David M. Kietrys

Peripheral neuritis and increased spinal cord neurochemicals are induced in a model of repetitive motion injury with low force and repetition exposure

Performance of high repetition tasks with or without force is associated with peripheral tissue inflammation, decreased nerve function and motor dysfunction. Here, we examined whether a low repetition task with negligible force (LRNF) produces fewer tissue and behavioral pathologies than previously observed with high repetition tasks using our rat model of repetitive motion injury (RMI). Thirty-seven rats were randomized into control or LRNF groups, the latter reaching and grasping a 45 mg food pellet at a rate of 3 reaches/min. This task was performed in 4, 0.5 5 h sessions with 1.5 5 h rest periods for 3 days/week for up to 12 weeks. Examination of distal median nerve, forelimb flexor tendons and bones for ED1-positive cells (macrophages and osteoclasts) revealed increases in nerve and bone in week 12. The nerve also contained increased TNF-alpha expressing cells in week 12. Examination of spinal cord dorsal horns revealed increased immunoexpression of Substance P in week 8 and neurokinin-1 in weeks 8 and 12 in the superficial lamina. Motor behavioral analyses showed no changes in reach rate across weeks, slightly reduced task duration (a measurement of voluntary task participation) in week 12, but significantly increased extra arm movement reversals during reaching in week 8. These extra movement reversals were corrections for missed food pellets during a reach. Thus, performance of even a low repetition, negligible force upper extremity task for 3 months can induce mild peripheral tissue inflammation, neurochemical increases in spinal cord dorsal horns, and declines in fine motor control.

Peripheral and central changes combine to induce motor behavioral deficits in a moderate repetition task

Repetitive motion disorders, such as carpal tunnel syndrome and focal hand dystonia, can be associated with tasks that require prolonged, repetitive behaviors. Previous studies using animal models of repetitive motion have correlated cortical neuroplastic changes or peripheral tissue inflammation with fine motor performance. However, the possibility that both peripheral and central mechanisms coexist with altered motor performance has not been studied. In this study, we investigated the relationship between motor behavior changes associated with repetitive behaviors and both peripheral tissue inflammation and cortical neuroplasticity. A rat model of reaching and grasping involving moderate repetitive reaching with negligible force (MRNF) was used. Rats performed the MRNF task for 2 h/day, 3 days/week for 8 weeks. Reach performance was monitored by measuring reach rate/success, daily exposure, reach movement reversals/patterns, reach/grasp phase times, grip strength and grooming function. With cumulative task exposure, reach performance, grip strength and agility declined while an inefficient food retrieval pattern increased. In S1 of MRNF rats, a dramatic disorganization of the topographic forepaw representation was observed, including the emergence of large receptive fields located on both the wrist/forearm and forepaw with alterations of neuronal properties. In M1, there was a drastic enlargement of the overall forepaw map area, and of the cortex devoted to digit, arm-digits and elbow-wrist responses. In addition, unusually low current amplitude evoked digit movements. IL-1 beta and TNF-alpha increased in forearm flexor muscles and tendons of MRNF animals. The increases in IL-1 beta and TNF-alpha negatively correlated with grip strength and amount of current needed to evoke forelimb movements. This study provides strong evidence that both peripheral inflammation and cortical neuroplasticity jointly contribute to the development of chronic repetitive motion disorders.

Aging Contributes to Inflammation in Upper Extremity Tendons and Declines in Forelimb Agility in a Rat Model of Upper Extremity Overuse

We sought to determine if tendon inflammatory and histopathological responses increase in aged rats compared to young rats performing a voluntary upper extremity repetitive task, and if these changes are associated with motor declines. Ninety-six female Sprague-Dawley rats were used in the rat model of upper extremity overuse: 67 aged and 29 young adult rats. After a training period of 4 weeks, task rats performed a voluntary high repetition low force (HRLF) handle-pulling task for 2 hrs/day, 3 days/wk for up to 12 weeks. Upper extremity motor function was assessed, as were inflammatory and histomorphological changes in flexor digitorum and supraspinatus tendons. The percentage of successful reaches improved in young adult HRLF rats, but not in aged HRLF rats. Forelimb agility decreased transiently in young adult HRLF rats, but persistently in aged HRLF rats. HRLF task performance for 12 weeks lead to increased IL-1beta and IL-6 in flexor digitorum tendons of aged HRLF rats, compared to aged normal control (NC) as well as young adult HRLF rats. In contrast, TNF-alpha increased more in flexor digitorum tendons of young adult 12-week HRLF rats than in aged HRLF rats. Vascularity and collagen fibril organization were not affected by task performance in flexor digitorum tendons of either age group, although cellularity increased in both. By week 12 of HRLF task performance, vascularity and cellularity increased in the supraspinatus tendons of only aged rats. The increased cellularity was due to increased macrophages and connective tissue growth factor (CTGF)-immunoreactive fibroblasts in the peritendon. In conclusion, aged rat tendons were overall more affected by the HRLF task than young adult tendons, particularly supraspinatus tendons. Greater inflammatory changes in aged HRLF rat tendons were observed, increases associated temporally with decreased forelimb agility and lack of improvement in task success.

