Believe it or not, how dolphins can swim so fast has been something of a riddle for researchers since the 1930s.

But a new study has laid to rest one of the most vexing questions plaguing scientists about dolphin speed: How can their muscles produce enough thrust for such high speeds?

"It's been controversial for a while," said Frank Fish, a marine biologist at West Chester University in Pennsylvania.

Now he has the answer: Bottlenose dolphins can produce the power they need to swim circles around whatever they wish by using their powerful tails, new experiments show.

The paradox began in 1936 with a British researcher named Sir James Gray, who conducted the first study on dolphin swimming, said Fish, a co-author