The Baseball Observer - Jan/ Feb 2016
16
Understanding Body Part Injury:
Dead-Arm
Baseball Observer Staff
While dead arm might not be a true clinical term, its one ailment a pitcher can easily identify. A pitchers overall velocity might not change much, if at all, but the liveliness of pitches do. Sliders, cutters, sinkers and curve balls don’t have the same movement – they just seem to spin – no bite.
In most cases, dead arm is not an actual injury. There is no structural damage, tear or inflammation. It's just over use or the lack of recovery time for the arm. Many describe the following:
Generally, dead arm is associated with arm fatigue from overuse.
"Dead arm syndrome starts with repetitive motion and forces on the posterior capsule of the shoulder. The posterior capsule is a band of fibrous tissue that interconnects with tendons of the rotator cuff of the shoulder. Four muscles and their tendons make up the rotator cuff. They cover the outside of the shoulder to hold, protect and move the joint." (Wikipedia)
Dead Arm seems to first show up in spring training for pro's, after winter break for college and January/ February for High School. Players coming in resume a more intense schedule after the offseason.
The second time seems to be past mid-season – depending on the amount of innings pitched (starters more so than closers). A third time, for High School players or college players participating in a summer collegiate league, is mid-way through those summer seasons.
It must be noted that some pitchers introduce a new pitch during the season. Say they start throwing a slider. The new pitch might stress other areas of the arm/ shoulder that haven’t been utilized as much to that point and are weaker. Therefore they aren’t as strong or have as much endurance so they fatigue quicker.
"Dead-arm syndrome" varies so much in its degrees and its causes that even its name "has become sort of a bucket term," Dr. Michael Hausman, the vice-chairman of orthopedics at Mount Sinai Hospital.
specific fatigue