Noeryoung6403

Greater rectus femoris activation during the failed trials was identified during 88-100% of the flight phase, as well as 1-4% and 71-97% of the landing phase. Greater gluteus medius and biceps femoris activation was also identified in the failed trials during 54-72% and 76-89% of the landing phase respectively. These findings indicate that the control of proximal joints has an important role in determining if a participant will fail a landing; and that how athletes prepare for a landing may be more relevant than the kinematics following ground contact.In nature, many insects have evolved hard cuticles to shelter their soft body, which is thought to be the "body-armour" for insects to protect against predators' sharp teeth or dynamic load damage caused by harsh environments. In recent years, researchers have found that the "body-armour" is composed of multi-layer materials with different elastic modulus from inside to outside. The gradient change rule of the formed material modulus reflects the evolutionary history of insect cuticle's adaptation to external changes. In this article, the mechanical properties of spatial hierarchical architecture of insect cuticle, especially for the shield-like beetle elytra under impact loading, was investigated to reveal the impact resistance strategy and in-depth mechanisms of crashworthy protection. The results show that both discontinuity at the cuticle layers interface and the distributions of stiffness gradients through layers' thickness have a great influence on preventing stress wave propagation and improving impact-tolerance. Insect cuticle such as beetle elytra with discontinuous exponential stiffness gradient (DC-EXP) along the thickness has been identified to result in the minimum values of stress and interaction force under impact loading, which leads to the best impact resistance property and defensive effect. Furthermore, we compared and discussed the protective properties of insect elytra with different sclerotized endocuticle under quasi-static compression and impact loading, respectively. The knowledge gained from this work reveals the advantages of nature's choice of the stiffness distribution and may serve to inspire further research of developing advanced multifunctional structures with improved impact resistance capability by programming reasonable stiffness distribution.Two simulation experiments are presented to gauge the accuracy of a new inverse kinematics method based on Bayesian inference (BIK; Pataky et al., 2019) in more realistic models than were considered previously. The first application concerns planar kinematics in the presence of soft-tissue artefacts and the second application concerns rigid body kinematics in 3D with finite helical axes (FHA). The percentage of simulations in which BIK was more accurate than least-squares based methods was only high in cases of relatively large noise magnitudes (noise SD >5 mm) or when the rotation magnitude was very small (⩽5 deg) in the 3D FHA model. Correlated parameters are the likely culprit of the low performance of BIK. Also computation time is a major deficit of the BIK approach (±20 s for the movement between two time frames). These results indicate that more research will be necessary to improve the accuracy of BIK for complex biomechanical models at realistic noise levels and to reduce computation time.Knee joint sounds contain information on joint health, morphology and loading. These acoustic signals may be elicited by further, as yet unknown factors. By assessing potential elicitors and their relative contributions to the acoustic signal, we investigated the validity of vibroarthrographic assessments during different movement conditions with the aim to derive recommendations for their practical usage. Cross-sectional study. Nineteen healthy participants (24.7 ± 2.8 yrs, 7 females) performed five movements level walking, descending stairs, standing up, sitting down, and forward lunge. Knee joint sounds were recorded by two microphones (medial tibial plateau, patella). Knee joint kinematics and ground reaction forces were recorded synchronously to calculate knee joint moments (Nm/Kg). The mean amplitude (dB) and the median power frequency (Hz) were determined. A repeated measures mixed model investigated the impact of potential predictors (sagittal, frontal, transverse plane and total knee joint moments, knee angular velocity, age, sex, body mass index (BMI) and Tegner Activity Score (TAS)). Most of the amplitudes variance is explained by between-subject differences (tibia 66.6%; patella 75.8%), and of the median power frequencies variance by the movement condition (tibia 97.6%; patella 98.9%). The final model revealed several predictor variables for both sensors (tibia sagittal plane, frontal plane, and total knee joint moments, age, and TAS; patella sagittal plane knee moments, knee angular velocity, TAS). The standardization of the execution of the activities, a between-group matching of variables and the inclusion of co-variates are recommended to increase the validity of vibroarthrographic measurements during different movement conditions of the knee joint.Excessive postural sway while standing can lead to falls and injuries. A designed wearable balance assistance device which consists of scissored-pair control moment gyroscopes and a two-axis inclination sensor is introduced to reduce fall risk from excessive sway among the elderly. The prototype has dimensions of H50cm × W44cm × D30cm and weighs 15.03 kg. This study aims to investigate the effects of generated torque of the prototype on human subjects and aims to determine if the two-axis inclination sensor can detect sway amplitude and sway direction during an occurrence of excessive sway. Two healthy male subjects participated in the