Chronic Cardio or Good Tool in the Health Toolbox?

Kent Altena October 2, 2019 CarbSmart Magazine, Fitness, Research & Science, Running Leave a comment 444 Views

Originally published in the October 2013 issue of CarbSmart Magazine, Updated 09/25/2019.

Where does running fit in a healthy exercise plan?

What is Chronic Cardio?

To some, chronic cardio refers to long-duration steady-state training done at > 80% of Max Heart Rate (for most runners that would be race pace). To others, it is any prolonged cardio event, such as “marathons, training for marathons, triathlons, 60 minutes or more on a treadmill/bike/Stairmaster at a constant high heart rate.”

My problem with such a definition is that they obviously have never done any sort of heart rate training for a marathon. During long or easy runs, most coaches recommend between 60-75% of your Maximum Heart Rate. Most plans have tempo or hard runs only once or twice a week at much shorter distances.

Any look at low carb or Paleo web sites will lead to a variety of opinions about running or doing cardio, but most often it is criticism by those who used to run but now have seen the light. Mark Sisson, a former elite-class triathlete who developed arthritis in his ankles, is a primal critic of “Chronic Cardio.” From his 2007 post named A Case Against Cardio:

“The popular wisdom of the past 40 years – that we would all be better off doing 45 minutes to an hour a day of intense aerobic activity – has created a generation of overtrained, underfit, immune-compromised exerholics.” – Mark Sisson

He has made repeated posts on this same topic pointing to the dangers of cardiac arrhythmias, cortisol increase, oxidative stress, and atherosclerosis found in many endurance runners. He also states:

“The fact is, our hunter-gatherer ancestors didn’t ramp up their heart rates significantly for over an hour every day, and I don’t think we should either.”

The History of Running

First, let’s deal with our heritage as humans and running. One anecdote many marathons runner hear is the fate regarding Pheidippides, the runner for whose achievement the marathon event was named. They fail to recall the whole story of his fateful run from Marathon to Sparta to Marathon and finally back to Athens to deliver the news, a distance of 168 miles not 26.2 miles over the course of a couple days.

My point in mentioning this anecdote is not to justify running only 26.2 miles, but to illustrate the physical feats accomplished in ancient times. There are also numerous examples of African tribal hunting practices in which hunters use their endurance and Persistence Hunting to wear out their prey. There is a tribe in Mexico, the Tarahumara, who credit low carb Chia seeds for their ability to run 50-100 miles in a single day for enjoyment or as part of hunting.

Second, let’s deal with the mounting reams of scientific studies, which have been a mixed bag both for and against marathon running and training as being the lynchpin of cardio exercise. It is usually the same type of epidemiological studies that point to the cardiac arrhythmias or the high levels of inflammations in the typical marathon runner.

This ignores the dietary component most low carbers understand is the source for much of the body’s inflammatory response. My personal markers for inflammation and CRP (Cardio Reactive Proteins) are extremely low because I follow a low carb diet while running 20-40 miles per week.

By eliminating the inflammatory sugar and wheat in my diet, my body is able to handle the stress of the training and adapt to it. That is the goal of any training program – to get better at doing what you are doing and adapt to it.

Let’s handle his remaining criticism point by point

Requires large amounts of dietary carbohydrates (SUGAR)
This seems to proven false by studies by Dr. Stephen Phinney has produced showing equal or better endurance by ketogenic athletes as his control group of athletes.
Decreases efficient fat metabolism
This criticism seems counter-intuitive as endurance running actually makes the body more productive at burning visceral fat for energy rather than consuming glycogen stores. This study demonstrates cardio exercisers lost more weight and specifically more visceral fat than did people following resistance training. Endurance training makes the body easier to tap into those long term energy stores to fuel workouts than did anaerobic sprint activities.
Increases stress hormone cortisol
This is a true statement. Any stress-inducing activity does cause a cortisol release; however, the amount of cortisol product is related to efficiency and training of the runner. It does speak to gradually increase your mileage weekly rather than potentially overtraining to the point of injury. This study showed a hormonal response only immediately after a marathon, but levels returned to normal for all levels of runners (elite, well-trained, and novice) within days.
Increases systemic inflammation.
Mark goes on to say, “carbohydrate-fueled high-intensity aerobic lifestyle was promoting a dangerous level of continuous systemic inflammation, was severely suppressing other parts of my immune system and the increased oxidative damage was generally tearing apart my precious muscle and joint tissue.” This seems a “which came first a chicken or the egg” scenario. Which caused the inflammation – the carbohydrate-fueling or the high-intensity aerobics? In either case, it does not seem related to most well-planned marathon training schedules, which feature hard-days and easy-days. By following a low carb plan and fueling my runs almost exclusively on the dietary and stored fat reserves, I eliminate much of pre-race and mid-race carbohydrate fueling most runners endure.
Increases oxidative damage (free radical production)
This study counteracts that finding that after 19 hours of endurance swimming, none of the well-trained swimmers had any significant increase in the blood oxidative stress markers. The science behind the damage from oxidative stress is unclear at best as well.
Boring!
It is hard to argue about taste or personal preference, but if it seems boring to you, perhaps you should find something else to do. I find running to be stress relieving and generally the most calming part of my day.

In my perspective, the dangers of running or having a portion of an exercise plan in cardio-based activities is greatly over-blown especially in light of the health benefits. In one ACSM report on exercise, they reported, “programs involving higher intensities and/or greater frequency/durations provide additional benefits. For example, it was shown in one study that individuals who ran more than 50 miles per week had significantly greater increases in HDL cholesterol (the good fat) and significantly greater decreases in body fat, triglyceride levels, and the risk of coronary heart disease than individuals who ran less than 10 miles per week.

In addition, the long-distance runners had a nearly 50% reduction in high blood pressure and more than a 50% reduction in the use of medications to lower blood pressure and plasma cholesterol levels.” Periods of 30 minutes or more of exercise has been related (epidemiological studies admittedly) to reduced rates of some types of cancers. In addition to these health benefits, running is particularly effective at increasing the exercise efficiency (or VO2 Max) and endurance capability of the body to consume the oxygen within the blood. Finally, running has been proven effective at reducing depression, improving sleep habits, and increasing energy levels.

Photo by Morgan Sarkissian on Unsplash

Overtraining is a danger that can affect many exercisers.

Overtraining, defined as a collapse in performance which occurs when the body gets pushed beyond its capacity to recover, is typically increasing the length, frequency, or intensity of exercise too quickly or not allowing for adequate rest after exercise. It is common in most sports or fitness activities not simply cardio or running.

If the critics of cardio were attributing their criticism to overtraining, I could go along with their criticism, but to relate all cardio-based exercise as being chronic no matter the training level is wrong. A good recommendation to prevent over-training is to include multiple cross-training days into one’s workout schedule.