Interestingly, many past studies comparing brief HIIT routines and longer, moderate workouts did not hew to formal exercise recommendations, because scientists wished to match the workouts’ frequency or other measures. So, volunteers in these studies typically worked out three times a week, whether completing a few minutes of HIIT or half an hour of brisk walking.
But the exercise guidelines for each type of activity differ. Medical and sports groups suggest we interval train no more than three times a week, to avoid overstraining muscles and cardiovascular systems, meaning if we exercise only with HIIT, we are inactive four days a week or so. Comparable guidelines for moderate exercise suggest getting out and moving at least five…
