Foundational Cardio Protocols

Training

Foundational Cardio Protocols
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Many people are simply not familiar with the variety of cardio protocols out there. So far in this exercise series, we have discussed some of the things you need to take into account when programming cardiovascular training. However, I realise that some of you may not be as familiar with various cardio protocols as you may be with resistance training protocols, or you may have only been exposed to poor cardio protocols and are thus still unsure about how to fully flesh out the cardiovascular component of your training programs.

So, the goal of this article is to build out your understanding of some cardio protocols, which will allow you to make much better choices with your cardio programming and thus allow you to get much better results.

If you haven’t already, it would be incredibly helpful to also read our articles on why exercise is important, the goals of exercise, the types of exercise we have available to us, and to have a rough idea of the general exercise guidelines. It would also be very beneficial to read Why Do Cardio Training? and Cardio Programming as they help frame the discussion of cardio protocols in this article.

You can also visit our exercise hub for more content on exercise, and you can find the resistance training article there too.

Before we get stuck in, I would just like to remind you that we offer comprehensive online coaching. So if you need help with your own exercise program or nutrition, don’t hesitate to reach out. If you are a coach (or aspiring coach) and want to learn how to coach nutrition, then consider signing up to our Nutrition Coach Certification course. We do also have an exercise program design course in the works, if you are a coach who wants to learn more about effective program design and how to coach it. We do have other courses available too.

Now, with all that out of the way, we can actually get stuck into some cardio protocols!

Cardio Goals 

As I have noted several times throughout this series on exercise, we first need to be clear on exactly what we are trying to accomplish with our training, and this is especially true when it comes to selecting which cardio protocols we bring in. While training in and of itself is generally good (until you get to extreme quantities or intensities), you can be more specific in your modalities and thus accomplish your goals in a more time-efficient manner.

Now, as stated previously in this article series, to go into absolutely every specific adaptation you could target with cardiovascular training is beyond the scope of this article (as most of them apply more to sports), however, there are 3 broad categories we can discuss, and then we can somewhat refine our approach from there.

In general, most people are introducing cardio into a program for one or a combination of the following three reasons:

  1. They are trying to increase energy expenditure (i.e. they are using cardio as a means to burn calories).
  2. They are trying to target mitochondrial or metabolic adaptations, both local and systemic (e.g. someone may be doing high-intensity interval training to deplete glycogen, or to increase their ability to handle acidosis, locally in the muscle used, or systemically).
  3. They are trying to target cardiovascular adaptations (e.g. they are trying to improve cardiac function such as improving cardiac output or cardiac power).

Remember, that using cardio to burn calories isn’t always for fat loss (some individuals just want to have a larger amount of calories to eat each day, even when in a maintenance or gaining phase), but usually, it is for fat loss. This means that the individual will likely be lower in freely available energy, and thus fatigue is likely to be higher. This is a good reminder that when we are looking at our cardio protocol options, we must also factor in the diet, and of course, the rest of the training program. This stuff doesn’t just occur in isolation and we must keep our eye on the bigger picture when designing a protocol.

So, you must be clear on your goals, as different protocols are more or less appropriate for different goals.

Are you trying to use cardio to burn calories? Are you trying to target specific cardiovascular adaptations? Are you trying to target specific metabolic adaptations? Are you trying to target specific muscular adaptations? Are you just trying to improve fitness for health purposes? Are you doing cardio for your mental health or just because you enjoy cardio? Are you short on time or do you have more time to spend on your cardio?

All of these (and many other goals/questions) will have better and worse cardio protocols that can be used to target them. So, you have to be clear on your goals before you can answer the question of what is the best cardio protocol for you. Most discussions online paint a very simplistic picture of what kinds of cardio you should do, and unfortunately, things are generally more complex. While we can give some baseline recommendations, in reality, the specific cardio protocols you should use will need to be tailored to your specific goals and situation.

To better help you better understand what adaptations you are trying to target, a quick refresher on the cardiovascular system would be helpful.

Refresher On The Cardiovascular System

The cardiovascular system, also known as the circulatory system, is fundamental to maintaining life by delivering oxygen and nutrients to tissues while removing waste products. It plays a crucial role in supporting the body’s metabolic needs, especially during physical activity, and consists of the heart, blood vessels, and blood.

The heart is an organ divided into four chambers: the right atrium, right ventricle, left atrium, and left ventricle. It functions as a dual pump, with the right side circulating deoxygenated blood to the lungs for oxygenation (pulmonary circulation) and the left side pumping oxygenated blood to the rest of the body (systemic circulation). This dual system ensures that oxygen-rich blood is continuously supplied to tissues, and metabolic waste is efficiently removed.

