Reviewers examined the available literature and evaluated their methodological quality. They included 23 studies in their paper.
Based on those studies, they determined there was moderate evidence of multiple exercise-triggered abnormal immune responses in ME/CFS when compared to healthy controls. Those abnormalities included:
- More pronounced response in the complement system;
- Oxidative stress;
- Altered gene expression profile in the immune cells, including increases in post-exercise interleukin-10 and toll-like receptor 4 gene expression.
They found no difference in circulating cytokines, either pro- or anti-inflammatory.
The reviewers state that many of the immune changes related to post-exertional malaise, which is a key feature of ME/CFS.
People with ME/CFS don't recover from exercise like healthy people do.
For example, on Monday, a healthy person exercises until they feel worn out, then feels recovered on Tuesday and can repeat their performance.
Also on Monday, a person with ME/CFS exercises to the same point of fatigue. On Tuesday, they not only haven't recovered from it, they may also have flu-like symptoms (body aches beyond what's normal from exercise, sore throat, fever, extreme fatigue, etc.)
That's post-exertional malaise. Depending on how severely ill they are, it may take several days or even weeks for them to fully recover.
Fatigue & The Immune System
It may seem strange that immune system abnormalities can make someone feel sick. However, many of them symptoms you feel when you are ill are a result of your immune system kicking into overdrive.
It takes a lot of resources to fight an infection, so your body diverts a lot of its energy to the fight – producing and deploying specialized cells, hunting down the infectious agents and destroying them. A fever is often part of that defense, making your body too hot for the invader to thrive.
We don't yet know what causes the immune system of someone with ME/CFS to behave the way it does, especially after exercise, but as we learn more about what's going on, it'll get researchers closer to understanding why.
Nijs J, et al. Exercise immunoloy review. 2014;20:94-116. Altered immune response to exercse in patients with chronic fatigue syndrome/myalgic encehalomyelitis: a systematic literature review.