Question: is hiit aerobic or anaerobic?
Answer: Steady-state cardio is aerobic: It requires oxygen and is fueled mostly by stored fat. HIIT, by contrast, is anaerobic: The work intervals don't rely exclusively on oxygen, and are fueled mostly by stored carbohydrates. (Counterintuitively, HIIT makes you breathe harder, and burns more fat, than steady-state cardio.