Post-exertional malaise (PEM), sometimes referred to as post-exertional symptom exacerbation (PESE)[1] or post-exertional neuroimmune exhaustion (PENE),[2] is a worsening of symptoms that occurs after minimal exertion. It is the hallmark symptom of
myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and common in
long COVID and
fibromyalgia.[3][1] PEM is often severe enough to be disabling, and is triggered by ordinary activities that healthy people tolerate. Typically, it begins 12–48 hours after the activity that triggers it, and lasts for days, but this is highly variable and may persist much longer.[4][5][6] Management of PEM is symptom-based, and patients are recommended to
pace their activities to avoid triggering PEM.
History
One of the first definitions of ME/CFS, the Holmes Criteria published in 1988, does not use the term post-exertional malaise but describes prolonged fatigue after exercise as a symptom.[7] The term was later used in a 1991 review summarizing the symptoms of ME/CFS. Afterwards, the
Canadian Consensus Criteria from 2003[8] and the
International Consensus Criteria from 2011[9] used the term, as well as
later definitions.
Description
Post-exertional malaise involves an exacerbation of symptoms, or the appearance of new symptoms, which are often severe enough to impact a person's functioning.[10] While
fatigue is often prominent, it is "more than fatigue following a
stressor".[6] Other symptoms that may occur during PEM include
cognitive impairment, flu-like symptoms, pain, weakness, and
trouble sleeping.[6][4] Though typically cast as a worsening of existing symptoms, patients may experience some symptoms exclusively during PEM.[6] Patients often describe PEM as a "crash", "relapse", or "setback".[6]
PEM is triggered by "minimal"[5] physical or mental activities that were previously tolerated, and that healthy people tolerate, like attending a social event, grocery shopping, or even taking a shower.[4] Sensory overload,[10] emotional distress, injury,
sleep deprivation, infections, and spending too long standing or sitting up are other potential triggers.[6] The resulting symptoms are disproportionate to the triggering activity and are often debilitating, potentially rendering someone housebound or bedbound until they recover.[11][6][12][4]
The course of a crash is highly variable. Symptoms typically begin 12–48 hours after the triggering activity,[5] but may be immediate, or delayed up to 7 days.[6] PEM lasts "usually a day or longer",[11] but can span hours, days, weeks, or months.[6] The level of activity that triggers PEM, as well as the symptoms, vary from person to person, and within individuals over time.[6] Due to this variability, affected people may be unable to predict what will trigger it.[4] This variable, relapsing-remitting pattern can cause one's abilities to fluctuate from one day to the next.[1]
However, its presence can be difficult to assess because patients and doctors may be unfamiliar with it.[1][14] Hence, the WHO recommends that clinicians explicitly ask long COVID patients whether symptoms worsen with activity.[1]
The
2-day Cardiopulmonary Exercise Test (CPET) may aid in documenting PEM, showing apparent abnormalities in the body's response to exercise.[16] Still, more research on developing a diagnostic test is needed.
There is no treatment or cure for PEM.
Pacing, a management strategy in which someone plans their activities to stay within their limits, may help avoid triggering PEM.[24]
Physical therapy for people with long COVID must be modified to avoid triggering PEM in susceptible patients.[25]
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abc"Terms: Post-exertional malaise". Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management - Recommendations. NICE (Report). October 29, 2021. NICE guideline NG206.
Archived from the original on December 29, 2021. Retrieved May 12, 2022.
^
ab"1.2 Suspecting ME/CFS". Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management – Recommendations. NICE (Report). October 29, 2021. NICE guideline NG206.
Archived from the original on December 29, 2021. Retrieved May 12, 2022.
^"1.11 Managing ME/CFS". Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management – Recommendations. NICE (Report). October 29, 2021. NICE guideline NG206.
Archived from the original on December 29, 2021. Retrieved July 17, 2022.