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Elbow joint loading was evaluated during a forward fall at various elbow initial flexion angles, in order to determine which is the best elbow initial flexion angles to prevent the elbow injury during a fall. Subjects were asked to perform a forward fall and followed by a push-up motion in different elbow initial flexion angles: 0°, 20°, 40° and unrestricted group. Fall on the outstretched hand is the leading cause of upper extremity injury. There are far more extension type of supra-condylar fracture of the elbow than flexion type. Flexion of the elbow may represent the effects of damper and spring. Using the motion analysis system, the kinematics and kinetics of the elbow joint were investigated under various elbow initial flexion angles. The loading biomechanics of the elbow joint differed with various elbow initial flexion angles. The ground reaction forces decrease with increase of elbow flexion upon impact. Different initial elbow flexion angles would affect the biomechanics of upper extremities during falls. Forward fall with elbow in extension is more dangerous. Knowledge of elbow kinematics and kinetics may be helpful in preventing injuries by reducing the ground reaction force with changes of the elbow initial flexion angles during a fall.

The purposes of the present study were to (1) investigate the effects of the arm movement and initial knee joint angle employed in standing long jump by the ground reaction force analysis and three-dimensional motion analysis; and (2) investigate how the jump performance of the female gender related to the body configuration. Thirty-four healthy adult females performed standing long jump on a force platform with full effort. Body segment and joint angles were analyzed by three-dimensional motion analysis system. Using kinetic and kinematic data, the trajectories on mass center of body, knee joint angle, magnitude of peak takeoff force, and impulse generation in preparing phase were calculated. Average standing long jump performances with free arm motion were +1.5 times above performance with restricted arm motion in both knee initial angles. The performances with knee 90° initial flexion were +1.2 times above performance with knee 45° initial flexion in free and restricted arm motions. Judging by trajectories of the center mass of body (COM), free arm motion improves jump distance by anterior displacement of the COM in starting position. The takeoff velocity with 90° knee initial angle was as much as 11% higher than in with 45° knee initial angle. However, the takeoff angles on the COM trajectory showed no significant differences between each other. It was found that starting jump from 90° bend knee relatively extended the time that the force is applied by the leg muscles. To compare the body configurations and the jumping scores, there were no significant correlations between jump scores and anthropometry data. The greater muscle mass or longer leg did not correlated well with the superior jumping performance.

Degenerative osteoarthritis is the consequence of impact force applied to articular cartilage that results in surface fissuring. Soft cushions and flexed posture are two important factors to reduce the impact force; however, no quantitative information of how soft should the cushion be to prevent the injury and the mechanism of force attenuation of knee joint at neutral and flexed posture was not well documented yet. The objective of current study is hence to find the quantitative shock attenuation of knee joint using different stiffness of cushions when the knee is at neutral posture and flexed posture. A “drop-tower type” impact apparatus was used for testing. Nineteen fresh porcine knee joints were divided into two posture groups, i.e. neutral and flexed posture. All specimens were tested using stiff, medium, and soft cushions. The axial reaction force, anteroposterior shear force, and flexion bending moment were recorded for analysis. We found the flexed posture decreased the axial reaction force and anterior shear force but increased the flexion bending moment. The effect of stiffness of cushions on the mechanical response of knee joint during impact loading was significant for neutral posture but not for flexed posture.

The aim of this study was to evaluate the influence of implant length and bone quality on the biomechanical aspects in alveolar bone and dental implant using non-linear finite element analysis. Two fixture lengths (8 and 13mm) of Frialit-2 root-form titanium implants were buried in 4 types of bone modeled by varying the elastic modulus for cancellous bone. Contact elements were used to simulate the realistic interface fixation within the implant system. Axial and lateral (buccolingual) loadings were applied at the top of the abutment to simulate the occlusal forces. The simulated results indicated that the maximum strain values of cortical and cancellous bone increased with lower bone density. In addition, the variations of cortical bony strains between 13mm and 8mm long implants were not significantly as a results of the same contact areas between implant fixture and cortical bone were found for different implant lengths. Lateral occlusal forces significantly increased the bone strain values when compared with axial occlusal forces regardless of the implant lengths and bone qualities. Loading conditions were found as the most important factor than bone qualities and implant lengths affecting the biomechanical aspects for alveolar bone and implant systems. The simulated results implied that further understanding of the role of occlusal adjustment influencing the loading directions are needed and might affect the long-term success of an implant system.

