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New study of baseballs suggests potential cause of surge in home runs and blisters

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Much has been written over the last year since suspicions about a change in the makeup of balls used by Major League Baseball were raised. Five Thirty Eight’s Rob Arthur has been at the forefront, pointing out last year that newer baseballs have a lower drag coefficient, which leads to longer fly balls. Arthur and Tim Dix also X-rayed some baseballs, finding cores that were less dense than those used years prior.

For a while, commissioner Rob Manfred denied that the makeup of the baseballs changed. But MLB’s own investigation reached the same conclusion: something changed; the balls have a lower drag coefficient.

We now have a new study that shows the potential cause of the surge in home runs, but also for the rise in blisters for pitchers. Dr. Meredith Wills, an astrophysicist, took apart some baseballs and studied the composition in a study for The Athletic. Keeping the components as in tact as possible, she measured the seams used to stitch together the covers on the baseball and found that the seams in newer baseballs are nine percent thicker than seams used on 2014 baseballs.

Wills points out that thicker laces make the baseball less likely to deform after contact with the bat, keeping spherical symmetry. In the executive summary from MLB’s independent committee, they wrote, “[M]anufacturing advances that result in a more spherically symmetric ball could have the unintended side effect of reducing the ball’s drag.”

Furthermore, thicker seams could explain the increase in blisters. Blue Jays starter Marcus Stroman said last year after developing a blister, “I feel like it’s an epidemic that’s happening across the big leagues now, a bunch of pitchers getting blisters, guys who have never had blisters before. So for MLB to turn their back to it, I think that’s kind of crazy. I have no theory. But obviously, I mean, it’s not a coincidence that it’s happening to so many guys all of a sudden. It’s not a coincidence.” He added, “I’ve never had a blister ever in my life. Nothing even remotely close. It’s crazy. It’s extremely frustrating. Extremely frustrating.”

Wills makes the connection between the “prouder stitches” and rise in blisters. She writes, “Since blisters are often associated with tightly gripping or rubbing the seams, the rougher texture could be a strong factor in higher rates of blistering.”

While we still don’t have conclusive causation yet, Wills’ study is another important data point. The ultimate cause could have been simple manufacturing error, a change that Rawlings might not even have been aware of. Whatever the case, we are getting closer and closer to the root of the issue.