In the dark about pace

I went back to my 4:00 AM run routine this morning. It was the first time in almost two weeks that I did this early morning outdoor workout. The stage was set for a good run as I was coming off a non-running day. The air was relatively cool and I'd had a good night's sleep although I did feel a bit tired as I made my way outside. I knew once I hit the street I'd be fine.

When I started my run I felt some initial leg tightness but not too much pain. I was conscious of my speed and I tried to maintain a brisk pace. I was slightly more alert than I'd been in previous runs in the dark and I hoped that this, plus top-of-mind awareness of my speed and form, would land me below 9:00/mile. I was at the 20 minute mark when I turned onto the road that would lead me home and I decided to put even more energy into my pace. Based upon how I'd run I expected to finish with about an 8:50 overall pace. When I arrived home I checked my Garmin: 2.44 miles in 22:55. 9:24 per mile. Huh?

I don't get it. I did everything I could to maintain a good pace. I lifted my knees, kept my head up and concentrated on staying upright and practically sprinted the last half mile. I'll Gmap my run later today as a check against the accuracy of the Garmin but I know that it will match closely. There's either something about the dark or a flawed expectation that I can run efficiently at such an early hour. No matter, it was still a good run and a good workout and I enjoyed being back on the street at 4:00 AM.