The best aerobic training for mountaineering mimics what you'll do on the mountain: long, slow, uphill grinding. Good options include hiking, trail running, stair climbing, and, at the gym, the elliptical trainer, inclined treadmill, and step mill. However you get your cardio fix, here's how hard to push it for the aerobic workouts in our "Peak Fitness" training plan.
Recovery A very comfortable pace that won't make you feel tired or breathless (heart rate 65 percent of max)
Moderate You can sustain this intensity for well over an hour and talk in short phrases (HR 65–75 percent of max)
High Highest intensity you can sustain for 30 minutes (HR 75–85 percent of max)
Interval Hard enough that you won't be able to keep it up for more than one to two minutes (HR above 85 percent of max)
Ups and Downs
Backpack hill repeats help you quickly ramp up your cardio conditioning, lower body endurance, and core strength for intensive mountain hiking with a load. They're no replacement for putting in long hours hiking in the mountains, but for flatlanders and those on tight schedules, they can be a powerful supplement. (1) First, find a steep trail or stairs that will let you go nonstop for 2-3 minutes. (2) Wear a pack loaded with 30-40 pounds, and warm up. (3) Push your limits. Do each hill climb at your interval pace (see intensity guidelines above). (4) Take it easy on each downhill to recover. Your workout should last 30-40 minutes.