Context: Shoulder injuries are common in athletes involved in overhead sports, and scapular dyskinesis is believed to be one causative factor in these injuries. Many authors assert that abnormal scapular motion, so-called dyskinesis, is related to shoulder injury, but evidence from 3-dimensional measurement studies regarding this relationship is mixed. Reliable and valid clinical methods for detecting scapular dyskinesis are lacking.Objective: To determine the interrater reliability of a new test designed to detect abnormal scapular motion.Design: Correlation design using ratings from multiple pairs of testers.Setting: University athletic training facilities. Videotapes from randomly chosen participants were subsequently viewed and independently rated for the presence of scapular dyskinesis by 6 raters (3 pairs), with each pair rating 30 different participants. Raters were trained to detect scapular dyskinesis using a self-instructional format with standardized operational definitions and videotaped examples of normal and abnormal motion.Main Outcome Measure(s): Scapular dyskinesis was defined as the presence of either winging or dysrhythmia. Right and left sides were rated independently as normal, subtle, or obvious dyskinesis. We calculated percentage of agreement and weighted kappa (k w ) coefficients to determine reliability.Results: Percentage of agreement was between 75% and 82%, and k w ranged from 0.48 to 0.61.Conclusions: The test for scapular dyskinesis showed satisfactory reliability for clinical use in a sample of overhead athletes known to be at increased risk for shoulder symptoms.Key Words: shoulder, upper extremity, kinematics, assessment Key Points N Trained athletic trainers and physical therapists can recognize and distinguish between abnormal scapular movement patterns and normal patterns in young, athletically active adults.N The scapular dyskinesis test provides a reliable method for clinical examination of overhead athletes.

This study investigated changes in motor skills and tissues of the upper extremity (UE) with regard to injury and inflammatory reactions resulting from performance of a voluntary forelimb repetitive reaching and grasping task in rats. Rats reached for food at a rate of 4 reachedmin, 2 h/day, and 3 dayslweek for up to 8 weeks during which reach rate, task duration and movement strategies were observed. UE tissues were collected bilaterally at weekly time points of 3-8 weeks and examined for morphological changes. Serum was tested for levels of interleukin-la (IL-1) protein. The macrophage-specific antibody, E D l , was used to identify infiltrating macrophages and the ED2 antibody was used to identify resident macrophages. Rats were unable to maintain baseline reach rate in weeks 5 and 6 of task performance. Alternative patterns of movement emerged. Fraying of tendon fibrils was observed after 6 weeks in the mid-forelimb. After 4 weeks, a general elevation of EDl-IR macrophages were seen in all tissues examined bilaterally including the contralateral, uninvolved forelimb and hindlimbs. significantly more resident macrophages were seen at 6 and 8 weeks in the reach limb. At 8 weeks, serum levels of IL-la increased significantly above week 0. Our results demonstrate that performance of repetitive tasks elicits motor decrements, signs of injury and a cellular and tissue responses associated with inflammation.

BackgroundWe examined the relationship of musculoskeletal risk factors underlying force and repetition on tissue responses in an operant rat model of repetitive reaching and pulling, and if force x repetition interactions were present, indicative of a fatigue failure process. We examined exposure-dependent changes in biochemical, morphological and sensorimotor responses occurring with repeated performance of a handle-pulling task for 12 weeks at one of four repetition and force levels: 1) low repetition with low force, 2) high repetition with low force, 3) low repetition with high force, and 4) high repetition with high force (HRHF).MethodsRats underwent initial training for 4–6 weeks, and then performed one of the tasks for 12 weeks, 2 hours/day, 3 days/week. Reflexive grip strength and sensitivity to touch were assayed as functional outcomes. Flexor digitorum muscles and tendons, forelimb bones, and serum were assayed using ELISA for indicators of inflammation, tissue stress and repair, and bone turnover. Histomorphometry was used to assay macrophage infiltration of tissues, spinal cord substance P changes, and tissue adaptative or degradative changes. MicroCT was used to assay bones for changes in bone quality.ResultsSeveral force x repetition interactions were observed for: muscle IL-1alpha and bone IL-1beta; serum TNFalpha, IL-1alpha, and IL-1beta; muscle HSP72, a tissue stress and repair protein; histomorphological evidence of tendon and cartilage degradation; serum biomarkers of bone degradation (CTXI) and bone formation (osteocalcin); and morphological evidence of bone adaptation versus resorption. In most cases, performance of the HRHF task induced the greatest tissue degenerative changes, while performance of moderate level tasks induced bone adaptation and a suggestion of muscle adaptation. Both high force tasks induced median nerve macrophage infiltration, spinal cord sensitization (increased substance P), grip strength declines and forepaw mechanical allodynia by task week 12.ConclusionsAlthough not consistent in all tissues, we found several significant interactions between the critical musculoskeletal risk factors of force and repetition, consistent with a fatigue failure process in musculoskeletal tissues. Prolonged performance of HRHF tasks exhibited significantly increased risk for musculoskeletal disorders, while performance of moderate level tasks exhibited adaptation to task demands.

