Fins and Kicks

[Marek K]

Listening to the Intro to Tech video they said regarding the backward kick that it utilizes the side of the fin as well as the top. What I noticed if you look there is a very slight angle to the fin, it has similar resistance in the water that a fan blade would have.

First... can someone pu-leeze confirm to me that the backward kick uses the "top" of the fins -- primarily -- to push against the water?

I think "using the side of the fin" as such is probably a misnomer... you mean that in the backward kick, the fins aren't perfectly vertical (almost impossible physiologically to keep them that way), and that therefore there's a... let's see... an upward force component on the feet? Which would explain why a lot of people -- me included -- find they tip head-downward after a couple of backward kicks. Right, TSandM?

I suspect that experienced backward-kickers unconsciously compensate for that through body angle...

But why wouldn't there be a corresponding downward force component to your feet when doing a (forward) frog kick? Your fins aren't perfectly bottom-to-bottom vertical there either... I think there is a downward component, but it's for some reason it's much easier to compensate for...

--Marek

 

[TSandM]

If you watch the 5thD-X videos, you see that AG's fins are almost completely horizontal during the back kick, and he really is using mostly the side of the fin, and just a little tiny bit of the top, for the propulsion.

My Fundies instructor says the tilt comes from not dorsiflexing the ankle enough (toes pointing a little bit up). Joe Talavera suggested on this board that allowing the head to drop during the back kick would create the "shrimp dance". I don't know the answer, because I haven't solved the problem yet.

 

[onfloat]

I find the motion for the back kick similar to kicking a Hacky Sack with your ankle when your trying to get it to come from behind you and over your shoulder and down your chest.

 

[Marek K]

If you watch the 5thD-X videos, you see that AG's fins are almost completely horizontal during the back kick, and he really is using mostly the side of the fin, and just a little tiny bit of the top, for the propulsion.

Yeah, that's what's so confusing about those videos.

Again, I may be wrong (and often am), but I don't think they'd be able to use the side of their fins for propulsion. Too little surface area there to do much practical good.

I agree though, that what may be happening is that the fins are more horizontal than vertical, because it's really tough to contort -- um, dorsiflex? -- ankles that way very far... but maybe there's enough vertical to give a reverse propulsion force component.

"Shrimp dance"... I like that...

--Marek

 

[Marek K]

I find the motion for the back kick similar to kicking a Hacky Sack with your ankle when your trying to get it to come from behind you and over your shoulder and down your chest.

Man, that doesn't help this non-hacky-sacker very much. Would you use, like the side of your ankle for that?

 

[onfloat]

Your ankle to your pinky toe.