Two days ago (7pm in the evening), I ran a recovery run and my heart rate averaged approx. 160-165. I just got a watch with a built in HR sensor so I don't have much of a baseline, but about a year ago I used a chest strap for about a week and remember my heart rate typically being around there.
Yesterday (7:30pm) I did an uptempo run with a friend. We did a 2 mile warm up at about 8 minute pace and a 35 minute tempo at about 6:10 pace, then 1 mi slow cool down. Heart rate during warm up was again around 160-165 for the majority. HR during tempo was the same.
Today (11am) I did a 3 mile recovery run and I tried to do some experimentation with my HR. The first two miles I ran at about 8:30 pace to try to keep my HR low. But it would not to below 160. The last mile I sped up the pace to see if my HR would move up. However this pickup dropped it to 155.
Some background: I've run 15:03 for 5k and am not in the best shape right now (3rd week back from a post season break) - however I'm not in bad shape right now either.
I'm very confused as to why my heart rate is the same running an 8 minute pace warm up and a 6:10 pace tempo, especially when the 6:10 pace definitely felt much harder and I was breathing significantly heavier. I also checked my Heart rate manually today to ensure that my sensor is accurate and it is.
If anyone has any insight it would be much appreciated as I have no idea what could be behind this.