The release and transfer are arguably the most important parts of the turn - as they will set up all the elements for the next turn as well. The purpose of the release is to end the previous turn by basically releasing the edges from the previous turn, whether carving or not.
In general, the release movements start with softening the outside leg, to remove weight from the outside ski and continuing with the ankles and the feet, to flatten the skis, then knees and hips and so on moving into the new turn, but sometimes the "COM is released first" i.e. the relaxation of muscles will "release" the upper body before the skis.
At the most basic level, edge release starts in the ankle and progressively moves up the skiers kinetic chain. USSA GS Technique and Tactics
There are a few ways to release the skis, which can be combined with the subtle ankle movements above:
The extension is most frequently seen in recreational skiing while the others are typical for expert and high-performance skiing and racing.
The others are merely different tactical variations of the same release process, based on timing, intensity, what do we move/relax first etc. Some of the interesting variations, like the Weighted release have their own name and topics, since they have specific uses and practice is important.
There is a large spectrum of releasing, between extension, pushing, up and over and flexing, between pushing hard on the skis at the end of the turn to throw the body upwards, versus a complete flexing and retraction of the legs, to allow the body to "fall" downwards. Weight transfer could start late or early as well... so when characterizing a release, we will look for the dominant characteristic. Here is how the types of releases contrast or combine:
Another way to look at this is how the muscles are being used:
If we resist the forces of the turn with a longer outside leg, we use isometric and perhaps eccentric contractions.
From here, two options are available:
We can also look at the releases based on how many and which feet are involved. The PMTS system has a good way of cataloguing them:
One of the important elements of a release is to extract energy from the turn - this is related to floating.
Some perceive the flexed release as wasting the energy of the turn. That is though one of its advantages and why it is used in performance skiing and high-level racing. In high-performance skiing, we generate a lot of energy, as you see in the frames above: even with the strong absorption and the boots still came off the snow.
The energy generated in a turn is in direct relationship to the edge angles at the apex and carving. The energy is highest in a pure carved turn on the ice at maximum edge angles and lower in skidded turns at low edge angles (the skidding dissipates energy as the snow can't "push back") on soft snow.
Extension releases are generally used in low-energy turns, skidded and pivoted and/or without much edge angles, where little energy is generated in the turn and the skier ads to it with pushing "up" to be able to disengage the ski.
It is a high-level skill to extract as much energy from the turn, in the desired direction, as needed but not more! This is generally what we refer to as getting Impulse.
The Speed control with retraction releases is a high-level skill (we cover that at the black levels). Easy speed control is why an extension with skidding is often used on steeper slopes.
Let's look at the release concept itself first. This skier needs to end the one turn and transition to the next. When should this skier do what?
See When to relax to release for a detailed discussion, but briefly:
If the skier did nothing in b) and kept that outside leg long and strong, think about a stick: the bottom of the stick keeps falling away down the slope while the top of the stick is moving at 90 km/h (or less, at recreational speeds) down the hill. The top of the stick will basically vault over the entire stick, basically above, the body will vault and be sent up and over the long outside leg.
This will result in the skis eventually disconnecting from the snow as they're dragged over by the "vaulting" hips. That's not a release! The release is a controlled dis-engagement of the skis, which requires some flexion throughout several joints, to be able to decouple the feet from the hips and allow the skier to unweight and flatten the skis while the hips move where they're meant to go.
The COM release is sometimes seen in speed skiing. The basic idea is that the body is released before the skis, generally via relaxation of specific muscles. At the same time, the skis are rolled off the edge, but it may result in something resembling an A-frame around the transition.
Think about the skier above, again. If at b) he relaxed the core muscles but kept the leg engaged a bit longer, the upper body will start going over and down the hill before the ski was disengaged - you can see a small element of that in c) as the upper body seems to be already moving down the hill slightly ahead of the skis.
These are normal variations dictated by terrain, line and circumstances, to which the skier adapts to. Some are practiced during specific sessions or drils.
Related to up-unweighting, this is based on a push and/or an extension of the legs, especially the outside leg, which will tend to push the hips and body "up". This will afterwards take the weight off the skis and allow them to end the previous turn. Afterwards means when the pushing is completed, usually around skis flat.
This is very similar to the stick vaulting analogy above - instead of passively letting the hips be vaulted over a long outside leg, the skier even adds some to that process, by pushing the hips up!
It is an older technique, called "up-unweighting" and usually followed by a pivoting of the skis - while the skis are disconnected from the snow and any rotation efforts or momentums easily affect their rotation.
Typically, the skier, in this case, will flex the outside leg throughout the turn (giving into pressure) and then extend/hop at the end of the turn, to release the edges, hence the name "up-unweighting".
It is very common but less effective, as it usually leads to excessive up and down movements as well as a loss of control (while the hips are "flying" up and down, all you can do is wait for them to come down, to get the pressure back on the skis).