Journal of Mechanics in Medicine and Biology

Modeling of thermomechanical behavior of soft tissues is vitally important for the development of surgical simulation of hyperthermia procedures. Currently, most literature considers only temperature-independent thermal parameters, such as the temperature-independent tissue specific heat capacity, thermal conductivity and stress–strain relationships for soft tissue thermomechanical modeling; however, these thermal parameters vary with temperatures as shown in the literature. This paper investigates the effect of temperature-dependent thermal parameters for soft tissue thermomechanical modeling. It establishes formulations for specific heat capacity, thermal conductivity and stress–strain relationships of soft tissues, all of which are temperature-dependent parameters. Simulations and comparison analyses are conducted, showing a different thermal-induced stress distribution of lower magnitudes when considering temperature-dependent thermal parameters of soft tissues.

Objective: This study quantified the time-dependent concentration of ${}^{18}$F–NaF in critical organs according to a simplified compartmental biokinetic model with clinical verification. Methods: The eleven volunteers were given $232.9\pm 33.8$MBq ${}^{18}$F–NaF administration, then scanned (with 15min-collection, every 20min, for 200 consecutive min) with a Philips Gemini GXL PET/CT. The empirical data were collected and normalized as the input dataset for MATLAB program. A six-compartmental model was created as a set of time-dependent differential equations and analyzed by the MATLAB to optimize the correlation between the in vivo data and calculated results. The six compartments were: body fluid, bone, kidney, liver, remainder and excretion, while kidney and liver compartments were conventionally split into two subunits with different half-lives to fit properly the empirical data. Results: The average biological half-lives of body fluid, bone, kidney-1, kidney-2, liver-1, liver-2 and the remainder (rest of body) were assessed as $577\pm 150$, $770\pm 255$, $138\pm 64$, $25\pm 6$, $138\pm 29$, $33\pm 9$, and $84\pm 23$min, respectively. A dimensionless AT index of disagreement between the empirical data and MATLAB optimal solutions was proposed of validating the applied acquisition system and analytical method feasibility. The body fluid and bone AT values did not exceed 20%. The proposed refined equation yielded the internal dose from both gamma- and beta-rays ($0.409\pm 0.076$ cSv as $0.00176\pm 0.00033$ cSv/MBq), which exhibited good correlation with literature (0.00168–0.00270 cSv/MBq). Conclusion: The proposed MATLAB-based fitting of in-vivo data with the theoretical results was instrumental for assessing the radiation dose received by the PET/CT bone scan participants.

Scans without evidence of dopaminergic deficit (SWEDD) refers to patients with a normal dopamine transporter scan among patients clinically diagnosed with Parkinson’s disease (PD). It is essential to differentiate SWEDD from PD in order to avoid costly and inappropriate treatments. We investigated differences of gait pattern in PD patients and SWEDD patients. Twelve patients with SWEDD and 8 patients with PD participated in the gait test. All participants were instructed to walk along the GaitRite linear walkway at comfortable velocity. As outcome measure, various spatio-temporal gait variables were derived from commercial GaitRite software. Independent sample $t$-tests were evaluated to investigate statistical differences between SWEDD patients and PD patients. SWEDD patients walked more quickly with longer step length compared to PD patients ($p<0.05$). PD patients exhibited a longer stance phase with increased double-limb support period than SWEDD patients ($p<0.05$). Step time difference of SWEDD patients was smaller than that of PD patients ($p<0.01$). These findings suggest quantitative gait variables could be helpful for the identification of potential SWEDD patients. Also, understanding of gait strategies of SWEDD patients might be contributed to their effective medications and treatments.

Living body or corpse could be replaced with the virtual human tissue model for biomechanical experimental study, which effectively avoids the non-reusability, great social controversy, huge costs and difficulty in extracting parameters, and finally, the accurate analysis results are obtained. Unlike the previous lower limb models, the finite element models of hip and thigh were established based on the concept of muscle group in this paper. The cortical bones of hip bone and femur were set as *MAT_PIECEWISE_LINEAR_ PLASTICITY. The material of cancellous bone was set as *MAT_ELASTIC_PLASTIC_ WITH_DAMAGE_FAILURE. The material of articular cartilage was set as *MAT_ISOTROPIC_ELASTIC. The materials of muscle and fat were set as *MAT_VISCOELASTIC. The accuracy of the finite element model was verified by dynamic three-point bending experiment of the thighs. Mechanical simulation was carried out to the stump-prosthetic socket and the comfort of socks by the established model. The simulation results were all between the upper and lower bounds of the experimental results in the dynamic three-point bending experiment of the thighs where the loads were separately applied to one-third of the distal end of thighs and the middle part of thighs. The simulation results of the stump-prosthetic socket example show that the optimal elastic modulus of silicone pad is 2.5MPa. Simulation results of socks comfort show that the distribution of stress and deformation of the anterior and posterior thighs is different when the human lower limbs are in stockings. The established simulation model meets the accuracy requirement and can replace the living body or corpse to carry out biomechanical experimental study. The finite element simulation results converge, and the time to complete a finite element calculation is less than or equal to 10min.