Blood vessels are the highways of the cardiovascular system. Arteries carry oxygen-rich blood away from the heart to the tissues, while veins return oxygen-poor blood back to the heart. The capillaries, the smallest blood vessels, facilitate the exchange of gases, nutrients, and waste products between blood and tissues. The blood itself, composed of red blood cells, white blood cells, platelets, and plasma, serves as the transport medium for these essential substances.

The cardiovascular system supports two primary energy systems: the aerobic and anaerobic systems. The aerobic system, which relies on oxygen to produce energy (ATP), is essential for prolonged, moderate-intensity activities. This system utilises oxygen in the mitochondria of cells to produce ATP through a process called oxidative phosphorylation.

aerobic metabolism exercise

Carbohydrates and fats are the primary substrates used in this process, which is highly efficient for activities lasting longer than two minutes, such as long-distance running or cycling. The by-products of the aerobic system, carbon dioxide and water, are easily expelled from the body, making this system sustainable for extended periods. The aerobic system’s efficiency in oxygen delivery and utilisation significantly enhances cardiovascular health and endurance.

In contrast, the anaerobic system generates energy without relying on oxygen, making it suitable for short, high-intensity activities. This system includes two key processes: the ATP-PCr (phosphagen) system and glycolysis. The ATP-PCr system uses creatine phosphate to quickly regenerate ATP, providing energy for about ten seconds, ideal for explosive movements like sprinting or weightlifting. In general, this doesn’t lead to lactate as a byproduct, so it is often called an alactic.

Glycolysis breaks down glucose into pyruvate, producing ATP and lactate, effective for activities lasting up to two minutes. Carbohydrates are the primary substrates for anaerobic metabolism, and the production of lactate can lead to muscle fatigue. Despite this, the anaerobic system is crucial for enhancing muscle strength, power, and high-intensity performance.

anaerobic metabolism

During exercise, the cardiovascular system dynamically adjusts to meet the metabolic demands of active muscles. This involves an increased heart rate to enhance blood flow, vasodilation to improve oxygen delivery and waste removal, and the redistribution of blood flow to prioritise active muscles over less active organs. These adjustments enable the body to sustain physical activity and improve overall fitness levels.

Understanding the cardiovascular system’s role in supporting both aerobic and anaerobic activities is essential for developing effective cardio protocols. Aerobic training improves cardiovascular efficiency, oxygen delivery, and endurance, while anaerobic training boosts muscle strength, power, and high-intensity performance capabilities.

energy systems

The specific protocols utilised must take into account both how to target the specific adaptation and how that specific system is recovered. For example, you will often see anaerobic protocols that have you pushing hard for 20-60seconds, which does effectively target that anaerobic glycolytic system. However, they then inadvertently make these less effective by not allowing for sufficient recovery. The anaerobic system is recovered by the aerobic system, and generally takes 2-5 minutes to recover.

You very rarely see protocols that allow for this level of recovery, and as such, while the first effort is anaerobic, the subsequent efforts become more and more aerobic. This isn’t an issue if that is what you are actually trying to target, but naturally, if you aren’t trying to target the aerobic system with these efforts and want to actually develop the anaerobic system, then you will have to allow for more recovery.

So, it is important that you have a baseline knowledge of how the energy systems of the body work, along with the specifics around the adaptations you are trying to target. However, if you just want to improve your fitness more generally, you can just follow the baseline exercise guidelines for cardio.

The general guidelines for exercise suggest that you should perform 150-300 minutes of moderate-intensity aerobic exercise per week (half that for vigorous exercise). For most goals, simply improving the aerobic system will lead to the greatest return on investment. So we generally advise people to train that as the priority. After you have a good baseline of aerobic cardio, then you can start introducing more anaerobic training.

Now, with that in mind, we can go through some common protocols. There truly are thousands of protocols, as there are thousands of very niche goals, so we simply can’t go into the minute details of every single one. However, I would still like you to come away from this article with an idea of how to program some common protocols into your program.

Foundational Cardio Protocols

Below you will find a number of cardiovascular training protocols, along with a description of what adaptations they are mainly used to target. The list is not a complete list, but it does cover some of the more frequently used methods, along with the main adaptations they target.

Low-Intensity Steady State (LISS) Aerobic Exercise (Zone 2 Cardio)

Aerobic cardio, often called low-intensity steady state cardio, is a type of cardio that most people are familiar with, although the vast majority of people don’t actually do this type of training very well (they go too hard). This method is often also called the “cardiac output” method or “Zone 2 cardio”. 

