Chronic Fatigue Syndrome

Why Daily Activities Magnify Exhaustion for Chronic Fatigue Patients

The mechanism that causes high-performance athletes to “feel the burn” turns out to be the culprit in what makes people with chronic fatigue syndrome feel exhausted by the most common daily activities, according to research done at  University of Florida Health and published in February 2015 in the journal Pain.

A release from the university reports that the study shows that the neural pathways that transmit feelings of fatigue to the brain might be to blame. In those with chronic fatigue syndrome, the pathways do their job too well.

The findings also provide evidence for the first time that peripheral tissues such as muscles contribute to feelings of fatigue. Determining the origins of fatigue could help researchers develop therapies or identify targets for those therapies.

Researchers focused on the role of muscle metabolites, including lactic acid and adenosine triphosphate, or ATP, in the disease. The study has demonstrated for the first time that these substances, released when a person exercises his or her muscles, seem to activate these neural pathways. Also, UF Health researchers have shown that these pathways seem to be much more sensitive in patients with chronic fatigue syndrome than in patients without the disease, something that hasn’t been studied before.

Chronic fatigue syndrome, which the Institute of Medicine recently renamed systemic exertion intolerance disease, or SEID, is characterized by extreme chronic fatigue. Because its chief symptom — fatigue — is often associated with many other diseases, it can be difficult to diagnose SEID for the more than 1 million people who actually have the disease, according to the Centers for Disease Control and Prevention. The disease has no root medical cause, and researchers don’t know what triggers it. But they are studying aspects of the disease to figure out ways to treat it.

The release quotes Dr. Roland Staud, a professor of rheumatology and clinical immunology in the UF College of Medicine and the paper’s lead author, as saying, “What we have shown now, that has never been shown before in humans, is that muscle metabolites can induce fatigue in healthy people as well as patients who already have fatigue.”

During exercise, muscles produce metabolites, which are sensed by metaboreceptors that transmit information via fatigue pathways to the brain, according to the researchers. But in patients with SEID, these fatigue pathways have become highly sensitive to metabolites and can trigger excessive feelings of fatigue.

“For most of us, at the end of strenuous exertion we feel exhausted and need to stop — but we will recover rapidly,” Staud said. “However, these individuals tire much more rapidly and sometimes just after moving across a room, they are fully exhausted. This takes a toll on their lives.”