The geometric shape and mechanical structure of RBFPD compared to conventional FPD are relatively complex and unstable. The low retention rate between the retainer and abutment affects the prosthesis/abutment interface de-bonding, and closely relates to the design of the prosthesis and varied occlusion status. This study used reverse engineering (RE) and computer-assisted design (CAD) to construct two solid models of anterior RBFPD with different span lengths. After mesh generation, biomechanical interactions of span length in RB prosthesis with two loading conditions (axial and lateral) were performed by FE analysis. The simulated results indicated that lateral occlusal force increased significantly 2-3 times maximum stress than that of axial occlusal force. For different span lengths simulation, the analysis on static movement finds that longer pontic would lead to high stress to the prosthesis. Thus, the length of the pontic has significant effect on the overall intensity of the prosthesis under static clenching loading, and the effect of lateral loading exceeds that of axial loading.

Recently, there are more people jogging with a treadmill at the gym or the home setting. The main available selected modes for treadmill jogging are speed and slope of incline. Increased speeds and incline slopes will not only increase the cardiopulmonary loading but may also alter the lower extremity (LE) movement patterns. There are few systematic investigations of the effect of the speed and incline on LE kinematics. Most studies have used 2D methods which focused on movements in sagittal plane only and this has limitations in the acquired data since lower extremity movements also include frontal and transverse planes. The current study aimed to investigate LE movement during jogging at different speeds and incline slopes using a high speed three-dimensional (3D) motion analysis system.

Eighteen young healthy males were recruited. The video-based motion capture system with six CCD cameras, HIRES Expert Vision System (Motion Analysis Corporation, CA, USA), was used to collect kinematic data at a sampling frequency of 120Hz. Nineteen passive reflective markers were attached to bilateral lower extremities of the subject. The joint angle is calculated by Euler angle using the rotation sequence: 2-1-3 (y-x′-z″). Four speeds were selected: 2 m/s, 2.5 m/s, 3 m/s, 3.5 m/s with the slope at 0, and four slopes were selected: 0%, 5%,10%,15% at a speed of 3 m/s. Repeated-measures ANOVA was used to test hypotheses regarding changes in jogging condition on LE kinematic variables. The significance level was set at 0.05.

As the jogging slope increased, the hip, knee and ankle demonstrated a significantly greater maximum flexion in swing phase (p<0.001), but the maximum extension angles in stance phase were relatively unchanged. Increased LE flexion during swing phase is important to ensure foot clearance with increased slope. For increased speed, the hip and ankle joints had significantly greater maximum joint extension angles during stance phase and the hip and knee joint had significantly larger maximum flexion angles in swing phase (p<0.001). Increased motion during swing phase account for a larger step length and increased motion during stance phase may facilitate the generation of power during forward propulsion as the jogging speed increased. As the slope and speed increased, LE movement patterns were changed in the transverse plane: the significantly increased (p<0.01) internal hip rotation at terminal stance, the increased toe-in of foot (p<0.001) during terminal stance phase and decreased (p<0.05) toe-out during swing phase. Increased hip motion in transverse plane could lengthen the stride distance and increase foot toe-in for providing a stable lever for push off to increase propulsion force as speed or slope is increased. By way of systematic 3D kinematic investigation of the LE in jogging, the results further elucidate the effect of changing speed and incline on LE joints movements. This information could provide guidelines for rehabilitation clinicians or coaches to select an appropriate training mode for jogging.

