TNF and musculoskeletal system disorder: Consistent with our original hypothesis that treadmill running should be an efficacious treatment in this upper extremity work-related musculoskeletal disorder model [18, 60–62], the pro-inflammatory cytokines IL-1β and TNFα levels were lower and the anti-inflammatory cytokine IL-10 was higher in serum of HRHF+treadmill animals than in the untreated HRHF animals.