Is swimming a real drag? (How do drag forces influence my body in swimming?)

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Feb 19, 2011

Is swimming a real drag? (How do drag forces influence my body in swimming?)

"Streamline, streamline, streamline", if I had a dollar for each time I say this word, I'd be a multi-billionaire at this stage, live in a mansion and have my own private 50 meter pool with retractable roof. If you visit this swimming blog often, you have read it over and over in my posts. So, what is this mysterious streamline and why is it so important in swimming that everyone obsesses about it so much?

In laymen's terms, streamline, in swimming, means manuevering your body into a position of least resistance while in the water. So when you swim through the water, your body is as stretched out and straight as possible. Just think of a regular 1 meter straight pole like a broomstick without the broom part as opposed to a small tree with branches sticking out. If you throw the broomstick in the water in a vertical position, then it nicely slices the water until it hits the bottom. If you do the same with the small tree, chances are that it will not even get fully submerged. The same principle applies to your body in the water, the more streamlined your body is, the easier and faster you can swim with less effort. So if you think, this is only for competitor swimmers and not for me, think again. The better you are positioned in the water, the more enjoyment you will have from swimming and the more you can swim and learn.

Streamline graphic from the book
Swimming Fastest by Ernie W. Maglischo
The main force that we are fighting in the water when we learn to swim is gravity. If we didn't take a breath, our body would sink as a rock due to gravity. However, after we overcome the gravity factor and are strong and skilled enough to float without a hassle, we start focusing on reducing or eliminating other forces, mainly active drag forces. The swimming science experts have currently identified 3 types of drag: form drag, frictional drag and wave drag. The form drag is caused by our human non-fish like body shape which cuses the turbulance around our body when we swim. The friction drag is the result of the water flowing over your body and thus causing friction and slowing you down. The wave drag, as described in the Journal of Biomechanics in the scientific paper Wave drag on human swimmers is caused by the energy required to cause the waves which follow your body when you swim and it also accounts for a larger chunk of the drag on a human body from the three drag types. There are of course other forces that act on our body when we swim, but these are secondary in the streamline discussion.

Ok, now we know what slows us down in the water. So, how can we decrease these drag forces to become faster and more efficient in our swimming? Since the wave drag seems to play the biggest role on slowing our swimming down, let's focus on it first. As described in the many scientific publications, wave drag increases as our swimming speed increases. In other words, as you swim faster, you are also causing more waves to be formed behind you. And as we said above, the more waves you generate around you, the more wave drag.

1) Push off the walls at lower depths. Do not push off the wall at the surface. The research has shown that the wave drag is very small or non-existant in greater depths, so if you push off at about 1 - 1.5m under water you will actually swim faster than if you were at the surface. That is one of the reasons why underwater dolphin kick is the fastest stroke out there and was unofficially coined the "fifth stroke". This is also the reason why FINA has made a rule that a swimmer cannot swim more than 15 meters underwater from any turn or start.

Streamline by axeb
2) Hold your streamline when you push off the wall or right after start. Here we get into the term of real streamline and the form and friction drag reduction. When you read in my posts or hear your coach say, hold your streamline, this is what he/she means. Arms are extended above your head. Palms of your hands are on top of each other and are locked together by the top thumb. Arms are fully straight and are squeezing your head right behind your hears. If you are flexible enough, you can also try to overlay as much of a forearm over the other as possible and try to reach out of your shoulders as far as your body allows you to, so there are no airpockets around your neck.

3) Maintain a proper head position. Do not look where you are going and reduce the drag forces acting on your body at the same time. Always look down when swimming freestyle and up when you swim backstroke. On butterfly, your head is down for most of the stroke and only comes up to skim the surface during the recovery (when the arms come out of the water). On breaststroke, it is the same, your head is basically just an extension of your spine and it does not move at the neck it is still and only moves when your body moves.

4) Keep a proper body rotation. Rolling from side to side on freestyle and backstorke with one arm extended in front is another way to reduce the drag. By extending your body forward in a straight line we are aligning our body into more streamlined position, thus reducing our form drag and more than likely wave drag as well.

5) Wearing a swimming cap reduces the frictional drag as the surface on your head is more smooth. As well as wearing a more unconspicious goggle type helps reduce some drag.

6) If you ever wondered why competitive swimmers shave their bodies. Now you have your answer. Smoother, hairless skin reduces the friction that the swimmer body is subdued to in the water, thus making the swimmer glide better in the water.

7) Some swim suits also reduce drag and this is one of the reasons FINA (Swimming governing body) has band the full body suits from competitions and why there were so many world records borken in the last few years. The suits compacted the body into a more streamlined position and helped the body with friction.

And here you have it. So next time you are doing your laps or training in swim practice, remember, streamline is the key to success and repetition is the way you will get there. Why not learn more about how your specific swimming style can be improved to reduce drag?
Be seen, keep your stuff dry and take a break when needed.

1 comments:

Bikini said...

These are some great tips, thanks for sharing