The first mile is always a good warmup, I expect it to be slower and I expect to build into the run and increase to a comfortable pace. Not today, the second mile my7 legs just turned to rubber and that was that. Results below

Overall
4 mile run
1 mile walk - cooldown
   avg hr: 173 bpm (max of 191 bpm)
   avg speed: 6.9 mph (max of 8.4 mph)

1st mile - 9:06 min
   avg hr: 157 (max of 172 bpm)
   avg speed: 6.6 mph

2nd mile - 8:00 min
   avg hr: 176 (max of 179 bpm)
   avg speed: 7.5 mph

3rd mile - 7:58 min
   avg hr: 183 (max of 184 bpm)
   avg speed: 7.5 mph

4th mile - 7:52 min
   avg hr: 188 (max of 190 bpm)
   avg speed: 7.6 mph

     After that second mile and my legs going out the door I knew it would just be a struggle to get through the run and complete it. It was very much a struggle, but also very much a success. To make it through that run in the condition my body was in was a huge success. The times were not terrible and HR was a bit lower than normal, but overall it was a still a decent run and still 4 miles. I do know though that in order to hit these long days in stride I really got to get hydrated the night before!