Key Takeaways

  1. The primary way COVID-19 kills people is by causing acute respiratory distress syndrome (ARDS), which reduces your lung’s ability to supply oxygen to the body.
  2. New research shows that cardiovascular exercise may reduce your risk of ARDS caused by COVID-19.
  3. Keep reading to learn how exercise protects against ARDS, how much you should exercise to get the benefits, whether or not you can exercise too much, and more!

Over the past few weeks, you’ve been bombarded with contradictory, confusing, and complex facts and figures about COVID-19.

At this point, the story most often repeated in the media goes like this: 

  1. Aside from social distancing, washing your hands, and (maybe) wearing a face mask, there’s nothing you can do to avoid getting COVID-19.
  2. If you do get COVID-19, there’s nothing you can do to hasten your recovery or reduce the severity of your symptoms except wait for your body to get rid of the virus.
  3. If you’re one of the unlucky few who develops severe symptoms like respiratory failure, the best doctors can do for you is put you on a ventilator, give you some drugs to ease your discomfort, and hope for the best.

While this story is more right than wrong based on the available evidence, it paints a grim, overly simplistic picture.

Here’s how Dr. Zhen Yan, the director of the Center for Skeletal Muscle Research at the University of Virginia’s Robert M. Berne Cardiovascular Research Center, puts it

“All you hear now is either social distancing or ventilator, as if all we can do is either avoiding exposure or relying on a ventilator to survive if we get infected.”

Dr. Yan takes a more optimistic and, as you’ll see, evidence-based approach to the problem. 

In a review study published by Dr. Yan and his colleague Hannah Spaulding at the University of Virginia, they explain how regular exercise can prevent or at least reduce the severity of one of the deadliest symptoms of COVID-19, a condition known as acute respiratory distress syndrome (ARDS).

Scientists have known for quite some time that exercise improves immune function and reduces your risk of getting sick, but it’s rarely mentioned in discussions about COVID-19. 

In this article, you’ll learn how exercise may be particularly helpful for combating the symptoms of COVID-19, how much you should exercise to get the benefits, whether or not you can exercise too much, and more. 

How Exercise May Protect You from the Effects of COVID-19

Fight the Symptoms of COVID-19

One of the primary ways COVID-19 kills people is by triggering what’s known as acute respiratory distress syndrome (ARDS).

For example, a study conducted by scientists at Fudan University on patients in Wuhan China found that around 40 percent of the people admitted to the hospital with severe symptoms of COVID-19 developed ARDS, and around half of those people died as a result.

ARDS occurs when tiny blood vessels in the lungs rupture, leaking fluid into the small air sacs in the lungs where oxygen is delivered to the blood. 

When these little sacs, known as alveoli, become filled or surrounded with fluid, they can’t properly oxygenate the blood, which leads to a lack of oxygen throughout the body, organ failure, and eventually, death. 

Here’s a video that explains how this works: 

How does COVID-19 cause ARDS? 

We don’t need to get into the nitty gritty details, but the long story short is that in some people, COVID-19 causes the immune system to release a cascade of inflammatory molecules into the lungs. This “cytokine storm” causes inflammation in the alveoli and blood vessels in your lungs, leading to ARDS.

In most cases, the treatment for ARDS involves using various methods to increase oxygen levels in the blood (mechanical ventilation, nasal oxygen, etc.) and restricting fluid intake, but other than that, there’s not much doctors can do.

Why do some people get ARDS and others don’t? 

First of all, the vast majority of people who develop ARDS as a result of COVID-19 already have one or more other diseases. 

Thus, COVID-19 rarely causes ARDS by itself in otherwise healthy people, but instead acts as the last straw that breaks the camel’s back in people whose health is already tenuous.

Second, ARDS is much more likely to occur in older people (~60+) with compromised immune systems, whereas younger people are far less likely to develop ARDS or other severe symptoms of COVID-19.

And if Dr. Yan’s research proves to be correct, people who exercise regularly should also have a much lower risk of developing ARDS. 

According to Dr. Yan’s review study, the reason for this has to do with a molecule known as extracellular superoxide dismutase (EcSOD). 

This molecule is a powerful antioxidant that protects the body’s cells against inflammation caused by viruses like COVID-19, which means it could help reduce the risk of ARDS.  

