Partly from spring fever, I've been getting up to the town walking track behind my house three times a week for the last three weeks.
My "natural" pace over that time is 20 minutes for one mile (four laps), never faster, as slow as 21 minutes.
Today I used jog.fm to grab a play list for a 17 minute pace and put it in my phone and dug through my drawers till I found my ear buds .
I clocked in over the mile at 16:50 seconds.
I.am.amazed. And I know from my heart rate and muscle feel I didn't just miscount how many laps I took! I know in theory that's how it's supposed to work, but it amazes me it was that dead nuts accurate and it was really the only variable that dropped me from 20 minutes on Monday to 17 minutes on Wednesday.