my HIITs vary.
todays was with the treadmill starting at 2%incline walk @3.6 for 2min, slow it down to 2 and lunge for 1 min, bring it up to 6 at run for 2min
adjust incline to 5% and walk 2min, lunge 1min, run 2min
adjust incline to 8% and repeat walk, lunge, run
adjust to 10% and then 15%...