Thanks to everyone for kind words on my brush with the flu lite. I really appreciate it.
Tonight I ran at the gym for first time since my sickness and since my long run last Saturday. I thus had 6 days of rest before this run. I decided to run slowly and not push the pace and dial back the intensity. My pace was around 9:00 minutes per mile on the treadmill, about a minute per mile slower than normal for me. It was a every odd run. My pace seemed soooooooo slllllooooowwww. I truly was jogging it seemed. And my heart rate was really low - like in the 120's. I ran 4.5 miles and called it a night. But it was a decent workout. Heart rate ended up averaging 72% of max. That is a perfect endurance workout as per some training plans. I stepped off and felt like it was a walk in park - even though my pace was only 1 minute or slower than normal. Definitely eye opening - the recovery from this run I think will be very easy. Indeed that is why the runs are supposed to be done at this HR and pace - the easy recovery and lessened injury risk. Before though,to get this heart rate in a workout I basically had to walk. And I could never train that way. But now I am in much better shape,so I can run at this rate. I will definitely have to consider this in my training.
It may also be the case that the layoff produced a lower heart rate. I'll have to see. But count me as a fan of the 75% heart rate workout. For what it's worth, Macmillan likes faster endurance runs, ones that average 80 to 83%.