"Pretty good shape" is subjective - going from sedentary to 15 minutes of exercise a day is going to make you feel quite a bit better, but you wont be winning t

"Pretty good shape" is subjective - going from sedentary to 15 minutes of exercise a day is going to make you feel quite a bit better, but you wont be winning triathalons or anything. Also note the poster said 3 to 4 hours plus "a lot of walking and or running". I'm guessing this adds up to something like an hour a day of exercise, which is quite a bit. Much more than that and you'd need a proper plan to not injure yourself.