Cardio: LISS, HIIT or Interval Training?


Runner, cardio, sunset

"Cardio"...


(short for cardiovascular - the heart & lungs)...


By definition; any type of training that...


  • focuses on using...

  • challenges...

  • and hopefully improves the health & performance of...


...the cardiovascular system...


(Your heart and lungs, plus their connected parts eg. the arteries and veins that carry blood and oxygen around your body).


So in theory, anything that causes a significant increase in your heart rate, and / or your breathing rate, can be classified as 'cardio'.


Worth considering: That could even apply to an incidental side-effect. For example, you might be doing a dedicated strength training session, and notice an increase in heart / breathing rate after finishing a set. Arguably that's not the 'most effective' way to train cardio... but potentially a nice bonus anyway if you programme the session appropriately?


However, 'cardio', as well as directly improving the health of your CV system, has a number of very useful 'side effects'...


In fact most people will include this type of training, primarily for those side effects (eg. fat loss)...


The very significant health benefits are almost considered as the 'bonus' in many cases.




Types Of Cardio Training


Ok... so in reality, cardio is obviously a bit more complicated than simply raising your heart / breathing rate for an indefinite amount of time.


As with any workout, you need to first understand;


  • what you are trying to achieve

  • where you are currently (in terms of your current fitness level, compared to your goal)


...and then programme accordingly.


The type of training that you could/should be focussing on, the amount, frequency, structure and difficulty will all vary depending on those key factors.


Already... you can see that designing your workout is a little more sophisticated than just picking out a popular video on YouTube!



Misunderstanding Goals...


Before diving into a workout...


Think properly about what you really want to achieve...


"I want to get a bit fitter"...


Is not really a goal.


It's too vague...


And doesn't allow you to properly design a training programme to achieve a specific outcome...


This happens to be one (of the many) reasons why so many (most) people get bored / disheartened with their training plan and quit after a relatively short time... Once the novelty wears off, and you realise that you are putting considerable effort into regular exercise, without any specific direction or plan, it's inevitable that the effort will seem relatively pointless. You will feel infinitely more motivated, when you have a clear goal, a system in place for measuring your progress toward that goal, and clear evidence that you are successfully achieving it.


So what outcome are you hoping to see?


Fat or weight loss?


Improved heart health?


Improved endurance?


Quicker run times?


A mixture of any/all of the above?


These choices determine the type of training that you might want to focus on.


However...


Don't make the mistake of thinking that there is always a "best" type of cardio training for your goal that you must be doing.


Your choices would also depend on other factors, such as how often you're training and your current fitness level...


If the "best" type of training for your long-term goal appeared to be extremely intense training...


And you considered your fitness level to be very low (if you're just getting started, for example)...


You would have a very good reason to consider starting with a different type of training, to build up that initial fitness level...


With the aim of gradually introducing the more intense workouts later, when your fitness/exercise capacity has increased.


With that in mind...


These are the broad options available when designing your cardio training plan...



LISS / LSD (Low Intensity Steady-State / Long Slow Distance Training)



Walking, cardio, fitness, LISS
LISS Training: Continuous exercise at a challenging but sustainable intensity...


Pretty much what the name suggests...


This type of training has a relatively simple structure...


It's relatively slow / 'easy' compared to the other options below...


And you keep going until you complete the pre-determined time or distance (or whatever other variable you use to measure the 'amount' of exercise completed).


The idea of this type of training is to rely more or less solely on the "aerobic energy system".


Basically, that means that your body can cope with the level of exercise relatively comfortably;


  • You are able to breathe in adequate oxygen

  • Your heart is able to move that oxygen around the body to the muscles as and when required

  • And you can remove any waste products, preventing a build up which prevents you from continuing


So, when done correctly, there shouldn't be any need to stop or slow down to "catch your breath".


Example; going for a long walk, or a slow jog (depending on fitness levels) where you maintain a steady pace throughout.


A continuous training workout will look different for different people... somebody who is accustomed to long-distance running could consider a steady 10km as a comfortably maintainable workout.


Somebody else may not be able to maintain a running / jogging pace over that distance (in which case the intensity is too high... this would not then qualify as LISS for that person).



Continuous training should produce the following effects DURING the workout...


  • elevated heart rate

  • elevated breathing rate

  • increased body temperature


But generally, nothing too unbearable or unsustainable...


The whole point is to maintain your speed / difficulty.


So you shouldn't be experiencing any of the following;


  • muscle 'burn'

  • a level of breathlessness that forces you to slow down or stop

  • inability to hold a clear conversation


Due to the necessity for intensity to be deliberately kept low, LISS can be especially useful for building a base level of fitness...


Ideal if you're just getting started.


