The Role Of High Intensity Cardio

Up until this point in my blog series on cardio (Part 1, Part 2, Part 3, Part 4, Part 5) we have mainly focused on low intensity cardio. This is primarily due to the fact that nearly everyone has too much stress in their lives.

High intensity exercise is another added stress on the body, but low intensity aerobic cardio that we have been talking about thus far, can be a stress relief or at the very least is not adding any additional stress (in most cases).

I also know that most people are going to choose high intensity exercise when given the choice. The problem is that every workout turns into a high intensity workout.

Why is that a problem?

You can’t do back to back to back workouts at that high of an intensity so what you end up doing is a workout that is kind of hard. You end up in the “black hole” of intensity where you are not working hard enough, but it’s not easy enough to fall within that aerobic level of intensity that we have been talking about.

This is why I spent so much time talking about easy aerobic cardio because I know most people will not choose this level of intensity and are working harder than they should be when they think they are doing an easy workout.

That all said, high intensity cardio exercise plays an important role in health as well, and it’s something I include in almost all my client’s training to some degree. Just like low intensity cardio training can improve our health and performance so can high intensity exercise.

Here are some of the adaptations we see with high intensity cardio exercise

https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP273196

Many of these, like mitochondrial content, blood volume, VO2 Max, stroke volume, cadiac, output, capillary density are also adaptations we see with low intensity cardio exercise.

You might be wondering what intensity of cardio exercise improves these adaptations more?

It appears to depend on the adaption.

VO2 Max and mitochondrial content appear to increase more with higher intensity cardio. Where stroke volume, cardiac output, and capillary density appear to see greater changes from low intensity cardio exercise [1].

We also discussed how cardio exercise can improve blood lipids. However, it does not appear that high intensity exercise or low intensity cardio is superior for making changes to total cholesterol, LDL, or triglycerides. However high intensity cardio does appear to be superior in raising HDL [2]

When it comes to blood pressure, neither low or high intensity cardio appears to be superior (at least in hypertensive adults) [3].

If we look at all the research comparing low intensity cardio vs high intensity cardio there does not appear to be a clear winner when it comes to the health benefits. It appears that mitochondrial, VO2 Max, and HDL improvements are greater for high intensity cardio, but low intensity cardio appears to be better for capillary density, stroke volume, and cardiac output, so we can’t say one is definitely better than the other.

There are some other considerations we need to consider as well in addition to the physical health benefits we get from cardio exercise.

First is personal enjoyment. I always say the best exercise modality is the one you enjoy the most because that will be the one you stick to for the long term. So if you enjoy high intensity cardio more than low intensity exercise it’s probably worthwhile prioritizing it over lower intensity exercise. It appears that some people do enjoy high intensity cardio over low intensity cardio [4], but I am not one of them.

Second is stress. Take a complete look at your exercise routine, is high intensity exercise present somewhere else? For example, are you already doing CrossFit/Orange Theory/F45 or other high intensity training? If so you probably don’t need to do high intensity cardio in addition to that, you are already getting the benefits from those workouts. Your cardio probably should be low intensity in order to decrease the overall stress load on their body while getting the benefits of low intensity cardio.

Third is time constraints. Where high intensity cardio crushes low intensity cardio is from a time perspective. Since most of us have time constraints this is an important benefit of high intensity cardio. However this is also the reason why people tend to abuse high intensity cardio, it’s not like people are busy just 1 day a week, they are busy 7 days a week so every time they work out they want to make it as short as possible. High intensity exercise seems like a good choice but since it’s not true high intensity exercise (due to the fact every workout is high intensity) they are really missing out on the benefits.

Lastly there can be other impacts on social connection, sleep, and food choices that need to be considered as well. If you have the opportunity to do a high intensity cardio workout with some friends and you struggle with social connection….by all means do it!!!! The social connection benefits outweigh anything else. On the other hand if you have a later workout and you have to make a choice between high intensity cardio or low intensity cardio, you are probably going to be better off choosing low intensity cardio because it’s less likely to negatively impact your sleep.

When it comes to high/low intensity cardio’s impact on food choices, there can be a highly individualized effect. Some people may find they want to eat everything in sight after a high intensity workout, others might find it severely suppresses their appetite. These can both be good or bad things, but it depends on the context of the individual and what their goals are. It is just something to be mindful of.

Having said all this, I think it is clear that high intensity cardio plays an important role in the average person’s exercise routine. The question then becomes how do you program it? At what frequency, duration, and intensity should you be incorporating high intensity cardio?

We will address the answers to those questions in the next blog post. To be the first to be notified when it is released be sure to sign up for my newsletter using the form below!

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  1. “Physiological adaptations to interval training and the role of exercise ….” 17 Oct. 2016, https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP273196. Accessed 13 Apr. 2022.

  2. (2019, December 17). HIIT is not superior to MICT in altering blood lipids – NCBI. Retrieved April 13, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6937112/

  3. (n.d.). Effects of High-Intensity Interval Training Versus Moderate … – PubMed. Retrieved April 13, 2022, from https://pubmed.ncbi.nlm.nih.gov/29949110/

  4. (2017, January 11). High-Intensity Interval Training Elicits Higher Enjoyment than … – PLOS. Retrieved April 14, 2022, from https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166299

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