Endurance or High Intensity Intervals training?

The quiz tackling Endurance vs High Intensity Intervals Training is a time-honored debate. In fact, it’s one that seems to be of great importance to the coaching world. Like BMW vs Mercedes is to the automotive world; Or like Ronaldo vs Messi is to the soccer world; Or Nicola Tesla vs Thomas Edison to the world of power and energy. Suffice it to say, it’s at the top of the game.

But, it shouldn’t be this way. And, venerable or not, in reality, there is a huge misconception among people regarding this dilemma. It lies in the fact that we can’t really compare two methods created for different purposes; much more so when they’re designed to stress the trainee in completely different ways. And that’s science in training.

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Let’s have a look at the two methods. And we’ll soon discover there is no real dilemma to be solved here. 

The intensity domain 

One of the most important parameters in aerobic performance, one that determines the kind of adaptations that will occur, as far as the trainee is concerned, is the intensity of the exercise. In physiology, there are three key domains of exercise intensity. Each of them promotes different stress levels and brings different adaptations to the table. 

Road cycling stress curve, UK
Road-cycling stress curve (UK)

Let’s take a graph illustrating the stress curve when road-cycling in the UK. As it becomes evident in Figure 1, the three domains are separated by lactate (LT) or ventilatory (VT) thresholds. 

Up to the 1st LT or VT threshold, we can find the “moderate” range coaches and athletes mainly use for endurance continuous training; but rarely (probably never) use for interval training. 

Above the 2nd LT or VT threshold, we can find the “severe” domain intensity. This is the range where High Intensity Intervals Training is mostly applied. 

There is a great difference between these two ranges. Especially in cardiovascular and muscular stress in energy utilization, as well as in molecular adaptations, etc. As a result, their effect on the human body is quite dissimilar.


Another key factor in aerobic training is the duration. When referring to endurance training we usually have slow, long distance running, cycling, or swimming in mind. No less than 2-6 hours, depending on the type of the sport, the athlete, the period, etc. And, in contrast, High Intensity Intervals Training would bring a very short but very intense bouts of repetition; lasting anywhere from 15 seconds to 10min. Of course, there’s a very specific correlation with intensity. No one can execute a 3 hour running session in the “severe” intensity domain. Likewise, the total exercise duration can affect body adaptations extremely differently.

Internal vs External load

A serious misconception in training is thinking we can compare two different workouts based on duration or distance. But, think about it! A low intensity 10km run compared with a 10x1000m interval run at a marathon pace, is utterly different. Although the external load is the same (10km) in both cases, the internal load (the stress the exercise causes to the trainee) is different in all the ways that matter. And, it will consequently not cause the same adaptations. 

So, we cannot compare two methods, after all. Especially since, by their nature, they virtually never bring the same internal load to the athlete’s body. And there’s no doubt that, regarding endurance, this kind of comparison will always bring forward the same winner. The method that will invariably bring significantly higher stress in the vast majority of cases, is High Intensity Intervals Training. 


As a result, the endurance and high-intensity interval training methods will always offer different adaptations. And, undoubtedly, VO2 max will always bear better levels of improvement with High Intensity Intervals Training. On the other hand, fat utilization and exercise economy will always be improved more efficiently with endurance training.

We know, it seems like a tough nut to crack. But you can read more about adaptations here.

If Running Economy is the goal…

What a delightful thought, isn’t it? A satisfying one, rather. If running economy is, indeed, the goal, then endurance training will always be the best method to implement. Nonetheless, if we wanted to improve VO2max, the golden standard of a method would always be High Intensity Intervals Training. 

Be mindful, though. This doesn’t mean that one method is superior to the other. To make heads or tails from all this, we always need to answer these simple questions: 

  1. With whom will we be using each training method?
  2. Why will we be using a specific training method?
  3. When is it best to use each training method?
  4. To what end do we intend to use each training method?

Think smart, plan ahead, answer these 4 questions and use each training method in the best possible way. Besides, what better way to bring better results in the optimal amount of time? And, come to think of it, how about some periodization, as well?

Endurance or High Intensity Intervals training? was last modified: July 27th, 2022 by Aris Myrkos