The gyms are closed and I've recently picked up running again; while I'm only really interested in 5k distances, I've started including a long slow run of 10k at the weekend. Heart rate zones are apparently the thing to watch for this, as you don't get the same aerobic benefits if you go too hard.
But I'm really struggling to keep my heart rate low on the long runs, regardless of pace - it just keeps gradually creeping up! Last week I did some testing for later comparison:
1mile at 7:03mM with a peak HR of 165 (max effort).
3k at 7:18 pace with a peak of 166 (max effort).
10k at 8:48 pace with a peak of 185 (regular run).
Here's today's 10k where I just left my Garmin on the zone screen and kept reducing my pace as the HR went up. It made little to no difference! For the last half mile or so I consciously tried to relax my chest and other muscles, which seemed to drop it 20bpm immediately - I don't know if that was the Garmin getting it wrong.
Is it normal for longer runs to have a slow relenting increase in heart rate regardless of exertion? I wasn't remotely tired or worn out.