Thursday, July 30, 2009

How Polyurethane Swimsuits Affect Swimming Mechanics

The World Swimming Organization FINA has recently made rules which will ban the new polyurethane swimsuits in spring next year. The FINA World Championships are taking place this month in Rome. Records are being broken, wins are being challenged and the polyurethane suit as at the center of all this controversy.

At the 2008 Olympic Games, Speedo introduced the LZR Racer swim suit that included some polyurethane panels over areas of the body at which the highest drag is experienced. The idea was to squeeze any loose body tissue (muscle or fat) that could cause water resistance. This would reduce drag and therefore increase the swimmers' speed in the water. Recently swimsuit manufacturers decided that instead of just making panels of polyurethane they would create the complete suit from polyurethane.

A full body polyurethane suit allows an air pocket to be created between the water and the skin. The resistance of air is much lower than that of water and therefore the drag in the water is reduced. The suit also aids in increasing buoyancy. Buoyancy is a measure of how well the swimmer floats in the water. A swimmer (without a polyurethane suit) will generally use more of his kicking power to stay on top of the water. The advantage of the higher buoyancy is that he can now use that kicking power to propel himself forward.

This decrease in drag and increase in buoyancy brings up two important questions: does the polyurethane suit change the biomechanics of the swimmer and will the swimmers need to change their kicking motion or even their stroke, when they are forced to abandon their speed suits next spring? Video analysis can definitely play a part in identifying how the biomechanics may change.

At the FINA World Championships, Michael Phelps finished second to Paul Biedermann of Germany. Phelps was swimming in his Speedo LZR swimsuit with polyurethane panels, while Biedermann was wearing a full body polyurethane suit. Biedermann also smashed Phelps' world record in the same race. Did the full polyurethane suit provide an advantage?
Take a look at the video here:

Unfortunately this is TV broadcast video and often the angles are not great for analyzing video. However as you watch, notice how Biedermann remains high up in the water particularly at the end of the race compared to Phelps. In the final 25 meters of the race we can see how Biedermann's legs remain above the water and kicking hard. His kick at the top of the water is propelling him forward quickly. Phelps' legs are deeper in the water and he therefore is using much of his kicking power to stay above the water rather than to propel him forward.

Before we jump to any conclusions that the polyurethane suit gave Biedermann the advantage, we need to remember that there are numerous other factors. Fatigue would definitely be a factor. If Phelps was fatigued at the end of the race and Biedermann was still strong, this would explain how Biedermann continued kicking at the top of the water. Of course the buoyancy of the polyurethane suit may have allowed him to conserve energy throughout the race. We also do not know what normal kicking (without a suit) is like for both swimmers.

To truly understand whether the ban on the polyurethane suit will make a difference to the swimmers' biomechanics we will need to analyze the swimmers independently, comparing their swimming motion in the suit and how they swim without the suit.

We will continue to watch the FINA World Swimming Championships with interest and will also look forward to seeing how the ban on the polyurethane suit will affect the swimmers technique in the future.

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