Swimming: Hard for Triathletes, Even Worse for Scientists

In FASTER, I give an explanation of how we generate propulsion with our hands in the water. Basically, pulling your hand through the water works the same as when you try to pedal a bike forward through the air. Just like drag holds you back on the bike, it also pulls backward on your hand. Except in the case of swimming, that drag force actually pulls you in the direction you want to go.

There’s a little secret I’ll let you in on, though: I could be wrong. The primary force acting on your hand might actually be lift. The debate over this has been going on since the 1960s, and all science has been able to do thus far is complicate the issue. Though we might be closer to a final answer, no one is sure yet. It makes for an interesting bit of drama, though, not to mention a good teaching point on how the scientific study of athletics continues to evolve.

FASTER swimming drag vs. lift

Back in the 1950s and 1960s, conventional wisdom held that swimmers should move their arms through the water in a circular, almost windmill-like fashion known as the “deep catch” method. Swimmers were told to simply use their arms like oars on a boat and pull for all they were worth. Then came James “Doc” Counsilman, the famed coach of Indiana University and the US Olympic swim teams. Counsilman began studying how elite swimmers moved by filming them underwater, and his observations led him to make some astounding claims about the science of successful technique.

Counsilman observed that the fastest swimmers made the unique “sculling” motions with their hands in the water, deviating from the windmill pattern and “swerving” their hands in a sort of s-curve. In effect, the hand was moving side-to-side like a karate chop at times. From this observation, he concluded that instead of just using the arm like a paddle, a swimmer could also use it somewhat like the propeller on a boat. While a paddle works off of drag, a propeller generates lift.

So the great debate began.

Was it lift or drag? Paddles or propellers? Counsilman’s ideas held sway for many years due to his success in coaching some of the best athletes in the world. But scientists were challenged to verify his claims experimentally. Not only were they split on how the arm should move, they also made conflicting discoveries about the relative contribution of lift and drag. For every claim that was made about having “resolved” the issue, another scientist came up with an explanation for why the solution was wrong. One of the biggest critics of Counsilman’s theories is Professor Brent Rushall, of San Diego State University. A thorough (albeit lengthy) summary of his arguments against the theory of lift in swimming can be found here.

All kinds of studies have tested these arguments since they were first proposed. Some scientists tried to model the motion of the hand in different reference frames to see if there was some sort of “optical illusion” generated as the body passed it in the water. Others attached different sensors to the hands and arms to assess the forces acting on the entire limb throughout the swimming stroke. The en vogue technique since the 1990s has been to model fluid flow using computers. They all have relative strengths and weaknesses, though. The primary weakness they have in common is the very substance they’re trying to evaluate—water.

It’s very easy if you want to test the aerodynamic properties of a bike. You can just stick it in a wind tunnel and measure away. But things are much more difficult with a swimmer’s arm in the water. While there are such things as water tunnels, they often don’t have a convenient location for the swimmer to get their arm out of the water to reach for the next stroke, and that’s to say nothing of the need to breathe air. They also don’t move water at speeds you would expect to see out of swimmers, so they are not the greatest tools for approximating the pool (or ocean) environment.

Computers face similar challenges. Water is a complicated fluid. It requires highly sophisticated algorithms to model its behavior, and even then there is room for error. The interaction between the arm and body is difficult to model, because even elite swimmers have different styles of arm pull. How the hand moves through a small portion of the stroke will affect how it moves further along, as well as the water around it.

Most recently, Professor Rajat Mittal of Johns Hopkins University announced that he’d been able to conclusively end the debate with a new computerized fluid dynamics model. His result was quite surprising, because it concluded that both theories were correct. Mittal says that the deep catch method is more efficient, but that it makes more use of lift than drag. He shared this information with the US Olympic Swim Team ahead of the 2012 games, but it’s uncertain if any of the athletes were able to incorporate the information into changing their stroke effectively before competition.

There are a few reasons I stuck with of drag in FASTER and did not mention the study by Mittal. To begin with, my primary intent was to give uninitiated athletes a good foundation for understanding the scientific principles of the sport. Going into the fine details of this debate went beyond what I thought was appropriate. Secondly, Mittal’s findings were only published in 2012. There hasn’t been sufficient time for his work to be examined by others. Science requires thoroughness, and more than one scientist has been proven wrong.

The final reason was more triathlon specific. Mittal’s final conclusion says the deep catch method is better for Olympic swimmers in a pool environment. These are highly specialized athletes in different water conditions competing at much shorter distances. What works better for them may not be best for triathletes swimming generally much longer distances. There is also the wet suit to consider, which other studies have shown can contribute to extra fatigue over time. So perhaps what a sprinter may find to be a more powerful stroke translates into a more tiresome one for a half-Iron distance swimmer. I’m optimistic that someone will take Dr. Mittal’s results one step further and compare them to an open-water scenario.

So even after 116 years of Olympic swimming, we’re still refining our scientific understanding of the best way to move through the water. Being right or wrong isn’t as important as being curious and making progress. Is it lift or drag? Deep catch or sculling? We don’t know for certain just yet, but people are looking into it and getting us closer to the answer. Science isn’t easy, but that’s what scientists and triathletes have in common: the belief that nothing worth doing is ever easy.

If you’re interested in getting faster, you’ll be fascinated by FASTER: Demystifying the Science of Triathlon Speed. In Faster, astronautical engineer and triathlon journalist Jim Gourley explores the science of triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and slow down your racing. With this knowledge on your side, you can make easy changes that add up to free speed and faster racing.

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