Why should you listen to me? I have a background in exercise science (B.Sc) and epidemiology (PhD). Since the pandemic hit, I read and wrote a lot about the coronavirus, including a review of cost-effective interventions to suppress COVID-19 and a series of long-form articles with Tomas Pueyo that have been viewed about 60 million times. I work for public health in Montreal, I curate the COVID-19 Science Updates, and I was recently in the news and on TV to discuss the virus. This article has been liked, shared, and commented on 1,614 times on Facebook.
If you’re an athlete, a lifter, or just someone who likes to keep fit, and you’re wondering if it’s safe to work out with the coronavirus around, you’ve come to the right place.
Want a summary checklist? COVID-19: Returning to the Gym Safely—5 Things to Consider.
Working out is good for your health. It prevents 26 diseases and can extend your life by 0.4 to 4.2 years (Reimers et al. 2012). But with this virus around, is it safe? In this article, we’ll look at:
- 5 things athletes do that could increase your risk of getting sick from the virus
- How to work out in a gym safely (is it even safe?)
- Returning to training after COVID-19
- Exercise, your immune system, and proven ways to strengthen it
- Questions and answers from the community, including some of the best minds in exercise science
5 things athletes do that could increase your risk of getting sick from the coronavirus
Cutting weight and getting very lean suppresses your immune system. For example:
- Tsai et al. (2011) found that taekwondo athletes who trained hard and cut weight before a national competition had suppressed mucosal immunity and more upper respiratory tract infections.
- Hagmar et al. (2008) found that athletes striving for leanness reported being ill more often in the last 3 months.
In short, now is probably a bad time to try to get very lean. But what if you carry extra weight?
It’s likely you would benefit from losing some, as obesity is a risk factor for COVID-19 hospital admission in patients younger than 60 years (Lighter et al. 2020). I’d just avoid cutting weight drastically. On that note, people who lose weight gradually and steadily (about 1 to 2 lbs a week) are more successful at keeping weight off, according to the US Centers for Disease Control (CDC, 2020).
If you train too much, too hard, for too long, you may develop a condition called “overtraining syndrome”. To be fair, this condition is usually seen in high‐performance athletes. So if you only train a few times a week to keep fit, it’s unlikely you’ll end up overtraining.
But if you get there, it can take weeks to recover from. You risk supressing your immune system, putting you at risk for upper respiratory tract infections (MacKinnon, 2000). So just to play it safe, now more than ever, if you’re looking to exercise more, it would be wise to start slowly, and increase gradually. I’d avoid abruptly training a lot more (or a lot harder) than usual.
Long, hard workouts
In a review, Gabriel and Kindermann (1997) found a potential problem with long, hard cardio workouts (at an intensity higher than 100% of anaerobic threshold or lasting 2–3 hours). Those suppressed the immune system more than moderate workouts.
So, you may want to avoid long, hard workouts for the time being, especially if you’re not used to them. If you must train long and hard, I’d avoid mingling with other people in the next 24 hours, while your immune system recovers.
In a review, Marshall-Gradisnik et al. (2009) found that steroids adversely influence the immune system, including lymphocyte differentiation and proliferation, antibody production, natural killer cytotoxic activity and the production cytokines.
A note to swimmers, cyclists, and athletes from other low-impact sports
If you usually practice a low-impact sport and you’re taking up another sport to keep fit, remember to do so gradually. Case in point:
I’m friends with a swimmer who competes at the state level. Before the virus, she used to swim 10-15 hours a week. When pools were closed, she started jogging and running 10-15 hours a week. Now, she has shin splints, and her ankles hurt.
This is anecdotal, but makes sense when you consider basic exercise guidelines. As an athlete, keep in mind that your body may not be able to tolerate the same amount of training with impact (e.g. running) than without impact (e.g. swimming).
Your immune system, exercise, and the coronavirus
Harvard Medical School explains how your immune system protects you from viruses, including the coronavirus. This involves B cells, T cells, and other cells. If you’re exposed to the coronavirus (SARS-CoV-2) and your immune system does not manage to fight it off, you’ll develop the coronavirus disease 2019 (COVID-19).
COVID-19 is a respiratory disease, but recent research suggests it’s also a circulatory disease that’s associated with substancial inflammation (Driggin et al. 2020; Shi et al. 2020; Tay et al. 2020).
