4 Miles at MGP

I’m 3 and a ½ weeks out from the Chicago marathon, and we have now switched our track workouts to dialing-in our marathon goal pace. On today’s agenda was a 1.75 mile warm-up, 1.75 mile cool down, and 4 miles at MGP on the track so we could get accurate time splits and work on figuring out our pace.
My goal is to run 7min 24 second miles, which translates to 1min 51 seconds for a 400meter lap.
Here’s how I did:

1.47
1.52
1.46
1.49
1.47
1.49
1.48
1.49
1.48
1.49
1.47
1.50
1.47
1.48
1.46
1.50

I just could not nail 1.51’s and was between 2 and 4 seconds too fast. It doesn’t sound like much to be off by 4 seconds, but it’s not a good thing for the long term. 4 seconds is 16 seconds on a mile, which is a 7:08 mile, which translates to a 3 hour 6 min marathon. 2 seconds fast on a 400 is a 3hr 10 min marathon. The seconds add up, so even though I felt ok, running 4 miles like that, it may take its toll when I reach mile 20. Then again, I’ve been feeling really strong the last couple of months, so maybe it won’t kill me. We’ll just have to wait and see.