Shouldn't your HR be lower in the mornings?
I do most of my runs under 8 miles during the week in the late afternoon at 5-6pm. My paces at MAF HR are between 9:00-9:20 min/mi depending on the temps. But my long runs I do early Saturday mornings at 6-8am. The mornings are usually cooler than my afternoon runs obviously, but my HR always seems 6-10BPM higher than my afternoon runs. My paces at MAF HR are between 9:30-10:00 on my morning runs.
I consistently get 7-8hrs of sleep every night and I'm not stressed so I have no idea why my HR on morning runs is consistently higher than afternoon runs. I've tried not eating before the run, eating carbs before, eating protein before, eating a mix of both before the run but it doesn't seem to affect the HR one way or another.
A lot of times my HR will actually start going down after about an hour on a two hour run. This is so weird!
Could be a few things. If where you live is like where I live, the humidity is always about 90% in the morning, then it burns off as the morning goes. That can slow you at the same effort. Sometimes resting HR is higher in the morning due to dehydration. If you sleep through the night, you might not of had fluids for 8+ hours. Could be it.
Sometimes mine is high in the morning, and I recheck in the early afternoon and it is normal. I've rehydrated, eaten, and come alive.
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Hmmm good points. I do sleep through most nights, but I drink 16-24oz of water shortly after getting up. Dehydration does make sense though.
And I live in Florida, so our mornings are always 80-100% humidity. The afternoons are hotter, but usually much less humid.
So maybe its a combination of both working against me.
There might be some other reason, but I just it put it in the "is what it is" category and keep going.
Strangely enough, I am just the opposite. I get much better times in the morning at 5am then I do at 5pm. As the day goes on, I must get worn out.