Other than that... the long-term benefits of continuous, low intensity training include;


  • contributes to overall energy ouptut (but doesn't necessarily optimise the efficiency of 'calorie burning' - remember though, that doesn't always make this an inferior choice for weight / fat loss)

  • increased strength of heart muscle (more blood can be pumped from the heart per beat)

  • decrease in your resting heart rate

  • improved 'capillarisation' of muscles (greater ability to provide oxygen and nutrients to muscles, via increased blood flow, during exercise. Also increases ability to remove waste products, lactic acid for example, from muscles during higher intensity exercise

  • increased capacity to breathe in air and absorb oxygen to be used by the body (during exercise and rest). That means a lower breathing rate is required to provide a given amount of oxygen to the muscles during exercise. In other words, if you struggle with running, cycling, swimming, sports etc due to struggling with breathing... "gasping for air"... you can improve this significantly with continuous aerobic training

  • multiple psychological benefits including improved mood.



One of the great practical benefits of LISS training is that, because of the relatively low intensity, post-workout recovery times can often be reduced.


While regular rest days are still important as part of your programme, LISS could reasonably be scheduled on consecutive days.


If programmed carefully, certain LISS workouts could also be used to fill gaps between more advanced / higher intensity workouts in your weekly schedule.


Both of the options above are extremely useful if you are trying to maximise total training volume in a given period of time.


Still, this doesn't remove the need for proper rest days. So although the workouts may seem relatively simple, plan and schedule them carefully.



Possible disadvantages of LISS:


  • arguably the most tedious type of training. The whole point of LISS, is that it is steady, and relatively long in duration. You'll need to stay focussed, making sure that you are following the workout plan properly, and find a way to remain motivated. Don't be fooled by the supposed 'low intensity'... this doesn't mean easy! And when the workout starts to get uncomfortable... you need to keep going! Hence why most runners you see out on the streets have their headphones in for added motivation / distraction!

  • you may feel that LISS is relatively inefficient compared to other types of cardio workouts. Various studies may show that other workout formats can/do "burn more calories in less time"... (but that doesn't automatically mean that LISS shouldn't have a place in your workout schedule).

  • it's time consuming which can create barriers for busy people trying to "squeeze workouts in". When you're short on time, we will usually encourage you to do a short workout, simply because the overall physical and psychological benefits will be infinitely higher than if you do nothing! However, taking into consideration travel (if relevant), getting changed, warming-up, actually doing the full LISS workout, cooling-down, stretching, showering etc... this type of training might not be ideal for those situations.



Interval Training


Note: 'Interval training' does NOT automatically mean 'High Intensity Interval Training' / 'HIIT' (see below)...


Interval training is based on the idea of alternating blocks of relatively low versus relatively high exercise intensity.


Emphasise again... 'higher' intensity does NOT always have to mean HIIT!


For example, the NHS 'Couch to 5K programme includes walk-jog workouts, where you (predictably) alternate between walking and jogging.


The jogging sections of the workouts in Week 4, last for 2-3 minutes or more... so by definition, while they are obviously a higher intensity than walking... they do not require you to work at (or even close) to your maximal ability (which a proper HIIT workout would).


This means that interval workouts can realistically be considered as part of any programme aimed at improved cardiovascular health or performance.


Even for relative beginners.


(Obviously this would need to be programmed appropriately for your current fitness level. But as you'll see from the list of potential benefits, interval training can be extremely useful as part of any training plan).


Again, depending on current fitness levels, this will mean something different for each person... there is no "right speed" to run at for example.


The higher intensity intervals allow you to briefly push outside of your comfort zone.


In contrast to LISS, here you are deliberately looking to make things more uncomfortable. Maintaining a workload that you can sustain is no longer a priority.


The lower intensity intervals (or rest intervals, depending on the programme), allow you to recover and go again.


Your body should then be able to achieve two things...


  • exposure to the higher (uncomfortable) intensities stimulates the body to adapt to better deal with those intensities later

  • limited recovery windows improve your body's ability to recover (especially useful in most sports?)


One of the key things to remember before and during interval training, is that the success of that workout depends on properly planning and following a workout plan...


Interval training means following structured patterns of those alternating intervals...


Not making up the speeds / resistances / times as you go along... Interval training is not random.


That 'correct' workout structure would, as always, depend on the goal of the workout / programme.


Different relative intensities produce different results...


Different interval timing structures produce different results...


Different interval intensities affect the interval times...


Different interval times affect the interval intensities...


And so on.


You absolutely must design (beforehand), what your interval structure is going to look like in any given workout. Otherwise your chances of achieving the specific goal that you set out to achieve, disappear!


So if you haven't already...


Take the time to think about what you're training goals are...


What do you actually want to see happen as you progress through your workout plan?


Potential disadvantages;


  • higher intensity exercise might be unsuitable in certain cases (some health conditions, injuries etc)

  • high intensity exercise, by it's very nature, is physically demanding. This often puts people off of exercise (they associate all exercise with the discomfort of high intensity exercise)

  • a poorly planned (or poorly followed plan) will not produce the desired result. This is easily done, especially when the voice in your head begins to tell you that you are struggling

  • judging exercise intensity can be challenging. Heart rate monitors can help but it's not always easy to concentrate on monitoring and hitting targets as you go along.



