it has been a long time since i had any cardio training, at least, 7 years or so, i thought walking would help appaerently not i could walk 8 or 9 miles no problem, i tried running 2 miles or so and i was beat after the first 1/4 mile all i know is i need to do it everyday at least 4 or 5 days a week, since im retraining, i dont want to pull anything.