I didn't quite make the summit of Mont Blanc but have some input. I cross trained, not specifically for one sport to help the other, but because I liked several sports - Rock climbing, mountaineering, bike racing and Badminton at International level, now recognised at the fastest sport in the world. The training was brutal, and I took great precaution against injury by warming up, stretching. After activity, warming down and more stretching. The one time I didn't adequately warm up, I injured my knee. Now 55 I keep up the stretching and bike hard and play Tournament Badminton without any problems. I figure that the range of motion, the different stresses all combined to create a solid system. One activity type can leave parts of the body weaker. If you want to stretch, do it very progressively. Stretching increases strength without increasing mass and gives more power over an extended range of motion. Here is a top level sport whose action may surprise many of you. View full screen.
http://www.youtube.com/watch?v=Knv0Mbcq ... re=related
If I do run, I go off road.
My general activity, whatever sport is: Warm up, stretch. When away from the mountains, a daily Bike 10 miles or a Hike, then stretch. For extra strength training, I've mainly worked on the ligaments as a torn one takes much longer to repair than a muscle.