You can protect yourself from inflammation with regular exercise, which also strengthens your immune system via other pathways (Nieman and Wentz, 2019). Active people get sick less often, and regular exercise (without overtraining) protects you from respiratory infections specifically (Nieman, 2000).
How often should you work out? There is evidence that your immune system gets a short-term boost after every workout, and also a long-term boost from regular exercise (Campbell and Turner, 2018). So, if you’re looking to keep your immune system primed to fight off any potential coronavirus infection, it would make sense to exercise daily. “Whole-body dynamic cardiorespiratory exercise” is best, according to Dr. Richard Simpson, PhD, writing for the American College of Sports Medicine (ACSM, 2020).
If you’re an athlete or a lifter who likes to train hard, remember that you don’t need to go all out to benefit. A brisk walk or a recovery workout should be enough to stimulate your immune system.
Other (proven) ways to strengthen your immune system
Sleep to boost your immune system and physical performance
Lack of sleep creates low-grade inflammation, and weakens your immune system (Besedovsky et al. 2012). Sadly, one in three Americans doesn’t get enough sleep (CDC, 2016). This could have serious implications in the current pandemic.
Athletes fare no better. In a systematic review, Gupta et al. (2017) found that sleep duration of athletes was similar to that of non-athletes, who don’t sleep enough. Even worse, sleep quality was lower in athletes. As an athlete, this is something you should avoid, as it’s been shown that athletes who sleep more perform better (Watson, 2017).
So how long should you sleep? At least 7 hours a night (CDC, 2016). For tips to sleep better, check out this video with Dr. Michael Breus, PhD, aka “The Sleep Doctor”:
Vitamin D3 to prevent COVID-19
Emerging evidence suggests vitamin D might protect you from COVID-19. Let’s recap:
- We already know that Vitamin D supplementation prevents acute respiratory tract infections (Martineau et al. 2017). This was a meta-analysis of 25 randomised controlled trials (11,321 participants aged 0 to 95 years). It found an adjusted odds ratio of 0.88 (95% CI = 0.81-0.96). In other words, risk was 12% lower, and the difference was statistically significant.
- In 20 European countries, low levels of vitamin D were associated with higher COVID-19 morbidity and mortality (Ilie et al. 2020).
- A retrospective cohort study of 780 cases with laboratory-confirmed infection of SARS-CoV-2 in Indonesia found that below normal Vitamin D levels were associated with higher COVID-19 mortality (Raharusun et al. 2020, preprint). Preprints are not peer reviewed, so these results await further validation.
On top of that, there is also evidence that having adequate vitamin D levels lowers overall mortality (Gaksch et al. 2017) and improves muscle strength (Chiang et al. 2017). You can get vitamin D from the sun, fish, and eggs. If you’re going to supplement, Examine.com suggests 1,000 to 2,000 IU daily. Take it with a meal (Mulligan and Licata, 2010) or at least some fat (Dawson-Hughes et al. 2015).
I’ve been taking vitamin D3 for years, and I upped my dose to 4,000 UI a day during the pandemic. This is the safe upper limit in the US and Canada.
Mind your ratio of carbohydrate/fat intake
Note: This section is contributed by Sergio Espinar, B.Sc. Sergio is a sports nutritionist with a background in pharmacy. He lectures on sports nutrition via his webiste and YouTube. You can also find him on Facebook and Instagram (all in Spanish).
Carbohydrate intake has an important role in athletic performance, however, it also could be interesting for a proper immune system functioning.
Intense (and prolonged) exercise leads to an increase of HPA axis activation, increasing cortisol and adrenaline levels and transient change in our immune system (Nieman, 1997; Suzuki et al. 2003). A few studies have shown that carbohydrate intake (especially during prolonged exercise) can counteract those changes, reducing the illness rates after a competitive marathon when you compare to placebo (Nieman, 1999). Although we need more studies in this field, everything points that carbohydrate intake leads to a reduction in pro-inflammatory cytokines and a diminished output of stress hormones, however, the claim that carbohydrate intake reduces the incidence of upper respiratory tract illness (URTI) is lacking (Bermon, 2017).
Nonetheless, as some papers point out, protocols in which the average intensity has been lower than that typically observed in competitions have found smaller changes in immune measures and little effect of carbohydrate ingestion on these. For this reason and considering the negative impact of low carb diets on the free testosterone: cortisol ratio (fTC) and recovery in athletes, assuring a correct carbohydrate intake could be beneficial to endurance athletes.
