Measuring HRV in standardized morning conditions is analogous to weighing oneself first thing in the morning under standard conditions to track personal changes.

“and the analogy is if I was going to weigh myself I'd want to weigh myself first time in the first in the morning in standard conditions I wouldn't want to have a meal and then go weigh myself I'd want to have very standard ways of measuring so I can see the changes because ultimately it's you changing against yourself that's the most informative”