The connection between this "off" feeling and possible neural and musculoskeletal injuries may not be immediately apparent to the employee or employer, since actual pain is rare at this early stage of injury. Over months, however, as inflammation worsens, chronic pain will eventually lead workers to seek clinical help.

While some employers might see the cytokine connection as a simple opportunity to slack off work, Barbe disagrees.

"Cytokines are self-protective," she says. "This undefined feeling of malaise may be telling the body to take some time off to heal, before things get worse."