Why Do Cardio?

Training

Why Do Cardio?
Updated on

Why do cardio? A very basic question, but understanding the answer does actually allow you to make much better decisions about your training program.

So far in this foundational programming article series, we have mainly been discussing resistance training principles and how to program for resistance training-related adaptations. However, to really understand how to design a training program, you need to be able to program your cardiovascular training too.

This is an area that a lot of coaches, especially on the more physique development side of things, are actually quite weak in. So it is only natural that most people who are interested in training also are not really aware of how to program cardio, as they mostly get their information from social media, where more physique-oriented content performs better. 

Cardio is often considered to be a bit of an afterthought, and not much attention is paid to the intricacies of how to program it. This isn’t surprising, given that resistance training is incredibly effective for transforming someone’s physique. However, not knowing how to program cardiovascular training is a major gap in your knowledge.

Even if you engaged with sports when you were younger, you may still not have a good level of understanding of how to improve cardiovascular fitness, as most sports coaches are simply not well versed in cardiovascular training programming either. They generally just follow what has always been done. But don’t worry, understanding how to program cardiovascular training, at a fundamental level, is actually quite easy to grasp.

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.

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 the discussion of why you should do cardio!

What Is Cardio

Cardiovascular training is a little bit more difficult to describe than resistance training, as it really can be anything that raises your heart rate and challenges your cardiovascular system. If you are very unfit, and have been sedentary for a long time, you may find walking for 5 minutes to be sufficiently challenging to your cardiovascular system. However, someone who has been engaging in a lot of cardiovascular training may find their heart rate barely elevates walking for 5 minutes, and they would not see it as being something anyone would call cardiovascular training.

So there is a degree of individual specificity here, and that does make understanding the adaptations a little bit harder too, as it does depend on what you have been doing previously.

Cardio can also be broken down into two energy providing systems (technically it can be further subdivided, but this isn’t generally necessary). These are the aerobic system and the anaerobic system (you do have another one, the ATP-PCr system, but for this discussion, we don’t need to include it). 

energy systems

The aerobic system requires oxygen to function effectively, and as such, it works better when your effort and heart rate is relatively lower as this facilitates you being able to breathe effectively (and thus breathe in oxygen and breathe out carbon dioxide). Once your level of effort goes up, or you are required to do movements that require very fast generation of energy, you must use the anaerobic system. This system doesn’t require the same oxygen that the aerobic system requires, and as such, it can work in low oxygen conditions, but the trade-off is that it doesn’t work for very long.

This is why you can’t sprint a marathon, the anaerobic system just can’t supply power for that long, and instead, the aerobic system must kick in, which can go for much longer, but can’t provide that “jet fuel” required for the higher intensities. This is important to understand, because some of the adaptations you get from doing higher-intensity cardio, you don’t get with lower-intensity cardio, and vice versa.

The manner in which you perform the cardio training does also matter. Just like there are differences between using your body weight or dumbbells for resistance training, there are differences between running, cycling, swimming, hiking, rucking, using the elliptical or fan bike, and so on. Some modalities are better suited to certain training methods than others.

For example, it may be difficult to do interval training on a treadmill, whereas doing it on a stationary bike may be much easier, practically speaking. However, doing it on a fan bike, even with the same training parameters (i.e. the specific interval program), may make it significantly harder as the fan bike provides more resistance than a stationary bike and challenges more muscles (as it uses the upper body too).

So, discussing cardio isn’t just a case of thinking about simply jogging or sprinting, there is a lot more nuance here. The body parts used can be significantly different, the injury risk significantly different, and the specific adaptations significantly different. 

However, even with all of this in mind, we can still broadly discuss cardio training in two distinct categories. These categories are low-intensity steady-state (LISS) cardio and high-intensity interval (HIIT) cardio. These shouldn’t be thought of as being completely distinct categories, and depending on how exactly you perform either of these there may actually be significant overlap.

For example, a lot of people perform “HIIT” workouts that go on for 30-40 minutes, and ultimately they just end up being largely aerobic sessions. There are different methods, programs and protocols you can use for each of these, depending on what exactly you want to develop.

Now, understanding what cardio is, and having the framework of low intensity and high intensity cardio is helpful, but it doesn’t answer the fundamental question of “why do cardio?”

Why Do Cardio?

Very often, when people are talking about cardiovascular training, they are discussing it from very different points of view, and thus, they are often talking past each other and this can leave people very confused about what to do. So why would we do cardio in the first place?

This can be answered on a general basis, and then we can also ask the more specific questions of why and what type of cardio is best.

In general, there are three main areas that cardio training is used for:

  • Manipulate calories: Often used as an aid to fat loss, although sometimes used to allow an individual to eat more. We could also label this category as “body composition”, although that doesn’t encapsulate all that is included here, as body composition change may not be the goal.
  • Improve performance: This is a very broad category that can get incredibly specific and it is not really the aim of this article to delve into all the nuances here.
  • Improve health: A broad, and often ill-defined category.

So as the first port of call, when thinking about how to program your cardio training, we need to be clear on what we are using the cardio for on a broader level. We may be using it to influence calorie expenditure, improve performance, improve health or some combination of all three (or potentially other goals, such as simply enjoying certain types of cardio). Being clear on this does allow us to make better cardio programming decisions.

From here, you can get more specific about tailoring or cardio to your specific goals. However, to be able to do this, we need to actually understand what the adaptations to cardio actually are. We have already discussed them when we talked about when we discussed The Goals Of Exercise and the Types Of Exercise, so this will be brief, but it is important to have it at the forefront of your mind for this discussion. But before we get to that, we need to just briefly discuss the actual calorie expenditure side of things.

Cardio As A Means To Manipulate Calories

Calorie expenditure isn’t an adaptation to cardiovascular training (although there are adaptations that potentially change calorie expenditure), but it is something that occurs as a result of doing cardio training. Most people are aware that doing cardio burns calories, and you will very often hear people discussing including cardio in their plan, as a means to burn more calories, very often in an effort to lose weight. This is fairly intuitive, and it makes sense. Doing any activity burns more calories than doing nothing, so doing more cardio will mean you are burning more calories, and thus weight loss should be easier. You are just manipulating the “calories in, calories out” equation by increasing the “calories out” side. 

exercise and calories

However, very often people make the mistake of thinking that just doing cardio will lead to fat burning, as if cardio has some sort of magical fat-burning properties. This is not the case. You will not lose fat or weight by bringing in more cardio, unless this leads to a net calorie deficit. If you do 500 calories of cardio, and then also eat 500 more calories, there won’t be any weight loss (although you may still be getting health and performance benefits). So if you are going to program cardio as a tool for fat loss, then calorie intake must also be controlled.

We must also factor in that just doing more cardio won’t necessarily lead to increased calorie expenditure across the day. Expending more calories via exercise doesn’t necessarily lead to a net increase in the “calories out” side of the equation. Calorie expenditure isn’t completely additive, and doing more cardio can very often reduce non-exercise activity thermogenesis (NEAT) and at extremes, it can also eat into many foundational bodily processes.

