On Saturday, I really got into the hill intervals and did four laps on Sleeper up at Mary Jane. I was able to crank out 2,800' of gain in under an hour (between 9,000 and 10,500 elevation). However, at some point during the training I somehow pulled/strained my left knee. As a result, I've had to take it easy this week to let it recover. Cross-country skiing is perfect for this, as it is a slightly different motion so it doesn't aggravate the knee. I really enjoy cross-country skiing, as it lets you get out into the deep woods during winter. However, covering the same distance takes about twice as long, especially if there is any climbing involved (it is fairly close to a long slow run pace). For example, today I did 9 miles and it took me 2:19, while in the summer running the same loop takes just over an hour. Maybe if I keep working on it and get faster (and don't have a hurt knee) I may be able to go faster, but certainly not as fast as running.