Are you following a particular method or program? Or your own? I'm curious to learn more :)
Also amused by this from Wikipedia article on HIIT: 'Some researchers also note that HIIT requires "an extremely high level of subject motivation" and question whether the general population could safely or practically tolerate the extreme nature of the exercise regimen'.
I'm following a strength program which has Hiit in it, but I've found a progression on a body building website to build into it. It's not ideal, so if you find a nice progression I'd be interested to see it!
You're my training inspiration & source (not that I folliw through...)! So sadly...don't have a progression to offer :(
Hope things are settling down after your super busy last few months!