Stop with the exercise therapy
One useful takeaway is that โexerciseโ is not a single intervention. In people who develop post-exertional malaise, vigorous activity may function less like training and more like a trigger for symptom worsening. That distinction matters because much public health advice assumes deconditioning is the main problem, when the biology here appears more complex and potentially self-amplifying.
The study adds mechanistic clues, but it does not make every form of movement unsafe. It focused on a small group of long Covid patients after a brief high-intensity cycling test, so the findings are most relevant to people who already experience PEM. It cannot be used to generalize to all long Covid, all fatigue, or all exercise prescriptions. The practical lesson is narrower: symptom pattern should guide activity advice, not a one-size-fits-all fitness message.
For readers, the real-world issue is pacing versus pushing through. When post-exertional crashes are present, the priority is avoiding repeated flare-ups that may compound disability and undermine daily function. That has implications for rehabilitation settings, where well-intended escalation can backfire if clinicians miss the hallmark delayed crash pattern.
There is still uncertainty about who is vulnerable, what biological pathways drive the damage, and which interventions eventually help. But the article highlights an important shift in mindset: in some chronic illness contexts, preserving function may mean respecting limits first, then building any activity plan around recovery and symptom stability.
Toxic Exercise
Running a little harder on the treadmill or lifting heavier weights might give me some muscle pain the next day โ never crushing fatigue requiring three weeks of bed rest. But that was the case with some participants in an exercise study thatโs creating buzz online.
The research compared responses to 8-12 minutes of high-intensity cycling in a group of long Covid patients and a group of healthy people. All 46 of the volunteers had blood and muscle biopsies taken before and after for analysis.
All of the long Covid patients experienced a bout of debilitating fatigue known as post-exertional malaise. Lab studies showed signs of severe tissue damage, including dying muscle fibers, inflammation, immune activation, and metabolic disturbances in the post-exercise biopsies of patientsโ upper leg muscle, but not in those of the healthy controls.
After the exercise test, the energy-producing mitochondria of patientsโ muscle cells appeared impaired and there was also an increased accumulation of amyloid-containing deposits, which other studies have found in the blood vessels of long Covid sufferers.
The findings indicate that in people for whom vigorous physical activity brings on post-exertional malaise, or โPEM,โ exercise is far from beneficial โ it risks causing harm.
โThe pathology of PEM is completely different from being physically inactive,โ Rob Wust, an assistant professor in muscle physiology, who co-led the study, told me. Sufferers pushing themselves to improve their fitness could be making themselves sicker.
The body will try to repair the damaged muscle tissue, Wust said. Trouble arises when a PEM sufferersโ activity harms muscles that havenโt completely recovered. The damage is likely to be cumulative and occur with less activity, creating a vicious cycle of increasing susceptibility and worsening damage.
PEM is a common symptom among long Covid sufferers and a hallmark of myalgic encephalomyelitis/chronic fatigue syndrome. Many ME/CFS patients have known for decades the harms of causing PEM crashes, and use a โstop, rest, paceโ approach to avoid them.
Unfortunately, doctors, physical therapists, and researchers unfamiliar with the condition have continued to prescribe exercise therapy, unwittingly inflicting more pain and suffering on patients whose worsening symptoms and distress are often labeled as โpsychological.โ
In these cases health workers shouldnโt just not prescribe or suggest exercise, they must recommend avoiding it,ย said David Putrino, a neuroscientist at the Icahn School of Medicine at Mount Sinai in New York, who treats long Covid patients and studies the condition.
The lack of awareness is an even greater source of frustration for sufferers.
โWeโd all exercise if we could,โ said Carrie Anna McGinn, who has struggled from crippling PEM crashes and other long Covid symptoms for three years. โBut we canโt because it makes our condition worse.โ
Still, McGinn said sheโs encouraged that research is beginning to unravel the crushing problem vexing both long Covid and ME/CFS sufferers.
โIโm a science-minded person and really believe that science will one day find treatments and a cure.โ โ Jason Gale
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