Swimming Physics

 Many athletes decide to become triathletes without being able to swim or without good basic skills in swimming.  This often results in athletes arriving at a race having just achieved the ability to swim the distance, limited experience with open water, and a great deal of fear of the swim leg of the race.  

In fact, here's an article about that fear. 

A big part of the problem is undertraining, but another part is the limited availability of good triathlon swim coaches. Many swim coaches are great at coaching for speed in the pool, but open water swimming is much different.  Very few swim coaches can coach athletes for open water trials.  

A good start is to understand some of the physics of swimming.  In the series of drawings below, you can see some of the leading physics effects on swimmers.  

You can see essential good form and body position in the water in A.  The head is level with the water's surface, the legs are not bent, and the elbow is high for a good catch.  Most of the body is in, entering, or leaving the 2-inch slippery layer of the water.  The catch is well below the slippery layer where the water is heavy and unmoving, so the hand and arm push against a heavy layer of water for the motive force.  There is much less drag here.  

In B, the swimmer is looking forward and lifting the head slightly, but the legs, in response, drop a great deal because the center of gravity is at the chest area.  The legs end up in the heavy layer of the water and create a significant level of drag.  The arm is in a good position but has to work twice as hard to pull the body forward because of the drag on the legs. 

In C, the swimmer is kicking with bent knees, and even though the head is in the correct position and the catch is good, the legs are creating a great deal of drag.  The large leg muscles that weigh a lot are pulling the body down in the water, and when this swimmer tries to breathe, they will experience downward movement and end up with a lot of water in their mouth.  

In D, the swimmer raises their head to breathe, and the legs drop in response.  This happens with the swimmer in C; they then have to adapt to get a breath, so they lift their head.  The body is sinking with every breath, and the swimmer is struggling to progress because of the drag and sinking.  

Overcoming these issues requires that the swimmer understand that dropped legs and raised head are critically damaging to forward progress.  When a swimmer tries to go faster with these problems, they work very hard and often end up with disappointing results as they create a lot of turbulence, further slowing them down.  

In the water, speed is often not the result of working harder.  This article addresses that. 

Having said all that, moving from the pool to open water often means that we go slower.  30 sec to more slower than our pool 100 yd pace.  Why?  

1. There are no lines in open water so we often swim in zig zags
2. There are people in our way
3. We experience fear from all the chaos and inability to control our situation
4. We are racing in cold water and the heart rate is elevated, the blood vessels constricted and we feel breathless
5. We are swimming in a wetsuit that is tight and can feel like we can't get enough air
6. Our goggles fog up and we can't see where we are going
7. We have trouble sighting on buoys and sometimes miss the turns
8. Current, waves, jellyfish and other things in open water we don't encounter in the pool
9. The water is full of bacteria and can make us nauseous 

It is particularly important to understand how to keep good body position in the water in open water because many other things will slow us down.  If we are well trained in how to keep good body position, we don't have to think about that along with "how do I get around this bozo?"  

It can feel like we aren't making progress when all we do is focus on head and leg issues at first.  But once those are conquered and you experience the feeling of flying in the water effortlessly, you'll be glad you focused on the basics first and arrive at the swim finish feeling accomplished.