Background: Smoking has a number of well-documented negative effects on health. The seemingly common knowledge is that smoking causes low back pain. Cigarette smoking is associated with poor physical fitness and reduced muscle strength.¹ The specific effects of smoking on the efficacy of the lumbar extensors have been previously investigated where individuals with chronic low back pain often have weaker lumbar extensor muscles.² Rigorous exercises, however, reverse this weakness.

Hypothesis: This study hypothesizes that cigarette smoking is associated with deficits in the lumbar extensor strength that make the back susceptible to mechanical stress and injury.

Study Design: Cohort study.

Methods: The objective of this study was to determine the isometric lumbar extensor strength before and after fatigue challenge amongst smokers and nonsmokers. A pre-test and post-test design was used to determine the differences in the lumbar extensor endurance between smokers and nonsmokers.

Results: The result of the study confirms a relationship between reduced lumbar extensor strength and cigarette smoking. The negative impact of smoking on lumbar extensors suggests increased susceptibility to lumbar injuries and thereby low back pain.

Conclusions: Smokers demonstrated reduced muscle strength and fatigability of the lumbar extensors and they may perhaps be vulnerable to lumbar spine injuries. The study also confirmed that spinal extension exercises increased the endurance time of the lumbar extensor muscles.

Muscle contraction strength estimation using mechanomyographic (MMG) signal is typically calculated by the root mean square (RMS) amplitude. Raw MMG signal is processed by rectification, low-pass filtering, and mapping. In this work, beside RMS amplitude, another significant parameter of MMG signal, i.e. frequency variance (VAR), is introduced and used for constructing an algorithm for estimating the muscle contraction strength. Seven participants produced isometric contractions about the elbow while MMG signal and generated torque (resultant of muscle contraction strength) of biceps brachii were recorded. We found that MMG RMS increased monotonously and VAR decreased under incremental voluntary contractions. Based on these results, a two-layer neural network was utilized for the model of estimating the muscle contraction strength from MMG RMS and VAR. Experimental evaluation was performed under constant posture and sinusoidal contractions at 0.5 Hz, 0.25 Hz, 0.125 Hz, and random frequency. The results of the proposed algorithm and MMG RMS linear mapping were also compared. The proposed algorithm has better accuracy than linear mapping for all contraction frequencies. The mean absolute error decreased 6% for the 0.5Hz contraction, 43% for 0.25 Hz contraction, 52% for 0.125 Hz contraction, and 30% for random frequency contraction.

Background: The purpose of this case series was to quantify gait to study muscular dystrophy. In this research, the quantitative differences between normal and waddling gaits were assessed by force plate analysis.

Methods: Nineteen myopathy patients and 20 normal subjects serving as the control group participated in this research. In this study, quantitative analyses of gait have been used to investigate the differences in mobility between normal subjects and myopathy patients. Patient data were collected from Iranian Muscular Dystrophy Association members, and normal data were extracted from students of Azad University. All of the gait tests were performed using a Kistler force platform. Participants walked at a self-selected speed, barefoot, independently, and without assistive devices.

Results: Our findings indicate that there were no significant differences between the patients and the control group in the anterior–posterior components of the ground reaction forces; however, there were considerable differences in the force components between the groups in the medial-lateral and vertical directions of the ground reaction force. In addition, there were significant differences in the time parameters between the groups along the vertical and medial-lateral directions.

High-heeled shoes are associated with falling, leading to injuries such as fracture and ankle sprain. The study aimed to investigate the kinematic and kinetic adaptations in the lower extremities resulting from habitual use of high-heeled shoes. A total of 15 female experienced wearers and 15 matched controls walked with high-heeled shoes (7.3 cm) while kinematic and ground reaction force data were measured and used to calculate the joint angles and moments, as well as the temporal-distance parameters. Compared with inexperienced wearers, experienced wearers appeared to adopt a specific control strategy to improve the stability of the support ankle and knee while preventing excessive loading at the knee and hip. Increased hip abduction during early stance phase and increased pelvis rotation toward the ipsilateral side at contralateral heel-strike appeared to contribute toward the reduced step width for a better adjustment of the medio-lateral motion of the body's center of mass in order to maintain stability. At the hip, increased abductor moments may help to increase the pelvis stability and prevent excessive loading at the knee, and reduced internal rotator moments may reduce the torsional loading at the hip. At the knee, reduced ranges of flexion-extension and adduction-abduction motions may increase its stability. At the ankle, increased external rotation angles, together with increased pronator and external rotator moments through increased ground reaction force, may enhance the ankle stability. The current results identified the changes in the kinematics and kinetics of the lower extremities in females after long-term use of high-heeled shoes, providing a basis for future development of training programs and design of new high-heeled shoes to help those who have higher risks of falling and injuries during high-heeled gait.