Returning to training after getting COVID-19
If you catch COVID-19 and you develop symptoms, the US Centers for Disease Control (2020) recommends you stay home and keep in touch with your doctor. But once you’re well again, how soon can you return to training?
Dr. James Hull, a respiratory physician at the Royal Brompton Hospital (UK), gives the following guidelines (Hull et al. 2020). You should wait until:
- At least 10 days have passed from onset of symptoms
- At least 7 days have passed since your symptoms resolved
To be safe, wait until BOTH conditions are satisfied to resume training. This is to avoid any myocardial (heart) damage from COVID-19 (Shi et al. 2020).
Disclaimer: This is not medical advice, and you should consult with your physician before you return to training.
Returning to training after the quarantine
Note: This section is contributed by Dr. Jason Cholewa, PhD. Jason is an assistant professor of exercise science at Coastal Carolina University and writes about athletic performance, bodybuilding, health, and fitness on his blog. You can find him on Twitter and Facebook.
First, the bad news. Unless you have access to a private gym, you probably lost some muscle mass and strength due to partial detraining as a result of the quarantine.
The onset of detectable muscle loss seems to begin following 4-6 weeks of detraining with an average loss of about 1.5% every month thereafter, and a slightly faster rate of loss in the thighs compared to arms (Bickel et al. 2011). On the bright side, it appears the more trained the individual (i.e.: people who have maintained large amounts of muscle mass for longer periods of time) lose muscle at a slightly slower rate than those who are less trained (Staron et al. 1991).
Decrements in muscular strength and power follow similar, though faster timelines. Small, detectable strength loss appears after 2-3 weeks of detraining, with reductions occurring in the lower body to a greater degree than the upper body. Strength losses can be as high as 20% in as little as 10 weeks. Unfortunately, unlike muscle mass, the stronger someone is, and the heavier they were training prior to stoppage, the faster the rate of loss once it sets in (McMaster et al. 2013).
But, there’s good news. You probably didn’t lose as much as think you did, especially if you were able to do something resistance based (bands, bodyweight, etc.) during the quarantine.
In a study in novices, as little as 1/9th the volume it took to build the muscle is necessary to maintain it up to four months, and 1/3rd the volume can maintain muscle for half a year (Staron et al. 2011). In well trained men, doing just four sets of 1 repetition with 70% 1RM at maximal effort (done at maximum speed) was enough to maintain strength and muscle mass for 8 weeks (Pareja-Blanco et al. 2020).
Finally, the best news. You will gain it back a LOT faster and with less work than it took you to build it the first time.
In one study, young women trained for 20 weeks, detrained for 30 weeks, and the retrained for 6 weeks (Staron et al. 1991). In those 6 weeks they gained back all the strength and lean mass they had lost and made more gains than a group of young women who did not previously train. In another study, three cycles of training for 6 weeks followed by 3 weeks off (24 total weeks) produced equal gains to training for 24 weeks straight (Ogasawara et al. 2013a).
Why will you gain muscle back faster and with less work?
Consistent resistance training seems to desensitize the anabolic pathways associated with muscle hypertrophy (Ogasawara et al. 2013b). On the other hand, consistent resistance training increases the myonuclear content of muscle cells, and these additional nuclei are not lost with short term detraining. Short term detraining likely resensitizes the anabolic pathways to training and nutritional stimulation, therefore necessitating less volume to promote growth (Blocquiaux et al. 2020; Seaborne et al. 2018). Additionally, the greater number of myonuclei allow the muscle cell to respond faster and more efficiently to these stimuli. Both of these factors explain why young, healthy individuals rapidly gain muscle back following a period of detraining.
How should you return to training if you’ve done no training during quarantine?
I get it. You’re feigning to train, the gyms are going to open, and you want to crush it. But I’m going to explain why and how to ease back in for the best gains.
First, take advantage of your heightened anabolic response and don’t dampen it with unnecessary volume. Second, build up a repeated bout effect, or a protective effect against future muscle damage. Neither takes much volume. A good rule of thumb is to start off with about 50% of the volume you used before quarantine and to work at an intensity of effort of about 6 out of 10. This means ceasing most of your sets about 4 repetitions prior to failure.
