This article is from the In-Depth Report The Science of Baseball
60-Second Science

Big Consequence of Small Increase in Bat Speed from Steroids

By enabling just a 4 percent increase in bat speed, steroids may turn hundreds of a season's long outs into home runs. Steve Mirsky reports

It’s been a fun baseball season. But the storm cloud of steroids has hung over the game for years now, especially tarnishing Barry Bonds’s assault on the all-time home run record. Tufts University physicist Roger Tobin is a big baseball fan and recently did some calculations to evaluate just how much of an impact steroids could actually have on power hitting.

When he crunched the numbers, he found the following: steroids might bring about a 10 percent increase in muscle mass. That extra muscle could help a batter swing five percent faster. And that extra bat speed could cause a ball to jump off the bat 4 percent faster. Doesn’t sound like much.  However, if you add four percent initial velocity to a model distribution of trajectories of batted baseballs, you can increase homers by a full 50 percent.

Tobin’s research will appear in the American Journal of Physics. He notes that weightlifting and smaller ballparks also played a role in pumping up the number of home runs.  But the power surge of the ‘90s coincides with steroids more than the other factors.


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