This is the single best exercise for ski season prep and it is a bear!! I was given this as an exercise to do 4 times a week in PT after I hurt my knee. I started out doing 30 seconds in each position and attempting to accomplish 3 circuits. The exercise is called a VMO circuit as it focuses on the quads and specifically on the Vastus Medialis.
Initially I reccomend starting with 30 seconds in each position and working up to three sets where each position is held for 60 seconds. Once this is mastered, doing all the positions except for the linebacker squats on a slant board (heel higher than toes) will increase the intensity. I got to the point where I could do 4 sets on a slant board at 60 seconds in each position.
If you do this circuit 3 times, 3-4 times per week in conjunction with your regular tarining, you will be wonderfully prepared for ski season!!
Here is the link: http://www.box.net/public/rdn2e08t7s
If you have trouble understanding any of it PM me and I will try to explain.
Crank these hard from now until Dec 1, and you will be ready.
Enjoy!!