The main purpose of our study was to evaluate the biomechanics of different posterior cruciate ligament (PCL) reconstruction techniques. Seven fresh cadaver knees were collected. A 6-DOF robot arm was used to test the biomechanical parameters, including the posterior stability, the lateral stability and the rotation stability of different PCL reconstruction techniques. Each group was tested at the knee flexion of 0, 30${}^{\circ }$, 60${}^{\circ }$, 90${}^{\circ }$ and 120${}^{\circ }$, under the following conditions respectively: a posterior force of 134N, an internal and external rotation torque of 5$\mathrm{\text{N}}\cdot \mathrm{\text{m}}$, a varus and valgus torque of 10$\mathrm{\text{N}}\cdot \mathrm{\text{m}}$, and a combination of 100N posterior force and 5$\mathrm{\text{N}}\cdot \mathrm{\text{m}}$ external rotation torque. The posterior tibia translation and the rotational angle of the 4-tunnel double-bundle PCL reconstruction group were significantly lower than that of 3-tunnel double-bundle group and the single-bundle group; the posterior tibia translation valgus–varus-angle were lower at some specified flexion angle. No statistical difference was found between the anatomic 4-tunnel bundle group and the intact knee group concerning the posterior tibia translation, the rotational angle, and the valgus–varus-angle. This study showed that the biomechanics of PCL of 4-tunnel double-bundle reconstruction was closer to the intact knees than the other two reconstruction methods.

Many studies suggest that regular physical activity can reduce the opportunity of Alzheimer’s disease (AD) and slow its onset and progression. However, the exact mechanism is still unclear. Clinically, amyloid plaques and neurofibrillary tangles are the two characterizations of AD, which are associated with amyloid-$\beta$ and tau hyperphosphorylation, respectively. The PI3K/Akt signaling pathway regulates tau phosphorylation and has a pivotal role in the development of pathology in AD. Therefore, we try to investigate the effects of aerobic exercise on tau phosphorylation and examine whether these effects were mediated by the PI3K/Akt pathway in the hippocampus of APP/PS1 and C57BL/6J mice. 40 male APP/PS1 mice and 40 male C57BL/6J mice were randomly divided into four groups respectively: sedentary group, exercise group, sedentary with GNE-317 treatment group and exercise with GNE-317 treatment group. The mice in the exercise group and exercise with GNE-317 treatment group were given exercise training on a treadmill for 8 weeks. After 8 weeks of treadmill exercise, the morris water maze, immunohistochemistry and western blot analysis were performed. We found out that 8 weeks of aerobic exercise enhanced PI3K expression and increased p-Akt${}^{\mathrm{\text{Thr}}308}$, p-Akt${}^{\mathrm{\text{Ser}}473}$ and p-GSK3${\beta }^{\mathrm{\text{Ser}}9}$. Furthermore, 8 weeks of aerobic exercise reduced tau phosphorylation at multiple sites including Ser202, Thr231 and Ser396. In the morris water maze, the exercise group showed a reduced escape time and distance compared with those of the sedentary group, suggesting that aerobic exercise improved the cognitive ability in mouse. While the above-mentioned results were attenuated in the PI3K/Akt inhibitor GNE-317 treatment groups. Our study demonstrated that 8 weeks of aerobic exercise could reduce tau phosphorylation and improve cognitive functions by activating the PI3K/Akt pathway in the hippocampus of APP/PS1 and C57BL/6J mice.

Objective: To study the effects of square dance on bone mineral density (BMD) and bone turnover markers in patients with postmenopausal osteoporosis.

Methods: Fifty postmenopausal women (aging 45–60) with osteoporosis were randomly assigned to a research group and a control group. The patients in the research group received 600mg of calcium combined with square dance (5 times a week, 30 to 60 minutes each time) for 6 months while those in the control group only received 600mg of calcium. BMD, changes in bone turnover markers and bone pain were assessed before and after the treatment.

