Why is cardio always the hot topic of fitness discussion and seems to be the fat burning solution? As we have all learned and have written in the past, cardio is no longer the ultimate solution when it comes to body composition changes. New times have arrived and we have tons of research studies showing that weight lifting is much better for fat loss and body composition changes. But, even though we have these new findings, people still don’t get it and people still want to sit on bikes reading Kim Kardashian divorce magazines for hours on end. Do what you want, but I know I’m one of those types of people who want to get the most for their money when it comes to training. This leads me to write about what is the right type of cardio for you. I will do a comparison between HIIT cardio Vs LISS cardio, since these two forms of cardio are the most used. By the end of this article, you’ll have a pretty good idea of what type of cardio is right for you and how to use it effectively.
What the heck do these crazy acronyms HIIT and LISS stand for? HIIT stands for High Intensity Interval Training, which consists of short sprint intervals along with low to 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 normalize your heart rate and then repeat. LISS stands for Low Intensity Steady State Cardio, which is purely low to moderate intensity work. An example of this would be walking on the treadmill or riding a bike and being able to carry on a conversation (we tend to see a lot of this in gyms). Now that you have a basic understanding of the two ways, let’s dive into some more detailed stuff.
Why testing lactate threshold (LT) and anaerobic threshold (AT) is a good idea? AT and LT are extremely powerful predictors of aerobic (cardio) exercise performance. There are 2 ways that muscle can burn glucose (blood sugar) and that is through aerobic work (with air) and anaerobic work (without air). For example, LISS cardio long spikes are considered aerobic work and weight training or HIIT cardio can be classified as anaerobic work. The AT and LT are an excellent test for HIIT and LIIS cardio because they provide a great predictor of what type of work produces ATP (adenosine triphosphate). ATP is a quick burst of energy we get into our muscles when we contract them (for example, every time you do a biceps curl, you get a quick burst of ATP). HIIT produces better changes in exercise capacity compared to LISS cardio. High intensity training will hit the AT and LT, that is what causes the body to make metabolic changes. When you are doing LISS, you are considered below AT and LT. A simple test is being able to hold a conversation while doing cardio. When you do HIIT, you’re above AT and LT, and when you’re above AT and LT, you’re looking for a greater improvement in metabolism, which leads to better fat loss over time.
How can you change your metabolism? (1) If you want to change your metabolism, you have to increase muscle mass and increase the oxidative capacity of your muscle. Your muscles have these energy-producing units called ‘mitochondria’ and this is where ATP is produced and fat is 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 actually increases the number of mitochondria you produce.
Studies show that greater fat loss is obtained through high intensity training due to increased oxidative capacity. Whereas with LISS you are only burning calories at that precise moment, there is no 24 hour energy expenditure (increased metabolism) and it hurts later because your body adapts and you end up needing more to lose fat. With HIIT you are burning calories right now, but you actually change the metabolism of the muscles and it increases your metabolism because you increase the mitochondria density of your muscle, thus increasing the oxidative capacity of the muscles and actually burning more calories. What most people don’t realize is that you have to put your body into an uncomfortable mode and use maximum energy output. It’s supposed to hurt when you’re doing HIIT and if it hurts, you’re in an uncomfortable mode and that means you’re doing it right.
The body is very adaptable. (2) We often see many people doing hours and hours a week of LISS and by the calculations they should be losing pounds, but they can’t lose anything because their metabolism adjusts to low intensity exercise. It’s just not enough because it’s just a calorie burn at the time, not a 24-hour energy expenditure.
If you LISS all the time, you are basically trading calories and calories and you can reduce these same calories through diet and still get the same effects. Example: You burn 200 calories in 30 minutes of LISS, you can cut 200 calories through carbs or fat and get the same effect instead of getting a 24 hour energy blast through HIIT cardio.
(3) A study by Wilson et al. From the University of Tampa, FL, shows that when you add LISS you get a temporary boost in weight loss. The subjects lost a couple of pounds the first week and after that they lost nothing. This happened because their metabolism completely adjusted to it and that became their new set point of what they had to do to sustain themselves. LISS on a low calorie diet is terrible for fat loss and could cause muscle loss.
