Originally Posted by gramboh
Ankle weights aren't a good idea, they change the motor pattern of running and adding that level of resistance has almost zero benefit.
I would recommend you do basic novice strength training, with a routine focused on squatting and dead lifting, progressively adding weight to the bar while focusing on good safe form. I would also do some conditioning work 2-3 times a week, things like 400M repeats at a track, rowing intervals, high rep light weight dumbbell exercises. If you do it well you can keep your workouts to 6h a week over 4 days and get in great shape in terms of strength, endurance and flexibility.
This is good.
I would recommend building strength. Dead lifts, front squats, back squats, cleans, push press. But...you need to do them correctly and either in a group or at least with a partner. Avoid a routine.
If you can get on a concept II rowing machine, that can be part of a warm-up or post workout, or even a workout in itself say time a 2000m. You can rotate through, 500m row, cleans, push ups and say squats. Do maybe 4-6 reps. Do something totally different the next day.
Strong muscles will help your skiing. Many people will recommend core work which is important, but remember "core" is much more than sit-up (which you need to do). The leg work, and heavy lifts will all provide incredible core work. Treat legs and shoulders as core work.
"Change it up" - avoid a routine. Run 3k, 1k, 5x400m, Tabata (good stuff), sprints mixed in with the work-out.
Move through you work-out to increase intensity and make sure you feel the exhaustion when finished.
Minimum 4 times a week. Add your activities such as cycling, hiking, kayaking, ... things you like to do or would like to try.
Oh, and don't forget to go to work