But, as to how this informs recreational PMTS skiing, I'm not sure -- in short turns, is it nearly always best to use sufficient retraction to minimize vertical CoM movement, or are there merely specific skiing situations in which this should be minimized, or is it purely a personal choice on the part of the skier (in determining the character of short turn he/she wishes to make), such that it does not matter how much the hips come up, so long as flex is used to release?
Perhaps it's accurate to say this about short turns: (1) Weaker retraction is perfectly correct; however, aggressive retraction (resulting in the hips coming up as little as possible) represents higher-performance skiing, and allows you to get on your new edges earlier. [With a sufficiently strong and well-timed retraction, it's even possible to get some float with minimal hip rise.] (2) In certain situations (bumps, powder, steeps), strong retraction, to minimize hip rise, is particularly called for. I'll be interested to hear what the PMTS experts have to say on this.
Supporting no. 2, I found this, which is an excerpt from a larger quote about GS, below:
h.harb wrote:In slalom, which is the technique most closely related to recreational skier needs, in most situations, like bumps, steeps and powder, deep bending and flexing is very important, if not compulsory.
In writing the above, I'm thinking of short turns. For longer turns, where there's more time, perhaps there's no longer as clear a relationship between how much your hips come up and performance level -- consider von Grunigen's weighted releases in GS. See also:
h.harb wrote:In GS you have more time between turns so you can afford to let the outside leg get less bend and not immediately absorb all the energy from the arc. If you absorb too quickly in GS, you will begin an arc or turn immediately, as that movement projects your CG into the next arc and on to the new set of edges.
GS skiers have more distance between arcs, so they time the transitions with the release. You will see in a given GS run both methods depending on the course set. You will see bending and flexing releases and you will see some up and over transitions, but still with a bending move, they just avoid the deep bend. In slalom, which is the technique most closely related to recreational skier needs, in most situations, like bumps, steeps and powder, deep bending and flexing is very important, if not compulsory....Quick bending and flexing are slalom skier movements. Some GS movements are still applicable for the recreational skiers, but less so.
I'll add I searched the forums extensively, and was able to find little specifically on the topic of minimizing vertical CoM motion-- just statements saying that, in PMTS, we want to move the CoM down the hill, not up from the snow. However, these statements weren't specific enough to say whether, if you flex to release, but your CoM still comes up, you might want to try to flex more. The closest I found to saying you want the absolute minimum vertical CoM movement is this from 2006, but I don't know if it's authoritative:
John Mason wrote: We do flex at transition in PMTS in such a way that looks natural and the CM is traveling the shortest path even in terms of vertical motion.
Also, to forestall any misunderstanding of my question: (1) I understand we adjust the movements to control the CoM, we don't adjust the CoM to control the movements. The movements are primary, the CoM is merely a reference for what the movements are doing. (2) I understand the most important thing is that there be retraction -- any amount of retraction. This question uses that as a starting point to ask, as a refinement, if it matters how much there is.