I typically have 1.5 hours available for a workout once a day. However I can only really manage around 45 minutes of effective high intensity intervals or lactate threshold training in one session.
Is there a benefit in filling the remaining time with base aerobic training? Or is it a better use of that time to do strength training, or simply rest?
If there is value in combining different levels of aerobic, threshold + anaerobic exercise in the same session, what's a good way to structure it to get the most benefit?