Many people use cardio as a tool to facilitate fat loss, ideally coupled with eating in a caloric deficit. The purpose of a cutting phase is to lose as much fat mass as possible while maintaining muscle. An improperly structured plan may see an individual lose weight on the scale, yet still result in an undesirable physique. Choosing the right cardio method and timing it properly will lead to more lean muscle retention (or even growth in some instances) and proportionately greater fat loss.
While some argue that calorie restriction is the better method for inducing fat loss, cardio still provides health benefits that cannot be replicated with dieting alone.
There are two main cardio types, HIIT and LISS. HIIT stands for high intensity interval training, while LISS stands for low intensity steady state. When looking at research you may even see something called MISS, which is moderate intensity steady state. This article will focus on HIIT and LISS, as they are the most commonly referenced cardio types when it comes to fat loss.
HIIT and LISS cardio each have their pros and cons outlined below. You can achieve fat loss with either one, but after reading you’ll discover which is more suited to your needs. In addition you’ll learn how to structure a routine to get the most out of your cardio without sacrificing lean body mass.
HIIT Cardio Benefits
High intensity interval training is a series of high intensity and low intensity stages of exercise performed consecutively. In some instances, the low intensity cycle is a period of rest, with no activity performed at all.
HIIT is not bound to a specific exercise; it can be done in a multitude of ways. It can be performed while running, in a sprint/jog or sprint/rest fashion. It can be done on a rower, bike, or airdyne in a similar manner. It can even be done in a circuit or “bootcamp” style format, utilizing things like battle ropes, kettlebell swings, burpees, etc.
Depending on the workout itself, some would consider CrossFit a form of HIIT training.
The key with HIIT is reaching a high level of intensity, approaching one’s maximum heart rate. Since the training session is so intense, it is time efficient. Depending on the structure of the workout, a HIIT session can be done in about 20 minutes. This level of efficiency makes it convenient for people who don’t have a lot of time to work out.
In addition, HIIT cardio provides far greater EPOC compared with LISS cardio. EPOC stands for excess post oxygen consumption, which is a measure of the metabolic boost you get after you’ve finished working out. With HIIT, this effect lasts for hours after training until about the 24 hour mark where it levels off.
EPOC is an important consideration when comparing HIIT and LISS. A 60 minute low intensity cardio session may produce greater calorie burn compared to a 20 minute high intensity interval training session within the workout itself. However, once the LISS session is complete the uptick in calorie burning is pretty much finished, whereas it continues long after a HIIT session is completed.
A concern among individuals adding cardio to their workout routine is muscle loss. After all, what good is implementing cardio if all you’re losing is muscle instead of fat? Since HIIT is so intense, it is more similar to resistance exercise than LISS is. As a result, HIIT is more favorable for muscle retention than LISS. In some instances you may even gain muscle utilizing a HIIT program.
From an athletic performance perspective, high intensity interval exercise is better for increasing VO2 max. VO2 max is considered one of, if not the best measurement of overall cardiovascular fitness. VO2 max measures the maximum level of oxygen uptake utilized during exercise.
Red blood cells carry oxygen to muscles while exercising. The more oxygen that can be utilized by an individual, the better their overall performance will be.
LISS Cardio Benefits
With all the advantages outlined for HIIT training, it may seem like LISS has no place at all. But this is not the case; LISS has numerous benefits when used properly.
Unlike high intensity interval training, low intensity steady state cardio is much easier to recover from. HIIT may leave you feeling sore or fatigued for the next few days, particularly if you haven’t done it for a long time. This would negatively impact workout performance in those subsequent days.
It’s unlikely that LISS would do the same. A 45 minute walk on the treadmill, even if your cardiovascular fitness is poor, shouldn’t negatively affect the next day’s workout. You could even argue that the increase in blood flow from that LISS session would act as a recovery tool and boost performance going forward.
It’s important to still train hard (resistance training that is) when in a cutting phase. If you’re dieting, resources are limited, so LISS may be the better option if you feel HIIT is taking away from weightlifting performance. Again, the idea is not just to drop weight on the scale, it’s to improve body composition.
LISS can be less mentally draining too. If there is a day where I plan on going to the track to run sprints, I get anxious beforehand. I almost have to psych myself up to do it.
That’s not the case when I’m doing a brisk walk for a few miles while listening to music. If you’re someone with a busy lifestyle, you could easily send emails and take calls while doing LISS. Try doing that while whipping around battle ropes though.
Low intensity cardio is particularly effective at the beginning stages of a fat loss phase. You can get a decent calorie burn from low intensity cardio, under the assumption that you weren’t doing cardio before this phase. However, the body will soon adapt, and that calorie burn will begin to slow.
This is part of the reason why people like HIIT. Since you’re going all out each time, the body can only adapt so much. Even as you get into better shape, you’re just able to push harder. The overall total calories burned never really drops. With LISS, eventually a walk on the treadmill just isn’t going to produce the same results.
