Cardio (short for «cardiovascular training») is a form of aerobic exercise (as opposed to anaerobic,) and includes both «steady - state» activities — think running, biking or
swimming at a steady
pace — and
high - intensity activity like HIIT training or Tabata workouts (which can ALSO be done while you're running, biking or
swimming, but also in other ways which I'll talk more in a bit...).