Dont know if its also called HIIT but,
on my cardio i do on the bike
1 minute, minimal resistance, 50 rpm (extremely slow)
1 minute, 350 watt resistance, ~110rpm(the increase)
and back the extremely slow
i do 10 increases
i just call it "interval" is this also called HIIT or is that sth else
btw i know trendmill intervals are considered better, but i have had achillis tendenitis from running on hard underground in the past, so i stick to bike. that and i fucking love bikes.