The basic goal is for someone to train their overall aerobic capacity, and get all of the beneficial adaptations that go along with that, such as: 

  • increased mitochondrial biogenesis, 
  • lower resting heart rate, 
  • higher heart rate variability, 
  • increased VO2 max, 
  • improved cardio-pulmonary function and system, 
  • and increased recovery from anaerobic exercise. 

This method is often also used to simply burn calories. The basic setup is straightforward enough, even though most people don’t actually adhere to it.

You basically want to keep the heart rate at roughly 60-70% of your maximum heart rate (the exact figure depends on a lot of factors, and various people have different formulas they use and fitter individuals may actually still be in zone 2 at much higher heart rates), as this is roughly the top end of the range in which the aerobic system can work, without requiring much anaerobic metabolism. We have a handy heart rate zones calculator to work this out for you.

It does bear noting that the actual naming of the zones here is actually quite confusing. You will see people online refer to their training as zone 2, but see that interpreted and implemented incredibly differently. Realistically, we should base the zones on blood lactate concentration (as this tells us whether we are working aerobically or anaerobically, as lactate builds up as a byproduct of anaerobic metabolism).

However, blood lactate is tricky to measure while exercising. As a result, we tend to use heart rate as a proxy, as lactate and heart rate can be correlated pretty well.

cardio protocols

However, for individuals who are quite fit, or for individuals who are quite unfit, this isn’t always perfect. For fit individuals, you may be able to get to much higher heart rates, and still technically be in zone 2 (as you aren’t building up much lactate). Conversely, unfit individuals may find that they are actually using significant anaerobic metabolism even at rest, and thus are technically in much higher zones even while sedentary and at lower heart rates.

So, we tend to just use a more qualitative approach, and for zone 2 training, we recommend exercising at a pace where you can still just about hold a conversation (but the other person would know you were exercising) or work to a rating of perceived exertion (RPE) of 4-5 out of 10. This is quite an easy way of going about ensuring you are working at the right intensity level, as you don’t need any fancy heart rate monitor or specialist gear to track lactate. 

If you are supposed to be doing zone 2 cardio and you are extremely out of breath and can barely catch a breath, then you are likely working at a much higher heart rate than is desired for this method. This is where most people go wrong with this method, they go out and try to run for 60 minutes, but rather than staying at an aerobic pace, they simply try to run as fast as they can and thus this method quickly becomes extremely unenjoyable, as they are trying to maintain anaerobic metabolism far beyond what that system was designed for.

In general, to get many of the heart and vascular adaptations, we likely want to be working at an aerobic pace for 45 minutes or longer. In general, LISS is usually programmed for 45-90 minute blocks, although obviously, sports-specific aerobic training may require longer sessions. In general, this method can be programmed quite frequently, as it isn’t very fatiguing, once an individual becomes somewhat adapted to it (unless extreme volumes are used).

Cardiac Power Intervals (VO2 Max Intervals)

Cardiac power intervals are actually used quite frequently, although they are often done in a manner that really only serves to burn calories. The true benefit of cardiac power intervals comes in strengthening the heart and increasing the body’s ability to utilise oxygen at higher intensities. These are often called VO2 max intervals, because they are generally designed to have you training at your VO2 max. VO2 max is the maximum amount of oxygen an individual can utilise during intense exercise. It reflects the body’s ability to transport and use oxygen during physical activity. Generally, your heart rate is going to be 85% or above when at your VO2 max.

These types of intervals are quite effective for improving VO2 max (at least in the short term) and they are quite good at improving the strength of your heart. The basic protocol is something like this:

3-5 minutes of high intensity at >85% of max heart rate, then 3-5 minutes of rest/active rest, repeated for a predetermined number of sets (i.e. 5 repeats of the 3-5 minutes of high intensity efforts). 

These types of intervals can at first glance appear to be predominantly training the anaerobic system, but in reality, they are actually quite aerobic in nature. While the anaerobic system is generally used for high intensity efforts, it really doesn’t have the capacity to fuel 3-5 minutes of work. As a result, the intervals ended up being largely aerobically fueled. Generally, the efforts for these will require you to work at an RPE of 8-10, which is quite hard.

As a result, these intervals are still quite fatiguing, as you do get a lot of the negative effects of high intensity work, although these do work quite effectively for strengthening the heart and lead to the body being more efficient at utilising oxygen at higher intensities. They also lead to most of the same adaptations that you get from LISS cardio, although there are some slight differences.

These kinds of intervals can be programmed in combination with LISS cardio in a single session, or can be performed on their own. It is difficult to program these with resistance training in a single session, unless the resistance training is relatively short.

