Chronic Cardio: Are You Wasting Your Time?


The chronic cardio bug can bite any of us. What started out as an innocent urge to become more active has transformed into a ritual consisting of nothing more than running the same route or treadmill, on the same days, at the same times.

Chronic cardio, or the act of simply doing too much endurance training for sustained periods of time was brought up by Mark Sisson on the Joe Rogan Experience #752.

Mark Sisson, 62, is the author of “The Primal Blueprint and a fitness author and blogger. He’s also a former distance runner, triathlete and Ironman competitor. His mission is to inspire people to be open-minded, passionate, and enthusiastic about leading a healthy, happy, fit, balanced, active lifestyle, with the least amount of pain, suffering and sacrifice possible.

At one point during the interview, he remarked the following which caught my attention:

“Endurance training is antithetical to good health.”

On a personal level, I know several people who took up running and endurance sports as a means of becoming more healthy, active and enhancing their quality of life. While I’ve never focused entirely on endurance training myself, it made begin to question whether the conventional knowledge about distance running has flaws that the mainstream has bought in to.

I’ll point out here that this is a highly debated subject, with strong opinions and arguments for and against long, sustained bouts of cardio.

My post will be presenting what I’ve found against endurance training, however, I’m not ruling out summarizing the other side of the argument and combining it into a longer post in the future. For reference, Jason Fitzgerald from presents a solid rebuttal to Sisson’s work in the following post.

Let’s now kick off with some basics.

What is Endurance Training?

Put simply, endurance training involves training your aerobic system, as opposed to your anaerobic system. Both of these systems are the result of synthesized adenosine triphosphate (ATP) which is used by your body for muscular activity.

The aerobic system uses oxygen from the bloodstream, where the anaerobic system involves no oxygen. For reference:

Aerobic training:

  • Steady state cardio (distance running)
  • Cycling
  • Swimming

Anaerobic training:

  • Sprinting
  • Powerlifting
  • High Intensity Interval Training (HIIT)

When we think about endurance, two types come to mind – general and specific.

General endurance refers to non-athletes (the majority of us) who simply want to acquire a higher baseline of general fitness and to accelerate the rate of fat loss.

Specific endurance refers to both athletes and non-athletes that are focused on acquiring endurance for a specific sport or activity. Think cycling, football, or swimming.

Michael Yessis, author of Secrets of Russian Sports Fitness & Training quotes the following:

It can be shown that endurance in sport is closely tied to the execution of skill and technique. A well conditioned athlete can be defined as, the athlete who executes his or her technique consistently and effectively with the least effort.

Whether we’re training aerobically or anaerobically, the end game is to excel in our pursuit as to execute with consistency and effectively with least effort. 

Chronic Cardio and Your Heart

Now that we understand the idea of endurance training, let’s delve into the idea of chronic cardio.

Chronic cardio refers to long periods of endurance training at a steady state for over 75% of your maximum heart rate.

Common examples include maintaining a high heart rate on a bike or treadmill for over an hour, and competing in marathons or triathlons.

Your maximum heart rate is easy to find, and the most simple way of working it out is by subtracting your age from 220. For example, a 30-year-old would have a maximum heart rate of 190bpm (220 – 30).

The word chronic is synonymous with a long-term illness, which makes it even more interesting see it placed aside a form of exercise – “cardio”, considered to be the conventional yardstick for measuring how perceivably “fit” someone is.

In his post the evidence continues to mount against chronic cardio, Mark Sisson begins by describing the role our heart plays during cardiovascular exercise.

The heart, he explains, is an involuntary muscle. It responds to demands placed on it through the biochemical signals it receives from changes in your blood chemistry.

As an example, these blood chemistry changes can come about through stress (cortisol levels), changes in insulin or lactic acid. To help visualize this, think about how fast your heart starts to beat when you’re nervous, stressed or anxious.

Now, if you’re abiding by the idiotic no pain, no gain mantra burned into the belief system of the mainstream when it comes to distance running, you may begin to experience issues. Especially during long bouts of frequent endurance in the range above 75% of your maximum heart rate.