For example, reducing fertility, such as occurs in many female athletes who lose their periods due to excessive output and under-consumption of food. This was previously called the Female Athlete Triad, but is now called Relative Energy Deficiency in Sports (RED-S), as it also occurs in men, and also in non-athletes so they may need to change the term in future! So we don’t want calorie expenditure to get too high, even if calorie intake is still relatively high, and while this is usually only a concern for athletes who are training quite a lot, it does sometimes happen in the general public. 

additive model of energy expenditure vs the constrained model of energy expenditure

But either way, the fact that calorie expenditure isn’t completely additive, and increasing levels of cardio training can reduce NEAT, means we should be accounting for NEAT before we introduce additional cardio. The easiest way to do this is to track daily step count and to have a set daily target.

The very low-intensity cardio training that is daily steps, is a very powerful tool for increasing calorie expenditure and is also very often the first thing that is reduced when someone brings in more formalised cardiovascular training.

Now, we haven’t actually touched on what type of cardio you should be programming if energy expenditure manipulation is the goal, and that is quite important! As discussed previously, in general, we can break cardio down into two categories, anaerobic (high-intensity) and aerobic (low-intensity) cardio. Both of these have their pros and cons, but before we get into them, I just want to reiterate that cardio doesn’t have magical fat-burning properties, and to manipulate weight/fat, the “calories in, calories out” equation has to change (i.e. if you aren’t actually in a deficit, you won’t lose weight/fat).

So should you be programming low-intensity or high-intensity, if calorie manipulation is the goal?

In general, it is probably better to use low-intensity cardio for calorie manipulation. This is because lower-intensity cardio doesn’t generally burn as much glucose/glycogen as higher-intensity cardio, and thus allows better recovery for resistance training. It also generally isn’t as fatiguing or hard on the body, unless done in excessive quantities.

However, the issue is that low-intensity training just takes more time to equate to the same level of calories that can be burned during higher-intensity cardio. You can knock out 100 calories worth of cardio in a very time-efficient manner by doing higher intensities, while doing the same 100 calories of cardio with low intensity can take 2-4 times as long. Some people will also argue that by doing higher-intensity cardio, you also burn more calories later in the day (via an effect called EPOC), however, the contribution of this is usually negligible. 

Some people will accept the trade-off of lower recovery and reduced subsequent training performance, and the time efficiency that higher-intensity cardio offers. But for most goals, it generally isn’t actually a good trade-off. In the vast majority of cases, lower-intensity cardio is a better return on investment over the longer term. That doesn’t mean we never program higher-intensity cardio, but as a general rule, we are usually going to prioritise lower-intensity cardio when trying to create a calorie deficit through cardio. You have much more leeway if calorie intake is actually sufficient, however, even then, higher intensities are still quite draining.

Now, you may be thinking, “I will just program moderate intensities and get the best of both worlds”, and unfortunately, this isn’t really a good option and usually just leads to the worst of both worlds. Humans are pretty awful at the moderate intensity zones, and the beneficial adaptations are usually either maximised at either end of the spectrum and are only moderately accomplished by working at a moderate intensity. While moderate intensities are better at burning calories than lower intensities, for a given unit of time, they do still lead to increased fatigue and decreased recovery. 

A lot of people end up doing cardio at moderate intensities, as they do 20-40 minute “HIIT” (High-Intensity Interval Training) classes. The unfortunate thing is that there is absolutely no way to do high intensities for 20-40 minutes. You can’t sustain high intensities for more than 30-120s, and then you require a 2-3 minute recovery period at a minimum. So trying to do 20-40 minutes of “HIIT” means you don’t get up to the truly high heart rates and output of true higher intensities or you are too far above the heart rates of lower intensities. 

Beyond heart rate, you also aren’t really working with the energy systems your body is capable of using. You are going for too long for the anaerobic system to work effectively, and you are just working aerobically, but as heart rates are so high, you aren’t getting some of the aerobic adaptations we want. Overall, you are kind of just at this in-between zone where you aren’t optimising the adaptations from either end of the spectrum. So don’t program this middle zone unless you have specific reasons to, either stick to truly high intensities or low intensities, not somewhere in between. We will expand on this a bit more when we discuss cardio protocols.

Cardio For Health and Performance

Beyond calorie expenditure, we may also do cardio for performance-based adaptations or health-based adaptations. There is obviously a huge degree of crossover between them, but if we are trying to target certain adaptations, we can make better choices with our choice of cardio.

The main 4 areas that can adapt to cardiovascular exercise are the heart, the vascular system, the lungs, and the actual muscles/muscle cells themselves. These different areas of adaptation can be targeted by different types of cardiovascular training, but ultimately lead to:

  • Improved lung function,
  • improved heart endurance, 
  • improved heart strength,
  • improved resting heart rate,
  • improved vascular system,
  • improved blood pressure,
  • improved daily function and ability,
  • improved exercise tolerance,
  • improved endurance,
  • improved stress management,
  • improved metabolic health,
  • reduced disease(s) risk,
  • and improved longevity/life expectancy or reduced mortality. 

Cardio is probably something you want to include in most programs in some manner, although it is often overlooked. You also don’t need a huge amount to get a lot of benefits.

When people think of running, cycling, or swimming, they often associate those activities with “exercise for health”. While cardiorespiratory fitness is an important contributor to health and longevity, so too are muscle mass and strength. Therefore, when thinking about “exercise for health”, you should ultimately be thinking about resistance and cardio training as being complementary to each other. It isn’t an either-or discussion, doing both should be the baseline. This is why both are in the exercise guidelines.

When you perform exercise aimed at improving cardiorespiratory fitness, you get some different adaptations to those you may get from resistance training. For example, if we take blood pressure, both running on a treadmill and doing some squats have the potential to reduce your blood pressure, but with slightly different mechanisms. Similarly, while your heart rate will elevate in both types of training, the adaptations that you get over time in terms of your body’s ability to pump out more blood and oxygen, and uptake those into your tissues, will be superior with training aimed at improving cardiorespiratory fitness.

If we take a real-world case of someone who gets tired going up the stairs, you may ask yourself “should they get stronger, or improve their cardio fitness?”. The answer is both. Your muscles ultimately need to have the strength to be able to produce the force required to make each step. But, you also need to have the cardiorespiratory fitness to endure that over and over again, to continuously supply those muscles with blood, and to do so without excessive strain.

Fatigue is a complex phenomenon, as it encompasses both psychological and physiological variables that are ultimately “measured” by you/your brain (no need to get too caught up on that for the moment). So, if you are constantly struggling to get up the stairs, and it requires your heart to beat at its max, then you will accrue more fatigue than if you had 1) stronger muscles, and 2) higher cardiorespiratory fitness. The key message here is that it does not have to be one type of training versus the other when it comes to health.

We discussed the health effects of exercise pretty extensively in our article on why exercise is important so I won’t linger on this too much. But needless to say, cardio is good for your health.

It is consistently associated with improved health and longevity, along with decreased mortality from pretty much everything. If you care about your health and you aren’t doing cardio, you are leaving a lot on the table.

Cardio can also be used to improve your performance, and by performance, I mean both performance in specific sports/activities and in everyday life. As noted above, cardio training is associated with:

  • Improved lung function,
  • improved heart endurance, 
  • improved heart strength,
  • improved vascular system,
  • improved exercise tolerance,
  • improved endurance,
  • improved stress management,
  • and improved metabolic health.

These are generally the very same systems that are used for sports. In most cases, sports are actually just high-skill requiring cardio training. So, it makes sense that doing cardio training is going to have a high degree of carry-over to improving sports.

