Not even elite athletes can escape the effects of post-COVID-19 fatigue, though their experiences may vary from the average patient's.
This is one of the findings of a new study out of the United Kingdom, published on Feb. 17 in The British Medical Journal (BMJ).
In the paper, researchers from the Academic Department of Military Rehabilitation, Oxford University Hospitals NHS Trust and Royal Brompton Hospital present a case study involving an elite athlete in his late 30s whose athletic performance suffered for months after a mild case of COVID-19.
Not only does the case offer insight into how post-COVID-19 symptoms affect athletes, but the researchers wrote that it improved their understanding of how to distinguish serious post-COVID-19 side effects like myocarditis – a potentially serious heart condition associated with COVID-19 infections – from other, less deadly post-COVID conditions.
"Following an apparently mild initial COVID-19 presentation, patients frequently suffer prolonged symptoms such as fatigue, breathlessness and chest pain. These symptoms, commonly experienced post-COVID-19, are also hallmark symptoms of myocarditis," the study reads.
"Distinguishing between patients suffering from significant cardiopulmonary pathology, those suffering from a typical post-viral fatigue syndrome or dysfunctional breathing can be challenging."
The unnamed "elite distance runner" tested positive for COVID-19 in February 2021, after experiencing some of the most common symptoms of an infection: dry persistent cough, shortness of breath, fever, fatigue and sore throat. At the time, he was not vaccinated against SARS-CoV-2. His acute symptoms faded after about six days, but that's when his struggle with post-infection symptoms began.
First, he suffered from three episodes of left-sided chest pain, the second of which was serious enough to land him in an emergency room. Doctors ran blood and ECG diagnostics to rule out a heart attack or heart disease and released him. About three weeks after testing positive for COVID-19, he started running again, but the results were discouraging.
During his first run after contracting the virus, it took the athlete 35 minutes to cover 6.4 kilometres – a distance that would have taken 28 minutes prior to the infection. He said he'd lost his "kick" – his ability to rapidly accelerate. On top of that, he described feeling worn out after exercising.
"After the run and the following few days, I found myself feeling quite unwell again, fatigued, headaches and some mild heart symptoms (palpitations, mild chest discomfort and arrhythmia straight after my run)," he is quoted saying in the study. "I felt that poorly after my first few runs that I had to have large gaps in-between (six to seven days), before building up gradually."
At six weeks post-infection, a doctor told the runner he should keep running as long as the results from a planned five-day Holter heart monitor, an echocardiogram and exercise tests were promising. All the tests came back clear.
However, doctors still wanted to rule out other potential causes of his symptoms. So they tested for acute myocarditis – potentially deadly inflammation of the heart muscle – pericarditis, pulmonary embolism, lung fibrosis, mononucleosis infection, Lyme disease, diabetes, thyroid dysfunction and vitamin D and iron deficiency. They even tested for Q-fever, a bacterial infection caused by inhaling dust contaminated by infected animal feces, urine, milk and birth products, that the U.S. Centers for Disease Control and Prevention say causes flu-like symptoms. Everything came back clear.
Doctors were also able to prove the runner hadn't just become de-conditioned due to taking a break from training by measuring his peak oxygen uptake. In someone who has become de-conditioned, doctors would expect to see a lower peak oxygen uptake – the maximum amount of oxygen the body can utilize during exercise – but this figure hadn't changed in the runner.
One thing that had decreased was his anaerobic threshold. A person's anaerobic threshold is the highest exercise intensity they can sustain for a prolonged period before lactic acid – a byproduct of energy being made from glucose – starts to build up in the blood.
When someone reaches their anaerobic threshold during exercise, they tend to feel fatigue and a burning sensation in the muscles, according to research on endurance training. This threshold is different for everyone and can change over time.
Anaerobic threshold is a function suspected by scientists to be affected by COVID-19 infections and associated with post-COVID chronic fatigue syndrome. In other words, their investigation of the runner's symptoms led the authors of the study to conclude he was most likely suffering from some of the same post-COVID fatigue symptoms many patients have reported, albeit to a different degree, thanks to his pre-COVID fitness level.
"The lack of ability of an elite athlete to "kick" might be considered akin to the general population struggling in their performance of more routine activities," the authors wrote.
With this in mind, the runner built a fitness recovery routine that allowed him to gradually improve his anaerobic threshold.
By four months post-infection, he could run up to 16 kilometres without chest pain. By seven months, he'd regained his "kick" and was able to run steeplechase races. And eleven months after contracting COVID-19, the authors wrote, he managed to run 10 kilometres in 33 minutes and three seconds, "a time (one minute) faster than run 17 months prior to his acute illness."
The authors concluded by saying that, while fatigue, chest pain and lower exercise tolerance can be symptoms of serious COVID-19 side effects like lung and heart disease and injury, they can also be symptoms of post-COVID fatigue.
That they were able to confirm this in an elite athlete by ruling out other potential causes of his symptoms and testing his anaerobic threshold offers some hope for other patients looking to diagnose their post-COVID-19 symptoms.