LISS vs. MISS Cardio
LISS is often confused for MISS, or moderate intensity cardio. When we say low intensity in low intensity steady state, we mean it. Low intensity is considered 50-70% of your max heart rate, which is quite a low range when you do the math. Using a 30 year old male as an example:
220 – 30 = 190bpm max heart rate
190 x .50 = 95bpm
190 x .70 = 133bpm
Low intensity cardio would be considered between 95-133bpm for a healthy 30 year old male.
If you’ve ever tracked your heart rate you know that it doesn’t take much to get to 133bpm.
When people think of LISS, they think of something like a light jog. But in reality a light jog would probably take you around 140-160bpm depending on your level of fitness. This would constitute MISS cardio rather than LISS. Low intensity cardio is more like an incline walk on a treadmill or a very light pace on a stairmaster.
The reason MISS cardio is undesirable is because it leaves you in no man’s land. The combination of moderate intensity plus the long duration creates an atmosphere that is not conducive to muscle retention.
LISS cardio works because the intensity is so low that muscle loss isn’t a huge factor. HIIT cardio works because it is so intense that it is similar to a regular weightlifting workout, and engages fast twitch muscle fibers. MISS cardio is this unusual in-between scenario that takes the worst of both. The intensity is just enough to where muscle loss can be a factor, coupled with its long time duration.
If you love MISS cardio, this information shouldn’t necessarily deter you from it. Just understand that it isn’t the optimal form of cardio for fat loss and muscle retention. On occasion I will ride my bike outdoors for 2-3 hours. I do it because I like it, even if it isn’t the best thing for body composition.
| Cardio Type | Intensity (as % of Max Heart Rate) | Examples |
| LISS | 50-70% | Walking on an incline |
| MISS | 70-80% | Jogging, Biking |
| HIIT | 80%+ | Sprinting, Circuit Training |
When to perform cardio
Most people do their cardio immediately after a training session, typically for convenience. This is not an ideal circumstance due to cardio’s effect on muscle, particularly long duration cardio.
Cardio can “block” the muscle building effects of a resistance training workout. In simple terms, cardio basically sends a signal via an enzyme called ampk telling the body to break down nutrients because energy is needed. This makes sense since cardio burns calories at a high rate, creating an increased demand for energy.
Resistance training, on the other hand, releases a protein called mtor, telling the body to build new muscle. When you combine resistance training with cardio, it creates what some people refer to as the interference effect. The body simply can’t move in two different directions. It cannot optimally build and break down at the same time.
As a result, the best practice is to space out cardio and resistance training as much as possible. In a perfect world, each one would be performed in isolation on its own day. But for some people this isn’t an option. If you must do both on the same day, the best approach would be to do cardio first thing in the morning and resistance training at night.
How to implement cardio
Cardio is a tool for fat loss just like dieting, supplements, and resistance training. The key with any tool is to use it strategically. If you implement a strict diet plus 5 days of cardio from the beginning, what happens when you plateau? It will certainly work for a while, but you’ve already used all your tools from the get go.
You always want a tool in your back pocket that can be used when needed.
As we mentioned earlier, LISS cardio is particularly beneficial in the beginning stages of a fat loss phase. 2 LISS sessions per week should be easy to implement without sacrificing any weightlifting training. As the LISS cardio becomes less effective, you can either add more LISS sessions or convert them into HIIT sessions (or a combination of the two).
There is no magical blueprint for exactly how much cardio to do, as each person will respond differently. You may be able to do LISS cardio the entire time and reach very low levels of body fat. But the key principle to remember is to maximize the effects of the routine before changing it. You never want to make arbitrary changes for no reason. If something is working, keep doing it.
The fat burning zone myth
The worst thing to ever be placed on gym cardio equipment is the chart breaking down exercise intensity and fat burning. This has confused many on the ideal method of cardio to lose weight.
While it is true that fat will be the main fuel source used during LISS and carbs will be the main fuel source used during HIIT, it is the overall calories burned that is most important.
Naturally, the calories burned doing 10 minutes of low intensity cardio will be much less than 10 minutes of high intensity cardio. So even if those calories come from fat, the overall number is so low that it’s irrelevant.
In addition, the fuel substrate you burn during exercise will be different than the substrate burned for the rest of the day. This is because the body always wants to achieve a state of equilibrium, or balance.
Let’s say you performed a high intensity interval training session. The substrate used for that workout would mainly be carbohydrates, as it is the ideal fuel for that type of workout. For the rest of the day the body would switch to burning a higher proportion of fat for fuel in order to balance the carbohydrates used during exercise. And if you recall, the HIIT session would increase calorie burning for the entire day because of its effect on EPOC.
The point is that no matter whether it’s carbs or fats being used during the workout, it always evens out for the rest of the day. Just aim for as many total calories burned as possible.
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