Originally Posted by Si
Maybe it's just me but I continue to see a major problem in using the term "rotary to talk about both forces applied to a ski and movements of joints. I've taken some of this from previous posts I made but I think it's directly relevant.
People here talk about the three things you can do to a ski: pressure, edging, and rotary. (While I think pressure and rotary are both ineffective terms and can be counterproductive I'll leave that for another time). From here I take a definition of rotary in terms of the force and/or torques one applies to the ski through the boot/binding interface. I try to differnetiate any other discussion of "rotary" as one dealing with body positions and movements (although many posts don't allow for this as they employ a vague concept of "rotary").
In theory it would be very simple to measure "rotary" torque applied to a ski by placing pressure sensors on the inside and outside of both the forefoot and the heel of the foot. (Alternatively we coul place the pressure sensors on each side of the binding toe and heel piece). If, for example, we measure an increased pressure on the outside of the forefoot and inside of the heel we know there is a net rotary torque being applied to the ski. Of course given this point of view perhaps it might be better to talk about "significant" rotary torque applied to a ski as it would probably be the rare case where there wasn't some slight differential in pressure gradient (as measured from some established neutral) on opposite sides between fore and aft of the foot.
If you want to talk about hip rotation (femur rotating within the hip socket) then I would suggest you need to invovle a complete description/analysis of the kinetic chain that gives the net effect in terms of action ON THE SKI. As I've said, you can have lot's of hip rotation without imparting any net rotary torque on the ski - just lift and tip your foot without rotating it to see a demonstration. I just don't see or understand the importance so many people seem to place on active and passive hip rotation or movevment around any particular joint. What's important from my point of view is what the net effect on the ski is. Typically, what I do at any joint is pretty much automatically accomplished based on my overall goal, i.e., tip the ski, rotate the ski, retract the ski, etc. Certainly in working on my skiing I may occasionally focus on specific movement about a single joint to try and improve or correct the kinetic chain, but in general it is not a point of focus as it rarely a single joint issue that needs to be addressed. I think one of the best things about PMTS is that it focuses on the most basic movement patterns (with appropriate cues for proper initiation and sequencing) without breaking things down in a conterproductive fashion.
I just haven't been around long enough and should keep my mouth shut, this topic is so heated and I certainly didn't help with my last post. As a race coach some of the things I read not just from the students but from the man himself just confuses the crap out of me and takes away from the what was apparently a very good idea- break high level skiing down for the recreational skier and into primary movements that are easy to understand and execute. Something got messed up along the way, or so it seems.
I'll stay out of this for now on, sorry if I offended anyone.