@richf: I typically glance at the HR when running if I feel like "I am moving way too slow here and I still seem pressed". Normally the case is that I am simply unable to get into normal competition HR, which means that I am still not in shape.
I.e. I don't use the Garmin to steer my training but to get feedback on what my shape's like.
Triggered by this thread I just reviewed a sample of my 2019 spring races:
Jan 14 England - Night race, easy course - 153 bpm average hr
https://tmsw.no/qr/show_map.php?user=terjem&ma...Mar 21 Asker - Street O, snow&ice 167 (this was max effort!)
https://tmsw.no/qr/show_map.php?user=terjem&ma...May 12 Oslo KVM forest, very good race 158 (won class very clearly)
https://tmsw.no/qr/show_map.php?user=terjem&ma...June 10 Kongsberg, first run after illness, 158 (second place behind brother Knut)
https://tmsw.no/qr/show_map.php?user=terjem&ma...June 29 Larvik O-Festivalen Middle, 158 (won H60)
https://tmsw.no/qr/show_map.php?user=terjem&ma...June 30 Larvik O-Festivalen Long, 158 (another win)
This was unexpected and therefore interesting! It seems like my race HR have in fact dropped by about 10 BPM over the last 8 years, but my max rate is still well above 180, I'm just not able to sustain 170+ for long periods any more, except for that single hilly street O which was easy orienteering but heavy running on snow-covered paths and roads.
It also seems like my HR effort is pretty constant but as we get into the forest season I'm slowly improving my terrain running speed, i.e. better running economy. :-)