Hi Nolo: We see the abstem or stem-step occur in our upper level instructors caused by two typical movement patterns. These instructors are usually moving toward their level II and in rare cases level III Alpine certification.
What happens in the L-II candidates, especially if the have been skiing for a long time, is that they have an upper body rotary movement, which is frequently caused by a circular pole swing instead of a pole swing generated at the wrist. As the pole is moved forward the arm pulls the shoulder and torso with it causing the upper body to move in the same direction with it, which in turn causes the hip to square up and rotate in the direction of the upper body. This then causes the old outside leg and ski lose its edge and then the stem occurs.
Typically, this skier has been turning in this movement pattern for so long that he / she can't feel it at all. These skiers frequently tend to ski with a relatively narrow stance, which further adds to the need to open the stance just prior to starting the next turn. If the stance is too narrow the inside and outside legs/feet/skis will bind up and not allow the release into the new turn direction until there is adequate space for the skier to move the skis / feet. Until they actually see themselves in slow motion video they don't believe that they are doing it.
We have found that one correction for this problem is to start by opening the stance to a wider than normally functional width. Now the skis/feet/legs can move independently of each other and not bind up. We also have them learn to feel the release into the new turn from the feet up by moving the old outside ski into the turn first with an active retraction just as the old inside ski starts to extend. This then moves the CM toward the new turn
with a smoother flow.
Now back to the upper body rotaional correction. We have them do all of this without their poles at first so that they truly feel the activity from the feet upward not the torso downward. Next we add the poles. We have them carry their poles with a goal of just moving the pole from the wrist itself. We try to keep the arm movements completely quiet, almost static until they begin to release toward the new turn from the feet first. Now it's milage for practice and alot of time, so that they don't revert back to their old habits.
Now the high level skier or level III candidate may from time to time have a slight abstem occur, slight as it may be. In this skier we have found that usually it's not a downstem or stem-step, which occurs. These skiers usually are very aggressive and confident on any terrain in most conditions, therefore we find that they tend to move toward the new turn so quickly that the old outside ski is not released as fast as they tend to extend their old inside ski, which causes the old inside ski to get on an earlier edge then the old outside is released. This in turn causes the old outside ski to lag in timing its release, which then shows up as a stem.
The difference here is that the old outside ski is still on its original path from the prior turn. To correct this we have found that alot of work on short radius turns is done with strong empathis on developing a very active old outside now new inside ski movement into the new turn. Sometimes it has helped to have them literally fall ove the outside ski at the start of the new turn. We also have them actively release and point the old outside knee now becoming the new inside knee into the turn just as they're retracting it, kind of like a cyclist points his /her knee into a turn.
Frequently, linked hockey slides and brecauge practiced until they're completely at home with these maneuvers helps them with short turn development and improves the active inside leg, so both legs turn simultaneously not sequentially.
In any situation these are some of the hardest movement patterns to change. Without video it's almost impossible to convince this level skier that he / she is actually doing a stem in the first place.
Happy Trails *****