From the standpoint of physics, muscle begets bat speed, which begets power.
That part is simple, as physicist Alan Nathan has shown. “A 10% increase in muscle mass can lead to about a 3.8% increase in bat speed,” Nathan found, and that sort of bat speed increase can lead to an increase of 4.3% in batted ball distance.
And so this year, Mariners shortstop Brad Miller decided to put on more weight. Was it about the power? “Oh yeah. I want to get as physical as I can,” Miller admitted before a game with the Athletics this year. So he put on 15 pounds in the offseason and came into the season weighing 220, instead of the 205 he weighed to finish the season in 2014.
We don’t have yearly heights and weights for players, but we do have *a* listed height and weight for each player. Despite being of dubious quality, let’s see how Body Mass Index is related to power factors. Turns out, it is significantly related to many power stats, with Home Runs per Fly Ball providing the cleanest look:
The relationship is significant (p value less than .0001), but the relationship isn’t the strongest. Your BMI explains about 15% of your power output as judged by HR/FB. Of course one of the problems is that these height and weight numbers are often outdated. Tony Gwynn Senior was listed at 199 pounds, which seams a bit light for the second half of his career.
Height doesn’t change! At least not much once you hit the major leagues. The relationship is clearer when you use height.
Now, height explains 26% of the variance in power. So being ‘big’ is useful for power. But it’s not everything, especially not for Brad Miller, whose increase in BMI predicts a surge in HR/FB… to 10.2% (from his career 9.6%).
But power wasn’t the only reason Miller put on the weight. Talk to him about his defense, and you’ll notice that Miller felt that the added size would help him there, too. “I think the working out thing really helps,” Miller said about playing shortstop. “If you know you’ve put the work in, and you feel strong, and your body feels good and you feel explosive, that helps you with everything.” It’s not as much of a stretch as it might sound — Ben Lindbergh found that most of the players claiming to be in the Best Shape of Their Life played to their projections, but he did find that there was possibly a difference when it came to health and defense.
Of course you can’t do the same kind of workouts to improve your power as well as be a better shortstop, but Miller kept that in mind when designing his offseason routine. “I’m in the middle of the diamond, so you want to be able to move, but I want to find out how much I can put on my frame and still hold it well,” Miller said of his bodywork. “Every work out was 45 minutes on the track, spring training, movement training, followed by a full body work out. Every time I lifted, we were running too. The weight gain was gradual. You want it to stick and be good weight.”
Miller has had his doubters. He acknowledges them but feels it’s an internal battle in the end. “In high school, you want to prove yourself,” he said of the people who feel he can’t be a major league shortstop. “Then it starts all over in college. Then it starts all over in the minors. Then it starts all over in the big leagues. There’s always work. It’s constant.”
Part of that work was noticing that he wasn’t doing enough with the one good pitch you might see in a typical at-bat. “I was fouling off and missing pitches that you gotta move,” Miller said of early 2015. “Some physical things there. That one fastball you get in the zone, you have to put in play. You get one to move and you gotta move it.”
Part of it was noticing improvements he could make in the field. “We’re all confident in our abilities, but you have to self evaluate and say, hey, I gotta get better at using my legs in the field, and improving my footwork,” Miller said of his work at shortstop.
And the grind of the season gets to you, and saps your strength gradually. Miller echoed much of what Brandon McCarthy said about skinny guys and keeping weight on during the season. “You get such a good routine at home during the offseason — you’re able to eat when you want and work out when you want — I always account for a good five pounds I’ll lose,” Miller said. “A lot of the skinnier dudes, we lose it like crazy.” Dustin Ackley nodded.
The key word throughout Brad Miller’s self-appraisal was ‘physical.’ So he spent the winter bulking up in a smart way, to help at the plate and with the glove. Let’s see if the power and defense improve in kind.
With a phone full of pictures of pitchers' fingers, strange beers, and his two toddler sons, Eno Sarris can be found at the ballpark or a brewery most days. Read him here, writing about the A's or Giants at The Athletic, or about beer at October. Follow him on Twitter @enosarris if you can handle the sandwiches and inanity.