• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.163-170
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• 2013

Purpose: The purpose of this study is to provide analysis of physiological, biomechanical responses occurring from the operation to lifting or twist lifting task appears frequently in agricultural work. Methods: This study investigated the changes of physiological factors such as heart rate, heart rate variability (HRV) and biomechanical factors such as physical activity and kinetic analysis in the task of twisting at the waist while lifting. Results: Heart rates changed significantly with the workload. The result indicated that the workload of 2 kg was light intensity work, and the workload of 12 kg was hard intensity work. Physical activity increased as the workload increased both on wrist and waist. Besides, stress index of the worker increased with the workload. Dynamic load to herniated discs was analyzed using inertial sensor, and the angular acceleration and torque increased with the workload. The proposed measurement system can measure the recipient's physiological and physical signals in real-time and analyzed 3-dimensionally according to the variety of work load. Conclusions: The system we propose will be a new method to measure agricultural workers' multi-dimensional signals and analyze various farming tasks.

• Journal of Biomedical Engineering Research
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• v.36 no.6
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• pp.276-282
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• 2015

Recently, during the multi-level fusion with pedicle screws, interspinous spacer are sometimes substituted for the most superior level of the fusion in an attempt to reduce the number of fusion level and likelihood of degeneration process at the adjacent level. In this study, a finite element (FE) study was performed to assess biomechanical efficacies of the interspinous spacer combined with posterior lumbar fusion with a previously-validated 3-dimensional FE model of the intact lumbar spine (L1-S1). The post-operative models were made by modifying the intact model to simulate the implantation of interspinous spacer and pedicle screws at the L3-4 and L4-5. Four different configurations of the post-op model were considered: (1) a normal spinal model; (2) Type 1, one-level fusion using posterior pedicle screws at the L4-5; (3) Type 2, two-level (L3-5) fusion; (4) Type 3, Type 1 plus Coflex$^{TM}$ at the L3-4. hybrid protocol (intact: 10 Nm) with a compressive follower load of 400N were used to flex, extend, axially rotate and laterally bend the FE model. As compared to the intact model, Type 2 showed the greatest increase in Range of motion (ROM) at the adjacent level (L2-3), followed Type 3, and Type 1 depending on the loading type. At L3-4, ROM of Type 2 was reduced by 34~56% regardless of loading mode, as compared to decrease of 55% in Type 3 only in extension. In case of normal bone strength model (Type 3_Normal), PVMS at the process and the pedicle remained less than 20% of their yield strengths regardless of loading, except in extension (about 35%). However, for the osteoporotic model (Type 3_Osteoporotic), it reached up to 56% in extension indicating increased susceptibility to fracture. This study suggested that substitution of the superior level fusion with the interspinous spacer in multi-level fusion may be able to offer similar biomechanical outcome and stability while reducing likelihood of adjacent level degeneration.

• Journal of Korean Neurosurgical Society
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• v.58 no.5
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• pp.412-418
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• 2015

Objective : To investigate the effects of posterior implant rigidity on spinal kinematics at adjacent levels by utilizing a cadaveric spine model with simulated physiological loading. Methods : Five human lumbar spinal specimens (L3 to S1) were obtained and checked for abnormalities. The fresh specimens were stripped of muscle tissue, with care taken to preserve the spinal ligaments and facet joints. Pedicle screws were implanted in the L4 and L5 vertebrae of each specimen. Specimens were tested under 0 N and 400 N axial loading. Five different posterior rods of various elastic moduli (intact, rubber, low-density polyethylene, aluminum, and titanium) were tested. Segmental range of motion (ROM), center of rotation (COR) and intervertebral disc pressure were investigated. Results : As the rigidity of the posterior rods increased, both the segmental ROM and disc pressure at L4-5 decreased, while those values increased at adjacent levels. Implant stiffness saturation was evident, as the ROM and disc pressure were only marginally increased beyond an implant stiffness of aluminum. Since the disc pressures of adjacent levels were increased by the axial loading, it was shown that the rigidity of the implants influenced the load sharing between the implant and the spinal column. The segmental CORs at the adjacent disc levels translated anteriorly and inferiorly as rigidity of the device increased. Conclusion : These biomechanical findings indicate that the rigidity of the dynamic stabilization implant and physiological loading play significant roles on spinal kinematics at adjacent disc levels, and will aid in further device development.