Having better fitness allows you to train harder, recover quicker and in most instances perform better at your chosen sport. Most sports are heavily aerobic, so developing your aerobic system will generally improve performance in most sports. Even the most anaerobic sports are mostly aerobic when you expand the time horizon you view, especially when you include recovery time

However, that doesn’t mean we only need to improve the aerobic system to see performance increases in sports. Improving the anaerobic system also has many advantages in a sporting context. Anaerobic training, especially at high heart rates can really improve the strength of the heart. Anaerobic training can also improve your ability to handle higher intensity work, which may be required in your sport.

Cardio doesn’t just improve sporting performance, it also improves cognitive performance and every day life performance. This is because it generally leads to better energy levels across the day, better focus and generally better mood. In fact, cardio is one of the best tools we have for improving cognitive performance. So if you want to perform better at work or in your studies, getting fit may be the answer.

Depending on the exact health or performance adaptations desired, different types of cardiovascular training may be chosen. We will provide a general framework for programming your cardio in future articles, but this is actually quite a big topic when you actually get into the nitty-gritty of it. This is especially true when we discuss performance. However, the beauty of cardio training is that there is actually a large degree of carryover, and the general framework we will discuss in future articles will actually allow you to accomplish a lot, without needing to be overly specific.

Why Do Cardio Conclusion

The reasons behind doing cardio are pretty straightforward. Cardio improves health and performance, and it can be used to burn calories, which may then improve body composition or allow for a higher calorie (and micronutrient) intake.

The specific protocols you use for your cardio will depend heavily on what exactly you want to achieve within these goals. With resistance training, it is much more clear cut, as you are generally using resistance training for strength gain and/or muscle gain. With cardio, things aren’t as clear cut.

As a result, you really do need to get very clear on what your goals are. Knowing what exactly you are trying to accomplish will allow you to make much better choices with your cardio programming.

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 Review of Resistance Training Guidelines and the next article in this series is Cardio Programming, 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.

References and Further Reading

Hottenrott K, Ludyga S, Schulze S. Effects of high intensity training and continuous endurance training on aerobic capacity and body composition in recreationally active runners. J Sports Sci Med. 2012;11(3):483-488. Published 2012 Sep 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3737930/

Jamka M, Mądry E, Krzyżanowska-Jankowska P, et al. The effect of endurance and endurance-strength training on body composition and cardiometabolic markers in abdominally obese women: a randomised trial. Sci Rep. 2021;11(1):12339. Published 2021 Jun 11. doi:10.1038/s41598-021-90526-7 https://pubmed.ncbi.nlm.nih.gov/34117276/

Doma K, Deakin GB, Schumann M, Bentley DJ. Training Considerations for Optimising Endurance Development: An Alternate Concurrent Training Perspective. Sports Med. 2019;49(5):669-682. doi:10.1007/s40279-019-01072-2 https://pubmed.ncbi.nlm.nih.gov/30847824/

Düking P, Zinner C, Trabelsi K, et al. Monitoring and adapting endurance training on the basis of heart rate variability monitored by wearable technologies: A systematic review with meta-analysis. J Sci Med Sport. 2021;24(11):1180-1192. doi:10.1016/j.jsams.2021.04.012 https://pubmed.ncbi.nlm.nih.gov/34489178/

Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Med. 2015;45(10):1469-1481. doi:10.1007/s40279-015-0365-0 https://pubmed.ncbi.nlm.nih.gov/26243014/

Herzig D, Asatryan B, Brugger N, Eser P, Wilhelm M. The Association Between Endurance Training and Heart Rate Variability: The Confounding Role of Heart Rate. Front Physiol. 2018;9:756. Published 2018 Jun 19. doi:10.3389/fphys.2018.00756 https://pubmed.ncbi.nlm.nih.gov/29971016/

Laursen PB, Shing CM, Peake JM, Coombes JS, Jenkins DG. Interval training program optimization in highly trained endurance cyclists. Med Sci Sports Exerc. 2002;34(11):1801-1807. doi:10.1097/00005768-200211000-00017 https://pubmed.ncbi.nlm.nih.gov/12439086/

Mrówczyński W. Health Benefits of Endurance Training: Implications of the Brain-Derived Neurotrophic Factor-A Systematic Review. Neural Plast. 2019;2019:5413067. Published 2019 Jun 24. doi:10.1155/2019/5413067 https://pubmed.ncbi.nlm.nih.gov/31341469/

Cadore EL, Pinto RS, Bottaro M, Izquierdo M. Strength and endurance training prescription in healthy and frail elderly. Aging Dis. 2014;5(3):183-195. Published 2014 Jun 1. doi:10.14336/AD.2014.0500183 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4037310/

Baquet G, van Praagh E, Berthoin S. Endurance training and aerobic fitness in young people. Sports Med. 2003;33(15):1127-1143. doi:10.2165/00007256-200333150-00004 https://pubmed.ncbi.nlm.nih.gov/14719981/

Vesterinen V, Nummela A, Heikura I, et al. Individual Endurance Training Prescription with Heart Rate Variability. Med Sci Sports Exerc. 2016;48(7):1347-1354. doi:10.1249/MSS.0000000000000910 https://pubmed.ncbi.nlm.nih.gov/26909534/

Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, Anderson JC. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. J Strength Cond Res. 2012;26(8):2293-2307. doi:10.1519/JSC.0b013e31823a3e2d https://pubmed.ncbi.nlm.nih.gov/22002517/

Tanaka H, Swensen T. Impact of resistance training on endurance performance. A new form of cross-training?. Sports Med. 1998;25(3):191-200. doi:10.2165/00007256-199825030-00005 https://pubmed.ncbi.nlm.nih.gov/9554029/

Foster C, Farland CV, Guidotti F, et al. The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity. J Sports Sci Med. 2015;14(4):747-755. Published 2015 Nov 24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657417/

Khanfir MA, Awicha HB, Masmoudi L, et al. Effects of Different Low-Intensity Exercise Types on Duration, Energy Expenditure and Perceived Exertion in Obese Individuals. Int J Environ Res Public Health. 2022;19(8):4893. Published 2022 Apr 18. doi:10.3390/ijerph19084893 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9032643/

Bishop DJ, Botella J, Genders AJ, et al. High-Intensity Exercise and Mitochondrial Biogenesis: Current Controversies and Future Research Directions. Physiology (Bethesda). 2019;34(1):56-70. doi:10.1152/physiol.00038.2018 https://pubmed.ncbi.nlm.nih.gov/30540234/

Huertas JR, Casuso RA, Agustín PH, Cogliati S. Stay Fit, Stay Young: Mitochondria in Movement: The Role of Exercise in the New Mitochondrial Paradigm [published correction appears in Oxid Med Cell Longev. 2021 Jan 18;2021:9274841]. Oxid Med Cell Longev. 2019;2019:7058350. Published 2019 Jun 19. doi:10.1155/2019/7058350 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6607712/

Sorriento D, Di Vaia E, Iaccarino G. Physical Exercise: A Novel Tool to Protect Mitochondrial Health. Front Physiol. 2021;12:660068. Published 2021 Apr 27. doi:10.3389/fphys.2021.660068 https://pubmed.ncbi.nlm.nih.gov/33986694/