You’re still going to feel sore the next day, especially in muscle groups like your pecs, hamstrings, and adductors. It may feel unproductive at the time, but it’s not.
Moving forward, add a set each session until you return to the previous volume. As you do this, reduce the repetitions in reserve each session until you are working close to muscular failure. Maintain this for a week or two, deload, and then get back after it.
What if you’ve been doing some maintenance work?
Again, take advantage of the heightened anabolic response, and resist the urge to crush it the first day back. In this case, add 25% more volume to what you’ve been doing during quarantine and start back with a similar or slightly greater intensity of effort. Increase your sets and intensity of effort about 1 per session until you return to normal volume.
Working out with a mask
As of Aug 14, 2020, the medical and scientific community is split on working out with a mask. The WHO is against it (WHO, 2020). Yet, scientists from the American Council on Exercise are for it (Kravitz et al. 2020).
For sure, if you work out outside alone, a mask is not needed. But if you work out inside a gym, a mask could prevent transmission. For a breakdown of advice from official bodies, doctors, and scientists, see Working Out & Lifting Weights With a Face Mask: What Do the Experts Say?
Questions from the community
I asked my colleagues in the exercise sciences community if they had questions about the coronavirus. I got questions from:
- Spencer Nadolsky
- Mike Israetel
- Luke Hoffman
- Luis Villasenor
- Jason Cholewa
- Alan Aragon
- Brandon Roberts
- Nick Nilsson
- Adel Moussa
- Szoták Andrei
Here’s what they said:
- Spencer Nadolsky said: “How much weight loss could impact immunity.”
- Mike Israetel said: “Are there long-term health decrements in most of the people who recover from coronavirus infection?”
Great question. On the one hand, obesity is a risk factor for COVID-19 hospital admission in patients younger than 60 years (Lighter et al. 2020). Overweight patients also often have heart and other conditions identified as risk factors for COVID-19 (CDC, 2020). So it’s likely that they would benefit from losing weight.
On the other hand cutting weight and getting very lean suppresses your immune system, as we’ve seen above. So in the end, for weight loss, I’d say it depends on your starting point.
Here’s what we know so far:
- Respiratory infections can damage lungs. “Patients with acute respiratory distress syndrome (ARDS), seen often in severe COVID-19 illness, sometimes develop permanent lung damage or fibrosis as well” according to Dr. Andrew Martin (Citroner, 2020).
- Trauma from intensive care. As you can imagine, needing (and surviving) intensive care can cause issues. Those include post-traumatic stress disorder (PTSD), anxiety, depression, and physical impairments like weakness and malnutrition (Citroner, 2020).
We also know that the virus can affect the heart (Madjid et al. 2020) and the brain (Mao et al. 2020; Pleasure et al. 2020). Some doctors also worry COVID-19 could affect fertility in men (Abobaker and Raba, 2020; Wang et al. 2020). We don’t know yet if this leads to long-term damage.
Yes, based on the limited evidence we have, it does seem that cardio athletes would be less susceptible than other exercising populations (I’m thinking lifters and strength sports). According to Dr. Richard Simpson, PhD, “whole-body dynamic cardiorespiratory exercise” is best (ACSM, 2020).
For resistance training, in a brief review, Simoson (2001) found that in the short-term, it had similar effects on the immune system as high-intensity endurance (aerobic) exercise.
In one study (Nieman et al. 1995), 10 young males with 9.2 +/- 1.4 years of weight training experience performed sets of 10 repetitions at 65% 1RM of the squat, with a cadence of one rep every 6 sec. They rested 3 min between sets and performed 98 +/- 14 reps before reaching muscular failure. The researchers then found “a strong leukocytosis, lymphocytosis, and lymphocytopenia, similar to what has been reported following high-intensity cardiorespiratory exercise.”
So, we would expect similar long-term benefits. However, Simoson (2001) also found that there did “not appear to be any long-term alterations in immune cell numbers or immune system function” in trained lifters. Based on this, if you’re a lifter who usually skips cardio, it seems safe to recommend you include some cardio in your training these days, if you wish to support your immune system.
Higher fat mass is a risk factor for COVID-19 hospital admission (see above).
For muscle mass, I could not find much evidence. Moderate exercise strengthens your immune system (Nieman and Wentz, 2019), and people who exercise generally have more muscle mass than people who don’t. This points to a benefit, but the relationship may not be causal.
