Due to the Corona virus, or COVID-19 pandemic, an increasing number of cyclists have spare time to kill at home and away from work.
It may be tempting to spend your days getting some extra quality time on Zwift or even riding outdoors.
The question is, should you?
EDIT: This is a situation that is changing rapidly and from day to day. This original post was written March 15. At this point Norway is in a state of semi-lock down; schools closed, businesses closed, health care workers forbidden to travel abroad and the health care system is preparing for the exponential increase in Corona patients to hit in the next few weeks. We are still allowed to move outdoors, but are being encouraged not to.
Note: Any advice provided in this post should be overridden by recommendations or laws imposed by your local authorities.
Several athletes and coaches have raised the question of whether training compromises immune function, thereby increasing your risk for contracting COVID-19.
As a medical doctor and keen cyclist I have to say that I’ve been pondering the same issue myself.
So here is a brief overview of the matter and some points of consideration before you go training (or not).
The basic facts you need to understand
This entire question is essentially a matter of weighing risk versus reward. And considering how your decision impacts yourself, as well as your family and neighbors.
And in order to do so we need to consider some basic facts:
As I am writing this (March 15th) there are currently 142 539 confirmed cases of COVID-19 on a global scale (1).
The Corona virus is highly contagious and is spreading with exponential rates in many countries.
The mortality rates have been reported in the range of 1.6-3.6% , that is 1-3 deaths in 100 infected subjects (2). However, there is much uncertainty pertaining to these numbers, and some authors suggest time-delayed estimated of 5.6% mortality and as high as 20% in Wuhan, the epicenter of the outbreak (3).
The risk of a severe outcome from Corona virus appears to increase with age.
As such, there can be no doubt we have a serious situation on our hand.
The mortality rate in people aged 60 and below is low. The real issue is the rapid spread of the virus and the vast number of globally infected subjects.
Based on the above mortality rates, the 142 539 global cases would yield 3278 deaths in the “low risk” population between 0 and 60 years of age.
Indeed, there are reports of deaths in young and healthy persons without prior illness or known risk factors, such as the young medical doctors in China.
I am not saying this to make you overly worried. However, I am urging you to understand the gravity of the situation.
The risk for severe outcomes from COVID-19 in a young and healthy athlete is still low.
However, the brief history of the virus, the scarcity of knowledge on its behavior and lack of effective therapy and vaccines that calls for caution to be taken.
Understand what society is trying to achieve
The grim results of a speedy Corona spread is currently evident in Italy. The harsh triaging of elderly patients is a grave example of what happens when too many people gets infected at the same time.
When the acute demand for emergency services exceeds the capacity, hospitals can no longer provide necessary and life-supporting treatment for seriously ill patients.
This is how bad the situation can get.
The pivotal point in avoiding a disastrous outcome from the Corona pandemic is to delay the spread of the virus so that health care services can cope with the amount of new cases – popularly coined as “flattening the curve”.
To this end, a stepwise ladder of increasingly invasive measures may be taken by Governments. The crux of these measures is limiting the number of contact points between people.
Without contact, the virus cannot spread.
HOWEVER, there is a secondary issue at hand here. One that involves anyone involved in activities with an increased risk of acute injuries – cycling is one such example.
It is all well and good to limit the outbreak of acute Corona cases. Yet, just because there is a pandemic at work, people are still going to get seriously ill with heart disease, chronic obstructive airway disease exacerbation, strokes, appendicitis or get injured in traumatic accidents.
The responsibility of young and healthy people does not stop at limiting social contact. It also involves taking measures to limit the risk of straining the health care system with emergencies unrelated to COVID-19.
To paint you a picture:
For the last year, I’ve been an observer during the reception of trauma patients at Norway’s most specialized trauma hospital.
When a patient enters with a suspected spinal cord injury or internal bleeding from a bike crash, that patient lays siege on:
- 1 gastric surgeon
- 1 orthopedic surgeon
- 1-2 anesthesiologists
- (potentially 1 vascular surgeon)
- (potentially 1 thorax surgeon)
- 1 radiographer
- 1 radiologist
- 1 biochemist
- and a handful of highly trained nurses
And that is just the minutes and hours during the acute reception. Then comes the time of the staff to monitor and treat the patient for the hours and days to come. And those are just the relatively rare serious injuries.
Then there is the more frequent milder injuries that occupy the waiting rooms of any acute outpatient wards. For reference, the acute outpatient trauma emergency room in Oslo where I used to work see upwards of 2100 cycling related injuries every year (4).
During the time of a pandemic, the health care system desperately needs for the number of these easily preventable injuries to go down. So that necessary resources can be directed at those that are critically ill with pandemic infections, as well as other non-avoidable medical emergencies.
If we healthy and fortunate ones can limit the risk of acute injuries by adjusting our behavior, I would say it is our duty to do so.
