HIIT VS LISS VS MISS

Cardio normally fits into 1 of 3 categories:

1) Low intensity steady state (LISS).
2) Moderate intensity steady state (MISS).
3) High intensity interval training (HIIT).

Three different training styles, almost always used for achieving the same outcome: getting fitter and burning extra calories. For the purpose of this article, I will emphasise the pros and cons of these training modalities in comparison to their fat loss and body composition benefits.

Just before we get into it, I want to stress the importance of remembering the outcome you want. Cardio is something people become too precious about. It is unproductive to panic about what time you should go for a run, or if your HRV is too low for cardio today. If you let variables like these influence your decision making around cardio then you are missing the point of what you are trying to do. The small details like these may be important to the very few elite athletes, who have all other variables under control. 

Low Intensity Steady State

First up we have LISS.

Often used by physique athletes, LISS is recognised for burning a high % of energy from fat. This is desirable for those with body recomposition goals, as the demands of activity don’t compromise muscle tissue. 

Additionally, because of the low intensity level, this puts less stress on the body – meaning lower recovery demands and it may even help lower cortisol levels (a major stress hormone).

While moving around and exercising is the recipe for good health, it’s important to remember that the human body is designed to move. Some perceptions of low intensity steady state cardio may be skewed since lots of things fall under this category but are not credible forms of cardio. You’ve probably heard of the term NEAT (non exercise activity thermogenesis) which counts for all of your physical activity that isn’t deliberate exercise. This includes a range of things from hitting 10,000 steps per day to tapping your hand on the desk. However, nothing in this category should count as cardio. The definition of LISS needs to be easy to interpret so that you don’t mislead yourself by not doing enough. So here is my definition. For something to qualify as LISS cardio it must meet the following criteria: 

1. No interruptions. For example walking the dog is not LISS since there are interruptions, changes of pace, stops etc. This intensity of training is low enough, we don’t need to give the body rest periods to regain energy. 
2. Must be intentionally programmed as a method of training. Something that you wouldn’t just be doing anyway. 
3. At least 30 minutes in duration 
4. Maintain a heart rate between 50-60% of maximum. This is commonly accepted as the ideal fat burning zone.

Be aware

When you do extended periods of LISS, studies have shown that this can lead to compensatory mechanisms that can actually detriment your fat loss goals. More cardio doesn’t always mean better as increased hunger and inevitable excess food intake will be a natural response to a higher calorie deficit. While hunger is a normal feeling when trying to lose body fat, it will not benefit you if your nutrition strategy is not well defined. In other words, have your nutrition foundations all set before thinking about doing more.

Pros

• Burn a higher % of fat per kcal used.
• Low recovery demand. 
• May lower cortisol. 
• Can be done by people of all abilities and is the most suitable for beginners. 
• Helps calm the nervous system into a parasympathetic state.

Cons

• More time consuming. 
• Easy to misinterpret. 

Medium Intensity Steady State

Next let’s take a look at MISS.

Moderate intensity steady state. This is perhaps the most common form of exercise for beginners trying to lose weight. 30 minutes on the treadmill at a sustainable pace is the most popular one I see. This is not wrong, and beginners with a weight loss goal will probably be able to burn more calories with this style of training.

This type of training is aerobic, meaning it requires oxygen. This gets the heart rate up higher and the lungs working faster, which will burn more calories than low intensity exercise. 

The concern many people have with moderate intensity training, like running, is the fear of burning muscle. While this isn’t the preferred energy source of the body, it may be possible in some circumstances, for example if the person is on a low calorie/low protein diet or they have a lot of muscle mass and low levels of body fat. In these situations the body may break down stored protein in tissues and use this for fuel. 

If choosing MISS as a method of cardio it may be a good idea to switch up your choice of exercise quite frequently, since the repetitive nature for long durations can become quite harsh on joints, especially running. I’d suggest alternating between running, cycling, & rowing. 

Important reminder

No form of exercise should be done at the expense of losing lean body mass. All forms of exercise are intended to improve our health in some way, and there is a strong correlation between a loss of lean body mass & rise in all cause mortality. The combination of low calorie intake, high exercise & recovery demands and consequently high cortisol levels means this could be a recipe for protein wasting if prescribed under the wrong circumstances.

