Research: Dolphin's tail a tale of speed

TROY, N.Y., Nov. 25 (UPI) -- U.S. researchers have finally solved the conundrum of how dolphins swim so fast when their muscles shouldn't support that feat -- tail strength.

A dolphin's tail creates about six times more force than an Olympic swimmer, Rensselaer Polytechnic Institute researchers said in a release. At peak performance dolphins produce between 300 and 400 pounds of force, compared with human swimmers' peak of about 60 to 70 pounds of force, said Timothy Wei, professor and acting dean of the Troy, N.Y., institution's School of Engineering.

For more than 70 years, scientists were perplexed by dolphins swimming at a clip more than 20 mph while their muscles weren't strong enough to support that kind of speed. The conundrum came to be known as "Gray's Paradox" after British zoologist James Gray who first noted the mystery.

"Sir Gray was certainly on to something, and it took nearly 75 years for technology to bring us to the point where we could get at the heart of his paradox," said Wei, professor and acting dean of Rensselaer's School of Engineering, who led the project. "The short answer is that dolphins are simply much stronger than Gray or many other people ever imagined."

Wei created water-flow diagnostic technology by modifying and combining force measurement tools with a video-based flow measurement technique.

Wei said the team could investigate flow dynamics and force generation of other marine animals, which could offer insight into how species evolved because of their swimming proficiency.