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.
That said, I enjoyed the article swimming on the freeway,
I enjoyed it too, and it also has what Gary Hall SR must believe contains the answer to poll's question:
"...when you dive into the water from a starting block for a split second you are going around 5 miles per hour. Yet, in just 5 seconds (without the help of a kick or pull out), you come to a virtual stop. That means every second in the water from the time you entered you slowed (decelerated) around 1 mile per hour each second. Or in a half a second you slowed 1/2 mile per hour and so on."
Accepting that you go from 5mph to a full stop in 5 seconds, I question his assertion that you lose 1mph per second. I think it much more likely that you lose speed exponentially.
The rapidity of exponential decays (sorry for the science-geek language) is characterized by the time/rate constant or, equivalently, by the "half-life" which is easier to understand for most. In chemistry it standard to consider a chemical is "gone" after 5 half-lives (theoretically it never completely disappears, right?).
So in this case if we take the half-life to be 1 second, that means you lose 50% of your speed in the first second after diving in, and 50% of the remaining one second later. Thus, it takes 2 seconds to lose 75% of your initial speed.
But that assumes no kicking, so I'm thinking it takes a little longer for someone in real life, especially for a good kicker. (Actually in real life you never lose 75% of your speed...1.25 mph is a slow swimming speed...)
That said, I enjoyed the article swimming on the freeway,
I enjoyed it too, and it also has what Gary Hall SR must believe contains the answer to poll's question:
"...when you dive into the water from a starting block for a split second you are going around 5 miles per hour. Yet, in just 5 seconds (without the help of a kick or pull out), you come to a virtual stop. That means every second in the water from the time you entered you slowed (decelerated) around 1 mile per hour each second. Or in a half a second you slowed 1/2 mile per hour and so on."
Accepting that you go from 5mph to a full stop in 5 seconds, I question his assertion that you lose 1mph per second. I think it much more likely that you lose speed exponentially.
The rapidity of exponential decays (sorry for the science-geek language) is characterized by the time/rate constant or, equivalently, by the "half-life" which is easier to understand for most. In chemistry it standard to consider a chemical is "gone" after 5 half-lives (theoretically it never completely disappears, right?).
So in this case if we take the half-life to be 1 second, that means you lose 50% of your speed in the first second after diving in, and 50% of the remaining one second later. Thus, it takes 2 seconds to lose 75% of your initial speed.
But that assumes no kicking, so I'm thinking it takes a little longer for someone in real life, especially for a good kicker. (Actually in real life you never lose 75% of your speed...1.25 mph is a slow swimming speed...)
