The 245 made MHR, HRR and LTHR zones simple to configure and view. The 255M is a giant step backward. I set default to HRR with no other sports and the watch keeps computing zones based on MHR which is ridiculously too low. When setting up a Running Sport, I default to HRR but unfortunately get MHR zones after the run. Why on the 255M is it impossible to set a simple HRR default, view the calculated zones, and not keep defaulting to MHR?
Update - Spoke with customer support and they mentioned this is a software bug that will be addressed in the next software release. Customer support was fantastic.