Exposure to Repetitive Tasks Induces Motor Changes Related to Skill Acquisition and Inflammation in Rats

ABSTRACT The authors elucidate exposure-response relationships between repetitive tasks, inflammation, and motor changes with work-related musculoskeletal disorders. Using a rat model of reaching and handle pulling, they examined effects of performing a high-repetition, low-force (HRLF); low-repetition, high-force (LRHF); or high-repetition, high-force (HRHF) task (2 hr/day, 3 days/week, 12 weeks) on reach rate and force, percentage of successful reaches, duration of participation, and grip strength. Reach rate and reach force improved with HRLF, and percentage success increased in all groups in Week 9, and in HRLF and HRHF in Week 12, indicative of skill acquisition. Duration and grip strength showed force-dependent declines with task performance. A subset of HRHF rats received ibuprofen in Weeks 5–12. Ibuprofen significantly improved reach rate, reach force, and duration in treated rats, indicative of an inflammatory influence on reach performance. Ibuprofen improved percentage of successful reaches in Week 9, although this increase was not sustained. However, declines in grip strength, a nocifensive behavior, were not prevented by ibuprofen. Examination of cervical spinal cords of untreated and ibuprofen treated HRHF rats showed increased IL-1beta, an inflammatory cytokine, in neurons. These findings suggest that only a preventive intervention could have addressed all motor declines.

Physical Therapy Interventions for Individuals with HIV Associated Distal Sensory Polyneuropathy: A Systematic Review

Study Design: Systematic Review. Objective: Explore the effectiveness of physical therapy interventions in individuals with human immunodeficiency virus associated distal sensory polyneuropathy (HIV‐DSP). Methods: Searches were performed on CINAHL and MEDLINE databases using the combined search terms (limited to English and human): HIV disease, HIV infection, HIV‐1, AIDS, acquired immunodeficiency syndrome AND neuropathy, distal sensory polyneuropathy, distal sensory peripheral neuropathy, polyneuropathies, peripheral nervous system, peripheral nervous system diseases, neuralgia, HIV‐related neuropathy, HIV‐associated neuropathy, HIV associated neuropathy AND physical therapy, physical therapy modalities, physiotherapy, rehabilitation, physical medicine and rehabilitation. Resulting articles were included in the review if they assessed the effects of physical therapy on patients with HIV‐DSP. Results: The initial search yielded 15 articles after combining key terms; after screening for inclusion criteria, 3 articles remained. Each was a case series and was thus assigned a level of evidence of 4. Interventions utilized in the reviewed articles included: electroacupuncture, microcurrent stimulation, stretching exercises, joint mobilization, soft tissue mobilization and desensitization activities. Physical therapy interventions were often used in combination. All interventions were shown to have a beneficial effect on HIV‐DSP symptoms and/or gait and/or function. Electroacupuncture was shown to improve H‐reflex parameters. Conclusions: There is paucity of literature regarding evidence‐based interventions for individuals diagnosed with HIV‐DSP. The small number of case series that have been published to date provide weak evidence to suggest that physical therapy may be of benefit, but there is a need for more research to further elucidate the effects of physical therapy on symptoms, function, disability, and quality of life in individuals with HIV‐DSP.

Contemporary Issues in Rehabilitation of Patients with HIV Disease: Part III: The Effects of Exercise on Individuals with HIV Disease

&NA; Editors Note: Part I: The Team Approach to Rehabilitation of Patients with HIV Disease and Part II: Complications of HIV Disease were both published in Rehabil Oncol 2002;20(1):21‐26.

On “An obese body mass increases the adverse effects…” Bauer LO, Wu Z, Wolfson LI. Phys Ther. 2011;91:1063–1071.

As physical therapists who have been working since the 1980s with patients diagnosed with HIV, it was a pleasure to read this well-done study.1 The Bauer et al article clearly reflects the fact that many individuals with HIV today have a greatly different set of problems and comorbidities than those affected in the 1980s, a time when HIV …