Upper extremity tendinopathies are associated with performance of forceful repetitive tasks. We used our rat model of repetitive strain injury to study changes induced in forelimb flexor digitorum tendons. Rats were trained to perform a high repetition high force (HRHF) handle-pulling task (12 reaches/min at 60 AE 5% maximum pulling force [MPF]), or a low repetition negligible force (LRNF) reaching and food retrieval task (three reaches/min at 5 AE 5% MPF), for 2 h/day in 30 min sessions, 3 days/week for 3-12 weeks. Forelimb grip strength was tested. Flexor digitorum tendons were examined at midtendon at the level of the carpal tunnel for interleukin (IL)-1b, neutrophil, and macrophage influx, Substance P, connective tissue growth factor (CTGF), and periostin-like factor (PLF) immunoexpression, and histopathological changes. In HRHF rats, grip strength progressively decreased, while IL-1b levels progressively increased in the flexor digitorum peritendon (para-and epitendon combined) and endotendon with task performance. Macrophage invasion was evident in week 6 and 12 HRHF peritendon but not endotendon. Also in HRHF rats, Substance P immunoexpression increased in week 12 peritendon as did CTGF-and PLF-immunopositive fibroblasts, the increased fibroblasts contributing greatly to peritendon thickening. Endotendon collagen disorganization was evident in week 12 HRHF tendons. LRNF tendons did not differ from controls, even at 12 weeks. Thus, we observed exposure-dependent changes in flexor digitorum tendons within the carpal tunnel, including increased inflammation, nociceptor-related neuropeptide immunoexpression, and fibrotic histopathology, changes associated with grip strength decline. Keywords: cytokines; inflammation; flexor digitorum tendon; repetitive task; PLF; CTGF; WMSD Tendinopathies of the hand and wrist tendons are associated with forceful repetition in the workplace. 1-3The incidence of flexor tenosynovitis is significantly higher in strenuous meat processing jobs: 25.3% for female packers, 16.8% for female sausage makers, and 12.5% for male meat cutters. The incidence in nonstrenuous jobs was less than 1% during a 31 month study period.4,5 Manufacturing workers performing highly repetitive and forceful jobs are 29 times more likely to develop wrist and hand tendonitis than workers performing low repetition and low force jobs. 5,6The etiology and pathophysiology of overuse-induced tendinopathies are still under investigation. Although the presence of an inflammatory component has not been identified by all investigators, 7-9 increased inflammatory molecules, for example, PGE 2 , have been found in tenosynovium of patients diagnosed with carpal tunnel syndrome (CTS), especially during the intermediate phase.10,11 However, PGE 2 was not found in tendon biopsies collected during the chronic painful tendinosis stage, although increased glutamate neurotransmitter and its receptor were evident. 8,9 The neurochemical Substance P is associated with chronic pain mediation 12 and has also been identif...

An increase in the synthesis of heat shock proteins that is induced in cells in vitro by hyperthermia or other types of metabolic stress correlates with enhanced cell survival upon further stress. To determine if a similar increase in stress tolerance could be elicited in vivo, rats were made hyperthermic, and then their retinas were tested for sensitivity to light damage. This treatment resulted in a marked decrease in photoreceptor degeneration after exposure to bright light as compared to normothermic animals. Concomitant with such protection was an increase in retinal synthesis of three heat shock proteins. Thus, a physiological rise in body temperature enhances the stress tolerance of nerve tissue, perhaps by increasing heat shock protein production.

Nuclear exclusion of the transcriptional regulators and potent oncoproteins, YAP/TAZ, is considered necessary for adult tissue homeostasis. Here we show that nuclear YAP/TAZ are essential regulators of peripheral nerve development and myelin maintenance. To proliferate, developing Schwann cells (SCs) require YAP/TAZ to enter S-phase and, without them, fail to generate sufficient SCs for timely axon sorting. To differentiate, SCs require YAP/TAZ to upregulate Krox20 and, without them, completely fail to myelinate, resulting in severe peripheral neuropathy. Remarkably, in adulthood, nuclear YAP/TAZ are selectively expressed by myelinating SCs, and conditional ablation results in severe peripheral demyelination and mouse death. YAP/TAZ regulate both developmental and adult myelination by driving TEAD1 to activate Krox20. Therefore, YAP/TAZ are crucial for SCs to myelinate developing nerve and to maintain myelinated nerve in adulthood. Our study also provides a new insight into the role of nuclear YAP/TAZ in homeostatic maintenance of an adult tissue.DOI: http://dx.doi.org/10.7554/eLife.20982.001

The formation of brain circuits requires molecular recognition between functionally related neurons. We report the cloning of a molecule that participates in these interactions. The limbic system-associated membrane protein (LAMP) is an immunoglobulin (Ig) superfamily member with 3 Ig domains and a glycosyl-phosphatidylinositol anchor. In the developing forebrain, lamp is expressed mostly by neurons comprising limbic-associated cortical and subcortical regions that function in cognition, emotion, memory, and learning. The unique distribution of LAMP reflects its functional specificity. LAMP-transfected cells selectively facilitate neurite outgrowth of primary limbic neurons. Most striking, administration of anti-LAMP in vivo results in abnormal growth of the mossy fiber projection from developing granule neurons in the dentate gyrus of the hippocampal formation, suggesting that LAMP is essential for proper targeting of this pathway. Rather than being a general guidance cue, LAMP likely serves as a recognition molecule for the formation of limbic connections.

Anatomical and physiological changes were evaluated in the median nerves of rats trained to perform repetitive reaching. Motor degradation was evident after 4 weeks. ED1-immunoreactive macrophages were seen in the transcarpal region of the median nerve of both forelimbs by 5-6 weeks. Fibrosis, characterized by increased immunoexpression of collagen type I by 8 weeks and connective tissue growth factor by 12 weeks, was evident. The conduction velocity (NCV) within the carpal tunnel showed a modest but significant decline after 9-12 weeks. The lowest NCV values were found in animals that refused to participate in the task for the full time available. Thus, both anatomical and physiological signs of progressive tissue damage were present in this model. These results, together with other recent findings indicate that work-related carpal tunnel syndrome develops through mechanisms that include injury, inflammation, fibrosis and subsequent nerve compression.