The Main Cause In The Increasing Rate Of UCL Injuries

The increase in arm injuries to the elbow’s UCL(Ulnar Collateral Ligament) is from incorrectly thrown “sliders” in which the forearm dangerously supinates at release. Supination of the forearm is what stresses the UCL. On correctly thrown fastballs, the forearm safely pronates after release. On correctly thrown curveballs, the elbow safely hinges after a karate chop motion after release. On change ups, the arm also safely pronates as it does on a fastball. Unfortunately, modern pitchers throw too many “sliders” in which the forearm dangerously supinates at release. Pitchers would be much better off developing a cutter instead of a slider so the arm can safely pronate after ball release.

Many occupational therapists have seen that severe supination of the forearm stresses the UCL. Right-handed carpenters using a traditional screwdriver will stress their UCLs when they repetitively tighten difficult screws by using supination. Left-handed carpenters will pronate their left arm when they tighten traditional screws, and their UCLs are not stressed. Left-handed carpenters stress their UCLs when they “un-tighten” difficult screws because they will supinate in the un-tightening motion. The best studies have been done in ergonomics by occupational therapists who try to prevent injuries in the workplace among construction workers and factory workers who constantly pronate and supinate their forearms as part of their jobs.

Also, studies have been done on tennis players. The fast “first serve” in tennis is not hard on the UCL because the arm safely pronates. It’s the soft “second serve” in which the player tries to add a curving and controlling “top spin” that unsafely supinates the forearm. The soft “second serve” in tennis is the culprit for UCL damage among tennis players. Tennis players would be better off if they always got their first serve in so they never had to spin in a second serve. When the radius bone in the forearm rolls to the outside of the ulna, the UCL is stressed like a stretched rubber band. The medial UCL bundles connect the humerus to the ulna inside the elbow. In young kids, the stress on the UCL will pull on the growth plates and cause inflammation (classic Little League elbow). However, in adults, the stress goes entirely to the UCL because the growth plates have already hardened into bone, and a tear in the UCL becomes more likely.

The link below shows that pronation is most stressful, with a limited range of motion, when the elbow is flexed, as it is on the backside when the humerus externally rotates during trunk rotation. As the elbow extends after trunk rotation, pronation becomes less and less stressful with a much greater range of motion. The opposite is true with supination. Supination is safe with a good range of motion when the elbow is flexed on the backside, but supination becomes increasingly dangerous with a limited range of motion as the elbow extends on the front side.

http://www.ncbi.nlm.nih.gov/pubmed/18332013

Basically, pronation is bad on the backside with a flexed elbow, but pronation is OK at release and beyond with elbow extension. Conversely, supination is OK on the backside with a flexed elbow, but supination is bad at release and beyond with elbow extension.

Article Source: Pitching.com