Steroid use by a Major League Baseball slugger may produce only modest increases in muscle mass and bat and ball speed but still boost home run production by 50 percent or more, according to a new study by Tufts University physicist Roger Tobin.
Tobin, a specialist in condensed matter physics with a long-time interest in the physics of baseball, will publish his paper "On the potential of a chemical Bonds: Possible effects of steroids on home run production in baseball" in an upcoming issue of the American Journal of Physics.
As Tobin's paper notes, Babe Ruth's record of 60 home runs in a single season stood for 34 years until Roger Maris hit 61 homers in 1961. For the next 35 years, no player hit more than 52 home runs in one season. But between 1998 and 2006, players hit more than 60 home runs in a season six times. Barry Bonds hit 73 home runs in 2001—topping Maris' mark by an astonishing 20 percent.
According to Tobin, the explosion in home runs coincides with the dawn of the "steroid era" in sports in the mid-1990s, and that surge quickly dropped to historic levels in 2003, when Major League Baseball instituted steroid testing.
While the increase in home runs has been clouded by suspected use of performance-enhancing steroids, many have wondered why home-running hitting would be particularly vulnerable to performance enhancement. They have also asked if it is even physically and physiologically plausible that steroids could produce effects of the magnitude observed. The answer to both questions, says Tobin, is "yes."
Home Runs Disproportionately Affected
"A change of only a few percent in the average speed of the batted ball, which can reasonably be expected from steroid use, is enough to increase home run production by at least 50 percent," he says. This disproportionate effect arises because home runs are relatively rare events that occur on the "tail of the range distribution" of batted balls.
"In most any statistical distribution -- of people's heights, SAT scores, or how far baseballs are hit -- there's a large bump where most of the values fall, with the graph falling rapidly as you move away from that region in either direction toward the rarer values," explains Tobin. "It's a well-known statistical property of such distributions that a relatively small shift in the center point of the distribution can produce a much larger proportional change in the number of values well above or below the center. Because the distribution's 'tail' is particularly sensitive to small changes in the peak and/or width, home run records can be more strongly affected by steroid use than other athletic accomplishments."
Muscle Mass Boosts Bat and Ball Speed
Tobin reviewed previous studies of the effect of steroid use and concluded that muscle mass, the force exerted by those muscles and the kinetic energy of the bat could each be increased by about 10 percent through the use of steroids. According to his calculations, the speed of the bat as it strikes the pitched ball will be about 5 percent higher than without the use of steroids and the speed of the ball as it leaves the bat will be about 4 percent higher.