When humans learn to swim, they are taught that the displacement of water is key to progress. From doggy paddle to the crawl to the frog kick, people swim in the belief that the best way to move forward in the water is by moving the water back to propel themselves.
Apparently, this is not the case. Generations of understanding may have been undone by researchers at Stanford University who have studied the swimming habits of eels. Some of the eels in their test swam like eels, and some were modified so that only their tail end flicked, causing them to swim more like humans. The researchers filled a shallow tank with millions of glass beads, which they rapidly and repeatedly photographed, in order to track the movement of particles as the eels passed through.
The data they collected enabled them to calculate pressure in the water. Surprisingly, as the eels undulated, pockets of low pressure were created inside each bend of their bodies, into which water was sucked back, allowing the eel to ripple ahead. “For nearly 100 years, it has been assumed that mimicking natural swimming meant finding ways to generate high pressure to push water backward for thrust,” says John Dabiri, a professor of civil, environmental and mechanical engineering who co-authored the research report. Now it is all about suction.
“This is similar to what swimmers do underwater when they do the dolphin kick,” says Stelios Psycharakis, a lecturer in biomechanics at the University of Edinburgh, who thinks the research is “an exciting finding indeed”. Look at images or footage of Michael Phelps performing this movement – arms stretched forward, hands clasped, knees bent, feet flipped up – and his body shape is not unlike that of an eel. In a sad twist, dolphin kicks have been banned by Fina, the international swimming body, for all but a race’s first 15m off the wall. (To witness this motion’s efficiency and grace, watch Hill Taylor smash nearly a second off the world record in 2011 by dolphin kicking his way through a university back stroke race. He was subsequently disqualified.)
Psycharakis says the results “need to be explored for other animals in an aquatic environment. There are normally four different types of undulatory motion, of which the researchers tested one: anguilliform swimming.”
In the meantime, if you want to try to swim like an eel, here is performance swimming coach Harley Hicks’s guide. “Imagine wiggling your hips forward and back, but begin the movement in the chest. It starts at the chest, goes through the hips, finishes at the toes.” Talking of toes, they need to be pointed. As for your upper body: “Arms squeeze your ears,” says Hicks. “One palm lies on top of the other hand, fingers interlocked, thumb coming round the side.” Like a little latch to keep your body in place. Got it? See you in the anguilliform Olympics.
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