So let's start with the fact that most of this is things that I have researched to create a foundation, and used observation as a key tool to come up with most of this stuff. Coaches from earlier generations didn't have the luxury of having science research and other forms of communication to talk about the science, but rather used their own observations to conclude many of the concepts. I am not going to say my thoughts are correct, but I can say that I have done a lot of observation and relating physics to come up with this stuff.
Let me begin by saying that the dominant source of propulsion is by resistance force. The hand pushes against the water to push the body in the opposite direction. The feet also push against water to create propulsion. This is the intuitive way to create propulsion, it is also the most important and taught form of creating propulsion.
When I was a young coach, I sifted through Ernie Maglischo's book, "Swimming Fastest," (I say sifted, as if anyone has seen the book, you'd understand why a college student may not try to delve into reading the entire book). This is the first time that I came across the idea of Lift Force in regards to swimming. Since then I have fought with myself how it came into play, but I always played with it in my head. In later interviews, Ernie did explain that in the 80's he might have put too much emphasis on the Lift Force Propulsion. I think that although Resistance Force is the main form, that Lift Force is something that shouldn't be ignored, but it does create some counter-intuitive ideas in regards to Drag.
Let's go into an example. Think about a car, a swimmers lead extended hand is like the hood of the car and the body and head is like the cabin. As an observer of a car being tested in a wind tunnel you see that the majority of air flows of the car to make more aerodynamic. In a car though, it needs some air to go underneath the carriage to create some down force to keep it on the road.
Now a swimmer doesn't need the down force, so water flowing over the body can then create some forward lift force, and reducing the moving air under the body actually reduces the down force (which we don't want in freestyle, fast swimming is swam high on the water.) The counter-intuitive aspect is the idea that a swimmer wants to push the top of the arm forward to feel the water up the back of the arm rather than slce the hand through the water fingers first. I watch so many adult lap swimmers while lifeguarding, and this is probably the most common problem. This makes sense though, as resistance force makes so much sense, and the idea of lift force isn't really thought about.
If the hand slices the hand and arm through the water not disturbing the path of the water, the water is still going to hit the head and shoulders. Back to the car example, slicing the hand forward would be like making the hood of the car needle like, and the first part that the wind will hit would be the big mass of the cabin. You can't escape some drag of the body to the water, so you might as well direct the water for positive effect.
This now blocks some water from moving under the body, and creating an area where there is slower moving water under the arm. This actually benefits the swimmer also as they make the catch and pull they will catch more water, as it is more powerful to push against slower moving water. So not only are you increasing your lift and propulsion during the extension, but you are creating a great path of slower moving water, so that your pull will push more water (increasing the resistance force).
To prevent the blog posts from being too long, I am going to stop there, and post more on science later in more posts.
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