Aerobic fitness is good for base conditioning, however, skiing is essentially a power sport. As a very hypothetical example, if you took 15 runs of 2000 vertical feet each in a day, you might take a rest stop every minute or two. That could equate to say 30+ reps of 90s duration. I would think that would be a pretty solid day. So training for that kind exertion level, performance skiers are looking to enhance primarily their muscle endurance, strength, agility and power (which is a measure of force production divided by time). Obviously other fitness basics: balance, coordination, flexibility, aerobic endurance, etc. are important, but there is only so much time in a day. So, at some point, the skier has to focus more specifically on high intensity, low volume activity. After a summer of consolidating an endurance base, sprint work, helps develop the metabolic pathways used in maximal effort over short durations. I find hill sprints particularly are an excellent means of developing power and muscle endurance in the legs hips and lower back. Doing hill sprints, leg turnover is typically slower than sprints at a track, however, the force projection through the leg into the ground is higher. Because you have to extend the hip, the hamstrings come into play as do the glutes. Well developed hamstrings have been shown to reduce the risk of ACL separation as well.
Edited by georgert - 6/9/11 at 10:52pm