study. According to the results, the detected body incline angle related to the acquired sway amplitude of COP trajectories with correlation factors of 0.92 and 0.88 for the two subjects. The detected sway angle related to the acquired sway direction of COP trajectories with the correlation factors of 0.99 and 0.98 for the two subjects. The maximum-allowable generated torque of the prototype with an assigned actuating angle varying within ±15.6° from the acquired sway direction of COP trajectories was able to drive the COP of 60-kilogram-weighted healthy subject maintaining balance at posterolateral limits of stability with an average body incline angle of 5.74° to pass his standing secure zone. The results indicate that the prototype has the potential of being a wearable balance assistance device which can reduce fall risk from excessive sway among the elderly; however, some improvements are still required in regards to shape, size, mass, generated torque, and strength.Previous studies have quantified the biodynamic responses to vibration with more focus on vertical vibration than horizontal vibration. This study reports the transmissibility to the head and spine measured under whole-body fore-and-aft vibration. Sixteen seated male subjects were exposed to sinusoidal fore-and-aft vibration with magnitudes 0.311-2.426 ms-2 r.m.s. and frequency range 2-6 Hz. The fore-and-aft (Txx), lateral (Txy) and vertical (Txz) transmissibilities to the head, three locations on the thoracic spine (T1, T8, T12) and L4 were measured. Txx, Txy and Txz showed high inter-subject variability at all locations. A peak in the range 2-2.4 Hz was evident at all locations indicating a whole-body resonance in this frequency range. Txy peak was smallest at T8 and greatest at the head with medians of 0.15 and 0.46, respectively. Txx peak was smallest at L4 and greatest at the head with medians of 0.65 and 2, respectively. Txz peak was smallest at T8 and greatest at the head with medians of 0.58 and 1.3, respectively. At T12 and L4 and at frequencies below 4 Hz, Txz was as high as or higher than Txx. At low frequencies, Txx decreased with moving down the spine while an opposite trend was found at high frequencies. Txz decreased with moving up the spine from L4 to T8. Trichostatin A Txz at T1, however, was higher than that at T8, possibly influenced by the high motion of the head. The results are useful for developing models that help better understanding of human response to horizontal vibration.Vibration transmission through vehicle seats is usually predicted using the biodynamics of the seated human body measured with a rigid seat, however how coupling between the body and the seat would affect the biodynamics of the body is not considered. This study investigated how dynamic forces distributed over a soft seat compared to that over a rigid seat wtih vertical vibration excitation. Fourteen male subjects sitting on a rigid seat and on foam cushions of two different thickness with four different heights of footrest were exposed to vertical whole-body vibration between 0.5 and 20 Hz at 0.5 ms-2 r.m.s. Dynamic forces were measured beneath the ischial tuberosities, the middle thighs, and the front thighs and the transmissibility of the cushion was measured to the three locations. The resonance in the transmissibility of the cushion was found around 4 Hz to the ischial tuberosities but around 6-8 Hz to the front thighs. Differences between the apparent mass measured with the cushioned seat and the rigid seat decreased with increasing height of footrest. A multi-body dynamic model that can predict the dynamic forces beneath the ischial tuberosities and thighs was applied to identify the cause for the differences. It was suggested the differences can be caused by the variations in vibration over the surface of soft seats, especially when the contact area beneath the thighs was large, and by changes in the effective stiffness and damping of the human body when the contact area beneath the thighs was reduced.Virtual finite element human body models have been widely used in biomedical engineering, traffic safety injury analysis, etc. Soft tissue modeling like skeletal muscle accounts for a large portion of a human body model establishment, and its modeling method is not enough explored. The present study aims to investigate the compressive properties of skeletal muscles due to different species, loading rates and fiber orientations, in order to obtain available parameters of specific material laws as references for building or improving the human body model concerning both modeling accuracy and computational cost. A series of compressive experiments of skeletal muscles were implemented for human gastrocnemius muscle, bovine and porcine hind leg muscle. To avoid long-time preservation effects, all experimental tests were carried out in 24 h after that the samples were harvested. Considering computational cost and generally used in the previous human body models, one-order hyperelastic Ogden model and three-term simplified viscoelastic quasi-linear viscoelastic (QLV) were selected for numerical analysis. Inverse finite element analysis was employed to obtain corresponding material parameters. With good fitting records, the simulation results presented available material parameters for human body model establishment, and also indicated significant differences of muscle compressive properties due to species, loading rates and fiber orientations. When considering one-order Ogden law, it is worthy of noting that the inversed material parameters of the porcine muscles are similar to those of the human gastrocnemius regardless of fiber orientations. In conclusion, the obtained material parameters in the present study can be references for global human body and body segment modeling.