If you normally live at sea level and travel to the mountains, remember that the air there is thinner. Each lungfull of air contains less oxygen, and it's oxygen you burn as you exercise. Consequently, you may find it's hard to get through your normal exercises, especially the running and jumping part. Don't push, just drop back a couple of rungs. If you spend an extended period of time at high altitude, you'll probably advance back to your original rung as your body adapts.
Regular exercise greatly reduces the effects of altitude. As you exercise, you increase the capacity of your heart to pump blood and your lungs to replenish the oxygen it carries. That's just what you need in the mountains, so don't be surprised how little you puff and wheeze on your first ski trip after a few months of regular exercise.