I differentiate between movements that merely release the g-forces of the turn--i.e. releasing the edges by flattening the skis, and steering the skis straight, akin to letting go of the steering wheel of a car and allowing it go straight--and vertical movements expressly intended to remove all pressure from the skis, possibly even lifting them off the snow. Only the latter fit the classic definition of true "unweighting."
ALL turns involve some sort of edge release from the previous turn or traverse. There is no centrifugal force during that moment of the transition from one turn to the next. But the full weight of the skier may still remain on the skis. Again, think of the car in a series of S curves. Centrifugal force throws the passengers from side to side, but the wheels never leave the ground in the transition.
True unweighting, as I define it, involves eliminating both the centrifugal force AND the pressure from the skier's weight--literally "unweighting" the skis. The simplest form involves jumping up in the air, but other forms include a quick retraction of the legs, going off a bump or jump, or rebounding with the help of the skis as they spring back like an archer's bow from the reverse-camber of a carved turn.
We do NOT need to unweight the skis--by my definition above--to go from one offensive gliding turn to another, any more than a car needs to get airborne between turns. (Indeed, like a car going over a frost heave just before a sharp curve, unweighting is a PROBLEM when trying to link precise direction changes!)
True unweighting is good for two things. 1) It can be fun! 2) It facilitates displacing the skis sideways, making it easier to get them into a defensive skid. On the steeps that Miles refers to, it helps us whenever we need to BRAKE. But it is counter-indicated, detrimental, and inefficient whenever we do NOT want to push the skis into a skid!
Modern slalom racers often take great pains to AVOID unweighting their skis between turns, absorbing the extreme rebound energy of their highly-bowed little skis with strong, perfectly timed retraction of their legs as they roll the skis off their edges and onto the new edges. This allows them to get the pressure needed to bend their skis and carve as early as possible in the new turn. But when they need to redirect their skis in the transition, they harness some of that rebound energy to unweight just enough to allow them to displace their skis as necessary.
To make a long story short, as others have stated above, expert skiers unweight whenever they WANT to (for fun), but otherwise only when, and only as much as, they NEED to accomplish the objective of any given turn.
But MOST skiers unweight a LOT in the steeps, in order to get their skis quickly from one aggressive braking skid to the next. Think of the hop turns that many so-called "extreme skiers" use to hack down the steeps. The very best glide....
(PS--I am NOT trying to open a debate about the "correct" definition of unweighting. No one needs to agree with my definition here, but you do need to recognize that it is what I mean when I use the term in this discussion.)[ March 16, 2003, 10:16 AM: Message edited by: Bob Barnes/Colorado ]