Oliveira AN, Richards BJ, Slavin M, Hood DA. Exercise Is Muscle Mitochondrial Medicine. Exerc Sport Sci Rev. 2021;49(2):67-76. doi:10.1249/JES.0000000000000250 https://pubmed.ncbi.nlm.nih.gov/33720909/

Memme JM, Erlich AT, Phukan G, Hood DA. Exercise and mitochondrial health. J Physiol. 2021;599(3):803-817. doi:10.1113/JP278853 https://pubmed.ncbi.nlm.nih.gov/31674658/

Roberts FL, Markby GR. New Insights into Molecular Mechanisms Mediating Adaptation to Exercise; A Review Focusing on Mitochondrial Biogenesis, Mitochondrial Function, Mitophagy and Autophagy. Cells. 2021;10(10):2639. Published 2021 Oct 2. doi:10.3390/cells10102639 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8533934/

Hood DA. Mechanisms of exercise-induced mitochondrial biogenesis in skeletal muscle. Appl Physiol Nutr Metab. 2009;34(3):465-472. doi:10.1139/H09-045 https://pubmed.ncbi.nlm.nih.gov/19448716/

Popov LD. Mitochondrial biogenesis: An update. J Cell Mol Med. 2020;24(9):4892-4899. doi:10.1111/jcmm.15194 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7205802/

Steiner JL, Murphy EA, McClellan JL, Carmichael MD, Davis JM. Exercise training increases mitochondrial biogenesis in the brain. J Appl Physiol (1985). 2011;111(4):1066-1071. doi:10.1152/japplphysiol.00343.2011 https://pubmed.ncbi.nlm.nih.gov/21817111/

Lee D, Son JY, Ju HM, Won JH, Park SB, Yang WH. Effects of Individualized Low-Intensity Exercise and Its Duration on Recovery Ability in Adults. Healthcare (Basel). 2021;9(3):249. Published 2021 Mar 1. doi:10.3390/healthcare9030249 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7999698/

Hua LP, Brown CA, Hains SJ, Godwin M, Parlow JL. Effects of low-intensity exercise conditioning on blood pressure, heart rate, and autonomic modulation of heart rate in men and women with hypertension. Biol Res Nurs. 2009;11(2):129-143. doi:10.1177/1099800408324853 https://pubmed.ncbi.nlm.nih.gov/19150992/

Robergs RA. A critical review of the history of low- to moderate-intensity steady-state VO2 kinetics. Sports Med. 2014;44(5):641-653. doi:10.1007/s40279-014-0161-2 https://pubmed.ncbi.nlm.nih.gov/24563157/

Steele J, Plotkin D, Van Every D, et al. Slow and Steady, or Hard and Fast? A Systematic Review and Meta-Analysis of Studies Comparing Body Composition Changes between Interval Training and Moderate Intensity Continuous Training. Sports (Basel). 2021;9(11):155. Published 2021 Nov 18. doi:10.3390/sports9110155 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8619923/

Stöggl TL, Sperlich B. The training intensity distribution among well-trained and elite endurance athletes. Front Physiol. 2015;6:295. Published 2015 Oct 27. doi:10.3389/fphys.2015.00295 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4621419/

Gaesser GA, Angadi SS. High-intensity interval training for health and fitness: can less be more?. J Appl Physiol (1985). 2011;111(6):1540-1541. doi:10.1152/japplphysiol.01237.2011 https://pubmed.ncbi.nlm.nih.gov/21979806/

Tse AC, Wong TW, Lee PH. Effect of Low-intensity Exercise on Physical and Cognitive Health in Older Adults: a Systematic Review. Sports Med Open. 2015;1(1):37. doi:10.1186/s40798-015-0034-8 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4612316/

Hackney AC, Hosick KP, Myer A, Rubin DA, Battaglini CL. Testosterone responses to intensive interval versus steady-state endurance exercise. J Endocrinol Invest. 2012;35(11):947-950. doi:10.1007/BF03346740 https://pubmed.ncbi.nlm.nih.gov/23310924/

Atakan MM, Li Y, Koşar ŞN, Turnagöl HH, Yan X. Evidence-Based Effects of High-Intensity Interval Training on Exercise Capacity and Health: A Review with Historical Perspective. Int J Environ Res Public Health. 2021;18(13):7201. Published 2021 Jul 5. doi:10.3390/ijerph18137201 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8294064/

Shepherd SO, Wilson OJ, Taylor AS, et al. Low-Volume High-Intensity Interval Training in a Gym Setting Improves Cardio-Metabolic and Psychological Health. PLoS One. 2015;10(9):e0139056. Published 2015 Sep 24. doi:10.1371/journal.pone.0139056 https://pubmed.ncbi.nlm.nih.gov/26402859/

Ito S. High-intensity interval training for health benefits and care of cardiac diseases – The key to an efficient exercise protocol. World J Cardiol. 2019;11(7):171-188. doi:10.4330/wjc.v11.i7.171 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6763680/

Wen D, Utesch T, Wu J, et al. Effects of different protocols of high intensity interval training for VO2max improvements in adults: A meta-analysis of randomised controlled trials. J Sci Med Sport. 2019;22(8):941-947. doi:10.1016/j.jsams.2019.01.013 https://pubmed.ncbi.nlm.nih.gov/30733142/

Gillen JB, Gibala MJ. Is high-intensity interval training a time-efficient exercise strategy to improve health and fitness?. Appl Physiol Nutr Metab. 2014;39(3):409-412. doi:10.1139/apnm-2013-0187 https://pubmed.ncbi.nlm.nih.gov/24552392/

Roy M, Williams SM, Brown RC, et al. High-Intensity Interval Training in the Real World: Outcomes from a 12-Month Intervention in Overweight Adults. Med Sci Sports Exerc. 2018;50(9):1818-1826. doi:10.1249/MSS.0000000000001642 https://pubmed.ncbi.nlm.nih.gov/29683919/

Vasconcelos BB, Protzen GV, Galliano LM, Kirk C, Del Vecchio FB. Effects of High-Intensity Interval Training in Combat Sports: A Systematic Review with Meta-Analysis. J Strength Cond Res. 2020;34(3):888-900. doi:10.1519/JSC.0000000000003255 https://pubmed.ncbi.nlm.nih.gov/31904713/

Karlsen T, Aamot IL, Haykowsky M, Rognmo Ø. High Intensity Interval Training for Maximizing Health Outcomes. Prog Cardiovasc Dis. 2017;60(1):67-77. doi:10.1016/j.pcad.2017.03.006 https://pubmed.ncbi.nlm.nih.gov/28385556/

Sousa AC, Neiva HP, Izquierdo M, Cadore EL, Alves AR, Marinho DA. Concurrent Training and Detraining: brief Review on the Effect of Exercise Intensities. Int J Sports Med. 2019;40(12):747-755. doi:10.1055/a-0975-9471 https://pubmed.ncbi.nlm.nih.gov/31476783/

Methenitis S. A Brief Review on Concurrent Training: From Laboratory to the Field. Sports (Basel). 2018;6(4):127. Published 2018 Oct 24. doi:10.3390/sports6040127 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6315763/

Berryman N, Mujika I, Bosquet L. Concurrent Training for Sports Performance: The 2 Sides of the Medal. Int J Sports Physiol Perform. 2019;14(3):279-285. doi:10.1123/ijspp.2018-0103 https://pubmed.ncbi.nlm.nih.gov/29809072/

