I've been a runner for a long time, but due to knee injuries from football, and then made worse by playing lots of tennis, I've had to move to an elliptical machine for my running now, and I do 12 miles per week, which is 4 miles a day, 3 days per week. I do weights also, but I've always considered the running as being what keeps me healthy the most, and what keeps me going the most.