It is rare for this type of interval to be used for calorie burning purposes, and it is generally used to either improve performance or for health reasons. 

High-Intensity Interval Training (HIIT)

There are a variety of protocols that fall under this category, and many of them are designed to target very specific adaptations. As a result, I am only going to cover a select few protocols, and instead, focus on the overarching methods used. HIIT is generally more aimed at targeting the anaerobic system, rather than the aerobic system.

HIIT results in some of the same adaptations that you get from more aerobic training, but due to the high intensities used, it is far more fatiguing. Most people also generally don’t push it hard enough to truly get the benefits of HIIT. They end up just working in this middle ground and not really maximising the benefits of either aerobic or anaerobic work. The adaptations to HIIT do also seem to level off much more quickly than the adaptations to aerobic cardio, so we must keep this in mind. 

When deciding on what HIIT protocol to use, the first thing to consider is whether we are going to be utilising a protocol with “full” (it is rarely truly full recovery, as that takes quite a long time) or incomplete recovery between efforts. If we are trying to improve certain metabolic and/or performance qualities, we will generally favour full recovery between efforts. This is generally what you would prioritise with an athlete trying to improve certain qualities for their sport. 

Very often, incomplete rest will also be used, both for the general public and athletes, however, you must remember that repeated sprint efforts with incomplete rest will become more and more aerobic in nature. Thus, if we are trying to target a specific anaerobic adaptation, we would be best served by utilising complete rest. If the goal is simply to burn calories or you are just trying to get some cardio in for a time-poor person, we may use incomplete recoveries. There are a variety of protocols, and again, we won’t be covering all of them, but the following are often used.

energy systems

Alactic Intervals

These are primarily concerned with improving the ATP-PCr system, and thus they have you doing 10-15s of effort, and if complete recovery is the goal, 2-5 minutes recovery periods are used. Very often you will see these done with incomplete recovery, which as a result, can lead to the build up of lactate, which does kind of defeat the purpose of these. However, it doesn’t negate all of the benefits. Some common protocols include:

  • 10s work, 50s recovery, for 3-15 minutes total
  • 15s work, 45s recovery, for 3-15 minutes total
  • 10s work, 20s recovery, for 3-5 minutes total

Of course, there are many other possible permutations, and specific protocols would be used for specific goals, but these should give you a rough idea. Alactic intervals aren’t overly fatiguing, unless very short rest periods are used. They can be a nice addition to a program, as you don’t build up an excessive amount of acidosis from them (unless very short rest periods are used), and as such, most people feel surprisingly refreshed after doing these. 

You can actually push yourself quite hard with these, although you don’t necessarily have to. Some people do actually intentionally use these to improve their aerobic fitness, while still working on their overall performance. 

Lactic Intervals

From the outset, I would just like to state that the body doesn’t produce lactic acid, it produces lactate. The burning sensation is just an accumulation of hydrogens, not a build-up of lactate. So these are not appropriately named, but I am not going to change the general convention, even if it is wrong.

With that out of the way, the goal of this method is to target glycolysis, and as such, generally, something like 20-120s of effort is used, although 20-40s of effort is usual. Ideally, if full recovery is the goal, we would like to also see 2-5 minutes of recovery used. If the goal is sporting performance, then we will generally use full recovery, or at least close to it. A good proxy for this is getting the heart rate below ~130 bpm before the next effort. However, very often people trying to burn calories will use incomplete recovery periods, so as to keep heart rate (and thus calorie burn) higher. Some common protocols include:

  • 20s work, 40s recovery, for 3-10 minutes in total
  • 30s work, 90s recovery, for 4-30 minutes in total
  • 60s work, 120s recovery, for 6-30 minutes in total
  • 120s work, 180s recovery, 10-30 minutes in total

Again, there are a variety of other protocols that you may see, which should only be used with a specific goal and adaptation in mind. We must also really consider what cardio equipment is being used for these, as it is incredibly different to do 120s of all-out effort on a fan bike versus a spin bike versus a sprint on an astroturf versus a sprint on the grass etc.

There are many other permutations of HIIT intervals, but these are some of the common ones you will see. Usually, there is no real rhyme or reason for the exact protocol used, especially if calorie burning is the goal. However, there are definitely better and worse ways to utilise HIIT. 

You can program these HIIT sessions as stand alone sessions, perhaps also combined with LISS cardio. However, if you are using these as a means to burn calories, and to really maximise the time efficiency aspect, most people do tend to program them after their resistance training. If your goal is to improve performance, then you may even program these before resistance training, however, this will generally lead you to being more fatigued going into the resistance training. This may mean you are less able to push yourself hard with the resistance training, and thus get a lower return on investment with regards to muscle/strength building. 

