How is it possible to thrust hips forwards as you retract (flex the knee?) I'm just curious as I didn't think that both can happen at the same time?
That's a good one jthski. I never thought of my movements as simply as that, because it's what I do repeatedly and it works well, but to explain how it happens has had me thinking.
Here are 2 pics, the turn finish and then another pic towards in the middle of the high "C", top 1/3 of the turn.
My knees are obviously bent at the turn finish above, but it happened from compression. My knees were under extension tension(pushing my feet slightly forward) up until this point, I was actually driving my inside foot further forward into the turn finish, timed with the pole plant.
Immediately after the pole plant, I release the old turn by flexing my knees quickly which pulls my feet back, retraction. To counter the knee flexion needed for retraction, I thrust my hips forward and open them.
Simultaneously, I'm opening my ankle to gain shovel edge snow contact. This pressures my ski shovels down.
The pic above shows me floating (feet off ground / in control / weightless obviously) in transition as I hook up my shovel edges for the next turn.
Ok, I think it can easily be seen that my hips have opened and my ankles have opened since the turn finish, but my knees have also opened and I'm saying I'm flexing my knees at this point.
So what's up? How can my knees be under flexion tension yet they are opening? It must be possible, since I know that's what I'm doing, but the picture doesn't lie, hmmm...
The answer is similar to why my knees close at the turn finish even though I'm extending my knees (opening them) into the turn finish, there are other forces that need to be compensated for.
While I'm opening my hips, my thighs move towards vertical and my back straightens up, my knees naturally open to compensate, even though they under flexion tension to pull / keep my feet under my Chest COM which has moved back as my back straightens.
As best as I can describe, that's what's going on while I'm floating weightless straight down a mogul field. I'm not afraid though because I know I can hook up the next turn and control my speed without having to slam/ impact anything.
So thrusting the hips forward, flexing the knees and opening the ankles simultaneously is quite doable, but it may have to be done while weightless, I'm not sure. I'll have to think about that more, maybe the next time I toss a back scratcher, which come to think of it combines the same movements, just more exaggerated.