I'm a personal trainer and lift 4-5 days a week during the off season, with some running or cycling thrown in about 3-4 day a week. When I start skiing I can't keep up with the weights, my body needs time to recover. I will usually create a total body workout that hits chest, 1 leg exercises, and core. I do this 1-2 days a week on my days off from skiing. I still try to get in 3-4 days of running or cycling, I can usually combine them with ski days, since I usually ski earlier in the day. If I do anything more strenuous than walking my dog prior to skiing, it really effects my skiing.