Just curious. I did a lot of doubles during the summer and leading up until now. I hit 85-100 miles a week most of the time but this week I changed it up. The last 2 days, I have run 2 hours straight through while monitoring HR and keeping it between 140-145 BPM. I have a HR monitor chest strap and but never used it until this week. I wanted to just double check that doing this is okay. Obviously, if I was hurting, I would stop but I felt really good running for 2 hours. The pace was really slow, like 9:40/mile. It's apparent I haven't been running easy effort, as running under 8:00/mile and sometimes even between 8&9/mile would put my average HR between 158-170.
If I'm not mistaken, I remember reading some of Hadd's Approach and it stating that you could pretty much run as much mileage as you wanted to if the HR was below 145 BPM. However, I also recall seeing a thread on here where he stated that running between 150-155 BPM on easy days would result in improved/faster pace and results could be seen around 4-6 weeks and longer. I believe it said something about this allowing the aerobic system to become more efficient and allowing the runner to increase mile pace but keep the same HR (150-155) while staying aerobic at a faster pace.
For reference here are my PRs in the last 18 months:
5K: 17:23
4 Mile: 22:46
13.1: 1:24:20
26.2: DNF @ Chicago in Sub-3 Attempt at 14mi mark
28 y/o, Male, 5'8, 149 lbs