Post-exertional Malaise (PEM) is an important aspect of chronic fatigue syndrome (CFS), a common co-existing condition in Fibromyalgia. Medical experts believe that the best way to understand CFS is to understand the concept behind this symptom. This symptom has helped a tremendous amount of research on CFS and is believed to be the key to conducting an objective diagnostic test for the condition.
Nevertheless, some medical experts are not convinced that the PEM actually exists. They blamed the avoidance of exercise in a psychological condition known as the kinesiophobia. Basically, the theory behind kinesiophobia is that those with CFS are just a group of people who are merely irrational and out of shape.
On the other hand, there are pieces of evidence that suggest there is a wide range of physiological abnormalities that is behind PEM. This explains why the symptom can substantially limit the amount of activity in people who have CFS and considerably lower their quality of living. In the most severe cases, PEM is what defines their lives.