Post-exertional malaise (PEM), sometimes referred to as post-exertional symptom exacerbation (PESE) or post-exertional neuroimmune exhaustion (PENE), is a worsening of symptoms that occurs after minimal exertion. It is the hallmark symptom of

myalgic encephalomyelitis/chronic fatigue syndrome Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disabling Chronic condition, chronic illness. People with ME/CFS experience profound fatigue that does not go away with rest, as well as sleep issues and problems with memory ...

(ME/CFS) and common in

long COVID Long may refer to: Measurement * Long, characteristic of something of great duration * Long, characteristic of something of great length * Longitude (abbreviation: long.), a geographic coordinate * Longa (music), note value in early music mens ...

and

fibromyalgia Fibromyalgia (FM) is a functional somatic syndrome with symptoms of widespread chronic pain, accompanied by fatigue, sleep disturbance including awakening unrefreshed, and Cognitive deficit, cognitive symptoms. Other symptoms can include he ...

. 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. Management of PEM is symptom-based, and patients are recommended to pace their activities to avoid triggering PEM.

History and terminology

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. The term was later used in a 1991 review summarizing the symptoms of ME/CFS. Afterwards, the Canadian Consensus Criteria from 2003 and the

International Consensus Criteria International is an adjective (also used as a noun) meaning "between nations". International may also refer to: Music Albums * ''International'' (Kevin Michael album), 2011 * ''International'' (New Order album), 2002 * ''International'' (The T ...

from 2011 used the term, as well as later definitions. The 2021

NICE Nice ( ; ) is a city in and the prefecture of the Alpes-Maritimes department in France. The Nice agglomeration extends far beyond the administrative city limits, with a population of nearly one million

Description

Symptoms

Fatigue Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself. Fatigue (in the medical sense) is sometimes associated wit ...

is often prominent in PEM symptoms, but it is "more than fatigue following a

stressor A stressor is a chemical or biological agent, environmental condition, external stimulus or an event seen as causing stress to an organism. Psychologically speaking, a stressor can be events or environments that individuals might consider dema ...

". Other symptoms that may occur during PEM include

cognitive impairment Cognitive impairment is an inclusive term to describe any characteristic that acts as a barrier to the cognition process or different areas of cognition. Cognition, also known as cognitive function, refers to the mental processes of how a person ...

, flu-like symptoms, pain, weakness, and

trouble sleeping Insomnia, also known as sleeplessness, is a sleep disorder where people have difficulty sleeping. They may have difficulty falling asleep, or staying asleep for as long as desired. Insomnia is typically followed by daytime sleepiness, low ene ...

. Though typically cast as a worsening of existing symptoms, patients may experience some symptoms exclusively during PEM. Patients often describe PEM as a "crash", "relapse", or "setback". Symptoms typically begin 12–48 hours after the triggering activity, but may be immediate, or delayed up to 7 days. PEM lasts "usually a day or longer", but can span hours, days, weeks, or months. PEM involves an exacerbation of symptoms, or the appearance of new symptoms, which are often severe enough to impact a person's functioning.

Triggers

PEM is triggered by "minimal" 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. Sensory overload, emotional distress, injury,

sleep deprivation Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep to support decent alertness, performance, and health. It can be either Chronic (medicine), chronic ...

, infections, and spending too long standing or sitting up are other potential triggers. The resulting symptoms are disproportionate to the triggering activity and are often debilitating, potentially rendering someone housebound or bedbound until they recover.

Variability

The level of activity that triggers PEM, as well as the symptoms, vary from person to person, and within individuals over time. Due to this variability, affected people may be unable to predict what will trigger it. This variable, relapsing-remitting pattern can cause one's abilities to fluctuate from one day to the next.

Diagnosis

PEM is a hallmark symptom of ME/CFS and is common in

. However, its presence can be difficult to assess because patients and doctors may be unfamiliar with it. Hence, the WHO recommends that clinicians explicitly ask long COVID patients whether symptoms worsen with activity. The 2-day Cardiopulmonary Exercise Test (CPET) may aid in documenting PEM, showing apparent abnormalities in the body's response to exercise. Still, more research on developing a diagnostic test is needed.

Epidemiology

PEM is considered a cardinal symptom of ME/CFS by modern diagnostic criteria: the

, the National Academy of Medicine criteria, and NICE's definition of ME/CFS all require it. The Canadian Consensus Criteria require "post exertional malaise and/or ost exertionalfatigue" instead. On the other hand, the older Oxford Criteria lack any mention of PEM, and the Fukuda Criteria consider it optional. Depending on the definition of ME/CFS used, PEM is present in 60 to 100% of ME/CFS patients. A majority of people with long COVID experience post-exertional malaise as well.

Management

There is no treatment or cure for PEM.

Pacing Pacing may refer to: In sport * Pacing, an athletic technique of spreading one's effort out over longer-distance track and field races (also in swimming) * Pacing (horse gait), a horse gait used in standardbred horse races * Motor-paced racing ...

, a management strategy in which someone plans their activities to stay within their limits, may help avoid triggering PEM.

Physical therapy Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

for people with long COVID must be modified to avoid triggering PEM in susceptible patients.

References

{{Chronic fatigue syndrome Myalgic encephalomyelitis/chronic fatigue syndrome Symptoms Long COVID