Baar K. Using molecular biology to maximize concurrent training. Sports Med. 2014;44 Suppl 2(Suppl 2):S117-S125. doi:10.1007/s40279-014-0252-0 https://pubmed.ncbi.nlm.nih.gov/25355186/

Sousa AC, Neiva HP, Gil MH, et al. Concurrent Training and Detraining: The Influence of Different Aerobic Intensities. J Strength Cond Res. 2020;34(9):2565-2574. doi:10.1519/JSC.0000000000002874 https://pubmed.ncbi.nlm.nih.gov/30946274/

Gäbler M, Prieske O, Hortobágyi T, Granacher U. The Effects of Concurrent Strength and Endurance Training on Physical Fitness and Athletic Performance in Youth: A Systematic Review and Meta-Analysis. Front Physiol. 2018;9:1057. Published 2018 Aug 7. doi:10.3389/fphys.2018.01057 https://pubmed.ncbi.nlm.nih.gov/30131714/

Leveritt M, Abernethy PJ, Barry BK, Logan PA. Concurrent strength and endurance training. A review. Sports Med. 1999;28(6):413-427. doi:10.2165/00007256-199928060-00004 https://pubmed.ncbi.nlm.nih.gov/10623984/

Huiberts RO, Wüst RCI, van der Zwaard S. Concurrent Strength and Endurance Training: A Systematic Review and Meta-Analysis on the Impact of Sex and Training Status. Sports Med. 2024;54(2):485-503. doi:10.1007/s40279-023-01943-9 https://pubmed.ncbi.nlm.nih.gov/37847373/

Scribbans TD, Vecsey S, Hankinson PB, Foster WS, Gurd BJ. The Effect of Training Intensity on VO2max in Young Healthy Adults: A Meta-Regression and Meta-Analysis. Int J Exerc Sci. 2016;9(2):230-247. Published 2016 Apr 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4836566/

Gim MN, Choi JH. The effects of weekly exercise time on VO2max and resting metabolic rate in normal adults. J Phys Ther Sci. 2016;28(4):1359-1363. doi:10.1589/jpts.28.1359 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4868243/

Gormley SE, Swain DP, High R, et al. Effect of intensity of aerobic training on VO2max. Med Sci Sports Exerc. 2008;40(7):1336-1343. doi:10.1249/MSS.0b013e31816c4839 https://pubmed.ncbi.nlm.nih.gov/18580415/

Yang Q, Li D, Xie H, et al. Effects of sprint interval training on maximal oxygen uptake in athletes: a meta-analysis. J Sports Med Phys Fitness. Published online October 5, 2021. doi:10.23736/S0022-4707.21.12815-4 https://pubmed.ncbi.nlm.nih.gov/34609099/

Bacon AP, Carter RE, Ogle EA, Joyner MJ. VO2max trainability and high intensity interval training in humans: a meta-analysis. PLoS One. 2013;8(9):e73182. Published 2013 Sep 16. doi:10.1371/journal.pone.0073182 https://pubmed.ncbi.nlm.nih.gov/24066036/

Lundby C, Montero D, Joyner M. Biology of VO2 max: looking under the physiology lamp. Acta Physiol (Oxf). 2017;220(2):218-228. doi:10.1111/apha.12827 https://pubmed.ncbi.nlm.nih.gov/27888580/

MacInnis MJ, Gibala MJ. Physiological adaptations to interval training and the role of exercise intensity. J Physiol. 2017;595(9):2915-2930. doi:10.1113/JP273196 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5407969/

Tanaka H. Effects of cross-training. Transfer of training effects on VO2max between cycling, running and swimming. Sports Med. 1994;18(5):330-339. doi:10.2165/00007256-199418050-00005 https://pubmed.ncbi.nlm.nih.gov/7871294/

Weltman A, Snead D, Seip R, et al. Percentages of maximal heart rate, heart rate reserve and VO2max for determining endurance training intensity in male runners. Int J Sports Med. 1990;11(3):218-222. doi:10.1055/s-2007-1024795 https://pubmed.ncbi.nlm.nih.gov/2373580/

Daniels JT, Yarbrough RA, Foster C. Changes in VO2 max and running performance with training. Eur J Appl Physiol Occup Physiol. 1978;39(4):249-254. doi:10.1007/BF00421448 https://pubmed.ncbi.nlm.nih.gov/710390/

Dolgener FA, Brooks WB. The effects of interval and continuous training on VO2 max and performance in the mile run. J Sports Med Phys Fitness. 1978;18(4):345-352. https://pubmed.ncbi.nlm.nih.gov/745381/

Seiler KS, Kjerland GØ. Quantifying training intensity distribution in elite endurance athletes: is there evidence for an “optimal” distribution?. Scand J Med Sci Sports. 2006;16(1):49-56. doi:10.1111/j.1600-0838.2004.00418.x https://pubmed.ncbi.nlm.nih.gov/16430681/

Pate RR, Durstine JL. Exercise physiology and its role in clinical sports medicine. South Med J. 2004;97(9):881-885. doi:10.1097/01.SMJ.0000140116.17258.F1 https://pubmed.ncbi.nlm.nih.gov/15455979/

Rivera-Brown AM, Frontera WR. Principles of exercise physiology: responses to acute exercise and long-term adaptations to training. PM R. 2012;4(11):797-804. doi:10.1016/j.pmrj.2012.10.007 https://pubmed.ncbi.nlm.nih.gov/23174541/

Kiens B, Richter EA, Wojtaszewski JF. Exercise physiology: from performance studies to muscle physiology and cardiovascular adaptations. J Appl Physiol (1985). 2014;117(9):943-944. doi:10.1152/japplphysiol.00874.2014 https://pubmed.ncbi.nlm.nih.gov/25277739/

Ferretti G, Fagoni N, Taboni A, Vinetti G, di Prampero PE. A century of exercise physiology: key concepts on coupling respiratory oxygen flow to muscle energy demand during exercise. Eur J Appl Physiol. 2022;122(6):1317-1365. doi:10.1007/s00421-022-04901-x https://pubmed.ncbi.nlm.nih.gov/35217911/

Pedersen BK. The Physiology of Optimizing Health with a Focus on Exercise as Medicine. Annu Rev Physiol. 2019;81:607-627. doi:10.1146/annurev-physiol-020518-114339 https://pubmed.ncbi.nlm.nih.gov/30526319/

Powers SK, Hogan MC. Advances in exercise physiology: exercise and health. J Physiol. 2021;599(3):769-770. doi:10.1113/JP281003 https://pubmed.ncbi.nlm.nih.gov/33521984/

Irvin CG. Exercise physiology. Allergy Asthma Proc. 1996;17(6):327-330. doi:10.2500/108854196778606356 https://pubmed.ncbi.nlm.nih.gov/8993725/

Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671. doi:10.1249/mss.0b013e3180304570 https://pubmed.ncbi.nlm.nih.gov/17414804/

Acevedo EO, Goldfarb AH. Increased training intensity effects on plasma lactate, ventilatory threshold, and endurance. Med Sci Sports Exerc. 1989;21(5):563-568. https://pubmed.ncbi.nlm.nih.gov/2607946/

