When leaning out I've always done 20mins cardio at 70-80% MHR immediately after weights on training days and 45minutes first thing in the am before food on off days.

I want to incorporate HIIT training for a while but I am concerned about possible muscle loss.

Will I be okay to switch to HIIT for half of my cardio (say 3 times per week)?

Will I need to avoid HIIT pwo or first thing in the am to avoid muscle loss?

Appreciate your input folks.