The 3 Intensity Zones in Endurance Training

Hi! I am the author and founder of Old School Calisthenics

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Hundreds of endurance athletes were tested in a laboratory designed to very precisely control and regulate the external workload and then measure physiological responses such as oxygen consumption, ventilation, heart rate and blood lactate. Studies were conducted for cycling, cross-country skiing, rowing and distance running.

Read the study here: Medicine & Science in Sports & Exercise.

From careful physiological testing, we can distinguish 3 general intensity training zones:

  1. The Green Zone: low intensity, relatively comfortable, talking pace.
  2. The Yellow Zone: high perceived exertion, pretty hard.
  3. The Red Zone: high-intensity gasping pace.

intensity training zones in endurance sports

Is “No PAIN, No GAIN” the Way the Best Athletes Train?

Based on the research conducted by Dr. Stephen Seiler, who examined some of the best athletes in the world across different sports, different countries, males and females, the answer is definitely not. About 8 out of every 10 of their training sessions are performed in their green training zone.

“They perform a high volume of low-intensity training (LIT) in addition to much smaller but substantial proportions of both moderate-intensity training (MIT) and high-intensity training (HIT) throughout the preparation period. 

The majority of descriptive studies present a “pyramidal” training intensity distribution (TID), with high volume of LIT, substantial MIT, and less HIT, whereas a few studies suggest athletes to adopt a “polarized” TID (reduced volume of MIT, somewhat higher HIT), which have been proposed to give superior endurance adaptations. However, although some evidence suggests superior responses by increased HIT in a clearly polarized TID, there is currently limited empirical data comparing different stimulus ordering approaches for the HIT component of training that is often seen as critical to maximizing adaptations.” (Source: ResearchGate).

Again, many top athletes don’t train very much in that medium-intensity training zone. I will have to quote Dr. Stephen Seiler now:

“…The point is that I can ride at 190 and 200 watts, at 65% heart rate and pretty comfortably for 2 hours. Me and other folks with limited talent and limited training time and real jobs, we could train with a professional cycling team on one of their easy days, on very flat roads for 2 hours of a 5-hour training session… The best athletes in the world do not train in the yellow or red zone every day because they can’t. They train a lot, yes, and sometimes they push themselves to levels of exertion and fatigue that most of us will never experience, but on most days, they train in the green zone at an intensity that is relatively comfortable for them that they can go for a long time and recover and repeat day after day. And that’s what brings success.”

The best endurance athletes train with discipline. Easy training sessions stay easy, whereas hard days are hard workouts.

To conclude, according to Dr. Stephen Seiler, the idea of “No Pain, No Gain” is false. Watch his TEDx Talk Show: How “normal people” can train like the worlds best endurance athletes:

Why Does This Polarized Approach Seem to Work Better than Training Hard More Often and Less Overall?

For the highest performance level to be attainable over time, the process, or the training process, has to be sustainable. Training is beneficial overall, but the same training can be a source of stress on the system, leading to burnout, stagnation, and overtraining.

It seems that athletes have learned that some low-intensity training days and some high-intensity training days apparently give an optimal balance between adaptive signals and systemic stress. I obviously discovered this through my own experience, and later the science came conclusive enough to support my beliefs. I think that everyone who isn’t a pro athlete can learn something from the pros’ experience and science. It’s the reason why I keep publishing articles such as this one.

Also read: Is Extreme Running Bad for Health?

Time-stressed amateurs often in their effort to get the most out of every training session. Almost every workout becomes hard with very little variation. I’ll quote Dr. Stephen once again:

“…it pulls our good training intentions into a chronic grind in the yellow zone when we slow down on most days and maybe go longer, and then train hard on Sundays because we got the energy and motivation to do it. Performances get better, and the process is more enjoyable and sustainable.”

I would say it applies to ambitious persons because most out there can’t face intensity and pain and actually avoid any endurance training. Perhaps it’s one of the reasons why so many go to the gym and lift even though their cardiovascular capacity is low and they carry around a huge belly. It appears that lifting at their level does not stress them so much, making the workouts doable and more enjoyable.

However, my moral duty as a coach or exponent of general fitness is to promote what’s best for others. I am not taking anyone from the sofa directly to yellow or red zone training. Every coach who does it lacks responsibility, knowledge and discernment.

The process of getting performant, fit, muscular, and strong is not about pain, suffering and brutal training. The process is about enjoyment, a long period of adaptation once it becomes a lifestyle. You have to develop other virtues such as persistence and patience.

I often recommend hard work even though I am not necessarily referring to red zone training. I’m presumably misunderstood sometimes. I train moderately and very consistently every week and keep it so throughout the years. Thus, that’s what I suggest to you, my dear reader: train in moderation, frequently, mostly in the green zone and sometimes in the yellow and red zones!

More concretely, I now do 2-3 light-moderate workouts in combination with another 1 or maximum 2 tougher training sessions weekly. I found it sufficient to keep myself in great shape. I include strength training as well in this program.

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