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Professor Puta, why are some people’s muscles no longer resilient after recovering from an infection?
Because the muscles no longer receive enough oxygen. On the one hand, there is increasing evidence of micro clots that disrupt blood flow. On the other hand, damaged red blood cells could be even more important. In healthy people they are smooth in shape and look like wine gums. In patients after a SARS-CoV-2 infection, they are literally frayed. Then the blood cells still transport oxygen, but because of the deformation they can no longer get everywhere. In addition, they bind oxygen more strongly and no longer release it to the muscles, or only to a small extent.
How does this damage the muscles?
The damage occurs indirectly. All cells contain small power plants called mitochondria. When a healthy muscle is stressed, it needs around 40 times more blood than when it is at rest. The mitochondria can produce energy in two ways, depending on the load. Either the muscle is only stressed for a short time, like when you stand up, then the power plants initially run without oxygen. Or the muscle is constantly stressed, like when walking, then it needs oxygen and, for example, sugar as input in order to generate energy.
Without oxygen, the power plants cannot burn their fuel properly. What happens then?
Without oxygen, mitochondria can only generate about six percent of the energy that would be possible with oxygen. First of all, this means that muscles then perform less. Additionally, without oxygen, the mitochondria produce several waste products that are harmful to the muscle. This includes the salt of lactic acid, which has to be broken down again.
How does the body break down these substances?
For this it also needs the mitochondria. And as garbage disposal they absolutely need oxygen. If this is missing, waste products such as lactate and calcium remain in the muscle after heavy strain and cause long-term damage. We do not yet know exactly to what extent the mitochondria themselves also suffer from the overload. But one thing is certain: they no longer work properly in this mode.
So the mitochondria are comparable to hybrid cars, which have a small but weak electric motor for short journeys and a more powerful combustion engine for long journeys. Could one say casually: the combustion engine is broken for Long Covid patients?
Exactly. With the weaker electric drive, hybrid cars don’t go far and have to recharge more often, but they work quite well on short journeys. It’s similar with mitochondria. One difference from a hybrid car is that our body can generate energy from three fuels: carbohydrates, proteins and fat. However, energy from proteins is problematic because it breaks down muscles. This is how we initially recognized the severe cases because they had lost a lot of muscle mass.
How can I as a sufferer tell whether I am suffering from PEM?
You can check your rapid force production with a simple experiment. You sit on a chair and stand up as quickly as you can for a minute and then sit down again. The power plants in your thighs generate energy quickly and without oxygen. Then the muscles burn even in fit people. Some even feel flu for five minutes. But after half an hour it works again. The first attempt is also going well for some Long Covid patients. But there is no energy for a second round.
Why?
There is a lack of regeneration. This would require oxygen so that the waste materials can be transported away. But this no longer works for Long Covid patients. That’s why the muscles usually hurt immediately after the first round and feel leaden and inflamed. Trying again after half an hour is impossible and not recommended at all. In general, it is important to only attempt such a test if you are not too ambitious about it.
Post-exertional malaise often occurs in spurts and with a time delay after stress. How do I know how much I can afford?
This is indeed difficult. Symptoms such as a strong flu feeling and pain often begin hours or days after you have been physically or mentally active. It’s best to pay attention to the first signs before such an exposure. An indicator of this is the resting heart rate. If you constantly measure it and it was 10 to 15 beats higher than normal during the night, then you should slow down and do less the following day. In case of doubt, the “Stop-Rest-Pace” rule applies to PEM anyway. So pause, rest and only be active within the limits of your energy.
Why is resting heart rate an important indicator?
A high resting heart rate indicates that our body is very busy, for example with inflammation. This can be promoted during a PEM episode by the muscular metabolic products. In healthy muscles, we see similar reactions after exercise. First an immune response is triggered, then small inflammation occurs. But a healthy body can handle it well. We also suspect that there are other factors that promote permanent inflammation in Long Covid patients, for example residues of the SARS-CoV-2 spike protein.
What experiences from sports science can help alleviate PEM episodes?
We know from high-performance athletes that magnesium improves the chemical balance in the muscle. You can easily consume up to 300 milligrams per day in total, even as a preparation. I can also recommend zinc and selenium, both of which inhibit inflammation. We also know from a new study that creatine may improve muscle strength and recovery time in some ME/CFS patients. However, this is only recommended for people with healthy kidney function.
How close is research to a cure?
We believe that in about six years we will have a good understanding of how PEM works in detail. At that point at the latest, medications can be used specifically in those areas of the body that have gone out of control after a viral infection. These can be agents that promote blood circulation or medications that directly strengthen the mitochondria. In clinical trials, existing drugs are tested off-label and new ones are developed. However, it will still take some time before approval is granted. Until then it’s time to hold on!