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.
Parents
Former Member
The velocity curves I am referring to were with a pull buoy strapped on my ankles to take the leg propulsion out of the picture and isolate the pulling force.
The peak velocity and trough velocity are repeatable occurring each time in the same place with each arm. The power is definitely not coming from the back end as the hand is actually moving forward again (trying to get back to the front asap).
Few realize the imposing drag forces that apply as we change our arm position from overhead in front to angled down, peaking when the arm is perpendicular to the body line. The bullet analogy should tell you how significant drag forces are...and a bullet is relatively streamlined.
What complicates the analysis of power vs velocity is that most objects don't change shape while moving through a medium. The human body swimming does. It goes from relatively streamlined to very unstreamlined (a brick) and back to relatively streamlined in a matter of a half second or so. The drag is so imposing in this process that even our powerful arm pulling up front do not keep us from decelerating.
The most compelling argument for accepting that the power is in the front is that we spend half of our stroke cycle time in that position. The other half is spent recycling our arm to get back to that position again. Unfortunately the route back creates huge drag issues.
Finally, the race dive involves going from air to water, just like the bullet. At the interface, a third drag is introduced that doesn't exist on the underwater pushoff, called surface or wave drag. It ,too, is significant...especially if you pancake into the water.
Gary Sr.
The velocity curves I am referring to were with a pull buoy strapped on my ankles to take the leg propulsion out of the picture and isolate the pulling force.
The peak velocity and trough velocity are repeatable occurring each time in the same place with each arm. The power is definitely not coming from the back end as the hand is actually moving forward again (trying to get back to the front asap).
Few realize the imposing drag forces that apply as we change our arm position from overhead in front to angled down, peaking when the arm is perpendicular to the body line. The bullet analogy should tell you how significant drag forces are...and a bullet is relatively streamlined.
What complicates the analysis of power vs velocity is that most objects don't change shape while moving through a medium. The human body swimming does. It goes from relatively streamlined to very unstreamlined (a brick) and back to relatively streamlined in a matter of a half second or so. The drag is so imposing in this process that even our powerful arm pulling up front do not keep us from decelerating.
The most compelling argument for accepting that the power is in the front is that we spend half of our stroke cycle time in that position. The other half is spent recycling our arm to get back to that position again. Unfortunately the route back creates huge drag issues.
Finally, the race dive involves going from air to water, just like the bullet. At the interface, a third drag is introduced that doesn't exist on the underwater pushoff, called surface or wave drag. It ,too, is significant...especially if you pancake into the water.
Gary Sr.
