Since I’m commuting on running shoes (a detailed lookback on this is coming…) I seem to be able to confirm a hunch I’ve been having for quite some time now.

My weekend long runs always start in the early hours (6-8 AM max) and it seemed my body always needed some waking up. It’s often that my heart rate/pace ratio only seem to normalize after about an hour of running. Often frustrating as it skews my training analysis, but I guess it’s part of the deal of doing long runs…

As I do the same run now often early in the morning and in the evening I can clearly see that my heart rate is a lot higher in the morning than it is in the evening.

Evening run may 08

Morning run May 08

You can see that the morning pace is slower and the heart rate always higher…

Evening run may 15

Morning run May 15

I don’t know whether this is due to ‘waking up’ or digesting (although I don’t always eat before my run) or hydration…
Googling the issue doesn’t really help much.
Most hits just babble about timing vs sleep etc.

http://running.about.com/od/motivation/f/Whats-The-Best-Time-Of-Day-To-Run.htm
http://womensrunninguk.co.uk/training/early-morning-evening-runs-best/
http://www.shape.com/blogs/ready-set-race/when-best-time-run

So I guess I’ll just have to live with it. Although nothing life threatening nor really important, it can be frustrating at times (especially when I get out the door just in time ;-))

Does anyone have the same experience? Or maybe just the opposite experience?
Can you explain it?