Post-exertional malaise (PEM) is a worsening of many ME/CFS symptoms as a result of physical or mental exertion. Patients, ME/CFS organizatons, clinicians and researchers that work in the ME/CFS field often referred to it as "the marker," i.e., the main symptom that differentiates ME and CFS from other fatiguing illnesses. 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
"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.
- In the International Consensus Criteria, postexertional neuroimmune exhaustion is required for a diagnosis of ME.
- In diagnosing Systemic Exertion Intolerance Disease (SEID).
- 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.
- In the Canadian Consensus Criteria PEM is an option with an and/or with fatigue although most researchers require PEM.
- In the Holmes criteria, prolonged (24 hours or greater) generalized fatigue after levels of exercise that would have been easily tolerated in the patient's premorbid state is an optional criteria for diagnosis, under the section Minor Symptom Criteria.
- 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
- Nov 4, 2016 Postexertion 'Crash,' not Fatigue per se, Marks Syndrome, MedScape By: Miriam Tucker
- Dec 30, 2015 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)
- 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?
- Johnson, C, Health Rising: ME/CFS Symptoms, retrieved 29 March 2016
- Fighting Fatigue, Post-Exertional Malaise – A Hallmark Symptom of ME/CFS, retrieved 29 March 2016
- What Is Post-exertional Malaise - Very Well - Adrienne Dellwo
- Post Exertional Malaise - Very Well - Adrienne Dellwo
- Chronic Fatigue Syndrome - Web MD
- PEM Series - Solve ME/CFS - Jenny Spotila
- What Health - International CFS/ME Awareness Day 2017 - CFIDS Association of America
- McManimen, SL; Sunnquist, ML; Jason, LA (2016), "Deconstructing post-exertional malaise: An exploratory factor analysis.", Journal of Health Psychology, PMID 27557649, doi:10.1177/1359105316664139
- Institute of Medicine report pages 84-86, search term exercise
- The CDC (Fukuda 1994) Definition for Chronic Fatigue Syndrome
- The 1988 Holmes Definition for CFS
- Meyer, JD; Light, AR; Shukla, SK; Clevidence, D; Yale, S; Stegner, AJ; Cook, DB (2 Oct 2013), "Post-exertion malaise in chronic fatigue syndrome: symptoms and gene expression", Fatigue: Biomedicine, Health & Behavior, 1 (4): 190-209, doi:10.1080/21641846.2013.838444
- Jason, LA; Zinn, ML; Zinn, MA (September 2015), "Myalgic Encephalomyelitis: Symptoms and Biomarkers", Current Neuropharmacology, 13(5): 701-734, doi:10.2174/1570159X13666150928105725
- Shukla, SK; Cook, D; Meyer, JD; et al. (18 December 2015), "Changes in Gut and Plasma Microbiome following Exercise Challenge in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)", Plos One, 10(12), doi:10.1371/journal.pone.0145453
- VanNess, M; Stevens, S; Bateman, L; Stiles, TL; Snell, CR (February 2010), "Postexertional malaise in women with chronic fatigue syndrome", Journal of Women's Health, PMID 20095909, doi:10.1089/jwh.2009.1507
- ME Blogg (30 Dec 2015), Suggestion to replace PEM by PAR
- Cook, DB (19 Nov 2015), "Deciphering Post Exertion Malaise: The Intersection of Biology and Behavior", Solve ME/CFS (video)
- Spotila, JM (2010), "Post-Exertional Malaise in Chronic Fatigue Syndrome" (PDF), Solve ME/CFS
- Spotila, JM (23 May 2012), "Post-Exertional Malaise: Cause and Effect", Solve ME/CFS
- About Health (8 Oct 2015), Definition of Post-Exertional Malaise
- Post-Exertional Malaise - The ME/CFS Ghost