Our muscle cells naturally produce some EcSOD at all times, but production spikes during cardiovascular exercise. What’s more, EcSOD doesn’t just protect muscle cells from inflammation damage. 

Instead, EcSOD produced in muscle cells is released into the bloodstream, where it travels around the body, protecting various organs from inflammation.

You can think of EcSOD as a kind of sprinkler system that turns on when inflammation begins to spiral out of control. And exercise seems to be the best way to keep that sprinkler system in tip top shape. 

To understand the beneficial effects of EcSOD, you only need look at what happens to the body when this sprinkler system is turned off. 

For example, Dr. Yan’s review details how low levels of EcSOD are associated with . . . 

  • Muscle wasting
  • High blood pressure
  • Atherosclerosis
  • Heart attack
  • Chronic obstructive pulmonary disease (COPD)
  • Kidney disease
  • Osteoarthritis

… and, of course, ARDS. 

Dr. Yan’s research also shows that increasing EcSOD, either through genetic modification or exercise, helps protect against the effects of all of these diseases (at least in animals). 

It’s still too early to say how effective exercise is at protecting against ARDS caused by COVID-19, but Dr. Yan’s research certainly opens the possibility that it’s an overlooked and underappreciated tool in safeguarding your health against the disease.

And what about prevention? Can exercise reduce your risk of getting sick in the first place? 

Well, no evidence currently shows that exercise can reduce your risk of contracting COVID-19, but there is quite a bit of evidence that shows exercise can reduce your risk of other respiratory infections.

Studies conducted by scientists at Aalborg University, the National Institute on Aging, Jagiellonian University Medical College, and the Harvard School of Public Health have all shown that regular exercise significantly reduces the risk of contagious diseases caused by viruses and bacteria. 

Scientists are still figuring out exactly how exercise improves immune function, but a few of the proposed mechanisms include: 

  • Improving the production and function of antibodies produced by white blood cells
  • Killing bacteria via the brief rise in body temperature that occurs during and after exercise
  • “Flushing” bacteria and viruses out of the lungs and airways
  • Improving the production and activity of white blood cells

In fact, research shows that exercise alters “. . . the behavior of almost all immune cell populations in the bloodstream . . .” 

One study conducted by scientists at the Lyon-Sud Hospital Center found that exercise particularly reduces the risk of upper respiratory tract infections in the elderly—which would make it seem like an ideal candidate for reducing the risk of COVID-19.

Summary: Cardiovascular exercises increases the production of an antioxidant known as EcSOD, which may help protect against acute respiratory distress syndrome (ARDS)—one of the most deadly effects of COVID-19.

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What Kind of Exercise Is Best and How Much Is Enough?

If you want to get the benefits of EcSOD, you probably need to do endurance exercise (aka “cardio”). Strength training doesn’t seem to help much in this regard.

As Dr. Yan explained in his review, “Exercise-induced EcSOD expression seems to be specific for endurance exercise, not induced by resistance exercise.” 

In other words, this is one of the benefits of cardio that strength training can’t replace.

That said, he also pointed out that since EcSOD is produced in muscle tissue, and lifting weights increases muscle mass, strength training could increase your body’s ability to produce EcSOD over time. 

That is, building muscle might increase the total amount of EcSOD you can produce, but you still need to do cardio to make your muscles produce EcSOD.

How much do you need to get the benefits? 

There’s very little research on how much you should exercise if you want to boost your EcSOD levels. That said, other research indicates that the more you exercise, the stronger your body’s natural antioxidant defenses become. 

For example, multiple studies on extreme endurance athletes such as Ironman triathletes have found that their bodies can produce significantly more natural antioxidants than sedentary people. 

So, the safe answer is that some cardio is better than none, and more is probably better than less. 

A good place to start would be something like 30 to 40 minutes of moderate cardio three to four times per week. 

Summary: Endurance training (“cardio”) is the only proven way to boost EcSOD levels, which may protect against ARDS caused by COVID-19. Start with two to three 30- to 40-minute cardio workouts per week to boost your EcSOD levels.

Is It Possible to Exercise Too Much (Or Too Intensely)?


Exercise and COVID-19

At this point, there’s more or less no question in the scientific community that moderate exercise (usually defined as 30 to 40 minutes of moderate intensity activity a few times per week) improves immune function and reduces the risk of illness. 

