Hi PeterWi,
I would look a little higher level at the training intensity distribution – so a session with moderate to high intensity intervals included in the main set, that work in those upper zones falls in the 20% bucket overall. Sessions in the low intensity zones are your 80%. The rest periods and warm up and cool downs included in the moderate to high intensity workouts are there to facilitate the harder efforts and provide appropriate workout structure.
When it comes to moderate to high intensity efforts – a little goes a long way.
Leyla