The Chronic Fatigue Syndrome — One Entity or Many?

Fatigue may be a normal consequence of intensive physical exertion or mental effort, or it may be symptomatic of a variety of specific illnesses. Because of its largely subjective nature, it may be difficult to define and quantitate. To the muscle physiologist, fatigue represents a failure to sustain the expected or required muscular force. Such a failure may represent an impairment at any site in the long chain from cerebral cortex to spinal cord to peripheral nerve to neuromuscular junction to muscle-cell membrane to release of intracellular calcium ion to actin–myosin cross-bridge formation.1 Thus, fatigue can be considered central in . . .