Sports Science: Olympics Edition ‒ Freestyle Swimming


August 6, 2016
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Every four years, the eyes of the world shift towards a global competition, complete with feats of strength, determination, talent and teamwork. The Summer Olympics are back, and I could not be more excited. The following post is one of three about some of my favorite events.

As a college student, one of my pre-Finals rituals was to stop studying 30 minutes before leaving for the exam and instead watch sports highlights videos to get pumped up. There was Vince Young coasting into the corner of the endzone in the 2006 Rose Bowl, Tracy McGrady scoring 13 points in 35 seconds to knock off the Spurs, Landon Donovan sending the U.S. to the knockout stages of the 2010 World Cup, and, the grand finale, the 2008 Men’s 4x100m freestyle relay, the race that earned Michael Phelps his second of eight gold medals at the Beijing Olympics.

That race was, to me, the most memorable moment of a historic run for Phelps. Set aside the volcanic eruption of American pride for a second, and just consider the physics at play as anchor leg Jason Lezak breaks French hearts and sends his teammates into delirium.

Mickey Kelly Swims

Freestyle swimming in and of itself is a case study in aerodynamic motion. The swimmer’s body must be in as straight a line as possible while moving through the water to reduce drag. The swimmer’s face needs to be down as much as possible to allow the round waterproof cap the opportunity to part the water most efficiently. Even when the swimmer turns his head to breathe, the horizontal line should be maintained and the deviation in motion should be minimized.

The body should be in a constant state of motion, and all motion should be synchronized as much as possible, with kicks matching the strokes of the arms. Deviations from this synchronization will cause drag. In addition, small, quick kicks are generally more effective than large kicks that require more time; essentially, the sum of many short accelerations is greater than one large acceleration.

So going back to Lezak’s final 50 meters in the relay, it is important to first set the scene: Lezak was trailing the world-record holder in the 100-meter freestyle, France’s Alain Bernard, by about 0.5 seconds heading into the last leg of the race. That lead had expanded to 0.6 seconds after the first 50 meters.

Lezak closed the gap, in part, due to a principle of physics common in racing of all kinds: drafting. The concept here is you get as close as you can to the racer in front of you; that racer absorbs the brunt of the drag, leaving a pocket of “clean” air (or water). The racer behind the leader uses less energy to go the same speed or can use the same energy to gain ground.

Note how Lezak is swimming at the top of his lane, as close as he could possibly be to Bernard’s slipstream. Even though he is not directly behind Bernard, his positioning is actually much more similar to the way that birds fly in a V-shape while migrating. The ideal position for this technique is at around the waist of the other swimmer, which you might notice is just where Lezak is at about the halfway point of the last length of the race. The disturbance that Bernard is causing in the water radiates outwards and creates a small pocket of clean water for Lezak to cut through.

Studies have shown that swimmers in open water races using slipstreams to swim consume about 10% less oxygen than others and reduce the rate of perceived exertion by 21%. And while it’s a technique that annoys people in the neighborhood pool, it’s something that helped Lezak make up a half-body length deficit in 25 meters and win the race by 0.08 seconds. Oh yeah, there’s also that Olympics Gold Medal.

Swimming events at the Rio Games begin Aug. 6 and conclude Aug. 13.

Sahil
Authored By Sahil Patel

Sahil has worked for HMNS in some capacity each summer since 2007 with the Moran Ecoteen Program and Xplorations Summer Camps. He quite literally grew up at the Museum; Sahil and his mom made biweekly trips at lunchtime until he started school at age 5, and he was a regular camper in Xplorations from ages 6-13. In 2014, he was hired full-time as Outreach Presenter, a job where his friends think he spends all day playing with alligators, tarantulas, and dinosaur fossils. He doesn’t like to contradict them.

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