Quartz (Oct. 11) -- It seems intuitive: baseball players with larger bodies should be able to hit a baseball harder. But do the physics and physiology agree that increased size yields better performance? In 2009, Alan Nathan, a retired physicist formerly at Illinois and long-time baseball enthusiast, authored a paper in which he calculated that if you assume a baseball player starts out with about 50 percent of their weight as muscle, every 10 percent of muscle mass he gains will translate into a roughly 3.6 percent to 3.9 percent increase in bat speed.