Originally Posted by justanotherskipro
It's time to call Physics Man and a Kinesiologist. IMO since we are talking about complex motion and rotation, planes seem more cumbersome than axis of rotation. After all we are talking about moving the vertical axis of rotation laterally to a point close to the inside hip socket and not through the CM. Additionally using inclination we tip the skis by moving the whole body around the long axis of the skis, not the CM. Same can be said about the fore/aft adjustments, the axis of rotation is in the ankle not the CM.
Maybe I am wrong, Tom can you help us?
I agree wiht you Jasper. PLanes are static, but it is impoortant to understand in what planes our movements takes place. Understanding this can help clear the confusion of how the body action taking place and a single joint's axis of rotation can be in a different place than the axis of rotation of the whole body.
Take the alpine tele turn versus waisteering. both seek to bring the body square to the direction (theoretical here). yet there is a difference in the body actions happening to do this and the movements are happening in different planes.
Pulling the inside foot back is an extension movement of the hip, that takes place in the sagital plane. The hip is being extended to draw back the leg and foot keeping the hips square to the direction of travel. While it does acomplish this, it does it with a movement in the opposite direction to the direction of travel. You could say it is a negative move to the direction of travel.
Waisteering on the other hand, uses the rotation of the inside hip (Bodes example) in the transverse plane. This does the same thing, brings the body back into square to the direction of travel, but it does so by moving the outer half in the same direction as the direction of travel. No negative effect to the direction of travel. Probably only really important in racing though.
So one could say that both are effective but one is more efficient to the direction of travel. because of this, one is better suited to exercise and the other to real skiing. So we can say that in skiing, when we want to move at the hip in the direction of travel, it needs to be rotation movements in the transverse plane, with respect to WS anyway.
This jibes with the graphic that Tommy put up. The confusing one, that I had such a hard time with. This helps me understand it finally. Maybe. The inside hip is rotating to draw the outside half forward, irrespective of the role of the abdominals in this and the alignment of the body.
Of course since I haven't experimented with WS on the snow it is just an observers oppinion. Later, RicB.