Back in 2011, I went through a phase in which I ran on the treadmill for 21 minutes several times a week. I would jog at 8-9 MPH for 2:15, then sprint all-out

Back in 2011, I went through a phase in which I ran on the treadmill for 21 minutes several times a week. I would jog at 8-9 MPH for 2:15, then sprint all-out for 45 seconds at 10.5 or 11 MPH. The only other exercises I did were some light-weight squats and a handful of oddball machine exercises. I was also on a paleo diet. After I had been doing this for a few months (not more than 4 months) a friend of mine invited me to take part in a half-marathon. Prior to the half marathon, I only went on two long runs with my friend (over ten miles). When the big day came I finished the race in 99 minutes -- which is a 7:30/mile pace for the entire race. I was 35 years old at the time. I was astounded at how well I performed given my training regimen -- I ended up near the top of my age class!