Rebecca, Scott, thanks so much for your answers.
The main question I have after your responses pertains to the second last para of Scotts reply.
Specifically about the “extensive fasted AM session”.
by this are you saying that in an adapted athlete, the fasted ‘fat adaptation’ session of low HR work can/could/should go on for an extended period of time and be the main session of the day? If so, then yes, I can see why a high intensity session later in the day might not be optimal.
However,
If we are looking at someone who is relatively well adapted, but wants to keep on top of their aerobic capacity- 3x a week 30min-1hr runs at zone 1 (which should be pretty easy), and thus probably wouldn’t be classed as a “hard workout”- so a High intensity session later in the day (strength session, explosive hill session etc)- if correctly fuelled would be fine?
(as ever, I can already hear the answer being “it depends!”.