Post-exertional malaise

Post-exertional malaise (PEM) is a worsening of many ME/CFS symptoms as a result of physical or mental exertion. It is often referred to as "the marker" by patients, ME/CFS organizatons, clinicians and researchers that work in the ME/CFS field. PEM can last for days to weeks after the exertion.

Worsening symptoms include chronic fatigue, flu-like symptoms, brain fog (cognitive dysfunction), unrefreshing sleep, chronic pain, orthostatic intolerance, neurally mediated hypotension, POTS and more. "As with the severity, the exertion needed to trigger PEM theories case-by-case. For some, it might kick in after a little bit of exercise on top of a day's regular activities. For others, is incredible as it may seem, it can just take a trip to the mailbox, a shower, or sitting upright for an hour." Onset of PEM can be delayed 24-72 hours.

A 2016 DePaul University study focused on deciphering if post-exertional malaise was a generalized, full-body fatigue and/or a muscle-specific fatigue. The results suggested that PEM is composed of two empirically different experiences, one for generalized fatigue and one for muscle-specific fatigue.

2015 Institute of Medicine report


This landmark report published in 2015 by the United States Institute of Medicine report, which assessed all the evidence available, concluded:

"'There is sufficient evidence that PEM is a primary feature that helps distinguish ME/CFS from other conditions'"

Pages 84-86 of the report describe the evidence for post-exertional malaise in ME/CFS patients.

Symptom recognition

 * In the Fukuda criteria, the symptom of post-exertional malaise can be used to help form a diagnosis. Unusually, it is not a required symptom for diagnosis.

Notable studies

 * 2016, Deconstructing post-exertional malaise: An exploratory factor analysis. "'Abstract: Post-exertional malaise is a cardinal symptom of myalgic encephalomyelitis and chronic fatigue syndrome. There are two differing focuses when defining post-exertional malaise: a generalized, full-body fatigue and a muscle-specific fatigue. This study aimed to discern whether post-exertional malaise is a unified construct or whether it is composed of two smaller constructs, muscle fatigue and generalized fatigue. An exploratory factor analysis was conducted on several symptoms that assess post-exertional malaise. The results suggest that post-exertional malaise is composed of two empirically different experiences, one for generalized fatigue and one for muscle-specific fatigue.'"
 * 1999, Demonstration of delayed recovery from fatiguing exercise in chronic fatigue syndrome
 * 2013, Post-exertion malaise in chronic fatigue syndrome: symptoms and gene expression, Meyer et al, 2013
 * 2015, Myalgic Encephalomyelitis: Symptoms and Biomarkers, Jason et al, 2015
 * 2015, Changes in Gut and Plasma Microbiome following Exercise Challenge in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), Shukla et al, 2015



Notable articles

 * Suggestion to replace PEM (Post Exertional Malaise) with PAR (Post Activity Relapse), ME Blogg, 2015

Talks & interviews

 * 2016, Inducing Post-Exertional Malaise in ME/CFS: A Look at the Research Evidence (Peter Rowe)
 * 2015, Post-Exertion Malaise: The Intersection of Biology and Behavior, Dane Cook, Solve ME/CFS
 * 2015, 72. Gene-expression and exercise / Gen-expressie en inspanning – dr. Lucinda Bateman (Lucinda Bateman, Science for Patients)
 * 2013, CFS gene expression after exercise (part 1) (Lucinda Bateman)
 * 2012, Top 10 Things You Should Know About Post-Exertional Relapse (Staci Stevens)

Learn more

 * International CFS/ME Awareness Day 2017 - What Health (PEM Definition Included) CFIDS Association of America
 * Post-Exertional Malaise in Chronic Fatigue Syndrome, Jennie Spotila, Solve ME/CFS, 2010
 * Post-Exertional Malaise: Cause and Effect, Jennie Spotila, Solve ME/CFS, 2012
 * Definition of Post-Exertional Malaise, About Health, 2015
 * Post-Exertional Malaise Video, ME/CFS Ghost, 2016
 * 2016, The Exercise Intolerance in POTS, ME/CFS and Fibromyalgia Explained?