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Last Friday was a mixed bag for fans of the fastball

. Early in the day, the Washington Nationals announced that phenom Stephen Strasburg, who hurled a 101-mph pitch in his debut in June, would likely require Tommy John surgery for his injured elbow; a procedure that could sideline him for up to 18 months. But later that night Aroldis Chapman, a 22-year-old Cuban defector pitching for the Cincinnati Reds' triple-A affiliate in Louisville, captured baseball fans' attention when he threw a pitch clocked at 105 mph

Chapman's pitch was one of the fastest ever recorded; one that pushed his body to the limit of human ability. And while athletes in other sports, like Usain Bolt in the 100-meter sprint, continue to rewrite the record books, don't expect pitchers to throw any faster than Chapman. In a laboratory at the American Sports Medicine Institute in Birmingham, Ala., Dr. Glenn Fleisig studies the biomechanics of pitching, inviting pitchers ranging from middle schoolers to major leaguers to throw on the mound he has set up. When asked about Chapman's pitch he says, "I've never seen anything like it."

Fleisig isn't alone; few others have seen 105-mph heat either. The Guinness Book of World Records still acknowledges Nolan Ryan's 100.9-mph pitch in 1974 as the fastest ever recorded. Yet pitchers Joel Zumaya and Mark Wohlers have since thrown 104- and 103-mph fastballs, respectively, since Ryan's throw, but Guinness didn't certify the results from the guns used to measure them. And that may be for good reason. In his lab, Fleisig says that pitchers generally throw about 5 mph slower than they've been clocked in games. He says that is due to a myriad of variables with the radar gun clocking the pitch, including the manufacturer and where it's positioned in relation to the pitcher.

However, even if the radar gun used last Friday gave Chapman 5 mph, his pitch still flirted with the maximum speed a human can throw a baseball, which Fleisig says is about 100 mph. Fleisig has found that adjustments to a pitcher's biomechanics, as well as better conditioning of the entire kinetic chain from the legs to the core to the arm, can improve a pitcher's velocity on his fastball. But he's discovered that as the pitcher approaches 100 mph, these tweaks and strengthening have diminishing returns.

Another cause of the 100-mph ceiling owes to this: the amount of torque needed to throw in excess of the century mark is greater than the amount of force the ulnar collateral ligament (the elbow ligament Strasburg tore) can withstand before giving out, according to tests Fleisig has done on cadavers. When a pitcher cocks his arm, where it is turned back to the point where the palm is facing toward the sky, there's about 100 Newton-meters of torque on the arm, which subjects the arm to the same amount of stress as if the pitcher had a 60-pound weight hanging from his hand in that position, Fleisig says.

From that cocked position, the arm snaps forward to its release point in 0.03 seconds, and at its peak speed, an elite pitcher's arm rotates at upward of 8500 degrees per second. If that single instant of speed could be maintained, then a pitcher's arm would spin around 24 times in a second.

"Shoulder rotation in baseball pitching is the fastest motion of any joint in any athlete," Fleisig says; moving faster than hip joints in sprinters or shoulders in elite tennis players.

While pitchers looking for an edge may be disappointed that science is showing there's a ceiling to their velocity, hitters will take that as especially good news, because the increased velocity of a pitch does little to aid a batter in hitting the ball farther, but it definitely helps them to strike out.

"[Pitch speed] has less of an effect than people think," says University of Illinois professor Alan Nathan, who studies the physics of baseball, with a focus on the collision between bat and ball. "Each additional mile per hour of pitch speed is worth about two-tenths of additional batted-ball speed, which only works out on a high fly ball to about a foot for every increased mile per hour."

The batter facing Chapman had only about 0.35 seconds to react before the pitch reached him. Of course, the speed of the 105-mph pitch is measured from where the pitcher releases the ball, so by the time it "crossed home plate, I'd guess it was going about 94 to 95 mph, because a pitch loses about 10 percent of its speed because of air resistance," Nathan says. For Matt McBride, the batter from the Columbus Clippers who faced Chapman's pitch, those 0.35 seconds weren't enough time to react. But now Major League hitters will get a chance to see if they can catch up to the Cuban's heat, with the Reds calling Chapman up to the big leagues on the heels of his performance.

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