I think we’ve found the editor for our next book. 29,000 copies sold and only now is it being truly appreciated and scrutinized. Actually, are you my editor? (Is that you, Rene?)
Seriously, these are great questions and add huge value to the Forums. I appreciate them!
What I meant there was executing the workouts at the top end of the range. There is a big difference between 4×8 minutes at low Zone 3 and 4×8 minutes at high Zone 3. So, if you find that you are executing all intervals at the high end of Zone 3, 4, and 5 then the only way to add volume is to add more duration (more workouts).
David