Ran 3x1600 meters today with a 400 meter jog between intervals. I forgot my watch (of course you forget it when you need it), but my body clock told me that I was running in the neighborhood of a 5:15 mile. Although the workout did not last a particularly long time, it sucked all the strength out of me by the last 800 meters. I believe this occurs because of the rest time (slow jog between intervals). My heart rate slows down and body becomes more relaxed, so when I take off again, my body needs to work hard to get back up to high "rpm's". I ran a one mile warm up and a one mile cool down. | 