I downloaded the HRV logger app and just did an ez endurance ride trying to nail in my level. Everything worked pretty well, results were completely unsurprising (using Garmin HRM dual).
One question I have is it seems a lot of folks here naturally want to push up against this barrier in their endurance ride. Is there any research or other reason to believe that doing your rides nudged up against lt1 results in better outcomes than giving it a wider birth and just staying below?