Hey /fit/,I'm new to cardio, (I've always been a lifter and I've never been fat/really skinny) and I usually only run for about 30 min on my treadmill at about 3 incline and 6.5-7 mph.What exactly is HIIT? I know so far that it is just running at your max, or sprinting for a short time. I've been active for quite a while and I have NEVER heard that something like hiit is good for you, other than the occasional sprints that keep your metabolism flying.How long does one 'hiit'? I've heard reports of 3 minutes to 40 minutes...most people have 40 minute cardio workouts anyway...