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Effects of Eccentric Exercise on Pain and Pain Sensitivity in Patients with Fibromyalgia and Normal Controls: Evidence of Functional Anti-Hyperalgesic Mechanisms
Roland Staud, MD1, Courtney Bovee1, Brianna Whittemore1, Nicholas J. Inosencio1, Steven Z. George, PhD2, Michael E. Robinson1, and Donald D. Price, PhD3. (1) Rheumatology, Division of, 1600 SW Archer Rd, D2-39 Health Science Center, Gainesville, FL 32610-0221, (2) Physical Therapy, Department of, PO Box 100154, Gainesville, FL 32610-154, (3) Oral and Maxillofacial Surgery, Department of, PO Box 100416, Gainesville, FL 32610-0416
Delayed-onset-muscle-soreness (DOMS) predictably occurs after eccentric-exercise, because of micro-injury of muscles and is a familiar experience for most people. Muscle-injury has been strongly considered for the pathogenesis of fibromyalgia (FM) but convincing evidence is lacking. We hypothesized that DOMS would result in clinical-pain and central-sensitization in normal controls (NC) and worsened pain and central-sensitization in FM-patients. Methods: We enrolled 10 FM-patients and 11 matched NC. Subjects underwent 2x12 repetition of eccentric forearm-exercise at 75% peak-torque using a BIODEX. Clinical-pain, muscle-soreness, heat-ramps, pressure-pain thresholds, and thermal-windup were tested at baseline, 24, 48hours, and 2weeks after eccentric-exercise. Clinical-pain was assessed daily for 2weeks by phone. Results: Initially mean (SD) clinical-pain of NC and FM-patients was 0.5 and 3.1 VAS-units, respectively, and did not significantly change after DOMS. Peak-torque of the exercised arm decreased by 50% after exercise and returned to baseline at follow-up. Mechanical pain-thresholds and thermal-ramp pain decreased from 400 to 180kPa and 2.8 to 0.8VAS units, respectively, in both arms after DOMS in NC and from 350 to 100kPa and 3.3 to 0.9VAS units in FM-patients, respectively. Muscle-soreness of the exercised arm increased from 0 (baseline) to 3.2VAS units (post-exercise) in NC and from 0 to 4.8VAS units in FM-patients, respectively. Compared to baseline, wind-up decreased at 48h after exercise, but returned to baseline at follow-up. Conclusions: Eccentric-exercise resulted in transient weakness/soreness in NC and FM-patients. Clinical-pain of FM-patients was not affected by DOMS. Although mechanical pain-thresholds decreased in the exercised arm in both groups, all subjects became less sensitive to painful heat-stimuli 48h after exercise and showed decreased central-sensitization (windup) in both upper extremities. Thus eccentric-exercise resulted in hypoalgesia for both groups and may be therapeutic for FM-patients