The structural organization of peripheral nerves enables them to function while tolerating and adapting to stresses placed upon them by postures and movements of the trunk, head, and limbs. They are exposed to combinations of tensile, shear, and compressive stresses that result in nerve excursion, strain, and transverse contraction. The purpose of this appraisal is to review the structural and biomechanical modifications seen in peripheral nerves exposed to various levels of physical stress. We have followed the primary tenet of the Physical Stress Theory presented by Mueller and Maluf (2002), specifically, that the level of physical stress placed upon biological tissue determines the adaptive response of the tissue. A thorough understanding of the biomechanical properties of normal and injured nerves and the stresses placed upon them in daily activities will help guide physical therapists in making diagnoses and decisions regarding interventions. [Topp KS, Boyd BS. Structure and biomechanics of peripheral nerves: nerve responses to physical stresses and implications for physical therapist practice.]

Background: Previous studies have shown that virtual reality (VR) is effective in reducing acute and chronic pain both in adults and in children. Given the emergence of new VR technology, and the growing body of research surrounding VR and pain management, an updated systematic review is warranted. Purpose: The purpose of this systematic review is to compare the effectiveness of VR in reducing acute and chronic pain in adults. Data Sources: A search was conducted in three databases (PubMed, CINAHL, Trip) using standardized search terms. Study Selection: Twenty experimental and quasi-experimental trials published between January 2007 and December 2018 were included based on prespecified inclusion and exclusion criteria. Pain intensity was the primary outcome. Data Extraction: We extracted data and appraised the quality of articles using either the PEDro or Modified Downs and Black risk of bias tools. Data Synthesis: The majority of studies supported the use of VR to reduce acute pain both during the procedure and immediately after. Numerous studies found VR reduced chronic pain during VR exposure but there is insufficient evidence to support lasting analgesia. There was considerable variability in patient population, pain condition and dosage of VR exposure. Limitations: Due to heterogeneity, we were unable to perform meta-analyses for all study populations and pain conditions. Conclusions: VR is an effective treatment for reducing acute pain. There is some research that suggests VR can reduce chronic pain during the intervention; however, more evidence is needed to conclude that VR is effective for lasting reductions in chronic pain.

respond to the mechanical stresses imposed upon them during movement. 27 Neurodynamic tests are used to assess the nervous system's mechanosensitivity through monitoring the response to movements that are known to alter the mechanical stresses acting on the nervous system. The most common lower quarter neurodynamic test is the passive straight-leg raise (SLR) test. 13,31 The basic SLR test consists of the tester performing passive hip flexion, with the patient in a supine position and the knee held in full extension. 9A recent systematic review of SLR testing indicated a lack of standardization, including the use of various criteria for determining the test end point. 31 The authors of this review reintroduced standardized methodology proposed by Breig and Troup 8 in 1979, including the use of the first onset of pain as the end point during the SLR test.31 Despite these recommendations, alternative end points, such as maximally tolerated symptom, are still utilized.17 Because SLR testing is performed in both symptomatic and C linical neurological examinations are an integral part of clinical decision making for determining neural involvement in individuals with altered physical function and activity participation. One aspect of a standard neurological examination involves assessing the sensitivity of peripheral nerves to limb movement, termed mechanosensitivity. Mechanosensitivity is thought to be a normal protective mechanism that allows the nerves to t STudy deSiGn: Cross-sectional, observational study.t objecTiveS: To explore how ankle position affects lower extremity neurodynamic testing. t backGround: Upper extremity limb movements that increase neural loading create a protective muscle action of the upper trapezius, resulting in shoulder girdle elevation during neurodynamic testing. A similar mechanism has been suggested in the lower extremities.t meThodS: Twenty healthy subjects without low back pain participated in this study. Hip flexion angle and surface electromyographic measures were taken and compared at the onset of symptoms (P1) and at the point of maximally tolerated symptoms (P2) during straight-leg raise tests performed with ankle dorsiflexion (DF-SLR) and plantar flexion (PF-SLR).t reSuLTS: Hip flexion was reduced during DF-SLR by a mean  SD of 5.5°  6.6° at P1 (P = .001) and 10.1°  9.7° at P2 (P.001), compared to PF-SLR. DF-SLR induced distal muscle activation and broader proximal muscle contractions at P1 compared to PF-SLR. t concLuSion: These findings support the hypothesis that addition of ankle dorsiflexion during straight-leg raise testing induces earlier distal muscle activation and reduces hip flexion motion. The straight-leg test, performed to the onset of symptoms (P1) and with sensitizing maneuvers, allows for identification of meaningful differences in test outcomes and is an appropriate end point for lower extremity neurodynamic testing.

'AbstractPurpose: This study investigated the biomechanics of the sciatic nerve with hind limb positioning in live and euthanized SpragueDawley rats after traumatic nerve injury.Methods: With radiographic analysis, sciatic nerve excursion and strain were measured in situ during a modified straight leg raise, which included sequential hip flexion and ankle dorsiflexion. Comparisons were made between nerves in uninjured, sham-injured m d mild crush-injured rats at the 7-day and 21-day recovery times.Results: Significant strain and proximal excursion of the sciatic nerve were observed in all groups during hip flexion, and additional increased strain was noted during dorsiflexion. Seven days after nerve injury, strain increased significantly during hip flexion Conclusions: Nerve bed elongation during straight leg raise causes sciatic nerve strain and excursion towards the moving joint with the greatest movement nearest the moving joint. In the first week after injury, the maximal strain exceeded the level previously 4hown to impair nerve conduction and circulation.

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