I ran the 3 miles again, but I was tired during the last half of the run. I ran two miles using a 45:30 (seconds) ratio for running and walking. During the last mile, I switched to a 45:60 ratio and then to a 30:60 ratio. I was tired during the run, and I think there are two reasons for my being tired. First, when I went from 2.5 miles to 3 miles, that was a 20% increase, and that is a big increase for me. I knew I was making a big increase, but I thought I could do it since I was running that distance before my last surgery for a skin cancer. I guess I'm getting old, and I'm not in as good a condition as I was before my blood clots a year ago. The second reason is that yesterday was a 1-mile walk rather than a rest day, and I'm not used to consecutive days of activity.
My wakeup heart rate was 60, higher than it has been on previous days, and that likely contributed to my being tired.