ShoeGoo wrote:

 

Today I ran an 8 mile run, it was a little above steady state for the most part, what I noticed, and this has happened several times before, is around mile 5, my heart rate drops a little and it seems easier to carry the same pace, sometimes the pace will even pick up a little. I thought earlier this year, it was just getting warmed up after the first mile or two or three, but now that it's hot out, I can really notice the change, and it's later in the run.

 

What's going on here?

Many many possible factors here (wheather, time of day, diet,...) . I would say most likely it's a psicological reaction to certain body signs. In my case, I used to experience a similar effect but reversed, from mile three to mile four it was difficult to keep the same pace, It was not that I could'nt but I would just struggle a bit. I used to think that this happened because there was a short slightly uphill part or because of the wind that usually hits frontally there, but I started changing course and the same happened.

In the end, I have learned that my body has some peaks and drops in performance, so I do not worry too much, some days it is really easy to keep a high pace and some others it is dnot. Even in the same run I can feel really tired in mile 3 and still finish 11-12 miles with a good time and feeling strong in the end.

IF this helps you sometimes I would start running faster after  even 45 minutes in really long runs. Of course I couldn't be still warming up that long could I? That happened to me here and there all the time when i used to be in good shape. It just means your engine is still getting fired up and that is a good sign. Just as you don't overtrain or run in direct July sunlight you will be fine dont worry about it.