My wakeup heart rate was 56, and I felt fine. I ran for 60 minutes (3.2 miles) and enjoyed the cool but sunny weather. Our low last night was 24 (F), and it was about 35 when I went running. I'm alternating 80 seconds of running and 40 seconds of walking. My wakeup heart rate was very high yesterday – 68. I felt tired all day with no energy for doing much other than sleeping and eating.
I don't know why it was high yesterday. I've been sleeping pretty good, so I don't think that is the reason. I didn't check my temperature or blood pressure, but I didn't have a runny nose or sore throat or other obvious symptoms. What ever it was, it seems to be gone.
Later: I've been tired during my past two or three runs. Perhaps yesterday was just the climax of being tired. I should have given myself more rest last week when I realized I was tired during my runs. Yesterday, my body really shouted at me, "I need more rest", and thankfully, I listened to my body.