This pertains to considering if you should be riding your bike outside at all (for those not yet placed in cerfew). And it pertains to how and where you ride your bike, if you decide to go riding at all.
I will leave this decision for YOU to make. The point is for you to understand that your decision contributes to our collective behavior. And that this behavior will directly impact the strain placed upon YOUR health care services when your friends, family and neighbors need it most.
If you crash your bike and sustain a fracture or potential internal bleeding during the Corona outbreak, don’t expect to have emergency services come running immediately. It may even take you a while to get through to them on the phone.
What about indoor training and immune function?
So what about Zwift sessions?
The prospect of spending your days punching out big hours on your trainer sure is appealing.
But how does acute training affect your immune system? And how does this affect risk of contracting COVID-19? And could training impact on the severity of symptoms and sequela should you happen to get infected?
Let us first consider the hard facts.
It is well known that acute training modulates the activity of the immune system.
The message commonly portrayed is that:
- Acute exercise temporarily modulates the activity of circulating immune cells (5)
- The “open window theory” suggests heavy exercise results in a temporary opportunity for infectious disease (6)
- Chronic training over time may results in enhanced immune function (7-8)
If this was indeed the case, the advice would be straight forward enough.
However, several authors have pointed to weaknesses in the data undermining the “open window theory”.
Most recently, Campbell and Turner make a compelling argument for why the “open window theory” may be based on weaknesses in prior studies rather than a true immunosuppressive effect of acute exercise (8).
In summary, the over-arching aim of this review is to rebalance opinion over the perceived relationships between exercise and immune function. We emphasize that it is a misconception to label any form of acute exercise as immunosuppressive, and, instead, exercise most likely improves immune competency across the lifespan.
Campbell & Turner. Frontiers of Immunology 2018
To put it briefly, scientists are still debating whether or not acute training results in true (temporary) depression of the immune system.
And even if it should happen to be the case, the clinical significance of this depression (how big is the effect) would still be unknown.
I must emphasize that I am no specialist in immunology. However, I would suggest that the gravity of the current Corona pandemic calls for some pragmatic caution.
Regardless of the “open window theory”…
…if I were to contract COVID-19 chances are good I will experience mild symptoms only
…but there is also a good chance that I will experience a severe and bothersome course of illness
…and there is a tiny, but real possibility of becoming seriously ill.
We can debate the clinical significance of acute training on immune function. However, there can be little doubt that heavy training puts the body in a state of acute catabolism.
Given the high risk of contracting COVID-19, and the real chance of falling ill, you would do well to ask yourself whether or not you want to put your body in such a state over the next few weeks and months.
A summary of practical considerations
For starters I would urge you to read up on and follow the advice from your governing body. In particular relating to rules for quarantine and isolation. Local and national authorities are the ones seeing the full picture of the situation where you are located.
To be clear, I am not suggesting no one should rider their bike ever.
That being said, you will probably do well to:
1 | Contribute to limiting the risk of events that may put additional strain on the health care services – in particular with regards to if you need to ride, and where and how you choose to do so.
2 | If you have symptoms, avoid training. Period.
3 | Given the many unknowns regarding risk and sequela of COVID-19 infections, consider resorting to your regular training load only. Or even lower it. Avoid excessive training periods that induce severe catabolism.
4 | The higher your age, the greater caution you should exercise (does NOT mean that younger athletes should behave carelessly).
- Coronavirus disease 2019 (COVID-19). Situation Report-54. https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200314-sitrep-54-covid-19.pdf?sfvrsn=dcd46351_6
- Coronavirus disease 2019 (COVID-19). Situation Report-41. https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200301-sitrep-41-covid-19.pdf?sfvrsn=6768306d_2
- Baud D et al. Real estimates of mortality following COVID-19 infection. The Lancet Infectious Disease, 2020. DOI: https://doi.org/10.1016/S1473-3099(20)30195-X
- Melhus K et al. Sykkelskader i Oslo 2014 Oslo Skadelegevakt. Oslo Universitetssykehus, Helsedirektoratet 2015
- CAM Goncalves et al. Effect of acute and chronic aerobic exercise on immunological markers: A systematic review. Frontiers in Physiology, 2020. https://doi.org/10.3389/fphys.2019.01602
- Keast, D., Cameron, K., & Morton, A. R. (1988). Exercise and the immune response. Sports Medicine, 5(4), 248–267.
- Sellami M et al. Effects of acute and chronic exercise on immunological parameters in the elderly aged: Can physical activity counteract the effects of aging? Frontiers in Immunology, 2018;9:2187
- Campbell JP and Turner JE. Debunking the myth of exercise-induced immune suppression: Redifining the impact of exercise on immunological health across the lifespan. Frontiers in Immunology, 2018. https://doi.org/10.3389/fimmu.2018.00648