Effort

I just wanted to very briefly state that I have basically been discussing most of this presuming you will be allocating a reasonable RPE to all of these, as the same rules that apply to resistance training and RPE apply here. We don’t need to go all out to get the benefits from cardio, however, certain protocols and adaptations do demand that you do actually push very hard, and much closer to RPE9-10.

Unfortunately, most people are not able to push this hard, and the ones who do, very quickly realise that doing lots of volume at that level of effort is incredibly fatiguing. Conversely, a lot of people go way too hard on methods that require lower levels of RPE, and thus, they don’t get the full benefits of those methods. For example, many people do LISS at too high an intensity, and as a result, get a lot of extra fatigue and a lower overall stimulus from the session (due to not being able to do as much due to the fatigue). This is why heart rate tracking can be really valuable. 

However, even heart rate tracking during cardio isn’t foolproof, as the specific heart rates that correspond to specific protocols can really only be found by virtue of doing some sort of metabolic/VO2 max testing. Most people don’t have the time or resources to do that. So we tend to just use heart rate targets as very rough guidelines, and to use RPE in combination with heart rate. 

ZoneRPE ScaleTalk Test
Zone 0 (at rest)RPE 0Baseline. You can easily hold a conversation.
Zone 1RPE 2-3You can still easily hold a conversation.
Zone 2RPE 4-5You can hold a conversation, but the other person probably knows that you are exercising.
Zone 3RPE 5-7Breathing is heavier, and you can only really speak in 1-2 sentences interspersed with heavy breathing.
Zone 4RPE 7-9Unable to hold a conversation outside of broken sentences and single words, breathing is very heavy.
Zone 5RPE 9-10Breathing is very heavy, you may be gasping for air, and you are unable to hold a conversation at all.

You can read more about this and calculate your heart rate zones in our heart rate zones calculator article.

Generally, people go too hard when they are supposed to be doing low intensity, and they generally go too easy when they are supposed to be doing high intensity. This isn’t always the case, but if you keep this in mind when you are training, it does help you to more appropriately allocate your efforts. 

Cardio Protocols Conclusion

So there you have it, the foundational cardio protocols. There are of course many more protocols you could call foundational, and there are many more specific cardio protocols you could use to target very niche and specific adaptations. However, these are generally the cardio protocols that most people use.

As noted earlier in the article, the general guidelines for exercise suggest that you should perform 150-300 minutes of moderate-intensity aerobic exercise per week (half that for vigorous exercise). For most goals, simply improving the aerobic system will lead to the greatest return on investment. So we generally advise people to train that as the priority. After you have a good baseline of aerobic cardio, then you can start introducing more anaerobic training.

So, for most people, spending the vast majority of their cardio time doing low-intensity steady state (LISS) aerobic cardio (Zone 2 cardio) probably makes the most sense. On top of this, you can then add in some more anaerobic cardio, as needed/desired.

As with everything, there is always more to learn, and we haven’t even begun to scratch the surface with all this stuff. However, if you are interested in staying up to date with all our content, we recommend subscribing to our newsletter and bookmarking our free content page. We do have a lot of content on how to design your own exercise program on our exercise hub.

If you would like more help with your training (or nutrition), we do also have online coaching spaces available.

We also recommend reading our foundational nutrition article, along with our foundational articles on sleep and stress management, if you really want to learn more about how to optimise your lifestyle. If you want even more free information on exercise, you can follow us on Instagram, YouTube or listen to the podcast, where we discuss all the little intricacies of exercise.

Finally, if you want to learn how to coach nutrition, then consider our Nutrition Coach Certification course. We do also have an exercise program design course in the works, if you are a coach who wants to learn more about effective program design and how to coach it. We do have other courses available too. If you don’t understand something, or you just need clarification, you can always reach out to us on Instagram or via email.

The previous article in this series is about Cardio Programming and the next article in this series is Review of Cardiovascular Training Guidelines, if you are interested in continuing to learn about exercise program design. You can also go to our exercise hub to find more exercise content.

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Paddy Farrell
www.triagemethod.com

Hey, I'm Paddy!

I am a coach who loves to help people master their health and fitness. I am a personal trainer, strength and conditioning coach, and I have a degree in Biochemistry and Biomolecular Science. I have been coaching people for over 10 years now.

When I grew up, you couldn't find great health and fitness information, and you still can't really. So my content aims to solve that!

I enjoy training in the gym, doing martial arts and hiking in the mountains (around Europe, mainly). I am also an avid reader of history, politics and science. When I am not in the mountains, exercising or reading, you will likely find me in a museum.