HIIT: High Intensity Interval Training


Sprint, spinning, cycling, HIIT
HIIT: Repetitive, structured bursts of highly challenging exercise, alternated with recovery windows.


An extremely popular way of training...


Mainly due to the promise that HIIT "gives you more bang for your buck", compared to other methods of cardio training.


The underlying principle, is that the relatively brief periods of very high intensity exercise, more than compensate for the relatively short workout duration, by causing effects that ultimately lead to a greater 'calorie burn';


  • by directly burning calories DURING the workout (could be less than, equal to, or more than a workout based on a different method)

  • and then by raising your post-workout metabolic rate AFTER the workout (even if the number of calories burned during the workout was actually LESS)...


As with 'standard' interval training above...


Another very good reason to consider HIIT is the deliberate, structured exposure to more challenging levels of exercise.


The major difference, is that you will actively be trying to reach your maximal (or very close to maximal) exercise intensity.


The time spent at this high intensity (and the process of recovering from it) is where the metabolism boosting effects occur...


This type of workout will be extremely challenging when done right...


So less likely to be recommended to beginners.


And ideally, NOT to be repeated too frequently... high intensity exercise demands adequate rest! (MINIMUM 48 hours as a general rule of thumb).


Note: Remember the above point regarding rest days when arguing about whether HIIT or LISS "burns more calories". Yes, HIIT might be more efficient in the short term... but LISS may allow more frequent training. So which one "wins" in the long-run? Or does a mixture make sense in the context of your goals?


Theoretically you should be able to build up your tolerance to these 'more difficult' exercises by consciously forcing yourself to adapt to them, rather than gradually building up the more steady forms of exercise that you would perform in LISS...


Example: By simply trying to gradually increase your (steady) speed over a 10km distance, it is inevitable that you will hit a plateau at some point (once again, this doesn't mean that this strategy is always wrong... remember to consider this in the context of your own current fitness levels... and what you are aiming to achieve!).


Based on the need for HIGH exercise intensity during HIIT, strictly speaking... "Interval Training' and 'HIIT' are different.


'Interval training' can refer to ANY structured training that follows a highER intensity vs low intensity alternating pattern...


For example 2 minutes of jogging vs 1 minute of walking (assuming that you can maintain the jogging speed for the full 2 minutes) qualifies as 'Interval training'...


It DOES NOT qualify as HIIT.


High intensity should, rather predictably, be very challenging.


Anything that you can only do for a maximum of 60 seconds would qualify (arguably less... although again, that would depend on your fitness levels).


As well as only being able to continue a single exercise interval for a very limited amount of time...


The overall length of the workout should be fairly short.


If you think you did a HIIT workout for 60, 90 minutes, or more...


Bad news...


You were almost certainly NOT training at 'High Intensity'!


You also need to consider that the structured rest periods are there for a reason...


Don't make the mistake of assuming that you did the workout 'better' if you reduced the length of the rests that were programmed (or even worse, ignored them!)


The danger is that you have not recovered adequately and the quality / intensity of the 'high intensity interval' has to be reduced...


Defeating the entire point of the workout!


So just like the 'Interval Training' workouts discussed above...


Plan the workout beforehand...


And follow the plan!



The Point Is...


You are exercising for a reason...


A specific reason that reflects your personal goals.


Those goals should be reflected in the type of training that you are doing in your workouts.


While that may seem blindingly obvious...


It's surprisingly common to see / hear from people who are effectively training in a random way...


Based on something that they have read...


Been told about by friends...


Or simply a random video they found on YouTube / social media.


(Keep in mind that you probably won't see many "social media influencers" talking about LISS training... HIIT looks and sounds a lot more appealing to a social media audience as it can be 'sold' as a shortcut or "fitness hack", and looks a lot more 'exciting' on video!... That doesn't necessarily mean that it's "better"!)


Being specific also comes into play when selecting exercises.


While there are no "best" exercises for any type of cardio training...


Some decisions will obviously make more sense in the the context of your targets and fitness level.


For example, if you are trying to increase your ability to run longer distances...


Run! And think about which methods help you to increase your distances... is a 20 minute HIIT workout in your back garden going to help here?


Alternatively, if you are designing HIIT workouts for increasing metabolism / fat loss, think about the exercises that get your heart rate/breathing rate up to the target level in the short time period that you have available (again, this might vary from person to person).



 

People often try to ask "what is the best exercise" or "the best programme" to achieve x, y or z...


The answer will always depend on a number of factors that are specific to you...


Do not fall into the trap of thinking that one popular method is the answer to all health/fitness programmes.


The types of cardio training above can be selected, or mixed and matched to produce a specific, desired long-term result.


So get clear on what it is that you are trying to achieve...


Then, you can start thinking about the exercise methods that may contribute to that goal.


You can get help with this here...