“You can’t coach height.” While that scouting advice is usually heard around high school and college basketball courts, it applies equally well to pitching prospects in baseball.

The trend towards taller, dominating pitchers has been rising for years. A quick check of this season’s MLB stats shows the average height of the top 10 pitchers with the most strikeouts this season is 6’ 5” compared to the average height of all MLB players of 6’ 1”.

In fact, the height of pro pitchers has been on the rise for the last 110 years and they're throwing harder. In the 2009 MLB season, all but two of the fastest 20 pitches thrown came from pitchers 6’ 2” or above. It makes intuitive sense that with greater height usually comes a faster pitch, but now a mechanical engineering professor at Duke has helped to explain why.

Tall pitchers are not alone in their domination of a sport. World record sprinters have gained an average of 6.4 inches in height since 1900, while champion swimmers have shot up 4.5 inches, compared to the mere mortal average height gain of 1.9 inches. During the same time, about 7/10 of a second has been shaved off of the 100-meter sprint world record time while over 14 seconds have come off the 100-meter swim record. Even in golf, the top 10 players in driving distance in 2010 were, on average, 2.5 inches taller than the bottom ten.

What do all of these athletes have in common? According to Adrian Bejan of Duke University, it is the “falling forward” motion of their athletic task. The taller the athlete, the more force they can put behind either themselves or an object that they want to propel forward. It is what Bejan calls the “constructal law” theory of sports, which he describes in this recent Ted Talk.

His latest research is reported in the current online edition of the International Journal of Design & Nature and Ecodynamics.

"Our analysis shows that the constructal-law theory of sports evolution predicts and unites not only speed running and speed swimming, but also the sports where speed is needed for throwing a mass or ball," Bejan said.

He compares the pitching motion with that of a trebuchet machine, (ala Science Channel’s Punkin Chunkin). "According to the constructal law predictions, the larger and taller machine, like a medieval trebuchet, is capable of hurling a large mass farther and faster," Bejan said. “In the case of the human thrower, the height of the mechanism is the height of the ball that is accelerated overhead. This height scales with the size of the athlete, in this case, the shoulder height plus the arm length. The other players on the baseball field do not have to throw a ball as fast, so they tend to be shorter than pitchers, but they too evolve toward more height over time. For pitchers, in particular, height means speed.”

Of course, there are always exceptions to the rule. Two-time Cy Young award winner Tim Lincecum, all of 5’ 11”, pitched a no-hitter this month. Still, scouts and manager have learned over the years that taller is better, even if they have no idea what the constructal law says.

Be sure to follow @AxonSports and check out the Axon hitting app for iPad.