I’d also suggest this may be undesirable for those who’s main interest is weight training and improving strength. We know there are 3 different types of muscle fibres in the body, type I, type IIA & type IIB fibres (slow-oxidative, fast-oxidative & fast-glycolytic respectively). Fast oxidative (type IIA) muscle fibres are adaptive and can inherit the characteristics of the more dominant muscle fibre. Of course, type IIB muscle fibres are more desirable for strength/physique athletes since they have a greater ability to grow and generate force. 

Pros

• A wide selection of exercises can be done.
• Burns calories.
• Low skill requirement.

Cons

• Risk of burning protein as a fuel if other nutrients are not available.
• Repetitive nature of weight bearing exercises may cause injury to joints over time.
• Adaptations to MISS are very specific to this style of training. It offers little crossover into other areas and is mainly good for those who want to improve at this style. It offers little additional benefits in comparison to the other 2 forms. 

High Intensity Interval Training

Lastly, let’s look at HIIT.

HIIT is characterised by short bursts of intense activity followed by a period of lower intensity on repetitive cycles. This is usually done at a ratio of 1:3 (work:recovery), however it can be modified to suit the athletic level of the person. 

This is the most relatable form of exercise to resistance training, since the muscles are asked to contract hard, fast & for shorter durations, making it a great way to retain lean body mass and preserve BMR (basal metabolic rate). 

While it possesses these benefits, plus the fact it allows us to burn more calories per unit of time, it is not best suited to most people, nor is it the best way of burning fat. 

This type of training is anaerobic, which means that it doesn’t require oxygen to burn fuel and therefore will not be burning much fat. In fact, at this level of intensity our bodies probably won’t be burning much stored energy at all as you won’t likely be able to maintain the effort for very long.

You also might mention the benefits of EPOC towards calories output (or the debt of oxygen this type of training creates) however scientific evidence shows that it might not be as much as what people once thought and more importantly, it might not be worth the recovery need this type of activity puts on the body.

However, there is an undeniable benefit to HIIT training – mental resilience. Without a shadow of doubt, this is the hardest method of cardio, and while this is the exact reason that most shouldn’t do it, it is a great way to train & match mental resilience to physical capabilities of those who are able to do it.

Pros

• Burns lots of calories per unit of time.
• Time efficient.
• Good for retaining muscle & preserving metabolic power.
• Causes higher increases in adrenaline, which can trigger the release of dopamine (a feel good neurotransmitter).
• Primes the body to be able to burn fat.

Cons

• Puts the body under greater recovery demand. 
• Causes larger elevations in cortisol.
• May be better suited to more advanced skill level.

My recommendations

With all of the information above I hope you can see how all 3 of these methods have their own merits and that each of them can be beneficial if used for the appropriate goal. 

If you are advanced and your recovery is excellent, try doing a hybrid of HIIT and LISS training to maximise fat loss. This would be a great method when trying to break through a plateau. 

Many people are under the misconception that they are burning fat during HIIT, however they don’t realise the true benefits that are actually happening: Heart rate has increased, lungs are working faster, blood flow is better, insulin is low, cortisol is high, adrenaline is high… THIS primes your body to mobilise fats! 

As a result of the high intensity, lactic acid would have built up in the body which may prevent you to keep training at this level of intensity for much longer. The solution: bring the intensity (and lactic acid) back down!

This is why I suggest following up with some low intensity cardio after your HIIT work since this removes lactic acid, shifts into a recovery state and burns fat as fuel.

Give this workout a go:

Order	Exercise	Duration	Rest	Sets
A1	Hill sprints/HIIT	10 seconds	30 seconds	10
B1	Cycle/LISS	30 minutes	–	1

If you have not plateaued, your recovery is not great, or you have just started training again, I would suggest MISS/LISS cardio. This will allow you to put the extra energy in the most important method of training for body-composition: resistance training. 

Give this rotation a go:

Order	Exercise	Duration	Rest	Sets
Monday	Running	30 minutes	–	1
Wednesday	Rowing	30 minutes	–	1
Friday	Cycling	30 minutes	–	1

Hopefully you have a clearer understanding of how each type of cardio training is different and what they are useful for. It doesn’t need to be so HIIT & MISS!