Many unwanted traumas occur in daily life, the result of which may be intertrochanteric fractures in the musculoskeletal system. An intertrochanteric femoral fracture is a serious trauma which can lead to pneumonia, pulmonary embolism or death. Therefore, accurate and stable fixation of these fractures is necessary. Schanz screws with a pertrochanteric fixator body are used for the stabilization of intertrochanteric fractures. The stability of fractures created by external fixators is dependent on the frame and bone interaction. The distance between the fixator body and the bone, called "sidebar-bone spacing", is one of the most important aspects of fracture stability. The primary objective in the treatment of these fractures is to maintain the stability of the fracture in the reduction position to allow early mobilization. In this study, an intertrochanteric femoral fracture was fixed with a pertrochanteric fixator, then the effect of sidebar-bone spacing on the fracture line under axial loading was analyzed using AnsysWorkbench software. Stress and strain values on the fracture line and schanz screws were calculated to understand this effect according to the von-Mises criteria. The sidebar-bone spacing was selected as 8, 6 and 4 cm. The von-Mises stress value on the fracture line decreased as the distance between the fixator body and the bone decreased, although strain values increased. In conclusion, decreasing the sidebar-bone spacing in the pertrochanteric fixator used on hip fractures provides stronger stabilization, and demonstrates safer axial loading.

Objective: The quantification of inter-segmental spine joint reaction forces during common workplace physical demands. Background: Many spine reaction force models have focused on the L5/S1 or L4/L5 joints to quantify the vertebral joint reaction forces. However, the L5/S1 or L4/L5 approach neglects most of the intervertebral joints. Methods: The current study presents a clinically applicable and noninvasive model which calculates the spinal joint reaction forces at six different regions of the spine. Subjects completed four ambulatory activities of daily living: level walking, obstacle crossing, stair ascent, and stair descent. Results: Peak joint spinal reaction forces were compared between tasks and spine regions. Differences existed in the bodyweight normalized vertical joint reaction forces where the walking (8.05$\pm$3.19N/kg) task had significantly smaller peak reaction forces than the stair descent (12.12$\pm$1.32N/kg) agreeing with lower extremity data comparing walking and stair descent tasks. Conclusion: This method appears to be effective in estimating the joint reaction forces using a segmental spine model. The results suggesting the main effect of peak reactions forces in the segmental spine can be influenced by task.

Biomedical engineering (BME) is a multidisciplinary field, resulting in a heavy course load from different fields. We hypothesize that the engineering curriculum be tailored according to the requirements of the BME profession. In this study, we focus on the teaching of the finite element modeling (FEM) technique by redesigning the course to address the needs of the BME profession by some custom-made changes to meet the unmet needs. After the completion of the course, evaluation methods of the students were analyzed and detailed over a survey providing feedback from the students. The surveys were related to the teaching the theory of FEM, the laboratory sessions, and the project sessions. The survey results were evaluated using statistical methods. The Pearson correlation coefficient showed a linear agreement between theoretical and practical sessions indicating efficient blending of skills because of the custom-made changes. The survey analysis showed that the students were in favour of the changes, allowing them to be more resourceful and confident with their skills. The positive results indicate a positive attitude among the students towards their profession. As the course design addresses the needs of the profession allowing students to fit in better, the students might follow their own profession after graduation. A wider follow-up study might be planned next to compare the results between who received tailor-designed courses and those who did not.