I can't remember which post made me think of posting this but it had something to do with using a smart sports watch to track one's heart rate during a run. I also can't remember the point of what follows; all I know is is I thought I should posti it but for whose benefit, if anyone's, and why, I've no idea. Right, I hope that's all unclear!
What I've been doing to gauge effort and, by approximate extension, observe/regulate my heart rate, is control and coordinate my breathing with my steps so that the number of breaths I take corresponds to effort but in conjunction with my strides. I do this with three specific breathing patterns (fwiw, each in and out breath takes place in harmony with my left foot striding on the ground):
easy - steady effort: In R L R, Out R L R / In R L R, Out R L R / In R L R, Out R L R / In R L R, Out R L R
steady - almost lactate effort: In R L R, Out R L R, In R Out R, In R Out R / In R L R, Out R L R, In R Out R, In R Out R
almost lactate - fast effort: In R Out R / In R Out R / In R Out R / In R Out R
The first breathing pattern tends to be used when I'm just easing myself into a run or when I'm just simply cruising along; the second comes into play when I pick up the pace till I'm almost at lactate threshold or when I'm running up a hill on an otherwise easy run; the third is employed when I'm hitting lactate threshold or faster. Obviously, the other variable not mentioned here is the depth of breath I take, but I'm sure you can imagine that that varies according to the given oxygen demands of my body at any given time during a run.
Like I say, I've no idea why I posted this, but there you go. That's how I breathe and observe/regulate my heart rate when I'm running.