Week 4: You're not going to want to hear this, but it's time to get serious about cardio. For flatlanders, cardiovascular exercise is the best way to prepare for extreme changes in elevation. For those of us with a belly and bad knees, a bicycle is the answer. Spinning classes are great, but that requires a gym nearby. As much as I hate it, I actually run on a treadmill. Anything to get that heart rate up and lungs burning. Aim for two hard 30-minute sessions this week, but feel free to slow or stop as needed. The rest of the week walk and climb those stairs, though you can cut these sessions down to 30 minutes if you'd like.