Post-Exertional Malaise in Fatiguing Diseases: What to Know

Identifying the phenomenon of post-exertional malaise (PEM) in patients with fatiguing conditions is critical because it necessitates a far more cautious approach to exercise, experts said.

PEM is a defining feature of the condition myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), and it is present in many people with long COVID. It is characterized by a worsening of fatigue and of other symptoms after previously tolerated physical or mental exertion, typically emerging 24-72 hours after the exertion and lasting days or weeks thereafter. The experience is often called a “crash.”

In a study presented at American College of Rheumatology (ACR) 2024 Annual Meeting, PEM was also identified in people with various rheumatologic conditions, ranging from 4% in those with osteoarthritis to 20% in those with fibromyalgia. The presence of PEM was also associated with worse pain, sleep, cognition, and other symptoms that are also characteristic of ME/CFS and many cases of long COVID.

“PEM assessment is becoming more important in those with long COVID, as we are assisting more of those with long durations of this condition…This is the first study we know of presenting PEM rates in a rheumatologic disease population,” Kaleb Michaud, PhD, director of FORWARD—The National Databank for Rheumatic Diseases and professor of rheumatology and immunology, University of Nebraska Medical Center, Omaha, Nebraska, said in his presentation of the data at the ACR meeting.

During the discussion period, study investigator Leonard H. Calabrese, DO, head of the Section of Clinical Immunology, Cleveland Clinic, Cleveland, commented, “PEM is seen with numerous post-acute infectious sequelae. It segregates with that population of patients who meet the diagnostic criteria for ME/CFS, of which 50%-70% of people will also meet criteria for fibromyalgia…This is a first step, but it has big ramifications regarding exercise.”

In an interview with Medscape Medical News, Calabrese said, “We recommend exercise to virtually everyone with fibromyalgia who doesn’t have ME/CFS,” but that the assessment tool used in the study, the 5-item DePaul Symptoms Questionnaire, isn’t adequate for assessing true PEM that would preclude exercise, despite being validated. “That instrument is inexact and lacks specificity…It just shows where the field is. We need better biomarkers.”

In Those With PEM, Exercise May Harm

Asked to comment, Brayden P. Yellman, MD, a rheumatologist at the Bateman Horne Center, Salt Lake City, Utah, told Medscape Medical News, “if there is an infection-associated chronic condition that meets criteria for what we would call ME/CFS or long COVID, and if there’s true post-exertional malaise, any graded exercise that ultimately leads to post-exertional malaise is harmful…There is a subset of people who have milder disease, who can sometimes do very mild exercise that does not trigger PEM, and they do see benefits over time very slowly with really carefully curated, carefully monitored exercise. But we have to be really careful.”

For the majority, however, the approach is to teach patients to pace their activities in order to avoid PEM, also referred to as staying within their “energy envelope.” Clinician resources are available on the Bateman Horne Center’s website.

This isn’t typically included in rheumatology training, Yellman noted. “Having completed an entire rheumatology fellowship and working in rheumatology, I was not taught at all about [then-termed] chronic fatigue syndrome. It was lumped under fibromyalgia. And of course, they teach about fibromyalgia because it’s a great mimic of a lot of inflammatory, rheumatological conditions, but the idea of [PEM], that pathognomonic feature that we see in infection-associated chronic conditions, was not once mentioned when I trained, in 2014 to 2016.”

Nonetheless, he added, “rheumatologists are definitely seeing this in their fibromyalgia patients and some of their other patients at a high rate, and I’m sure that they’re missing it, along with other comorbidities like orthostatic hypotension.”

Another expert asked to weigh in, Todd Davenport, PT, DPT, PhD, professor and chair of the Department of Physical Therapy at the University of the Pacific, Stockton, California, told Medscape Medical News, “Our experience is that the body’s responses to short bouts of exercise are abnormal, and graded exercise is unsuccessful and makes people worse…Clinicians should be particularly on the lookout for PEM in patients who are already reporting fatigue, such as with fibromyalgia and rheumatologic conditions that can have some diagnostic overlaps with ME/CFS, because you can get fooled into thinking that your well-meaning exercise program intended to help give them a little more juice during their daily activities actually might be harmful.”

There are several lines of evidence for abnormal responses to exercise in people with PEM, Davenport said. These include muscle worsening, cardiac preload failure and impaired systemic oxygen extraction, metabolic dysregulation, and abnormal immunologic and neurologic changes.

Several studies show impaired recovery after 2-day cardiopulmonary exercise testing, with the largest to date published in July 2024. Patients with PEM have also reported harm from prescribed exercise.

Yellman commented, “We think of PEM like an injury, where you need to recover. If you keep stacking injuries on top of it, that injury is never going to heal the same way again…We are still trying to understand the pathophysiology of ME/CFS in general, and of PEM. But if you think of it as a neuroinflammatory injury, and there’s some evidence suggesting neuroinflammation, you can kind of understand the approach of needing to heal and to recover.”

