Training question: hrm or pace for IM specific run

Triathlon Forum
1

So I’m starting the build phase for my full IM and was wondering how to execute IM specific runs.

If I use my previous IM as guideline my hrm will be around 150 and pace 5:20/km.

Without the fatigue of the bike, ik run 4:20 with a hrm of 150. No way I can sustain that during the race.

So what’s better, use hrm or pace? Or just mix it up?
Btw, I run about 55 km a week, a long slow run and interval run are already part of the plan.

Thanks for the input.

2

My coach had me doing something like 137-145 HR in a pace range of 8:55-10:00. If got above 10 I was to shut things down and go to a recovery pace of 12:00 for the rest of the run.
Basically he wanted me going at an easier pace and to keep my HR down.
This was for all my long runs.