McConell GK, Costill DL, Widrick JJ, Hickey MS, Tanaka H, Gastin PB. Reduced training volume and intensity maintain aerobic capacity but not performance in distance runners. Int J Sports Med. 1993;14(1):33-37. doi:10.1055/s-2007-1021142 https://pubmed.ncbi.nlm.nih.gov/8440543/

Belman MJ, Gaesser GA. Exercise training below and above the lactate threshold in the elderly. Med Sci Sports Exerc. 1991;23(5):562-568. https://pubmed.ncbi.nlm.nih.gov/2072834/

Ito G, Feeley M, Sawai T, et al. High-intensity interval training improves respiratory and cardiovascular adjustments before and after initiation of exercise. Front Physiol. 2024;15:1227316. Published 2024 Mar 11. doi:10.3389/fphys.2024.1227316 https://pubmed.ncbi.nlm.nih.gov/38529482/

Mølmen KS, Øfsteng SJ, Rønnestad BR. Block periodization of endurance training – a systematic review and meta-analysis. Open Access J Sports Med. 2019;10:145-160. Published 2019 Oct 17. doi:10.2147/OAJSM.S180408 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6802561/

Meyer T, Auracher M, Heeg K, Urhausen A, Kindermann W. Effectiveness of low-intensity endurance training. Int J Sports Med. 2007;28(1):33-39. doi:10.1055/s-2006-924037 https://pubmed.ncbi.nlm.nih.gov/17213964/

Ferretti G, Fagoni N, Taboni A, Bruseghini P, Vinetti G. The physiology of submaximal exercise: The steady state concept. Respir Physiol Neurobiol. 2017;246:76-85. doi:10.1016/j.resp.2017.08.005 https://pubmed.ncbi.nlm.nih.gov/28818484/

Neufeld EV, Wadowski J, Boland DM, Dolezal BA, Cooper CB. Heart Rate Acquisition and Threshold-Based Training Increases Oxygen Uptake at Metabolic Threshold in Triathletes: A Pilot Study. Int J Exerc Sci. 2019;12(2):144-154. Published 2019 Jan 1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6355121/

Zhu Z, Li H, Xiao J, Xu W, Huang MC. A fitness training optimization system based on heart rate prediction under different activities. Methods. 2022;205:89-96. doi:10.1016/j.ymeth.2022.06.006 https://pubmed.ncbi.nlm.nih.gov/35750282/

Lim AY, Chen YC, Hsu CC, Fu TC, Wang JS. The Effects of Exercise Training on Mitochondrial Function in Cardiovascular Diseases: A Systematic Review and Meta-Analysis. Int J Mol Sci. 2022;23(20):12559. Published 2022 Oct 19. doi:10.3390/ijms232012559 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9603958/

Shiraev T, Barclay G. Evidence based exercise – clinical benefits of high intensity interval training. Aust Fam Physician. 2012;41(12):960-962. https://pubmed.ncbi.nlm.nih.gov/23210120/

Laursen PB, Jenkins DG. The scientific basis for high-intensity interval training: optimising training programmes and maximising performance in highly trained endurance athletes. Sports Med. 2002;32(1):53-73. doi:10.2165/00007256-200232010-00003 https://pubmed.ncbi.nlm.nih.gov/11772161/

Kubukeli ZN, Noakes TD, Dennis SC. Training techniques to improve endurance exercise performances. Sports Med. 2002;32(8):489-509. doi:10.2165/00007256-200232080-00002 https://pubmed.ncbi.nlm.nih.gov/12076176/

Laursen PB, Shing CM, Peake JM, Coombes JS, Jenkins DG. Influence of high-intensity interval training on adaptations in well-trained cyclists. J Strength Cond Res. 2005;19(3):527-533. doi:10.1519/15964.1 https://pubmed.ncbi.nlm.nih.gov/16095414/

Esfarjani F, Laursen PB. Manipulating high-intensity interval training: effects on VO2max, the lactate threshold and 3000 m running performance in moderately trained males. J Sci Med Sport. 2007;10(1):27-35. doi:10.1016/j.jsams.2006.05.014 https://pubmed.ncbi.nlm.nih.gov/16876479/

Normand-Gravier T, Britto F, Launay T, Renfree A, Toussaint JF, Desgorces FD. Exercise Dose Equalization in High-Intensity Interval Training: A Scoping Review. Int J Environ Res Public Health. 2022;19(9):4980. Published 2022 Apr 20. doi:10.3390/ijerph19094980 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9104727/

Carey DG. Quantifying differences in the “fat burning” zone and the aerobic zone: implications for training. J Strength Cond Res. 2009;23(7):2090-2095. doi:10.1519/JSC.0b013e3181bac5c5 https://pubmed.ncbi.nlm.nih.gov/19855335/

Huang G, Wang R, Chen P, Huang SC, Donnelly JE, Mehlferber JP. Dose-response relationship of cardiorespiratory fitness adaptation to controlled endurance training in sedentary older adults. Eur J Prev Cardiol. 2016;23(5):518-529. doi:10.1177/2047487315582322 https://pubmed.ncbi.nlm.nih.gov/25901000/

Huang G, Gibson CA, Tran ZV, Osness WH. Controlled endurance exercise training and VO2max changes in older adults: a meta-analysis. Prev Cardiol. 2005;8(4):217-225. doi:10.1111/j.0197-3118.2005.04324.x https://pubmed.ncbi.nlm.nih.gov/16230876/

Katzel LI, Sorkin JD, Fleg JL. A comparison of longitudinal changes in aerobic fitness in older endurance athletes and sedentary men. J Am Geriatr Soc. 2001;49(12):1657-1664. doi:10.1046/j.1532-5415.2001.t01-1-49276.x https://pubmed.ncbi.nlm.nih.gov/11844000/

Rogers MA, Hagberg JM, Martin WH 3rd, Ehsani AA, Holloszy JO. Decline in VO2max with aging in master athletes and sedentary men. J Appl Physiol (1985). 1990;68(5):2195-2199. doi:10.1152/jappl.1990.68.5.2195 https://pubmed.ncbi.nlm.nih.gov/2361923/

Vajda M, Oreská Ľ, Černáčková A, et al. Aging and Possible Benefits or Negatives of Lifelong Endurance Running: How Master Male Athletes Differ from Young Athletes and Elderly Sedentary?. Int J Environ Res Public Health. 2022;19(20):13184. Published 2022 Oct 13. doi:10.3390/ijerph192013184 https://pubmed.ncbi.nlm.nih.gov/36293774/

Montero D, Díaz-Cañestro C. Endurance training and maximal oxygen consumption with ageing: Role of maximal cardiac output and oxygen extraction. Eur J Prev Cardiol. 2016;23(7):733-743. doi:10.1177/2047487315617118 https://pubmed.ncbi.nlm.nih.gov/26553969/

Montero D, Diaz-Cañestro C, Lundby C. Endurance Training and V˙O2max: Role of Maximal Cardiac Output and Oxygen Extraction. Med Sci Sports Exerc. 2015;47(10):2024-2033. doi:10.1249/MSS.0000000000000640 https://pubmed.ncbi.nlm.nih.gov/25680086/

Tanisho K, Hirakawa K. Training effects on endurance capacity in maximal intermittent exercise: comparison between continuous and interval training. J Strength Cond Res. 2009;23(8):2405-2410. doi:10.1519/JSC.0b013e3181bac790 https://pubmed.ncbi.nlm.nih.gov/19826281/

