WHICH CARDIO IS BEST FOR YOUR HEALTH, LISS OR HIIT?

 I have been diving into cardiovascular training again and wanted to go deeper in this blog compared to my last cardio blog, CARDIO FOR HEART HEALTH, NOT FAT LOSS.

There are many forms of cardio with LISS and HIIT being one of the most popular.

LISS stands for Low-Intensity Steady State cardio and HIIT stands for High-Intensity Interval Training.

There is a big difference between these two modalities, the biggest is the adaptation you get from them.

One obvious difference is in the name, one is low intensity and the other is high intensity. In this blog, I am going to explain both forms of cardio with their benefits, adaptations, and how to use them both.

ENERGY SYSTEMS

Before I go into the LISS and HIIT, I want to go over the energy systems that your body uses to produce energy.

Here they are:

1. Anaerobic Alactic System (ATP-PC)
2. Anaerobic Lactic System (Glycolytic)
3. Aerobic System

First is the ATP-PC energy system, also known as the anaerobic alactic system or the creatine phosphate system. This system is the fastest at producing energy (ATP), but only for about 10-15 seconds. This system relies on stored phosphocreatine and ATP in the muscle, so it runs out of supplies from the muscle very fast.

The alactic system is used primarily in your explosive, high-power type of movements such as a 1 RM lift, short sprints, jumps, and anything else that is quick and powerful in a short amount of time.

Next is the anaerobic lactic system, this system is slower than the alactic system at producing ATP but can produce it much longer. With the lactic system, you can produce ATP for up to a minute of work.

This system uses glycogen, stored glucose in the muscle, to produce ATP without the presence of oxygen, hence the name anaerobic lactic system. The byproduct is lactate, which acts as a buffer for the muscles from getting too acidic and fatigued.

This system is for longer bouts of power work like sprinting 200 meters, squatting heavy for 10 reps, anything thing that is greater than 15 seconds, and up to a minute of work.

Lastly, you have the Aerobic System, and this system requires the presence of oxygen to produce ATP. This is the slowest system in producing ATP but is the most efficient and longer lasting, up to hours of continuous work.

Here is the cool thing about the aerobic system, it helps recover the other systems, and if you build it up, can help them recover faster.

For example, the lactate produced from the lactic system can be reused in the presence of oxygen to turn glucose after some chemical changes. (I won’t get too sciencey with the details)

Before I go further, I want to point out that these systems are not used in isolation from each other. The last example with the lactate hopefully makes it clear that they work together. When you run 400 meters, some of the energy comes from each of the energy systems working together.

When it comes to your body, nothing is ever in isolation. Everything is connected and works together in some capacity.

So why does this matter? Why go over all this information about the energy system?

It is to help you understand the type of cardio you use has different energy systems. Training is very specific, and my goal is to help you realize the different energy systems being used and the adaptations to gain from HIIT and LISS.

LOW-INTENSITY STEADY-STATE CARDIO

What is low-intensity steady-state cardio (LISS)?

LISS cardio is when you train at 50%-70% of your max heart rate.

Training at this low intensity can improve your cardiac output. What this means is to make your heart more efficient at pumping blood out.

With LISS, you are dominantly training your aerobic system, which is one of the three energy systems your body uses that we discussed above.

Training your heart to be more efficient has many positive benefits to your health and well-being. When most people talk about cardio, they associate fat loss with it. When you are in a calorie deficit, this can be true.

Cardio is much more than for fat loss, and I will argue that fat loss should not be the goal with your cardio. The goal should be your health and performance.

Increasing your cardiac output will:

• Improve your cardiovascular function
• Deeper, more restful sleep
• Less stress and anxiety
• Mitochondrial health and function
• Faster recovery
• Increase insulin sensitivity
• Lower blood pressure and resting heart rate

As you can see, having a better aerobic system is very beneficial for your health.

Going to get a little into the physiology of the heart, but it’s to show you a physical difference between LISS and HIIT.

When you train your aerobic system, you are training your heart, to be more specific, the left ventricle of the heart. The left ventricle fills up with oxygenated blood before the heart pumps it out to the rest of your body. During your aerobic training, the body needs more oxygen so it can rid the body of carbon dioxide from the production of ATP. For the body to be more efficient with this demand, one of the adaptations is for the left ventricle to get bigger.

The larger ventricle means it can fill up with more oxygenated blood before it gets pushed out to the body. With each beat of the heart, more blood gets pushed out with less work. This increase in the left ventricle is called eccentric cardiac hypertrophy.

