Forced treadmill running reduces systemic inflammation yet worsens upper limb discomfort in a rat model of work-related musculoskeletal disorders.

BACKGROUND: Musculoskeletal disorders can result from prolonged repetitive and/or forceful movements. Performance of an upper extremity high repetition high force task increases serum pro-inflammatory cytokines and upper extremity sensorimotor declines in a rat model of work-related musculoskeletal disorders. Since one of the most efficacious treatments for musculoskeletal pain is exercise, this study investigated the effectiveness of treadmill running in preventing these responses. METHODS: Twenty-nine young adult female Sprague-Dawley rats were used. Nineteen were trained for 5 weeks to pull a lever bar at high force (15 min/day). Thirteen went on to perform a high repetition high force reaching and lever-pulling task for 10 weeks (10-wk HRHF; 2 h/day, 3 days/wk). From this group, five were randomly selected to undergo forced treadmill running exercise (TM) during the last 6 weeks of task performance (10-wk HRHF+TM, 1 h/day, 5 days/wk). Results were compared to 10 control rats and 6 rats that underwent 6 weeks of treadmill running following training only (TR-then-TM). Voluntary task and reflexive sensorimotor behavioral outcomes were assessed. Serum was assayed for inflammatory cytokines and corticosterone, reach limb median nerves for CD68+ macrophages and extraneural thickening, and reach limb flexor digitorum muscles and tendons for pathological changes. RESULTS: 10-wk HRHF rats had higher serum levels of IL-1α, IL-1ß and TNFα, than control rats. In the 10-wk HRHF+TM group, IL-1ß and TNFα were lower, whereas IL-10 and corticosterone were higher, compared to 10-wk HRHF only rats. Unexpectedly, several voluntary task performance outcomes (grasp force, reach success, and participation) worsened in rats that underwent treadmill running, compared to untreated 10-wk HRHF rats. Examination of forelimb tissues revealed lower cellularity within the flexor digitorum epitendon but higher numbers of CD68+ macrophages within and extraneural fibrosis around median nerves in 10-wk HRHF+TM than 10-wk HRHF rats. CONCLUSIONS: Treadmill running was associated with lower systemic inflammation and moderate tendinosis, yet higher median nerve inflammation/fibrosis and worse task performance and sensorimotor behaviors. Continued loading of the injured tissues in addition to stress-related factors associated with forced running/exercise likely contributed to our findings.

Racial Discrimination, Disease Activity, and Organ Damage: The Black Women's Experiences Living With Lupus (BeWELL) Study.

Black women are disproportionately affected by systemic lupus erythematosus (SLE), a chronic, potentially debilitating autoimmune disease, and they also experience more rapid progression and worse outcomes compared with other groups. We examined if racial discrimination is associated with disease outcomes among 427 black women with a validated diagnosis of SLE, who live in the Atlanta, Georgia, metropolitan area, and were recruited to the Black Women's Experiences Living with Lupus Study (2015-2017). Frequency of self-reported experiences of racial discrimination in domains such as employment, housing, and medical settings was assessed using the Experiences of Discrimination measure. SLE activity in the previous 3 months, including symptoms of fatigue, fever, skin rashes, and ulcers, was measured using the Systemic Lupus Activity Questionnaire; irreversible damage to an organ or system was measured using the Brief Index of Lupus Damage. Results of multivariable linear regression analyses examining the Systemic Lupus Activity Questionnaire and log-transformed Brief Index of Lupus Damage scores indicated that increasing frequency of racial discrimination was associated with greater SLE activity (b = 2.00, 95% confidence interval: 1.32, 2.68) and organ damage (b = 0.08, 95% confidence interval: 0.02, 0.13). Comprehensive efforts to address disparities in SLE severity should include policies that address issues of racial discrimination.