10 Miles The NordicTrack Way

Today was my first long run day of my marathon training. For a change of scenery, I ran on my parent's treadmill instead of mine since it was to cold outside. These are my baseline stats:

Mile	Heart Rate	Pace	Incline
1	80	N/A	0
2	143	11:06	0
3	152	10:42	0
4	150	10:42	0
5	151	10:42	0
6	153	10:42	0
7	157	10:42	2
8	146	10:31	2
9	150	10:31	2
10	154	10:31	2
10.5	104	17:08	Cool Down

Overall it was a good run. I maintained a comfortable pace(one that I could talk through and take it easy on the ankle). Gatorade and GU after mile 5.
-- Something to think about-- I wonder if around mile 8 the GU kicked in due to the decrease in heart rate?