During a low calorie diet, LISS cardio is more catabolic (loss of muscle mass) towards muscle compared to HIIT cardio, which is much more muscle sparing. The reason is that your metabolism adjusts so much to LISS and you constantly have to do more and more and people don’t understand when you’re on a low calorie diet it usually ends up being low carb so once you run out glycogen (carbohydrates stored in muscle), your body goes looking for energy to rely on and guess what it does? Protein! Once it goes after protein, you start to see catabolism (loss of muscle mass).
(4) In the same study by Wilson et al. It showed that LISS caused more muscle loss than HIIT. HIIT caused more muscle retention because when you’re doing LISS (for example, walking at a fast pace) you’re not activating the muscles in the same way as if you were lifting weights. So when you run, you have hip flexion, knee extension, and these are all weightlifting movements. HIIT is another way to overload the muscle. Just compare the body composition of a sprinter to a marathon runner, plus muscle mass!
So it’s really hard to argue with this study because HIIT activates hip and knee movements. Hip flexion and knee extension are the same movements when performing leg exercises. Also, by doing high intensity work you are activating muscle fibers and every time you activate muscle fibers you are primed for growth. Unfortunately, LISS cannot stimulate muscle fibers in the same way.
(5) In another study conducted by Naito et al. From Juntendo University in Japan, it was found that in rats, the enhancement of the satellite cell pool caused by resistance training is not influenced by the duration but by the intensity of the exercise.
So I know most of you are saying right that it was done in rats, but rats are very good models for protein synthesis (production of new proteins in muscle tissue) and metabolism because they have similar responses to amino acids and your metabolism. Also, for those who don’t know about satellite cells, it is necessary to increase the number of satellite cells in humans because it leads to the creation of new muscle fibers and the more muscle fibers you have, the more muscle growth will occur. So what’s interesting about this finding in this study is that when the rats performed HIIT, they received muscle stimulation, and that’s because HIIT overloads the muscle. When the rats performed LISS, there was no activation in the set of satellite cells. So, it shows that when it comes to cardio, intensity matters more than duration.
Now I know many of you have gotten the clue as to why HIIT cardio is more advantageous than LISS cardio for muscle retention and fat loss and it seems like I totally crushed LISS cardio. But note that this does not mean that LISS is useless. I am a big believer in doing HIIT and LISS combined. Here are the following reasons why:
– You can’t do HIIT 5-6 days a week because it will eventually negatively impact your weight training and interfere with growth.
– Many people have legitimate orthopedic, cardiac, and even psychological reasons to avoid HIIT, so LISS is your only option.
– HIIT could be dangerous if not used correctly and could lead to injury
– HIIT and LISS in a combined, cyclical or rotational way seems to be the best formula in my opinion
So sitting there and saying that HIIT is far superior to LISS for improving body composition is just as bad as saying that 6 reps per set is better than 20. I’m a firm believer that both HIIT and LISS cardio have unique benefits. themselves. I feel like both should be incorporated into your routines as each has specifically different effects. The bottom line is… Do whatever type of cardio you prefer. Whichever turns you on the most because you will most likely try harder. HIIT is faster, proves to be more effective for fat loss, creates metabolic changes, and helps with muscle retention, but not everyone can do HIIT. LISS is safer, but it takes twice as long to do similar things and still has its place for moderate amounts of fat loss, from a pure calorie burning standpoint (i.e. just burning calories and not make changes to your metabolism).
My intentions were not to favor one form of cardio and criticize the other, even if it sounded like that. My intent was to educate you and notify you that times have changed and science is showing some good things with HIIT cardio. But at the end of the day, it’s up to you which type of cardio is best for you. Hopefully after reading this article you should have a pretty good idea of what type of cardio is right for you and how to use it effectively. If you’re still confused… JUST DO IT! Peace!