Chronic Cardio


For example, the fatigue and hypertrophy (enlargement) we feel in our muscles during, as Sisson describes, a bicep curl is obvious.

We know for ourselves when we’ve reached our limit. We feel sore and incapable of continuing, and pushing past this point raises the likelihood of tearing a muscle.

Bad news.

However, unless you’re having a heart attack, your heart does not feel this same soreness or pain. A cardiac muscle, like the heart, does not tear like muscle such as a bicep. In fact, the heart undergoes hypertrophy without us even knowing about it and enlarges and thickens when overused.

This heart thickening, when pushed to extreme levels, can induce atrial fibrillation (AF) which is a type of arrhythmia – meaning the heart beats fast and irregularly. Sisson shows that AF is strongly linked to stroke and cognitive decline, and… surprise surprise, endurance athletes are at a greater risk of AF than the general, non-running public. 


Chronic cardio is the meandering, roundabout trail that will get you there with a ton of bruises, scratches, a tick or two, and a sprained ankle. Oh, and you might get eaten by a bear along the way. – Mark Sisson

The effect of chronic cardio or frequent long distance endurance training on the heart should make you sit up and take notice.

Now, let’s talk about another style of training.

The World of Interval Training

In his book Advances in Functional Training, author Michael Boyle discusses at length the inferiority of conventional aerobic training (chronic cardio) compared to interval training.

I’ll begin by quoting him.

Conventional aerobic training is only good to get a person fit enough to tolerate interval training, or to serve as a break from interval sessions.

But what is interval training?

Chronic cardio is synonymous with aerobic endurance training.

The difference is that interval training involves a series of low to high-intensity exercise workouts interspersed with rest or relief periods. This training is at, or close to anaerobic exercise (without oxygen).

Aerobic training is often performed over long stretches of time, interval training on the other hand, is performed at a very high intensity for a shorter amount of time.

For visual reference, I’m going to go for the low hanging fruit and offer a comparison between an endurance athlete and a sprinter.

Sprinter vs Jogger

Endurance Athlete vs Sprinter – who looks better?

Aesthetics aside, the benefits of interval training are backed strongly by research.

Boyle mentions an experiment conducted by Dr. Izumi Tabata who compared moderate intensity endurance training at 70% of VO2 max to high intensity intervals done at 170% of VO2 max.

The idea was to work at a very high intensity for 20 seconds and to rest for 10 seconds after this. This would be repeated a total of 7-8 times, totaling a 4 minute span. Known as the 20/10 or Tabata protocol, the results, unsurprisingly, showed that the high intensity style of training improved the VO2 max and anaerobic capabilities more than the moderate intensity group.

Martin Gibala, PhD, Professor of Kinesiology at McMaster University in Canada also published a study comparing interval training to steady state training.

The interval program used in the study took 20 minutes to complete, compared to a steady state program taking 90-120 minutes to complete.

It was found that the subjects got the same improvement in oxygen utilization from both programs. Each group trained three times a week with the interval group training for a total of 1 hour for the week, with 6 to 7.5 minutes of intense exercise, and the steady state group exercised between 4.5 – 6 hours for the week.

Astoundingly, the same aerobic benefits were observed. Even with the steady state group training up to 6x longer.

If these are the sort of results that are seeing the light of day, then why on earth are we wasting our time with regular steady state cardio; especially if we’re all as time-poor as we claim to be?

Achieving a Balance

Interval training, for all its benefits, shouldn’t form 100% of your training load. This style of anaerobic exercise complements a conventional strength training approach well, especially if you’re endeavoring to become well-rounded in the physical and performance sense. Lifting several times a week further improves your growth hormone release, helps with building added muscle mass and improves insulin sensitivity.

Eliminating chronic cardio and introducing interval training combined with strength work will leave you well placed to be physically strong, and competitive in sports involving periods of high intensity sprinting.

Provided, of course, that you eat, sleep and recover well.

To close, here’s a quote from Dr. Kurt G. Harris:

We should keep calling marathons, centuries on the bicycle and hours on those ridiculous stairmasters and treadmills “cardio” to remind us which organ we may be putting at risk.

Running a marathon is starting to look about as smart as boxing or playing football.