Find your perfect terrain spot - a hill which gets gradually steeper, or even a gradual downhill leading into an uphill, are ideal. Last week we used the first uphill on Burma, starting at the Fortune Lake lot, to get a run-in. Start your interval with zone 3 intensity, increasing to zone 4 intensity (around race-pace) as the terrain gets harder. Once you've hit the hard uphill, crank the intensity up to zone 5, meaning about as hard as you can go, and hold that intensity. A good duration for the zone 5 section can about a minute or a minute and a half, but you should judge by how you feel - once you can no longer keep your technique together, or you're going to keel over, make that your end point. Do this 4-6 times, or whatever you feel you can handle - don't bury yourself, you still want to be able to ski for the rest of the week!
This is a specific workout to do while getting ready for an important race or series of races. We do it once a week in weeks leading up to big competitions. The idea is to get yourself and your
body used to hurting, and the keeping going, all at a good speed. Don't do it too close to your race, though, we stop a week or two beforehand!
This workout can be done in dryland as well, especially if leading up to early-season races, but if it's as prep for a ski race try to do it with poles rather than just running. Focus on technique, and see if you can find terrain you want to work on for the race, or similar. This can give you an idea of how hard is, um, TOO hard. Above all, don't forget to do a good warm-down afterwards, preferably on easy trails, to get some lactates out of your legs. Finally, yes, it's painful, but don't hesitate to stop if you feel bad - after all, skiing is supposed to be fun, right?