Results: (1) After the 6-month treatment, BMD of L${}_{2-4}$ and the femoral neck significantly increased in the research group ($p<0.05$). No significant change was observed in BMD of the Ward’s region. BMD in the control group did not change significantly ($p>0.05$). (2) No significant difference was found in serum levels of calcium, phosphorus and alkaline phosphatase between the two groups both before and after the treatment ($p>0.05$). Serum levels of P1NP had a significant increase, while $\beta$-CTX’s level did not change significantly. (3) The bone pain in both groups has been effectively relieved. The pain in the research group was relieved significantly compared to the control group.

Conclusions: By improving the BMD and relieving the pain, square dancing can exert positive effects on women with postmenopausal osteoporosis. Square dancing may become a feasible strategy for osteoporosis prevention and treatment.

In recent years, the physical fitness of primary and middle school students in China has been declining. In addition to the unbalanced nutrition, the main reason is the insufficient load of physical exercise. The aim of this study is to explore the quantitative methods of sports load of primary and middle school students by means of training impulse (TRIMP), and to evaluate the feasibility and effectiveness of this method. In the study, 297 students (168 boys, 129 girls) were divided into intervention group and control group. All of students were tested with height, weight, vital capacity, sit-and-reach, 50m running, 50m $\times$ 8 round trip, one-minute sit-up, one-minute skip and other physical indicators in gym class, the change of resting heart rate, sport heart rate, exercise time were collected before and after by independent development of the heart-rate wrist belt. The mean sport heart rate, mean exercise time (the cumulative time of the heart rate between 120 and 200bpm), the time of different intensity exercise and the TRIMP were calculated. The results of correlation analysis showed that the change of TRIMP was positively correlated with the change of vital capacity and one-minute sit up, and increasing sports load could improve the physical health, verifying the feasibility of using the TRIMP to quantify the sports load. At the same time, the TRIMP was expressed in scores to make the understanding easy for the teachers and students or any audience in general.

The upper limb of a vehicle driver is vulnerable to injury in a car collision accident. In order to study the injury mechanism and biomechanical response of the upper limb, a finite element model of upper limbs including upper limb bones, muscles, ligaments and skin was established from CT scan data, and was validated by quasi-static and dynamic three point bending tests to the long bones, as well as airbag and forearm impact tests. Further, the influence of airbag parameters and driver’s postures on the upper limb injury were simulated and analyzed. The results showed that the risk of forearm fracture increased with the increase of the forearm radial speed. When the air mass rate of airbag reduced to half of the initial, the forearm distal-end average speed was decreased by 19.1%, and the peak decreased by 9.0% accordingly. When the distance between forearm and the airbag was selected from 0 to 15, 25 and 35mm, respectively, the forearm distal-end average speed was decreased by 23.8%, 45.1% and 56.7% accordingly, and the peak decreased by 1.6%, 28.4% and 42.0%, respectively. The simulation result indicates this model has a good bio-fidelity and can accurately reflect the dynamic response of the upper limb and quantitative injury mechanism, enabling the evaluation of vehicle safety restraint system.

According to the combination of lower limbs rehabilitative robot (LLRR), the effect of multi-point and single point driving form on muscle force and joint torque is explored, and the rehabilitation effect of the training mode of the active–passive rehabilitation training is studied. The musculoskeletal model of lower limbs is established based on the physiological structure of human lower limbs. And considering the position of the attachment points of each muscle, the mechanical properties of muscles and applied moment of joints can be obtained under different rehabilitative training strategies by inverse dynamic analysis. The rehabilitation training strategies of flexion–extension and abduction and adduction movements are put forward according to the movement of lower limbs. And using the wire-driven rehabilitation robot as the driving device of the rehabilitation training, the robot is used to simulate the motor function of patients’ lower limbs by modifying the parameters of muscle which can affect the resistance moment of joint motion, then the effects of driving form and the active–passive training mode are analyzed. The results show that single point driving form is better than multi-point on muscle strength and joint strength training; the rehabilitation training strategies of flexion–extension and abduction–adduction movements show different superiority.

Pneumatic muscle actuators (PMAs) have great potential in robotics and industrial applications. However, high non-linearities hamper the further applications in accurate performances. Pressure built-up process is highly non-linear due to non-linear elasticity of rubber tube of the PMA and air driving mode, and brings great challenges in approximation. This paper analyzes the experimental responses of charging and discharging process, respectively, and employs second-order linear system to model the charging and discharging dynamics inside PMA. Experiments are performed to validate the effectiveness of the established models and comparison between simulated curves and experimental data indicates that the built-up models can capture the dynamics of pressure changing processes inside PMA.

