Something strange...

So the other day I was skiing along on one of those straight, flat trails so I was naturally a little bit bored. So I decided to see how high I could jump. I pushed off the ground pretty hard and... got like 2 inches of air. I was pretty disappointed in myself so I tried again. This time a squatted down and pushed off the ground with as much force as my skinny legs could muster and... 2.5 inches. Whats wrong with me? So I stopped and tried to jump vertically while not moving and I got much higher (although it was still pretty embargoing). I stood there for a minute and tried to figure out what was going on. Why can I jump higher while standing still than while moving? Eventually I hypothesized that while standing still the vector of the downward force created to make the jump is directed normal to the ground, maximizing the reaction from the ground; however if you try to jump while sliding across the snow on your skis some of the force is applied parallel to the ground due to your forward motion, in effect creating the same magnitude of the resultant force vector but at an angle which trades some vertical height for horizontal distance. Or maybe I'm just really bad at jumping...