I am just going to echo the previous responses with my own personal program. I can't remember the last that I actually went to a gym; I just do not enjoy the experience. Instead I stay active all year round; snowshoeing in the winter and running, trail running, biking and hiking the rest of the year.

I would say that I average 10-13mile day hikes each Saturday or Sunday and then I complete two to four 5-8 mile hikes during the week after work. Just this Saturday I did a 10mile RT summit of Bergen Peak which has elevation gains of just under 2,000ft (14% grades). Tonight I have just got done with a 4.5 mile loop at Apex Park. I will probably hit the trail again Wednesday.

Combine a similar routine with cycling, running and even walking the dog for 2-3 miles each day and you will soon get your trail legs. Building muscle in a gym is not always necessary-- there is no substitute for the real thing.

When I did the CT I was averaging 10-12 miles per day and this didn't appear to be a stretch. Half the battle is learning to be more efficient with your time and your energy.