Skiing takes its toll on knee and hip joints. If you were to watch a high level skier coming down the slopes, he/she is absorbing the bumps and deep snow by using their legs as if they were suspension coils, absorbing all impact while their upper torso remains virtually still.
The Jack Knife is a classic exercise that can replicate this movement:
Place your feet on a Stability Ball, and hands down on the floor as in a push up position. Steady your torso, brace your abs, and keep your head LEVEL with your body! Take 1 second and tuck your knees towards your chest but not all the way; just about past 90 degrees. Slowly return the legs to the starting position WITHOUT caving in the lower back.
Why this works:
By tucking in quickly with an unstable implement, you are inherently replicating the absorption of a quick bump and then releasing slowly to control your core stability. Add this to your ski conditioning routine and watch how you will be plowing through the snow!