Ziemann E, Grzywacz T, Łuszczyk M, Laskowski R, Olek RA, Gibson AL. Aerobic and anaerobic changes with high-intensity interval training in active college-aged men. J Strength Cond Res. 2011;25(4):1104-1112. doi:10.1519/JSC.0b013e3181d09ec9 https://pubmed.ncbi.nlm.nih.gov/20661160/

Wang C, Xu Y, Zhang L, et al. Comparative efficacy of different exercise methods to improve cardiopulmonary function in stroke patients: a network meta-analysis of randomized controlled trials. Front Neurol. 2024;15:1288032. Published 2024 Jan 17. doi:10.3389/fneur.2024.1288032 https://pubmed.ncbi.nlm.nih.gov/38313560/

Mikkonen RS, Ihalainen JK, Hackney AC, Häkkinen K. Perspectives on Concurrent Strength and Endurance Training in Healthy Adult Females: A Systematic Review. Sports Med. 2024;54(3):673-696. doi:10.1007/s40279-023-01955-5 https://pubmed.ncbi.nlm.nih.gov/37948036/

Markov A, Hauser L, Chaabene H. Effects of Concurrent Strength and Endurance Training on Measures of Physical Fitness in Healthy Middle-Aged and Older Adults: A Systematic Review with Meta-Analysis. Sports Med. 2023;53(2):437-455. doi:10.1007/s40279-022-01764-2 https://pubmed.ncbi.nlm.nih.gov/36222981/

Heyne E, Zeeb S, Junker C, et al. Exercise Training Differentially Affects Skeletal Muscle Mitochondria in Rats with Inherited High or Low Exercise Capacity. Cells. 2024;13(5):393. Published 2024 Feb 24. doi:10.3390/cells13050393 https://pubmed.ncbi.nlm.nih.gov/38474357/

Nikolaidis PT, Knechtle B. Predictors of half-marathon performance in male recreational athletes. EXCLI J. 2023;22:559-566. Published 2023 Jun 22. doi:10.17179/excli2023-6198 https://pubmed.ncbi.nlm.nih.gov/37534223/

Daussin FN, Ponsot E, Dufour SP, et al. Improvement of VO2max by cardiac output and oxygen extraction adaptation during intermittent versus continuous endurance training. Eur J Appl Physiol. 2007;101(3):377-383. doi:10.1007/s00421-007-0499-3 https://pubmed.ncbi.nlm.nih.gov/17661072/

Sperlich B, Matzka M, Holmberg HC. The proportional distribution of training by elite endurance athletes at different intensities during different phases of the season. Front Sports Act Living. 2023;5:1258585. Published 2023 Oct 27. doi:10.3389/fspor.2023.1258585 https://pubmed.ncbi.nlm.nih.gov/37964776/

Cao M, Quan M, Zhuang J. Effect of High-Intensity Interval Training versus Moderate-Intensity Continuous Training on Cardiorespiratory Fitness in Children and Adolescents: A Meta-Analysis. Int J Environ Res Public Health. 2019;16(9):1533. Published 2019 Apr 30. doi:10.3390/ijerph16091533 https://pubmed.ncbi.nlm.nih.gov/31052205/

Monserdà-Vilaró A, Balsalobre-Fernández C, Hoffman JR, Alix-Fages C, Jiménez SL. Effects of Concurrent Resistance and Endurance Training Using Continuous or Intermittent Protocols on Muscle Hypertrophy: Systematic Review With Meta-Analysis. J Strength Cond Res. 2023;37(3):688-709. doi:10.1519/JSC.0000000000004304 https://pubmed.ncbi.nlm.nih.gov/36508686/

Burgomaster KA, Howarth KR, Phillips SM, et al. Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. J Physiol. 2008;586(1):151-160. doi:10.1113/jphysiol.2007.142109 https://pubmed.ncbi.nlm.nih.gov/17991697/

Hawley JA. Specificity of training adaptation: time for a rethink?. J Physiol. 2008;586(1):1-2. doi:10.1113/jphysiol.2007.147397 https://pubmed.ncbi.nlm.nih.gov/18167367/

Gibala MJ, Little JP, van Essen M, et al. Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. J Physiol. 2006;575(Pt 3):901-911. doi:10.1113/jphysiol.2006.112094 https://pubmed.ncbi.nlm.nih.gov/16825308/

Gibala MJ, Jones AM. Physiological and performance adaptations to high-intensity interval training. Nestle Nutr Inst Workshop Ser. 2013;76:51-60. doi:10.1159/000350256 https://pubmed.ncbi.nlm.nih.gov/23899754/

Ekkekakis P, Swinton P, Tiller NB. Extraordinary Claims in the Literature on High-Intensity Interval Training (HIIT): I. Bonafide Scientific Revolution or a Looming Crisis of Replication and Credibility?. Sports Med. 2023;53(10):1865-1890. doi:10.1007/s40279-023-01880-7 https://pubmed.ncbi.nlm.nih.gov/37561389/

Ekkekakis P, Vallance J, Wilson PM, Ewing Garber C. Extraordinary claims in the literature on high-intensity interval training (HIIT): III. Critical analysis of four foundational arguments from an interdisciplinary lens. Psychol Sport Exerc. 2023;66:102399. doi:10.1016/j.psychsport.2023.102399 https://pubmed.ncbi.nlm.nih.gov/37665861/

Ekkekakis P, Biddle SJH. Extraordinary claims in the literature on high-intensity interval training (HIIT): IV. Is HIIT associated with higher long-term exercise adherence?. Psychol Sport Exerc. 2023;64:102295. doi:10.1016/j.psychsport.2022.102295 https://pubmed.ncbi.nlm.nih.gov/37665824/

Coates AM, Joyner MJ, Little JP, Jones AM, Gibala MJ. A Perspective on High-Intensity Interval Training for Performance and Health. Sports Med. 2023;53(Suppl 1):85-96. doi:10.1007/s40279-023-01938-6 https://pubmed.ncbi.nlm.nih.gov/37804419/

Cochran AJ, Percival ME, Tricarico S, et al. Intermittent and continuous high-intensity exercise training induce similar acute but different chronic muscle adaptations. Exp Physiol. 2014;99(5):782-791. doi:10.1113/expphysiol.2013.077453 https://pubmed.ncbi.nlm.nih.gov/24532598/

Laursen PB. Training for intense exercise performance: high-intensity or high-volume training?. Scand J Med Sci Sports. 2010;20 Suppl 2:1-10. doi:10.1111/j.1600-0838.2010.01184.x https://pubmed.ncbi.nlm.nih.gov/20840557/

Ross A, Leveritt M. Long-term metabolic and skeletal muscle adaptations to short-sprint training: implications for sprint training and tapering. Sports Med. 2001;31(15):1063-1082. doi:10.2165/00007256-200131150-00003 https://pubmed.ncbi.nlm.nih.gov/11735686/

Soylu Y, Krustrup P, Mohr M, Arslan E, Kilit B, Radzimiński Ł. Effects of Two Different Self-Paced Training Modalities on the Aerobic Fitness Levels, Psychophysiological Responses, and Antioxidant Status in Physically Active Young Adults. J Clin Med. 2023;12(23):7232. Published 2023 Nov 22. doi:10.3390/jcm12237232 https://pubmed.ncbi.nlm.nih.gov/38068283/

