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November 30, 2012

Raising Aces

On the Other Hand

by Doug Thorburn

A pitcher's throwing arm is the hardest-working limb on the playing field, so it figures to get all the attention, but the oft-ignored glove-side arm has the potential to either aid the delivery or throw a wrench into the system. The non-throwing arm plays a non-trivial role in mechanical assessment—I have occasionally dropped a reference to a pitcher with a “sloppy glove” or one who “keeps the glove out in front of the body,” but I have yet to go into detail on the topic.

We have covered the basic tenets of Pitchology this season, from balance to momentum and hip-shoulder separation, but today will be an advanced lesson in the theory behind one of the finer elements of pitching mechanics. So if the class will indulge me for a lecture, I'll don the tweed jacket while the rest grab a mitt and meet me on the diamond for a virtual field trip.

Understanding the glove phenomenon begins with the kids. Young players lack the strength to coordinate a complicated pitching delivery on a consistent basis, and small issues are often magnified, such as the impact of wearing a 1.5-pound mitt. A pound-and-a-half might not sound like much, but for a growing kid who is trying to repeat a complex motion dozens of times in a row, it can be surprisingly difficult to coordinate the weight difference between the glove and a five-ounce baseball. At the NPA we advocated the use of a lighter mitt for Little Leaguers in order to minimize the potential problems caused by a heavier glove.

Professional pitchers are not nearly so troubled by the weight discrepancy, but the glove side still has an impact on mechanical efficiency. Shoulder rotation is a major element of the delivery, and it is the shoulder axis that naturally links the throwing and non-throwing arms, underscoring the give-and-take that one limb can have on the other. One of the more common references to the non-throwing arm comes when a pitcher's front shoulder is “flying open,” which is scout-speak for a pitcher who triggers trunk rotation too early, indicated by a front shoulder that begins opening up as the shoulder-axis starts rotating.

The terminology makes a lot of sense when considering the visual point-of-view of batters and catchers, as a pitcher is supposed to keep the shoulder-axis closed until a shade after foot strike in order to properly align the rotational links in the kinetic chain and to maintain a balanced position on two feet. It bears repeating that a pitcher who initiates trunk rotation too early is akin to a batter who triggers his swing mid-stride, before the front foot hits the ground.

The glove arm is sometimes overlooked during the phase prior to foot strike, as the throwing arm separates from the glove and prepares for the rotation. The two arms play a role in maintaining balance, akin to someone spreading their arms on a balance beam or a tightrope, and at the National Pitching Association we found that the best pitchers had a common trend of positioning their arms in a mirror image of one another into foot strike. There are myriad ways for these players to extend their arms, but the best pitchers almost always form equal arm-angles in opposite directions. A glove arm that fails to mirror the throwing arm can impact balance and disrupt the overall consistency of motion.