• Journal of Korean Neurosurgical Society
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• v.52 no.4
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• pp.281-287
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• 2012

Objective : To evaluate the effect of calcium supplementation on spinal bone fusion in ovariectomized (OVX) rats. Methods : Sixteen female Sprague Dawley rats underwent bilateral ovariectomy at 12 weeks of age to induce osteoporosis and were randomly assigned to two groups : control group (n=8) and calcium-supplemented group (OVX-Ca, n=8). Autologous spinal bone fusion surgery was performed on both groups 8 weeks later. After fusion surgery, the OVX-Ca group was supplemented with calcium in drinking water for 8 weeks. Blood was obtained 4 and 8 weeks after fusion surgery. Eight weeks after fusion surgery, the rats were euthanized and the L4-5 spine removed. Bone fusion status and fusion volume were evaluated by manual palpation and three-dimensional computed tomography. Results : The mean fusion volume in the L4-5 spine was significantly greater in the OVX-Ca group ($71.80{\pm}8.06mm^3$) than in controls ($35.34{\pm}8.24mm^3$) (p<0.01). The level of osteocalcin, a bone formation marker, was higher in OVX-Ca rats than in controls 4 weeks ($610.08{\pm}10.41$ vs. $551.61{\pm}12.34$ ng/mL) and 8 weeks ($552.05{\pm}19.67$ vs. $502.98{\pm}22.76$ ng/mL) after fusion surgery (p<0.05). The level of C-terminal telopeptide fragment of type I collagen, a bone resorption marker, was significantly lower in OVX-Ca rats than in controls 4 weeks ($77.07{\pm}12.57$ vs. $101.75{\pm}7.20$ ng/mL) and 8 weeks ($69.58{\pm}2.45$ vs. $77.15{\pm}4.10$ ng/mL) after fusion surgery (p<0.05). A mechanical strength test showed that the L4-5 vertebrae in the OVX-Ca group withstood a 50% higher maximal load compared with the controls (p<0.01). Conclusion : Dietary calcium given to OVX rats after lumbar fusion surgery improved fusion volume and mechanical strength in an ovariectomized rat model.

• Korean Journal of Applied Biomechanics
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• v.31 no.2
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• pp.133-139
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• 2021

Objective: This study aims to verify the conventional deadlift motions using by two different grips, thereby elucidating the grounds for effective training methods that can minimize the risk of injury. Method: Total of 18 healthy young adults were recruited for this study (age: 25.11±2.19 yrs., height: 175.67±5.22 cm, body mass: 78.5±8.09 kg, 1-RM: 125.75±19.48 kg). All participants were asked to perform conventional deadlift with two types of grips which are overhand grip (OG) and underhand grip (UG). In each grip, participant perform the deadlift with 50% and 80% of the pre-measured 1-RM. A 3-dimensional motion analysis with 8 infrared cameras and 3 channels of EMG was performed in this study. A two-way ANOVA (group × load) with repeated measure was used for statistical verification. The significant level was set at α=.05. Results: There were significant differences in grip type and weight on the right shoulder joint, and only significant difference in grip on the left shoulder joint (p<.05). The hip joint ROM was significantly increased as the weight increased in both types of grips on phase 1, while the ROM of hip joint was significantly decreased as the weight increased only in the case of OG on phase 2 (p<.05). In case of the OG, as the weight, increased significantly increased L1 ROM and L3 ROM were revealed on phase 1 and phase 2, respectively (p<.05). Moreover, as the weight increased, UG revealed significantly decreased L5 ROM on phase 1, while both grips showed significantly increased ROM on phase 2 (p<.05). In addition, the erector spinae and the biceps femoris, which are synergist for the motion, showed a significant difference in both types of grip according to the weight (p<.05). The muscle activity ratio of gluteus maximus/biceps femoris showed a significant difference only in the UG according to the weight (p<.05). Conclusion: In conclusion, beginners might be suggested to use the UG for maintaining the neutral state of the lumbar spine and focus on the gluteus maximus muscle, which is the main activation muscle. For the experts, it may recommend alternative use of the OG and UG according to the training purpose to minimize the compensation effect.