold earlier this week.
If you haven’t read the article its pretty evident that it compares muscle activation during the three variations of a pull-up. The chart below details activation of external oblique, erector spinae, pec major, lower trap, infraspinatus, bicep, and lat.
The lats are all highly active in all three variations which is no surprise but one of the most interesting points is that the pull-up actually has the highest activation within the lower trapezius, 56% for the pullup vs. 45% for the chin-up. The lower trap was also the first muscle active within the exercises as the scapula is in an upwardly rotated position at the bottom position.
I have talked at length about how important the lower trap is in athletes for proper shoulder function, especially overhead athletes. The lower trap is an often overlooked muscle that will shut down during times of shoulder trouble much like its partner the serratus anterior. Anything we can do to get more out of the lower trap is good. Conversely, the chin-up has the highest activation within the biceps as well as pectoralis major, but the lowest in the lower trap.
Something I would like to see is the activation of the pec minor, and lower during the pull-up and chin-up with retraction and depression vs. rounding over at the top, as well as the differences with the neutral grip pull-up.
All too often I see athletes that round over at the top of any pull-up / chin-up movement. They end up doing the chin poke at the top with their back rounded over like the hunchback of N0tre Dame. Essentially this is the upper crossed syndrome position and I am in full belief that you are eliminating the positive benefits of pull-ups for the scaps and reinforcing the negative ones that already persist in many athletes.
Mike Reinold, trainer for the Boston Red Sox, mentions that the pull-up may be a better option for a baseball player due to the fact that the lower trap is more active and the bicep and chest is less active vs. the chin-up.
I agree with Mike in that the pull-up may present be a better option because of activation. At the same time my concern is that when we look at the externally rotated position of the pull-up, this is a position of vulnerability when it comes to SLAP tears. High bicep activity in an externally rotated position can be a recipe for disaster. This is how orthopaedic surgeons generally diagnose SLAP lesions.
Just food for thought.