Post-exertional malaise (PEM) is one of the most defining and debilitating symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is increasingly recognised in long COVID. But what exactly is PEM, why does it happen, and what can we do about it? This article breaks down the latest scientific findings in a clear, easy-to-understand way.
What Is Post-Exertional Malaise?
PEM refers to the worsening of symptoms following physical, cognitive, or emotional exertion that would have previously been tolerated. Unlike regular fatigue, PEM is not relieved by rest and can last for days, weeks, or even months. Patients describe it as a complete energy crash, sometimes leaving them bedbound after seemingly minor activities like grocery shopping or even talking for too long.
An Everyday Example of PEM
Imagine having the flu and pushing yourself to do chores. Instead of just feeling a bit tired afterward, you wake up the next day feeling ten times worse—your body aches more, your head is pounding, and you can barely get out of bed. Now imagine that happening every single time you exert yourself, even slightly. That’s PEM.
The Science Behind PEM
While the exact mechanisms behind PEM are still being studied, researchers have identified key biological processes that help explain why it happens.
1. Metabolic Disturbances: A Body Struggling for Energy
Our cells rely on mitochondria to produce energy in the form of ATP (adenosine triphosphate). In people with ME/CFS and long COVID, research suggests that mitochondria are not functioning efficiently, leading to impaired energy production.
- Studies show that after exertion, individuals with ME/CFS have significantly lower ATP production, meaning their bodies are struggling to generate energy at a cellular level.
- Instead of efficiently using oxygen to produce energy (aerobic metabolism), the body shifts to anaerobic metabolism, leading to increased lactic acid build-up—causing pain and prolonged fatigue.
- Blood tests from ME/CFS patients after exertion have shown abnormal levels of metabolites, indicating that their bodies process energy differently compared to healthy individuals.
2. Neuroinflammation: The Brain’s Overreaction
The brain plays a major role in PEM, as increasing evidence points to neuroinflammation (inflammation of the nervous system) as a key factor.
- Brain scans have shown that people with ME/CFS have increased levels of inflammatory markers, particularly after exertion.
- Elevated levels of cytokines like TNF-alpha and IL-6 indicate an overactive immune response, which could be causing cognitive dysfunction, pain, and extreme exhaustion.
- Some studies suggest that the blood-brain barrier is compromised, allowing immune cells to enter the brain and trigger inflammation after even minor exertion.
3. Autonomic Nervous System Dysfunction: A System Out of Balance
The autonomic nervous system (ANS) controls automatic bodily functions like heart rate, blood pressure, and digestion. Many ME/CFS and long COVID patients experience dysfunction in this system, which may contribute to PEM.
- Studies show that people with PEM often have poor heart rate variability, meaning their bodies struggle to properly regulate heart rate after activity.
- Orthostatic intolerance (difficulty standing for long periods) is common, leading to dizziness, nausea, and increased fatigue after exertion.
- Dysautonomia in PEM patients can result in the body being stuck in a “fight or flight” mode, preventing proper recovery.
4. Muscle Dysfunction: The Painful Aftermath
In addition to systemic fatigue, PEM often involves significant muscle pain and weakness. Research suggests this is due to multiple factors:
- Studies show that people with ME/CFS experience delayed muscle recovery and prolonged soreness after exertion, even from mild activities.
- Oxygen delivery to muscles is impaired, leading to a build-up of metabolic byproducts like lactic acid.
- Muscle biopsies from ME/CFS patients have revealed mitochondrial abnormalities, further supporting the idea of impaired energy production at a muscular level.
What Can Be Done About PEM?
While there is currently no cure for PEM, several strategies can help manage and reduce its severity.
1. Pacing: The Key to Energy Management
Pacing is one of the most effective ways to manage PEM. It involves balancing activity and rest to avoid pushing past one’s “energy envelope.”
- The “Spoon Theory” is often used to describe energy levels: if you have only 10 spoons of energy per day, you must be mindful of how you spend them to avoid running out.
- The “Stop, Rest, Pace” approach encourages stopping activities before symptoms worsen, allowing the body to recover better.
2. Heart Rate Monitoring
Since PEM can be triggered by even minor exertion, keeping heart rate below a personal threshold can help avoid crashes.
- Some doctors recommend wearing a heart rate monitor and keeping exertion below 50-60% of maximum heart rate to prevent overexertion.
- Patients can use alarms on smartwatches to signal when they are approaching their limit.
3. Medication and Supplements
While no specific medication has been approved for PEM, some patients find relief through targeted treatments.
- Low-dose naltrexone (LDN) has shown promise in reducing inflammation and pain.
- CoQ10 and NAD+ supplements may support mitochondrial function.
- Beta-blockers are sometimes prescribed to help regulate heart rate and autonomic dysfunction.
4. Environmental and Lifestyle Adjustments
Small changes in daily life can make a big difference in managing PEM:
- Using mobility aids (like a wheelchair or cane) to reduce exertion.
- Breaking tasks into smaller steps with rest breaks in between.
- Avoiding sensory overload (bright lights, loud noises) that can contribute to cognitive fatigue.
Final Thoughts: The Need for Awareness and Research
PEM is one of the most disabling aspects of ME/CFS and long COVID, yet it remains poorly understood by many in the medical community. Increasing awareness and research into the biological mechanisms behind PEM is essential for developing effective treatments.
If you or someone you know experiences PEM, understanding the science behind it can help validate the experience and guide better management strategies. With ongoing research and advocacy, we can hope for a future where PEM is better recognised and treated.
Disclaimer
This article is for informational purposes only and should not be considered medical advice. Always consult a healthcare professional for medical concerns.
Long Covid Journey 