New research supports earlier findings that people with chronic fatigue syndrome (ME/CFS) develop amplified pain after exercise, while healthy people do not. The latest research also showed differences in the exercise/pain response between ME/CFS and chronic low back pain.
For decades, researchers have been trying to understand a key symptom of chronic fatigue syndrome called post-exertional malaise (PEM). It's an abnormal physical reaction to exercise that causes symptoms to heighten. While most people will get an energy boost from exercise, people with this condition will become intensely fatigued, feel increased flu-like symptoms, and often experience body-wide pain. PEM generally last for at least 24 hours, and can last for several days in some people.
This study looked at just the pain levels and not the other aspects of PEM. Researchers discovered that when participants with chronic fatigue syndrome exercised within their physical limits, their pain thresholds dropped, causing them to feel pain more easily. (The pain threshold is the point at which sensation, such as pressure or heat, is interpreted by the body as pain. It is not the same as pain tolerance.)
Researchers concluded that chronic fatigue syndrome involves abnormalities in what's called central pain processing. That means the central nervous system (brain, spinal cord and associated nerves) reacts strangely to signals and essentially "turn up the volume" of pain. This is called hyperalgesia.
Hyperalgesia is one of the defining characteristics of the related condition fibromyalgia.
This year alone, at least 5 published studies have explored aspects of PEM. Of those:
- 3 link it to abnormal pain processing: April 2010 Journal of Internal Medicine, Sept. 2010 Journal of Internal Medicine, and the one detailed here, Oct. 2010 Journal of Rehabilitative Medicine;
- 1 demonstrates that it's distinctly different from the consequences of a sedentary lifestyle: Feb. 2010 Journal of Women's Health;
- And 1 points to fluctuating levels of cytokines as a possible cause of this mysterious symptom: (July 2010 Psychophysiology).
Meanwhile, several researchers are looking for unique biomarkers of PEM in the hopes of finding an objective way to diagnose ME/CFS.
Does this research match your experience? What is post-exertional malaise like for you? How much exertion does it take to trigger it? Leave your comments below!
Learn more or join the conversation!
- Exercise: Friend or Foe?
- Chronic Fatigue Syndrome Symptoms List
- What Causes Chronic Fatigue Syndrome?
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