Tired Arms

After writing about J.P. Howell a couple weeks ago, and looking into splits based on the number of times a pitcher throws in the order, I got to thinking about why and how pitchers fatigue during their outings.

As anyone who has ever seen a baseball game, when a pitcher gets hit hard in the late innings, the announcer blames it on the pitcher being physically exhausted and the manager makes the call to the bullpen. For anyone who is familiar with DIPS theory and the Laws of Voros McCracken, the first thought is that the pitcher was unlucky because the hitter made a good swing or because it must have been a cheap hit.

This is true sometimes, but fatigue can do some strange things to a pitcher, especially their ability to locate a pitch. Analyzing pitch locations is about to be the next big breakthrough in DIPS theory. Pitch location is extremely important to how hard a hitter hits a ball, just ask Dave Allen. When a pitcher gets tired, a few things happen. 

The most commonly cited effects due to fatigue are a drop in velocity and a downward change in arm angle. These can happen separately or in tandem, as the body does not tire globally at the same rate. Conditioning is important and so is the type of activity being considered. Just because a pitcher is used to throwing one hundred pitches per game doesn’t mean that their deltoids are at the same state of fatigue as their biceps or their triceps.

(From here on out, note that I am not a kinesiology expert, so these inferences are based on what I’ve read and from experience in athletics.)  

Lift your arm to your straight in the air as if you were raising your hand in class, or to do jumping jacks if you liked gym class more. The muscles in your back (i.e. trapezius) and shoulders (i.e. deltoids) are put to work, while biceps are relaxed. 

This motion is important when considering a pitcher’s arm angle. If shoulder and back muscles are tired, the arm will be lower than expected when the pitcher is releasing the ball. This has a number of effects on the pitch. First, the ball will go in a different direction simply because the release point is now different. Second, and slightly more subtle, is a change in the rotational axis of the baseball, which will cause it to break slightly differently.

If a pitcher who usually throws overhand is now throwing in a 3/4 motion, the ball will rise less and break more laterally to their arm side. When the difference between a ball and a strike, or a home run and a pop out are just fractions of an inch, this difference can be monumental. Less accuracy leads the pitcher to throw to poor locations more often: more hits, more BB, more HR.

Velocity is the other major factor. I won’t pretend to know how fatigue affects velocity, but there are a number of factors that do: arm fatigue, leg fatigue, torso, pretty much anything can affect it. When velocity drops (assuming the arm angle stays constant, the pitch will change not change much in break, so don’t worry about that), the locations where a pitcher can throw and prevent giving up home runs changes drastically. 

For an explanation of these locations, see this article by John Walsh at The Hardball Times. If you don’t feel like reading the link, the gist is this: if your velocity drops, you will give up more home runs, especially when throwing inside.

Now try to imagine what could happen to a pitcher when his velocity decreases, especially with location lapses thrown in. The location and velocity lapses will combine to put the hitters in more hitter’s counts, and the pitcher, when trying to thread the needle or hit corners, will now throw to the kill zone.   

In summary, pitcher fatigue can have drastic affects on effectiveness, due to differences in pitch break, release point, and velocity drops. So, next time you shout at a manager for taking out a pitcher who has given up a few hits late in an outing, remember, not all pitches are created equal.

Thanks to The Hardball Times  and BaseballAnalysts.com for their contributions to this article.

Mike Silver recently completed his requirements for the Sport Management Major at THE University of Massachusetts-Amherst, where he is a brother of Theta Chapter of Theta Chi Fraternity, the best house in the country. He is a huge Red Sox and Bruins fan, and longs for the days of the REAL Boston Garden, Cam Neely, and the ultimate Dirt Dog Trot Nixon. If you have any questions, you can reach him at mjasilver@gmail.com. Have a good night readers, and know that Mike hopes to hear from you soon. If you quote Mike in an article, please let him know. He’d love to hear it.


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