I'm in my early 70's and try to get out once or twice a month during the three seasons. I live in the desert Southwest at about 3200'. I will spend one to three weeks in the Sierra at least twice each summer. I also hike in the Grand Canyon in spring and fall and in the Arizona mountains in fall, winter and spring. Altitude gains of 2000 to 4000 feet are pretty much a normal part of my hiking.

My fitness regimen is fairly simple. I bike 3-4 times per week for at least an hour at a heart rate of about 65-75% of maximum. On the days I don't ride, I walk for at least an hour on the gentle hills around my home. I do a limited set of weight exercises four days a week: squats, lunges and toe raises. And, I have a set of body core exercises that I do four days per week. I work hard to keep my weight between 170 and 175 lb and try to eat a healthful diet.

In preparation for a trip to the Sierra, I will try to get in a couple of 5-6 mile, 3000' altitude gain hikes a week in the month ahead of my hike.

Even with my exercise routine, the first day or so at altitude is a bit wearying. I know this so I plan as easy a schedule as possible until I have a chance to acclimate.

In fact, the only exercise that will really get you in shape for carrying a pack at high altitudes is carrying a pack at high altitudes.