Depending on intensity, eccentric exercise is experimentally and clinically documented to have opposing dual effects on skeletal muscle; intense eccentric exercise damages muscle, but daily low-load eccentric exercise prevents damage. To clarify the mechanisms of this dual effect, microscopic damage and oxidative stress were studied in rat quadriceps muscle. Oxidative stress was estimated from an immunostaining of advanced glycation end-products (AGE) and a measurement of muscle tissue preparations, the ability to scavenge reactive oxygen species (ROS). Intense eccentric downhill running (IEE) induced muscle damage that was, microscopically apparent 3 days later. Since AGE-positive cells and decreased ROS scavenging activity were observed earlier (on the day after IEE), cellular damage may be related to ROS production. Intense concentric uphill running (ICE) induced an immediate but transient decrease in ROS scavenging activity, which recovered within a day. Neither AGE-positive cells nor microscopic damage was observed after ICE. Since each contracting muscle fiber develops greater tension during eccentric rather than concentric exercise, the initial trigger of IEE-induced muscle damage may be damage to muscle fibers and connective tissues at the subcellular level. Daily low-load training of eccentric downhill running (LET), but not concentric uphill running, efficiently prevented muscle damage after subsequent IEE. No evident elevation of ROS scavenging activity was evident after LET. We concluded that LET prevents IEE-induced muscle damage not through elevated ROS scavenging activity, but through a suppression of initial subcellular damage that triggers subsequent ROS-producing processes, resulting in cellular delayed damage.

Abstract:The mechanisms of the protective effect conferred by heat shock preconditioning (HS) are currently unknown. The purpose of this study was to determine the effect of HS on muscle injury after downhill running and to address the mechanism of the effect. Female Wistar rats were assigned to three groups: HS, downhill running (E), and downhill running after heat shock preconditioning (HS + E). The HS and HS + E rats were placed in a heat chamber for 60 min (ambient temperature 42 ± 1.0°C) 48 h before downhill running. Reactive oxygen species (ROS) scavenging activity was determined by electron spin resonance (ESR), and heat shock protein 72 (HSP72) mRNA expression was measured in rat quadriceps femoris. Leukocyte infiltration and degenerated muscle fibers were determined histopathologically. ROS scavenging activity significantly increased at 3 days after HS (151 ± 18%) and HSP72 mRNA expression increased immediately after HS (1750 ± 1914%). No decrease in ROS scavenging activity was observed in the HS + E rats at 2 days after exercise compared with the E rats (102 ± 9% vs. 79 ± 5%). Degenerated muscle fibers in HS + E rats were significantly less than in E rats at 2, 3, and 7 days after exercise (0.8 ± 1.0 vs. 2.8 ± 1.6, 0.8 ± 1.0 vs. 1.8 ± 1.6, 0 vs. 0.3 ± 0.6, respectively). These data demonstrated that HS can reduce muscle injury after downhill running, and this effect may be mediated by increased ROS scavenging activity. Furthermore, HS may protect the antioxidant defense system in skeletal muscle by enhancing the adaptive HSP72 mRNA response.

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Cup setting with only an alignment guide has been reported to be inaccurate in the lateral decubitus position in total hip arthroplasty (THA). We assessed the accuracy of cup positioning using only the alignment guide technique via a modified Watson Jones approach in the lateral decubitus position. Methods: Two hundred hips of 189 patients underwent THA from October 2014 to September 2016 via a modified Watson Jones approach. In the final sample, 181 hips of 171 patients (35 males, 136 females) were included in this investigation. The alignment of the cup was evaluated by an anteroposterior radiograph of the pelvis 1 week after surgery. Measurements were divided into safe zone determined by Callanan and Lewinnek. Results: There were 168 (92.8%) acetabular cups that were placed within the safe zone for both inclination and anteversion based on the safe zones defined by Lewinnek, and 134 (74%) acetabular cups that were placed within the safe zone defined by Callanan. Multiple logistic analysis showed that the laterality and the addition of the confirmation method were indicators for malpositioning of combined inclination and anteversion. Conclusion: Our data suggested that even if special tools were not used in the lateral decubitus position, using only the alignment guide enabled cup positioning to be achieved with 92.8% accuracy in the Lewinnek safe zone and 74% accuracy in the Callanan safe zone. Multiple logistic analysis showed that the laterality and the addition of a confirmation alignment guide influenced the accuracy of cup positioning. Keywords alignment guide, modified Watson Jones approach, the accuracy of cup positioning, total hip arthroplasty Date

Vertebral fractures occur with only slight trauma in patients with diffuse idiopathic skeletal hyperostosis (DISH). However, a lumbar vertebra fracture, due to an intraoperative body position has not been previously reported. An 87-year-old woman with kyphosis sustained a left trochanteric fracture of her femur. The patient was placed in a supine position during the operation. Postoperatively, the patient experienced severe right thigh pain. Magnetic resonance imaging revealed an L4 vertebral fracture. Computed tomography revealed ankylosis from the upper thoracic spine to the sacrum. While in a supine position under general anesthesia, the contact of the patient's lower back with operating table likely created a fulcrum at her lumbosacral spine acting as a long lever arm, bearing the mass of her upper body. We performed L1-S2 posterior stabilization. DISH patients with kyphosis placed in a supine position have an increased risk for lumbar vertebral fracture.