Training for 8 min races

Thank you
Just one more clarification please
regarding zone 2, is it the best to use the heart rate based or maybe FTP based?
the pure zone 2 is derived from the lactate level (based on the podcast i copying below), ofc i do not have ways to assess this.
Any thoughts on this?
https://peterattiamd.com/inigosanmillan/

https://podcastnotes.org/the-drive-with-dr-peter-attia/201-inigo-san-millan-ph-d-pt-2-deep-dive-back-into-zone-2-the-drive-with-peter-attia/

Many thanks
Renata

55-75% of FTP if you have a power meter. Though I also find RPE is a very good gauge for z2 training, everybody who has spent time training for endurance sports has evolved a pretty good feel for that intensity which isn’t easy, but feels like it can be sustained indefinitely.

Thank you