Anyway my point is, if you're a good enough self coach to ensure you're doing
maximal efforts then I guess your intervals can be as long as you want and as long as your body allows you to without cardiac arrest
Other studies I've seen on intervals get it right, such as the study showing a 10 - 12 second all - out
maximal output
effort, followed by 2 - 4 mins of rest,
then repeat 3 - 4 more times.