This physical adaptation is very different compared to the HIIT style of cardio.

HIGH-INTENSITY INTERVAL TRAINING

Now, what is high-intensity interval training also known as HIIT?

HIIT cardio is training with equal to or greater than 85% of your max heart rate, compared to LISS which is 50-70%.

HIIT-style cardio is going to come more from the lactic energy system and the primary adaption is to generate power from the lactic system and lactic capacity.

This means generating a high amount of power quickly in a short amount of time. The trade-off is fatigue, so you can train your body to produce this power repeatedly before fatigue sits in.

That is what I mean by lactic capacity, being able to repeat the same quality of work. Compared to the aerobic system, the lactic system can produce ATP much faster, which is why you can produce a greater amount of power.

As mentioned earlier in this article, the byproduct of the lactic energy system is lactate when no oxygen is present. The downside of HIIT is the rate of fatigue. You are going to burn out of fuel way faster with HIIT than with LISS.

Hopefully going over the energy systems helps explains why for you.

So, what are the benefits of HIIT?

• Greater lactic capacity
• Increase insulin sensitivity
• Less time to complete
• Lowers risk of metabolic disease
• Relieves stress (when done appropriately)
• Stronger heart
• Lower resting heart rate

As you can see, HIIT is also beneficial for your health, when done correctly. Unfortunately, most people who perform HIIT cardio abuse it, doing more than they should, more on this later.

First, I want to go over the physical adaptation of HIIT cardio. Recap from LISS, the left ventricle of the heart will have an eccentric cardiac hypertrophy adaptation.

When HIIT is the primary training method, the heart’s response is to grow thicker walls. When you train with high intensity, the heart rate gets high. The heart beats so fast, it cannot fill up the left ventricle, so you don’t see the expansion as you do with LISS. Instead, the blood is going in and out of the heart quickly and forcefully.

This greater amount of force from the heart will cause concentric cardiac hypertrophy. Very different compared to LISS. Training with HIIT cardio isn’t making your heart work less or more efficiently, you’re teaching it to push blood in and out quickly.

This is beneficial with your lifting and power-type movements, but if all you do is HIIT, then your heart will not be efficient when it needs to do work for longer periods of time.

CARDIO PROTOCOLS

With the background of the energy systems, and the adaptions of both HIIT and LISS cardio, hopefully, you know which to focus on.

So, the question you might be asking is, which one should I do?

That depends on your goals. If your goal is to be the best endurance runner, obviously focus on LISS. Same with being a sprinter or a powerlifter, if your goal is to be as strong, and explosive for your sport, focus on HIIT.

Now if your goal is to move better, feel better, and just be healthy, then do both.

Here is a LISS cardio for you to do, but first let me say that this is not the only way. This is just one protocol out of many to increase your aerobic system.

• Pick a cardio machine that you will enjoy the most.
• Pick a movie, tv show, podcast, audiobook
• Get moving and get your heart rate up to 120bpm-150bpm
• Stay there for a minimum of 30 minutes
• Inhale and exhale through the nose. When you feel the need to inhale through the mouth, the intensity is too high so lower it.
• If you want to mix it up, do 15 minutes on one piece of equipment and 15 minutes on another
• Do these 3 – 5 days a week (if you are strength training, do this on your recovery days)

HIIT Cardio Protocol: the same thing, this is just one way out of many you can do to increase your lactic capacity and lactic power output.

• Use an Assault bike or jump rope if no bike
• Start a timer for 30 seconds and go hard
• Rest for 120 seconds. If you are on the assault bike, do a very light cycle, otherwise, just walk around, and get your breathing under control. (Preferably through the nose during rest)
• Repeat 4-6 times
• Do these 1 to 2 days a week with a minimum of 72 hours between sessions for optimal recovery.

Unlike LISS cardio, HIIT cardio is not rejuvenating. In fact, it’s highly stressful on the body, which is why you see the recommended amount so low. When you do HIIT many times during the week, you are not giving the body enough time to recover from this high amount of stress.

Over time you might see some chronic pain in the joints, low quality of sleep, lack of progress with goals, and increase cravings, all signs of chronic stress.

I hope this helps you understand the difference between LISS and HIIT and their adaptations. If you want to learn more and dive deeper into cardio and conditioning, I suggest you go check out Joel Jamiesons work, he is where get most of my information regarding cardio.