That said, you may have also heard that intense exercise can decrease immune function. 

For example, a review study published by scientists at the University of Illinois in 2010 opened with this bold claim: “Prolonged, intense exercise causes immunosuppression, while moderate intensity exercise improves immune function and potentially reduces risk and severity of respiratory viral infection.”

That is, long, intense workouts increase your risk of illness, whereas short, moderate intensity workouts lower your risk of illness.

The general idea is that immediately after a workout, your immune system actually becomes weaker for several hours before it has time to recover and grow stronger (just like your muscles do). 

Some scientists even refer to this period of time after a hard workout as an “open-window” for viruses and bacteria to cause disease while your immune system is out of commission.

Is this true, though? 

This idea originated when several early studies on endurance exercise (aka “cardio”) found that intense, prolonged workouts caused a drop in salivary markers of immune health, a decrease in white blood cell levels, and a higher risk of infection immediately post-exercise. 

Several studies in mice have also found that prolonged exercise increases the risk of infection after being exposed to influenza virus.

So, it would seem like intense exercise should increase your risk of infection, right? 


Thanks to the work of researchers John P. Campbell and James E. Turner, we know this isn’t the case. In a paper aptly called “Debunking the Myth of Exercise-Induced Immune Suppression,” the authors shred the core tenets of the “open-window” hypothesis:

1. Most of the studies showing an increased risk of infection post-exercise were based on anecdotal reports, and many of the athletes who supposedly had upper respiratory tract infections really had other issues like asthma or lung inflammation from breathing in lots of cold air during their workouts. 

For example, in one study where 37 athletes claimed they had an infection, lab tests proved only 11 of them (30 percent) were really sick.

2. Although some studies have shown that the fittest and fastest athletes have a slightly higher risk of infection, it’s highly unlikely this is due to getting sick right after their workouts. 

Instead, it more likely has to do with other factors such as anxiety, nutritional deficiencies, overtraining, undereating, being in close proximity to other athletes at races and workouts, frequent and prolonged travel, etc.

3. Most studies show that Olympic athletes get sick about as often as the average population (and that’s despite frequent travel, high training volumes, very low body fat levels, and other factors that should increase their risk of infection).

4. Most of the studies showing a significant decline in immune function and a higher risk of infection were in marathon and ultramarathon runners. 

It’s highly unlikely that going out for a brisk 30 to 60 minute run (often considered “intense” exercise by many) would cause similar effects, and very little data shows that other kinds of exercise (like cycling, weightlifting, swimming, etc.) cause the same negative effects.

5. Most importantly, many other studies have shown that intense, prolonged exercise is associated with a lower risk of infection and better immune function. 

One study on elite endurance athletes found that the athletes who trained the most had the lowest incidence of infection. Two studies on ultramarathon runners found similar results. On average the runners missed only 1.5 to 2.8 days of work per year to illness, whereas average non-athletes generally miss around 4.4 days per year due to illness. 

Campbell and Turner also point out that the measurement techniques often used in these studies can easily result in a “false positive” for compromised immune function in athletes, and more advanced testing shows there’s likely no significant decline in immune health after exercise. 

So, don’t worry about hurting your immune function by training “too hard” or “too much.” You probably aren’t. 

Summary: Research shows that long, intense workouts generally increase immune function. The idea that long, hard workouts increase your risk of getting sick is false.

The Bottom Line on Exercise and COVID-19

Although it’s easy to get the impression from the media that there’s nothing you can do to reduce your risk of contracting COVID-19 or lessen the symptoms, new research shows this may not be the case. 

A new scientific review shows that cardiovascular exercise can boost your body’s levels of a natural antioxidant known as EcSOD, which may protect against acute respiratory distress syndrome—one of the deadliest symptoms of COVID-19.

There’s no research on what kind of cardio or how much is best for increasing EcSOD levels, but a reasonable place to start would be three to four 30- to 40-minute cardio workouts per week.

Although some “experts” still claim that exercising too much or too intensely reduces immune function, there’s little evidence this is true. In other words, you probably don’t need to worry about exercising too much. 

All in all, this is just one more reason it’s a good idea to stay active during the COVID-19 lockdown (and for the months and years to come!).

What’s your take on exercise and COVID-19? Have anything else to share? Let me know in the comments below!

+ Scientific References