The point where the hand starts to move backwards in the water is a pretty definite point in my view.
It will never be super accurate, but you get a reasonable idea where you are.
You can compare 2BK swimmers for starters, like the straight arm girl.
DPS is also a rough number to judge stroke quality from.
You can have hard slipping pulls with a lot of glide in between and smooth fluient non slipping strokes with less glide giving the same DPS.
The same problem with kickpropulsion exisst in DPS efficiency marker. Big propulsive kick gives high DPS, but do you want it that way?
In the end , the good coach sees in 3 strokes if its good or not, so its all extra numbers to check first impression.
Had a look at the straight arm girl again, and I took the starting point also too early. hand was still moving forward.
New picture 1 and slipfactor will follow.
Slipfactor increases to 0.72 ( plus 0.15) with new starting point. Still very good.
What i find remarkable, is that the TI swimmers start pushing water back at a shallower arm angle than the competetive swimmers.
The competetive swimmers have a slightly more patient catch than the TI swimmers! (depending on the definition of patient)
You know my explanation for this difference by now I guess? .-)
Its also clear that everybody is pushing water down.
The arm is under 45 degrees or shallower when the backward pushing starts, so a lot of water is pushed downwards.
The Sun Yangs have their forearm and hand almost vertical when they start pushing back, so thats a big advantage.
Better for balance, better for propulsion.
Last edited by Zenturtle : 09-20-2018 at 10:09 PM.