A while back, I jumped on the triathlon website Slowtwitch and got attacked for saying that the power in the freestyle pull comes in the front of the stroke (hand entry to shoulder), not in the middle (shoulder to belly button) or back (belly button to release). Nonsense...they said. Didn't you read the article by Popov's coach showing the power is at the end of the stroke?
That never made sense to me. After all, at the end of the stroke there is only about one muscle still working, the tricep, and the hand is not in that position for very long.
At last, I got the proof I needed. A few weeks ago I was tested on the Velocity Meter, a very cool device that measures the speed of the body through the entire stroke cycle. It was VERY revealing and provided tons of information I could not get elsewhere.
Such as:1) the body speed slows by as much as 40% from the fastest to the slowest point during a single arm stroke. 40%!!! That is huge. The difference in speed is directly caused by the body going from a relative streamlined position to a very non-streamlined position and back again.
2) The fastest point in the stroke cycle is when the hand first enters the water and the slowest point is when the hand is about at the shoulder underwater. That is when the upper arm is pointing nearly perpendicular to the line of the body (ie most drag).
I realize that the speed of the body at any given instant is a result of the propulsive power minus the drag forces, that one cannot determine just from the velocity that the power is really greater in front. But when the speed drops from 2.5 meters per second when the hand is in front to 1.4 meters per second when it is in the middle, I have to believe that the power in front is greatest.
By the way, the propulsive power of the arm is created by both lift forces at the beginning and drag forces in the middle, as the hand shifts from forward motion to backward motion (then forward again as it releases).
Anyway, read my latest blog on our website www.theraceclub.com to find out more revealing secrets from the Velocity Meter.
Gary Sr.
Where's that physics prof?
Sorry to have been silent on the rest of this thread. I've been buried under a mountain of work, chairing our tenure committee with meetings deep into the evening, and pitching in while my wife dealt with her mother's decline/death this month.
The general principles, most of which are being discussed in this thread, are pretty clear -- thrust, drag, lift (in that it changes body position in the water), and turbulence. Beyond that, the specifics really require measurements of force as a function of time, speed as a function of time, etc. correlated with the motions of the swimmer. There is currently some research being done along these lines, and I expect we'll see some general principles come out of this work. They may not be that different from some of the general principles (like EVF) that have been around already.
However, the situation of each of our own bodies moving through the water is sufficiently complex, that what is really useful is to have your own personal self tested while you swim. Systems in development now will make that easier in the future, but now they are mostly in the research stage. I'll be tested myself in a couple of weeks using the research system at my college, but it is still a little early in the research cycle to be able to take the data and unambiguously relate motions, or changes in motions, to the data. Why is it so hard? Even subtle differences in body position create differences in drag; applying forces to the water creates turbulence, as does changes in body position, and turbulence decreases the effectiveness of the applied force, etc. Figuring out the relative importance of all of these individual components (with all the swimming motions together) when they are all combined to give only 2 pieces of information (the net linear force in the direction you are swimming, along with your speed, both as a function of time) is not as easy as you might think.
Happy Thanksgiving to all!
Where's that physics prof?
Sorry to have been silent on the rest of this thread. I've been buried under a mountain of work, chairing our tenure committee with meetings deep into the evening, and pitching in while my wife dealt with her mother's decline/death this month.
The general principles, most of which are being discussed in this thread, are pretty clear -- thrust, drag, lift (in that it changes body position in the water), and turbulence. Beyond that, the specifics really require measurements of force as a function of time, speed as a function of time, etc. correlated with the motions of the swimmer. There is currently some research being done along these lines, and I expect we'll see some general principles come out of this work. They may not be that different from some of the general principles (like EVF) that have been around already.
However, the situation of each of our own bodies moving through the water is sufficiently complex, that what is really useful is to have your own personal self tested while you swim. Systems in development now will make that easier in the future, but now they are mostly in the research stage. I'll be tested myself in a couple of weeks using the research system at my college, but it is still a little early in the research cycle to be able to take the data and unambiguously relate motions, or changes in motions, to the data. Why is it so hard? Even subtle differences in body position create differences in drag; applying forces to the water creates turbulence, as does changes in body position, and turbulence decreases the effectiveness of the applied force, etc. Figuring out the relative importance of all of these individual components (with all the swimming motions together) when they are all combined to give only 2 pieces of information (the net linear force in the direction you are swimming, along with your speed, both as a function of time) is not as easy as you might think.
Happy Thanksgiving to all!