The vibrations in blood pumps were often caused by high speed, suspension structure, viscoelastic implantation environment and other factors in practical application. Red blood cell (RBC) was modeled using a nonlinear spring network model. The immersed boundary-lattice Boltzmann method (IB-LBM) was used to investigate the impact of high-frequency vibration boundary on RBC. To confirm the RBC model, the simulation results of RBC stretching were compared with experimental results. We examined the force acting on RBC membrane nodes; moreover, we determined whether RBC energy was affected by different frequencies, amplitudes, and vibration models of the boundary. Furthermore, we examined whether RBC energy was affected by the distance between the top and bottom boundaries. The energy of RBCs in shear flow disturbed by the vibration boundary was also investigated. The results indicate that larger amplitude (A_m), frequency (F_r), and opposite vibration velocity of top and bottom boundary produced a larger force that acted on RBC membrane nodes and larger energy changes in RBCs. The vibration boundary may cause turbulence and alter RBC energy. When the blood pump was designed and optimized, the vibration frequency and amplitude of the blood pump body and impeller should be reduced, the phase of the blood pump body and impeller vibration velocity should be close. To alleviate the free energy of RBCs and to reduce RBC injury in the blood pump, the distance between RBCs and the boundary should not be less than 20$\mu$m.

Taking the lower maxillary incisors as an example and the orthodontic forces along the near–far middle direction, the orthodontic forces along the crown–root direction and the orthodontic moment around the tongue–cheek direction as loading condition, the biomechanical simulation of the tooth is carried out by the method of finite element simulation in this paper. The CT images of the skull are segmented and denoised by Mimics. The solid models of teeth, periodontal ligament (PDL), alveolar bone and brackets are established by Gomagic and Solidworks. The material characteristics of the PDL are defined by the two-order Ogden hyperelastic model. Taking the PDL capillary pressure as a criterion for orthodontic safety, combined with the stress response of PDL, the safe orthodontic force range of mandibular central incisors is obtained by ANSYS finite element software.

The impact of motors breakdown and failures on mobile robot motor bearing is an important concern for robot industries. For this reason, predictive motor lifetime and bearing fault classification techniques are being investigated extensively as a method of decreasing motor downtime and enhancing mobile robot reliability. With increasing attention on neural network technologies, many researchers have carried out lots of the relevant experiments and analyses, very plentiful and important conclusions are obtained. In this article, a classification method based on discrete wavelet transform (DWT) and long short-term memory network (LSTM) a proposed to find and classify fault type of mobile robot permanent magnet synchronous motor (PMSM). First, a set of mobile robot motor vibration signal were collected by the sensors. Second, the obtained vibration signal is decomposed into six frequency bands by the DWT. Haar function is selected as the mother function in the processing. The energy of every frequency band was calculated as a classification feature. Thirdly, four classification features with high classification rate are obtained. The feature vector is used as input of the neural network, and the fault type is identified by LSTM classifier with deviation unit. From the results of the experiments provided in the paper, the method can detect the fault type accurately and it is feasible and effective under different motor speed.

Objectives: A biokinetic model of iodine in the thyroid was developed and applied to a case-control study of hyperthyroid cat undertaken the NaI-131 dose administration using a gamma camera/8-slice CT with the in vivo study. Methods: The case-control hyperthyroid cats were administered 55.5 or 3.7MBq of I-131 radioactive solution and continuously surveyed by a gamma camera. The scan schedule was preset as 5- or 10-min counting per each hour from the initial time to the sixth hour, then on the 24th, 48th and 72nd hours, respectively. An in-house developed program run in the MATLAB was applied to evaluate the biokinetic model of iodine in the thyroid, in compliance with the ICRP-30 report regulations. The model was defined by five compartments (namely: stomach, body fluid, thyroid, whole body, and excretion) and allowed one to simulate the variations of time-dependent I-131 radioactive concentration among various compartments of each study subject. The numerical simulation via MATLAB was compiled with the empirical evaluation to optimize the time-dependent concentration of I-131 within the above compartments. Results: The derived biological half-life values for stomach, body fluid, thyroid, whole body, and excretion, respectively, were as follows: 17, 3, 10, 5 and 140h for hyperthyroid cat, 18, 1, 8, 2, and 40h for control #1 cat, and 22, 2, 12, 4, and 20h for control #2 cat. The cumulative radioactive doses from both gamma-ray and beta particles were assessed via a simplified algorithm as 0.135, 0.0082, and 0.005 Gy, for hyperthyroid cat, control #1, and control #2 ones, respectively. Conclusion: The derived biokinetic model was found to be helpful in the evaluation of the metabolic mechanism in case of feline hyperthyroidism. The revealed deviations from available human biomodels can be used for refining the radioiodine treatment of pets with hyperthyroidism.