I found only one study on that topic: adults with more fat-free (muscle) mass had lower levels of C-reactive protein and white blood cell count (Lassek and Gaulin, 2009). Both are measures of immunity, so this would suggest that having more muscle mass lowers your immunity. However, this is just one study. Also, it’s observational, so it’s open to a number of biases. Moreover, it did not control for training status. It could be that men with more baseline (natural) muscle mass have lower immunity, but that this relationship does not hold for muscle mass acquired through training.
All in all, I’m afraid I can’t give you a good answer.
You also asked about the best exercises to maintain (or even build) some muscle with minimal equipment if no gym is available. For that, I’d refer you to our guide on building muscle with bands.
This is definitely a concern I share. If possible, I’d avoid packed gyms. You could train during off-hours, where the gym is mostly empty. I would wear a mask, avoid touching my face, and wash my hands carefully after my workout. As Tomas Pueyo and I wrote elsewhere, your gym could limit attendance, reorganize floor space, require people to maintain a 6-feet distance, and/or have someone on staff keeping all spaces clean full time. These gyms do it well:
One last thing to keep in mind is that if you’re under 50 and in good health, your risk is quite low. I included these tips in the COVID-19 Checklist: Returning to the Gym Safely.
Yes, in a way, gyms are indeed more like a Petri dish than other places. I’m not aware of any report that the virus can be transmitted through sweat, but people breathing heavily is a concern. If they don’t have a mask on, they likely will exhale droplets that could contain the virus. If these droplets are not wiped off and the equipment disinfected, you’re at risk.
So if your gym is crowded, has people not wearing masks, or machines jammed together, I would think twice. Especially if you’re over 50 or have a condition identified as a risk factor for COVID-19. On the other hand, gyms with plenty of floor space (like the one in the video above) that keep all equipment clean should be relatively safe.
Based on all of the above, I would:
- Wait at least 10 days if I got symptoms of COVID-19, and at least 7 days after they’re gone
- Train from home or in a clean gym, off-hours, with lots of floor space, and people wearing masks
- Start off with about 50% of the volume I was used to, and work at an intensity of effort of about 6 out of 10 (4 reps short of failure)
- Ramp up gradually, avoiding long, hard workouts and staying far away from overtraining
For a summary of these tips (and more), get the COVID-19 Checklist: Returning to the Gym Safely.
That’s an interesting hypothesis. We know that exercise increases blood flow and that it protects from respiratory infections (Nieman, 2000). Are these effects mediated by increased blood flow? It could be:
During exercise “the antipathogen activity of tissue macrophages occurs in parallel with an enhanced recirculation [emphasis mine] of immunoglobulins, anti-inflammatory cytokines, neutrophils, NK cells, cytotoxic T cells, and immature B cells, all of which play critical roles in immune defense activity and metabolic health” (Nieman and Wentz, 2019).
For people aged 50 years or less, I would agree that the reports are optimistic. Less than 0.4% of people who test positive die (Roser et al. 2020). People under 30, the rate is even lower (0.22% or less). However, that rate goes up quickly after age 50 (0.4-1.3%), age 60 (1.8-3.5%), age 70 (4.8-12.8%), and age 80+ (13-20.2%) (Roser et al. 2020). But if you’re young, in good health, fit, and you follow the tips I outlined here and in this checklist, your risk is indeed low.
I would bring:
- A face mask
- Hand sanitizer
- Everything else I usually bring to the gym
Great point! As we’ve seen, athletes don’t sleep enough, and have worse sleep quality (Gupta et al. 2017). What’s more, lack of sleep creates low-grade inflammation, and weakens your immune system (Besedovsky et al. 2012). So if you don’t sleep enough, now would definitely be a good time to improve. Experts recommend at least 7 hours a night (CDC, 2016).
Conclusion: Young, healthy athletes should be able to return to training safely
Young, healthy athletes should be able to return to training safely. Still, to minimize risk, athletes should avoid cutting weight, overtraining, and anabolic steroids. If you’re an older athlete (50+), you may want to avoid gyms for now, especially if your gym is crowded.
Training at home moderately should be safe for most people. It can strengthen your immune system, as do good sleep and vitamin D3. For a summary of these recommendations, get the COVID-19 Checklist: Returning to the Gym Safely—5 Things to Consider.
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