[Scott Johnston]

Matthew: Nose breathing is definitely NOT required for Z2 running.  For many people, nose breathing is hard to pull off due to restrictions. While ‘ventilation’ is a great indicator of AeT it is best done in a lab using a gas exchange test.

dbroman: When you get over 2 hours you will likely see a more significant HR drift due to dehydration and an increase in core temp.  So, I would not be too concerned over those drift numbers.

I hope this helps,

Scott