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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Why Tiger Woods has a Perfect Golf Swing

This last weekend, we once again had the pleasure of watching Tiger Woods playing in a Major Golf Tournament, the 2009 Masters. He injured his knee prior to the 2008 US Open, and the last we saw of him was winning that tournament in a lot of pain.

He may not have won this year's Masters tournament, but his swing truly is exceptional and it is always worth taking a look at some video and snapshots of his swing to do some video analysis. So why does Tiger Woods have a perfect golf swing? The answer is TIMING.

Tiger shows an almost perfect example of a concept we discussed in our last post with Andy Murray's serve. Tiger creates club head speed by perfectly sequencing and timing the movement of his knees, hips, shoulders, wrists and club. In golf, this is known as the kinematic sequence. The kinematic sequence in a golf swing is a little different to that of a tennis serve, but in the end the idea for both is to create club head speed or racquet head speed by storing and then transferring energy from hips to shoulders to club or racquet, with perfect timing.

Let's have a look at Tiger Woods' swing in slow motion. We have seen this video before, but it is a really good one. In this video we have a side-on view of Tiger's swing (side-on to the direction he will hit) and we can see the club throughout the swing. This makes it a great video to analyze. The video was also filmed with a high speed camera with a high shutter speed, which is why we can see the club so clearly in each frame, even through ball impact.



OK lets analyse this swing by looking at the way Tiger stores and transfers energy to the ball through the golf club. If you stop the video at 0:33 seconds, you will see that Tiger is now at the top of his back swing. During his back swing he turned his hips and his shoulders away from the direction in which he will be hitting in order to store up energy for his swing.

Play the video from here and we will see how his hips start to move earlier and quicker than his upper body and that his shoulders are left behind. Tiger is starting his kinematic sequence by unwinding his back swing. The timing is important and he leads with his hips in order to create more separation between his hips and shoulders and therefore create more energy to be transferred.

His shoulders then follow and at ball strike we see that Tiger's hips are now facing the target while his shoulders are almost facing directly at the camera. This perfect timing has allowed him to transfer all the energy from his back swing, first to his hips and then from his hips to his shoulders.

Here are two images of Tiger at the top of his back swing and at ball strike, created with some free video analysis software and images of Tiger's swing.

Although these are 2 different swings, we can see how Tiger creates separation between his hips and shoulders in the image on the left and how his hips are turned toward the target at ball strike in the image on the right. The shoulders have rotated quickly as they follow in sequence from the hips, in fact they have caught up with the hips as energy was transferred from hips to shoulders and the hip rotation has slowed while the shoulder rotation has sped up. The angle between the hips and shoulders at ball strike is now much less than at the start of the down swing and we can see this in the images above.

Of course the golf swing does not end with the shoulders and there are still numerous places where the timing can be off and the golfer can lose club head speed. In the video above we can look at time 00:41 seconds and we can see that Tiger's wrists are still cocked. As we play forward from this point we will see the wrists release, transferring the energy from the shoulders and arms to the wrists and on to the club and club head at ball strike.

This last sequence happens very quickly and the golfer's timing has to be perfect. Tiger Woods is the master of this timing and we look forward to seeing more video of his swing now that he is back from injury.

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