A higher fall rate has been reported in elderly women than in elderly men. Muscle strength is one of the key fall risk factors. The aim of this study was to investigate gender differences associated with maximal voluntary hip flexion and extension torque in concentric, isometric and eccentric contractions among the elderly subjects. A total of 20 healthy elderly subjects (10 men and 10 women) participated in this study. A dynamometer was used to measure hip joint torque during various modes of isokinetic contraction in frontal plane. The peak torque was normalized according to each subject’s body mass. Independent $t$-tests were conducted to compare elderly women with elderly men. Elderly women exhibited weaker normalized peak torque during flexion and extension compared with elderly men in isometric contraction mode ($p<0.05$). Eccentric strength of elderly women was significantly lower than in elderly men primarily in hip extension ($p<0.05$). In contrast, no significant differences were observed in concentric contraction mode between the two genders ($p>0.05$). These results suggest that the decreased muscle strength per body mass, especially in isometric and eccentric contraction, may be associated with a higher frequency of falls in elderly women than in elderly men. This study suggests the need for effective muscle strength training and intervention for fall prevention in elderly women.

A systematic methodology for solving the inverse dynamics of a 6-PRRS parallel robot is presented. Based on the principle of virtual work and the Lagrange approach, a methodology for deriving the dynamical equations of motion is developed. To resolve the inconsistency between complications of established dynamic model and real-time control, a simplifying strategy of the dynamic model is presented. The dynamic character of the 6-PRRS parallel robot is analyzed by example calculation, and a full and precise dynamic model using simulation software is established. Verification results show the validity of the presented algorithm, and the simplifying strategies are practical and efficient.

Idiopathic scoliosis (IS) is a complex three-dimensional (3D) deformity. The non-operative treatments for IS have been developed for a long time. According to current studies, hard braces are more effective than soft braces for the treatment of scoliosis. Though current braces are proved to be effective for the treatment of IS, there are several shortcomings needed to be overcome: (i) Braces cannot realize precise control over a specific vertebra. (ii) Braces affect cardiopulmonary efficiency (braces limit maximal exercise performance). (iii) The brace is not modulated based on user’s needs. (iv) Braces, including motions during eating, tying shoes, sitting, and standing. (v) Braces apply forces on skin, which causes pain, skin breakdown, and abnormal deformation of bone. In order to solve these boring problems of the current braces, this paper proposed a new intelligent robotic spine brace based on the principle of human biomechanics, three point pressure treatment theory and parallel mechanism theory. This novel brace can offer 3D active dynamic adjustable corrective forces for the treatment of IS and some experiments are employed for verifying the effect of the proposed brace.

In this study, the effect of the dynamic bike fitting, which was defined as lower limb vertical alignment by inserted wedges, was evaluated. Twelve non-cyclists are participated in this experiment. For comparing pedaling performance between before and after fitting, sub-maximal pedaling tests were conducted for 2 min. The results showed that both the range of motion of the knee joint (medio-lateral direction) which represented pedaling trajectory and the coefficient of variance of pedaling power were decreased in non-cyclists. This result indicated that the dynamic fitting had a positive effect such as increased pedaling kinematic stability and kinetic efficiency on pedaling performance. Supplementary pedaling test was performed by one of the best cyclist, who was a member of the national team and a middle and long distance cyclist. The result of the cyclist test was also similar to the patterns of 12 non-cyclists. It is believed that this study has the meaning of the preliminary study to evaluate the effects of the dynamic fitting. Further study is necessary to evaluate the effects of the fitting through enough subjects and repeated tests by measuring muscle activities and forces.

We were investigating the muscle strength and aerobic function effect on the aged according to active and passive load using compact cycle system. We recruited twenty old participants and they performed shoulder rotating, upper cycling and lower cycling exercise. We measured the muscular activity, respiratory gas analysis and body heat. The result of muscular activity showed that the passive load could cause muscular activity at 15.4–65.9% compared to active load. We thought that the passive exercise could provide the prevention of spasticity and maintain effect of remaining muscle function in the elderly by caused muscular activity over 50%. The result of oxygen consumption showed that it is the active exercise that used the bigger oxygen consumption at 42.4% during lower cycling. We thought that the active exercise used the big muscles of lower limbs including trunk muscles during lower cycling. The result of body temperature showed that it rises with increase in oxygen consumption and heart rate, and it increased the bigger for lower cycling. The foundation of this study could apply to fundamental research for developing exercise load of indoor rehabilitation exercise system with convenience and easy use to the elderly.