Long, low intensity endurance sessions: When is Low too low? When is Long too long?

We know that successful, sustainable endurance training includes a lot of LIT- low-intensity training.  But, it is not very common to have athletes do 4hour training rides in the laboratory, so we do not have a lot of research on this vital component in endurance training.  In this video, I zoom in on LIT sessions and begin to lay out a process for individually determining what intensity and duration to use for these sessions.