What condition is characterized by pain in the muscle fibers?

Fibromyalgia is a condition primarily characterized by widespread musculoskeletal pain, which often includes pain in the muscle fibers. It is generally associated with other symptoms such as fatigue, sleep disturbances, and cognitive difficulties, commonly referred to as "fibro fog." The pain experienced in fibromyalgia is typically chronic and can vary in intensity. This condition is believed to affect how the brain processes pain signals.

The other options signify different health issues: Arthritis involves inflammation of the joints and can cause joint pain rather than muscle fiber pain; Rheumatism is a broad term that can refer to various painful conditions affecting the connective tissues, not exclusively muscle fibers; and Cervicalgia specifically pertains to neck pain, which does not encompass the widespread muscle pain characteristic of fibromyalgia. Thus, recognizing fibromyalgia as the condition primarily associated with muscle fiber pain accurately points to the unique features of this disorder.