I switched to barefoot running (vibram 5-fingers) last year, and have been really happy with how it has built my leg strength much better than my old heal strike running style.

I started out this summer doing alot of running (about 25 miles a week), and walking with a pack one day a week. The beginning of this month I bumped up my walking w/pack to 8 miles twice a week, and biking (mountain or road) 20 miles, 3 days a week.