SCIENCE NOTEBOOK

A Batter's Boost From Steroids Yields a Big Increase in Home Runs

When a baseball player uses steroids, how much harder can he hit the ball?

A new study by a Tufts University physicist found that, on average, taking steroids increases the kinetic energy in a player's swing by about 10 percent, raises his bat speed by about 5 percent and boosts the velocity of the hit ball by about 4 percent.

Could such small numbers explain the dramatic difference in home runs scored in recent years? The answer, Roger Tobin reports in the American Journal of Physics, is yes -- but the reason has less to do with physics and biology than with mathematics.

When a batter connects, some balls just dribble into the infield, and a few sail out of the park. If you plot on a graph the distances that struck baseballs travel, most are bunched in the middle. Only a few are at the extreme end of the curve: home run distance.

When a steroid-enhanced athlete regularly hits the ball just a little harder than before, it has the effect of moving the entire distribution toward the far end. And because the distribution usually falls away quickly from the average, moving the curve just a few percentage points can make a big difference in the number of home runs.

"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," said Tobin in a statement. "Because the distribution's 'tail' is particularly sensitive to small changes . . . home run records can be more strongly affected by steroid use than other athletic accomplishments."

Tobin titled his paper: "On the potential of a chemical Bonds."

-- Shankar Vedantam

Smoking in Films Linked to Adolescents' Habits

The likelihood that an adolescent will become addicted to cigarettes increases with every smoking scene he or she sees in movies, new research indicates.