Little JP, Safdar A, Wilkin GP, Tarnopolsky MA, Gibala MJ. A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. J Physiol. 2010;588(Pt 6):1011-1022. doi:10.1113/jphysiol.2009.181743 https://pubmed.ncbi.nlm.nih.gov/20100740/

Hood MS, Little JP, Tarnopolsky MA, Myslik F, Gibala MJ. Low-volume interval training improves muscle oxidative capacity in sedentary adults. Med Sci Sports Exerc. 2011;43(10):1849-1856. doi:10.1249/MSS.0b013e3182199834 https://pubmed.ncbi.nlm.nih.gov/21448086/

Gibala MJ, McGee SL. Metabolic adaptations to short-term high-intensity interval training: a little pain for a lot of gain?. Exerc Sport Sci Rev. 2008;36(2):58-63. doi:10.1097/JES.0b013e318168ec1f https://pubmed.ncbi.nlm.nih.gov/18362686/

Astorino TA, Schubert MM, Palumbo E, et al. Magnitude and time course of changes in maximal oxygen uptake in response to distinct regimens of chronic interval training in sedentary women. Eur J Appl Physiol. 2013;113(9):2361-2369. doi:10.1007/s00421-013-2672-1 https://pubmed.ncbi.nlm.nih.gov/23754097/

Hickson RC, Bomze HA, Holloszy JO. Linear increase in aerobic power induced by a strenuous program of endurance exercise. J Appl Physiol Respir Environ Exerc Physiol. 1977;42(3):372-376. doi:10.1152/jappl.1977.42.3.372 https://pubmed.ncbi.nlm.nih.gov/838658/

Habibi E, Dehghan H, Moghiseh M, Hasanzadeh A. Study of the relationship between the aerobic capacity (VO2 max) and the rating of perceived exertion based on the measurement of heart beat in the metal industries Esfahan. J Educ Health Promot. 2014;3:55. Published 2014 Jun 23. doi:10.4103/2277-9531.134751 https://pubmed.ncbi.nlm.nih.gov/25077148/

Losnegard T, Skarli S, Hansen J, et al. Is Rating of Perceived Exertion a Valuable Tool for Monitoring Exercise Intensity During Steady-State Conditions in Elite Endurance Athletes?. Int J Sports Physiol Perform. 2021;16(11):1589-1595. doi:10.1123/ijspp.2020-0866 https://pubmed.ncbi.nlm.nih.gov/33831841/

Zamunér AR, Moreno MA, Camargo TM, et al. Assessment of Subjective Perceived Exertion at the Anaerobic Threshold with the Borg CR-10 Scale. J Sports Sci Med. 2011;10(1):130-136. Published 2011 Mar 1. https://pubmed.ncbi.nlm.nih.gov/24149305/

Cunha FA, Midgley AW, Monteiro WD, Campos FK, Farinatti PT. The relationship between oxygen uptake reserve and heart rate reserve is affected by intensity and duration during aerobic exercise at constant work rate. Appl Physiol Nutr Metab. 2011;36(6):839-847. doi:10.1139/h11-100 https://pubmed.ncbi.nlm.nih.gov/22034854/

Hwang J, Moon NR, Heine O, Yang WH. The ability of energy recovery in professional soccer players is increased by individualized low-intensity exercise. PLoS One. 2022;17(6):e0270484. Published 2022 Jun 30. doi:10.1371/journal.pone.0270484 https://pubmed.ncbi.nlm.nih.gov/35771850/

Stanley J, Peake JM, Buchheit M. Cardiac parasympathetic reactivation following exercise: implications for training prescription. Sports Med. 2013;43(12):1259-1277. doi:10.1007/s40279-013-0083-4 https://pubmed.ncbi.nlm.nih.gov/23912805/

Buchheit M, Simon C, Piquard F, Ehrhart J, Brandenberger G. Effects of increased training load on vagal-related indexes of heart rate variability: a novel sleep approach. Am J Physiol Heart Circ Physiol. 2004;287(6):H2813-H2818. doi:10.1152/ajpheart.00490.2004 https://pubmed.ncbi.nlm.nih.gov/15308479/

Iwasaki K, Zhang R, Zuckerman JH, Levine BD. Dose-response relationship of the cardiovascular adaptation to endurance training in healthy adults: how much training for what benefit?. J Appl Physiol (1985). 2003;95(4):1575-1583. doi:10.1152/japplphysiol.00482.2003 https://pubmed.ncbi.nlm.nih.gov/12832429/

Weeks KL, McMullen JR. The athlete’s heart vs. the failing heart: can signaling explain the two distinct outcomes?. Physiology (Bethesda). 2011;26(2):97-105. doi:10.1152/physiol.00043.2010 https://pubmed.ncbi.nlm.nih.gov/21487028/

Tomlin DL, Wenger HA. The relationship between aerobic fitness and recovery from high intensity intermittent exercise. Sports Med. 2001;31(1):1-11. doi:10.2165/00007256-200131010-00001 https://pubmed.ncbi.nlm.nih.gov/11219498/

Børsheim E, Bahr R. Effect of exercise intensity, duration and mode on post-exercise oxygen consumption. Sports Med. 2003;33(14):1037-1060. doi:10.2165/00007256-200333140-00002 https://pubmed.ncbi.nlm.nih.gov/14599232/

Jones AM, Carter H. The effect of endurance training on parameters of aerobic fitness. Sports Med. 2000;29(6):373-386. doi:10.2165/00007256-200029060-00001 https://pubmed.ncbi.nlm.nih.gov/10870864/

Bell GJ, Snydmiller GD, Davies DS, Quinney HA. Relationship between aerobic fitness and metabolic recovery from intermittent exercise in endurance athletes . Can J Appl Physiol. 1997;22(1):78-85. doi:10.1139/h97-008 https://pubmed.ncbi.nlm.nih.gov/9018410/

Sloth M, Sloth D, Overgaard K, Dalgas U. Effects of sprint interval training on VO2max and aerobic exercise performance: A systematic review and meta-analysis. Scand J Med Sci Sports. 2013;23(6):e341-e352. doi:10.1111/sms.12092 https://pubmed.ncbi.nlm.nih.gov/23889316/

Lundberg TR, Larsson G, Alstermark R, Mandić M, Fernandez-Gonzalo R. Relationship between maximal oxygen uptake, within-set fatigue and between-set recovery during resistance exercise in resistance-trained men and women. BMC Sports Sci Med Rehabil. 2024;16(1):45. Published 2024 Feb 12. doi:10.1186/s13102-024-00830-8 https://pubmed.ncbi.nlm.nih.gov/38347629/

Saw AE, Main LC, Gastin PB. Monitoring the athlete training response: subjective self-reported measures trump commonly used objective measures: a systematic review. Br J Sports Med. 2016;50(5):281-291. doi:10.1136/bjsports-2015-094758 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4789708/

Muñoz I, Seiler S, Bautista J, España J, Larumbe E, Esteve-Lanao J. Does polarized training improve performance in recreational runners?. Int J Sports Physiol Perform. 2014;9(2):265-272. doi:10.1123/ijspp.2012-0350 https://pubmed.ncbi.nlm.nih.gov/23752040/

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.