If physical activity outdoors is more and more controlled to fight the epidemic of Covid-19, it is the sport at home which develops in this period of confinement. Like the French Rugby Federation which wrote to all of its practitioners this Friday to remind them that “exercises with a high workload increase the risks”, Jean-Bernard Fabre, specialist in the mechanism of fatigue and physical preparation, wishes to alert the French.
Director of the HumanFab research and expertise centers in Aix-en-Provence and Paris (8th arrondissement), he explains why home sports practiced too intensely can expose people more to the coronavirus.
Why did you want to react to the news?
JEAN-BERNARD FABRE. It comes from the fact that I watch a lot of youtubers, instagramers and other sports influencers on different networks, and I realized that the guys were all rocking tutorials. It’s like, “You are in your living room, so take bottles until you are exhausted, then you go on with this, then with that …” In fact, it made me crazy. Traditionally, if we follow a tutorial from a guy who improvises as a super sports coach, at worst we hurt ourselves, it’s not very serious. Here we are in the field of public health.
Explain to us…
First, you should know one thing: the fact that you contract a disease depends on the viral load with which you are in contact but also on your immune defenses. Solutions must therefore be found to stimulate them.
Does practicing an activity allow it?
Yes. Researchers have shown that indeed if you put yourself in motion, you will initiate a whole bunch of messages that will put the body on alert and therefore be ready to fight against external attacks. So that’s pretty good.
We feel that there is a but …
Absolutely. Research has indeed shown that physical efforts are followed by a problem: the window of vulnerability.
That is to say ?
That is to say that when you have just made a physical effort, you have, transiently, an immunodeficiency. The body is so busy reacting to sport-related stress – replenishing energy, etc. – that for some time your immune defenses are no longer focused on defending the body and you are vulnerable to external attacks.
And what does this period of vulnerability depend on?
The researchers have worked a lot and they have found that the most sensitive thing is the intensity of the effort. The vulnerability window can thus go from 3 to 24 hours. That is to say until the next day when you are going to go shopping and, hop, catch the virus!
So too intense a sport can make you fragile?
Yes and there is another problem, it is that this window of vulnerability involves the first defenses against external attacks which are located at the level of the mouth and the larynx. So it stimulates respiratory tract infections. That’s why, a lot of sportsmen, when they do too much, catch coughs, tracheitis, sore throat. So, facing Covid-19, if you don’t do the right thing in terms of physical activity, what could have been beneficial becomes extremely harmful and dangerous. That’s why you have to be careful.
Do certain features of the Covid-19 increase the risks?
The problem with this disease is that you can be an asymptomatic carrier. However, doctors have found that if you had this drop in immune defenses while you were an asymptomatic carrier, you increased your risk of having complications related to the disease. Particularly cardiac.
What is the criterion for knowing whether an effort is excessive and therefore dangerous?
It’s called the charge of a session. It depends on the duration and the intensity. Of course, it’s unique to everyone. But, despite everything, there are still rules. The rule says that an intensity considered too high from the standpoint of immune responses is when you get closer to 75% of your max heart rate. As soon as you make an effort that goes beyond that, you will have a longer window of vulnerability. And the Hiit (Editor’s note: very high intensity efforts) which is in fashion and which you have in all the tutorials, it is by definition beyond 80% of the max heart rate. There are even some of the best-selling apps in programs that run out!
And the duration?
It is not recommended to exceed 60 min. Not at the moment. What is recommended is moderate activity between 30 and 45 min. Better to do twice 30 min in the day than once 60.
With the spring temperatures, what do you recommend?
All the people who say: “The weather is nice, I want to sweat, I wear a k-way …” Especially not! The water balance must be maintained. So it’s about drinking well after exercise and not having fun sweating. Because that too, it tires the organism.
Is it a good time to start a diet?
This is the worst bullshit to do. Because to produce immune defenses, you need energy and in particular of slow sugars, therefore all that is carbohydrates. Restrictive diets and fast-diets, where you decrease your daily energy intake, are the worst enemies of the immune system.
What last recommendation would you make during this time of confinement?
Take care of your sleep. Take advantage of being teleworked to try to spend nearly complete nights and, as far as possible, avoid playing on your mobile phone before going to bed. It’s good to be able to cut. And then keep a positive mind. We realized that stress and anxiety could have a direct impact on the immune system. Tai-Chi, yoga are things that allow you to relax.