Painful and disabling musculoskeletal disorders remain prevalent. In rats trained to perform repetitive tasks leading to signs and dysfunction similar to those in humans, we tested whether manual therapy would prevent the development of the pathologies and symptoms. We collected behavioral, electrophysiological, and histological data from control rats, rats that trained for 5 weeks before performing a high repetition high force task (HRHF) for 3 weeks untreated, and trained rats that performed the task for 3 weeks while being treated 3x/week using modeled manual therapy (MMT) to the forearm (HRHF+MMT). The MMT included bilateral mobilization, skin rolling, and long axis stretching of the entire upper limb. HRHF rats showed decreased performance of the operant HRHF task and increased discomfort-related behaviors, starting after training. HRHF+MMT rats showed improved task performance and decreased discomfort related behaviors compared to untreated HRHF rats. Subsets of rats were assayed for presence or absence of ongoing activity in C- and slow Aδ- neurons in their median nerves. Neurons from HRHF rats had a heightened proportion of ongoing activity and altered conduction velocities compared to control and MMT-treated rats. Median nerve branches in HRHF rats contained increased numbers of CD68+ macrophages and degraded myelin basic protein, and showed increased extraneural collagen deposition, compared to the other groups. We conclude that the performance of the task for 3 weeks leads to increased ongoing activity in nociceptors, in parallel with behavioral and histological signs of neuritis and nerve injury, and that these pathophysiologies are reduced by MMT.
1Department of Biomedical Sciences, University of New England College of Osteopathic Medicine, Biddeford, ME 04005
2Department of Anatomy and Cell Biology, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, 19140, USA
3Squamish Integrated Health, Squamish, BC, Canada
Corresponding Author: Geoffrey Bove, DC, PhD, Department of Biomedical Science , University of New England College of Osteopathic Medicine, Biddeford, ME 04005, 207 590 8949, email@example.com