When skiing powder or freeskiing off piste terrain it's important to realise, especially if you haven't had too much experience in this type of environment, that certain things you may do on piste natuarlly may not work so well here. Upper Body Management
A common problem for many skiers moving from piste to off-piste is upper body management and this is directly related to their shoulders. When you ski on piste and are trying to make dynamic turns you tend to stand with rounded shoulders. This usually aids a dynamic stance.
If your shoulders are rounded in powder or off-piste terrain you may find them putting you out of balance. (The main reason for this is that when you are freeskiing you tend to find yourself trying to absorb large pressure shocks from the ever-changing terrain.)