I tried to suggest to Cressey to write an article on SLAP tears and kipping pull-ups, I guess it hasn't happened.
Let's just take a look at this website on SLAP tears:
How does a SLAP Tear Occur?
Now that we have discussed the different types and classification of SLAP tears to the superior labrum, I wanted to now talk about how these shoulder injuries occur. There are several injury mechanisms that are speculated to be responsible for creating a SLAP lesion. These mechanisms range from single traumatic events to repetitive microtraumatic injuries.
Repetitive Overhead Activities
Repetitive overhead activity, such as throwing a baseball and other overhead sports, is another common mechanism of injury frequently responsible for producing SLAP injuries. This is the type of SLAP lesion that we most often see in our athletes. In 1985, Dr. Andrews first hypothesized that SLAP pathology in overhead throwing athletes was the result of the high eccentric activity of the biceps brachii during the arm deceleration and follow-through phases of the overhead throw. To determine this, they applied electrical stimulation to the biceps during arthroscopic evaluation and noted that the biceps contraction raised the labrum off of the glenoid rim.
Burkhart and Morgan have hypothesized a “peel back” mechanism that produces SLAP lesion in the overhead athlete. They suggest that when the shoulder is placed in a position of abduction and maximal external rotation, the rotation produces a twist at the base of the biceps, transmitting torsional force to the anchor.
This mechanism has received a lot of attention and several studies seem to show its accuracy. Pradham measured superior labral strain in a cadaveric model during each phase of the throwing motion. They noted that increased superior labral strain occurred during the late-cocking phase of throwing. A recent study from ASMI simulated each of these mechanisms using cadaveric models. Nine pairs of cadaveric shoulders were loaded to biceps anchor complex failure in either a position of simulated in-line loading (similar to the deceleration phase of throwing) or simulated peel back mechanism (similar to the cocking phase of overhead throwing). Results showed that 7 of 8 of the in-line loading group failed in the midsubstance of the biceps tendon with 1 of 8 fracturing at the supraglenoid tubercle. However, all 8 of the simulated peel back group failures resulted in a type II SLAP lesion.
In theory, SLAP lesions most likely occur in overhead athletes from a combination of these 2 previously described forces. The eccentric biceps activity during deceleration may serve to weaken the biceps-labrum complex, while the torsional peel back force may result in the posterosuperior detachment of the labral anchor.
If this needs further exposition, please say so. If one notes the arm positions and eccentric forces in a kipping pull-up (any style), the trail of SLAP lesions that CF is leaving becomes obvious.
Eccentric bicep loading = the negative part of the pull-up, the arms straightening at the bottom
Arm deceleration = the swing into the kip
Abduction and external rotation = the position of the arms at the apex/reversal point of the kip
Just imagine the "peel-back" force in the shoulders when they are forcefully wrenched back at the apex/reversal point of the kip. If you really think about it, the head of the humerus is trying to push out the front of the glenohumeral (shoulder) joint, the kipper is trying to RELAX their muscles at the bottom to get the most out of their kip, leaving all the strain on the LABRUM (think of it as a suction cup on the scapula that holds the humerus on the body, with the greatest forces on the top/superior and the front/anterior parts), and the resultant forces--over time (repetition)--TEAR the TOP part of the labrum from the FRONT to the BACK...this is therefore a SUPERIOR LABRUM ANTERIOR-POSTERIOR injury mechanism, almost perfectly designed (as evidenced by the orthopedic doctors making a ton of money off of people who do them).
Steven, maybe we should write an article and do some videos on this for your blog.
No amount of KStar's mWODs is going to save anyone from the slow shoulder death that is kipping pull-ups at CF-style repetition levels.