As we have all learned and I have written about in the past that cardio is not the fix all solution when it comes to body compositional changes anymore. New times have rolled in and we have tons of research studies proving that weight lifting is far more superior for fat loss and body compositional changes. But, even though we have these new findings, people still don’t get it and people still want to sit on the bikes reading magazines about Kim Kardashian’s divorce for hours and hours.

HIIT stands for High intensity interval training, which consists of short sprint intervals coupled with low-moderate intensity work. An example of this would be a 30 second sprint followed by a 4 minute steady pace walk to cool down and bring your heart rate back to normal and then repeating it. LISS stands for Low intensity steady state cardio, which consists of purely low-moderate intensity work. An example of this would be walking on the treadmill or riding the bike and being able to hold a conversation.

 Lactate threshold (LT) and anaerobic threshold (AT)

Now that you have a basic understanding of the two forms, let’s dive into some more detailed stuff.

The AT and LT are extremely powerful predictors of performance in aerobic exercise (cardio). There are 2 ways that muscle can burn glucose (blood sugars) and that is through aerobic work (with air) and anaerobic work (without air). For example, long bouts of LISS cardio is considered aerobic work and weight training or HIIT cardio can be classified as anaerobic work. The AT and LT are a great test for HIIT and LIIS cardio because it gives a great predictor of which type of work produces ATP (Adenosine Triphosphate). ATP is a quick burst of energy that we get in our muscles when we contract them (Ex: every time you do a bicep curl, you are getting a quick burst of ATP). HIIT produces better changes in exercise capacity as opposed to LISS cardio. High intensity training will hit the AT and LT, that’s what causes the body to make metabolic changes. When you are doing LISS, you are considered below the AT and LT.

How can you change your metabolism?

(1) If you want to change your metabolism, you have to increase muscle mass and increase your muscle’s oxidative capacity. Your muscles have these energy producing units called ‘mitochondria’ and this is where ATP are made and fats are burned.

The more mitochondria you have and the more active they are the greater oxidative capacity you will have for fat loss. HIIT increases mitochondrial capacity and you actually increase the amount of mitochondria you produce.

(2)We tend to see a lot of people doing hours and hours a week of LISS and according to calculations they should be losing pounds, but they can’t lose anything because your metabolism adjusts to low intensity exercise. It just doesn’t cut it because it’s just a calorie burn at that time, not 24 hour energy expenditure. If you do LISS all the time, you’re basically trading calories in and calories out and you can cut these same calories through diet and still get the same effects.

(3) A study conducted by Wilson et al. From the University of Tampa, FL, shows when you add in LISS you get a temporary boost in weight loss. Subjects lost a couple of pounds the first week and after that they lost nothing. This happened because their metabolism completely adjusted to that and that became their new set point to what they had to do just to maintain. LISS with a low calorie diet is terrible for fat loss and could cause muscle loss. During a low calorie diet, LISS cardio is more catabolic (muscle wasting) towards muscle as opposed to HIIT cardio being much more muscle sparing.

The Bottom Line

Do the type of cardio that you have a personal preference for. Whichever one fires you up the most because you’ll most likely work harder at it. HIIT is quicker, proves to be more effective for fat loss, creates metabolic changes, and helps with muscle retention but not everybody can do HIIT. LISS is safer, but takes twice as long to accomplish similar things and it still has its place for fat loss in moderate amounts, from a pure calorie burning standpoint (meaning only to burn calories & not make changes to your metabolism).