Well, lucky for me, my job includes running up and down flights of stairs and walking all over the hospital for about 8 hours. Ill get as many as 5 miles in a day, its nice.
Between that, and walking to school, about 4 mile commute, I havent had to do any cardio at all.
All that walking around throughout the day has to have a positive effect on my insulin sensitivity. Not sure how good it is though for HGH and Testosterone levels...