How Prevalent Is PEM in Rheumatologic Conditions?

For the study presented at the ACR meeting, data of people with confirmed rheumatic diseases were taken from the ongoing longitudinal US-based research database FORWARD. Participants completed biannual self-reported questionnaires during January-June 2024 that included the 5-item PEM subscale from the validated DePaul Symptoms Questionnaire.

Questions relate to frequency and severity of each of the five items: “Dead, heavy feeling after starting to exercise,” “next-day soreness or fatigue after nonstrenuous, everyday activities,” “mentally tired after the slightest effort,” “minimum exercise makes you physically tired,” and “physically drained or sick after mild activity.” Participants are asked to rate each item on a scale from 0 if not present to 1 (mild/a little of the time) up to 4 (very severe/all of the time).

A positive PEM result was defined as a frequency of at least two and simultaneous severity of at least two on any survey item. Additional questions asked about recent and previous SARS-CoV-2 infections, long COVID diagnoses, and comorbidities.

Of 1158 individuals who completed the PEM questionnaire, 7.5% overall met PEM criteria. By individual condition, the proportions were 4.4% with osteoarthritis, 7.4% with rheumatoid arthritis, 12.2% with systemic lupus erythematosus, 13.8% with fibromyalgia diagnosed by rheumatologists, and 20.3% with fibromyalgia based on the 2016 revised ACR criteria.

The overall PEM prevalence was 8.3% among those reporting ever having COVID-19 and 9.5% among those who had COVID-19 during July-December 2023. The PEM prevalence increased more dramatically with more severe COVID-19 — 17.2% among those who had been hospitalized for COVID-19, 22.0% of those ever diagnosed with long COVID, and 28.1% with a long COVID diagnosis in January 2024.

By diagnosis, 50% of individuals who met the ACR’s 2016 fibromyalgia criteria and currently had long COVID scored positively for PEM.

Measures of pain, fatigue, sleep, patient global assessment, activity score, polysymptomatic distress, disability, depression, anxiety, and other functional scores were all significantly worse among those scoring positive for PEM (P

Better Tools Are Available

The developer of the DePaul questionnaire, Leonard Jason, PhD, director of the Center for Community Research and professor of psychology at DePaul College of Science and Health, Chicago, told Medscape Medical News that an updated 10-item screening tool specifically designed to screen for PEM adds some important elements missing from the 5-item version.

Here, patients are initially asked two questions: “Do you experience a worsening of your fatigue/energy related illness after engaging in minimal physical effort?” and “Do you experience a worsening of your fatigue/energy related illness after engaging in mental effort?” If they answer “yes” to either, the next question is “If you feel worse after activities, how long does this last?” Answers are coded from 0 to 6 (24 hours or more).

The fourth additional question then asks how quickly patients recover, while a fifth question asks whether the person is avoiding activity because it makes them feel worse (thereby potentially creating a false negative).

For those scoring positive on the 10-item screen, a more comprehensive measure could be used, such as this online screening tool, Jason said.

Yellman said that the Bateman Horne Center uses a “good day, bad day” questionnaire to tease out some of the same information. In addition, he noted that it’s important to capture the timeframe between the exertion and the onset of symptoms because PEM doesn’t start during or immediately after activity. “If somebody is mowing the lawn and they start feeling symptoms immediately, they’re probably, at least in ME/CFS, experiencing orthostatic intolerance. Post-exertional malaise occurs 12-72 hours later, when their function is severely reduced as compared to baseline.” 

And of course, Davenport noted, listening to patients is key. “Patients will tell you wildly unusual responses to activity before you even do the work of trying to figure out what the activity was. They’ll tell you things like they can’t think as well, that they have to be in bed for 3 days to a week to 2 weeks, depending on the level of exertion.”

Yellman, Davenport, and several other colleagues are currently working on a paper that will explain the differences between pacing and graded exercise, define PEM, and provide guidelines. They aim to submit it in time for publication early next year. In the meantime, the Bateman Horne Center’s website provides numerous resources for healthcare professionals and patients.

Yellman is also working to define minimum quality of care standards for infection-associated chronic conditions for state medical boards and to provide continuing medical education for clinicians on those standards. These would include recognizing and evaluating patients for PEM, as well as orthostatic intolerance, cognitive impairment, and other associated comorbidities.

Importantly, he said, the standards will include the principles of teaching people with PEM how to pace and will emphasize not prescribing them graded exercise as first- or even second-line therapy. “We need people to do some basic things. And the first thing is do no harm.”

None of the individuals quoted for this article had relevant financial disclosures.

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape Medical News, with other work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X: @MiriamETucker.