HIIT or LISS – Which Should I Be Doing?

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A constant question I get asked and a topic I spent a lot of time investigating myself (as it’s not Hit or Miss) is HIIT or LISS which form of cardio is better and which one should I be doing HIIT or LISS?

While both HIIT and LISS will improve your aerobic endurance and help with fat loss. HIIT will also enhance your anaerobic performance, speed up aerobic and fat loss results and also has a calorie afterburn effect (EPOC) which makes it a popular choice but, these benefits can come at a cost. 

As HIIT is high intensity, it requires more energy, it is more taxing on the body and muscles and requires more recovery time. 

Deciding which form is best for you will depend on your goals, your current training program/plan, time, and which of the two you prefer to do and can stay consistent with!

In this post, I will look at the different factors you should consider when choosing the right form of cardio for you.

Infographic for the blog post "HIIT or LISS" showing a matrix of for's and against's for both

HIIT and LISS the good the bad and the ugly?

High-intensity interval training (HIIT) has been becoming more and more popular over the last few years and for good reasons. 

  • HIIT enables you to improve aerobic and anaerobic performance which will allow you to tolerate high levels of intensity longer (your fitness lever will increase dramatically). As HIIT improves athletic performance, it is a great training protocol for athletes. 
  • HIIT has a calorie afterburn effect or EPOC – post-exercise oxygen consumption which means your body will still be burning calories after your workout has finished.
  • HIIT enables you to get more done in a shorter amount of time – HIIT is time effective a 20 minute HIIT session can burn as many calories as a 40-60 minute LISS session 

With all that being said you may at this point be sold on HIIT and think that it is a no brainer, I mean why wouldn’t you want all of the above benefits but nothing comes easy 

  • HIIT is far more challenging than LISS, you have to work harder, more intensely, and with less rest time then you are used too. While the benefits may seem appealing, it is not for everyone, and many people don’t enjoy it.
  • The risk-reward factor comes into play with HIIT, especially with beginners. If you are starting into health and fitness, jumping straight into the world of HIIT might be too much too soon. Higher intensity also increases the risk of injury, especially if you are using it in conjunction with other high-intensity styles of training.
  • HIIT requires more recovery time – many people use HIIT in combination with weight training which can be an extremely effective combination when done right. Still, due to HIITS high-intensity nature, your muscles and body require a longer time to recover which can have a negative effect on your main training sessions and can leave you vulnerable to injury or burnout if you are not allowing yourself enough time to recover.

Low-intensity steady-state cardio (LISS) as the name implies the aim of LISS is to increase your heart rate to around 50-70% of its max and maintain that state over a more extended period. 

  • The premise is when you work out less intensively; your body will use more of the stored fat cells as energy which is also why lower intensity training is referred to as the “fat-burning zone”. This does not mean you will burn more fat in total it just means that a greater number of calories burned will be taken from your fat stores.
  • Because LISS is low intensity, you can train more for longer. If you are training, outdoors you can take in your surroundings as you train as it is a more relaxing way to train. 
  • LISS is far easier to recover from meaning it has less of an effect on any other workouts you may be doing and also means you can do it more often with less fatigue. LISS is an excellent option for beginners and people who need to take a slow and steady approach to train.
  • LISS can also help in reducing cortisol levels which is beneficial to losing weight.

Now it becomes a bit more confusing cause LISS has its benefits to and they both improve aerobic performance and burn fat so what are the downsides of LISS.

  • LISS is time-consuming with an average LISS session taking from anywhere 30 minutes upwards, and I would consider 30 minutes a minimum to get the most from a session. 
  • It is easier to plateaux using LISS. HIIT has far more variables and it is easier to adapt and add more stimulus to make it more challenging. Whereas with LISS to keep it steady-state really the only way you can adapt it and make it harder is to increase the distance or time preformed. So if you have 30 minutes a day to spend jogging the benefits from that session are going to level out quickly. 
  • Doing too much LISS can have a negative effect on your body composition and result in a loss of muscle mass. By increasing distance, increasing time and by performing long bouts of LISS regularly can do you more harm then good if you are looking for well-rounded physic consisting of lean muscle mass. 
  • Just as HIIT isn’t for everyone, neither is LISS. Many people find LISS boring.
A man and a woman side by side in the gym both using battle ropes

So far, I have given you a general overview of the two so let’s get a little more specific to which one you should be doing and situations where one may be more beneficial than the other.

HIIT or LISS based on your goal or goals

As you probably know by now, I am very goal orientated in my approach to training and coaching. By focusing on your goal and what is more important to you, will help us to understand which is more beneficial for you to choose. 

For example, if your goal is performance-related, i.e. running 10k or a marathon, then LISS is going to be your primary choice for cardio.
Whereas if your goal is improved performance for sport, i.e. kickboxing, football or sprinting, then HIIT would be our go-to option.

In the above examples, there is a strong case for preforming both forms of cardio, but I am just highlighting which form will take precedence.

So what if our goal is fat burn, aesthetics or fitness because as discussed either form may get the required results. 

There are other factors which will influence our decision.

HIIT or LISS based on your current training program

If you already have a training program in place or you are starting a program and looking for a form of cardio to complement it, the type of program is going to influence your decision.  

If you are currently on a program that incorporates high-intensity training like intense weight sessions or intense fitness classes, then LISS will more than likely complement them better. 

Whereas if your program is already low intensity or you don’t feel challenged or feel like you could do more than HIIT will be a great fit.

A man on a bridge stretching his leg before starting a run

HITT or LISS based on your schedule or time constraints

These next two factors might be the easiest and quickest ways to decide.
If you need to get that cardio session in and you only have limited time in which to fit it in, then HIIT is going to be the one to choose

Which do you prefer HIIT or LISS

At the end of the day, we are looking for a form of training that is going to:

  • Suit us
  • That we can perform regularly
  • Stay consistent with
  • And enjoy and feel happy with

So you need to pick the one that is right for you. 

Give both a fair trial and if there is the one you detest or one that you just simply love, then it is an easy choice. 

Trainers Conclusion on HIIT or LISS

So what did I decide!

As I do a lot of Muay Thai, boxing (HIIT) and hit my weighted sessions at a moderate to high intensity (depending). 

I feel even an extra 20-minute session would just be too much (even though I love HIIT) so I opted for 30 minutes of LISS a day first thing in the morning on a cross-trainer. 

For me, this is more about getting an excellent start to the day. 

LISS complements my other training as everything else I do can be seen as high to moderate-intensity training, and I train often and regular.

Thirty minutes is perfect for me when it comes to extra cardio, and by using LISS on a cross-trainer, the workout is super easy to recover from. There is no impact or tightness in my legs that I get from everyday road running, and although I do love to run outside, I also live in Ireland, and we are entering the rainy season, so for this method is ideal. 

If you have any questions or are unsure which method would complement your training, please get in touch!

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