Originally Posted by Zenturtle
With objective measures I mean knowing how a certain swim stroke translates to a certain efficiency.
Even with the best footage its impossible to precisely say whats right or wrong.
TI assumes a certain style or streamlined position is best, but they cant proove it.
Neither can other swim schools.
So within certain limits we all are moving in an uncertain grey zone where the only tools are speed and relative effort to guide us to our personal optimal stroke.
An uncertainty about the spine bending for example:
The resultant arm force is acting outside the centerline, certainly if you pull on wide tracks.
This steers your vessel to the other side. making it move a bit from side to side.
Bending the spine a bit together with the pulling arm countersteers this effect, naking the upperbody move straight forward instead of slightly sideways.
This slight spine bending happens to also be the natural action to deliver maxinal force with the upperbody. We are talking details, but not beyond perception.
Nobody knows exactly what is optimal.
ZT, I think I agree with your comments above about objective measures.
Concerning wide tracks, it seems to me that looking at pictures of arm strokes in elite swimmers years ago, the S-shaped pull led to an arm stroke under the body. Of course, if the body is rotated enough, this pull is from the side in the water anyway, but I think if the body has a small enough rotation than the stroke is under the body and doesn't torque as much. My experience paddling a canoe is that at the end of each stroke you need to issue a correction for the torque, especially if you are the only person paddling. Anyway, if you finish your stroke with your elbow away from your body, your hand will be closer to your center line.