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The purpose of this paper was to investigate the anatomical location of the main axes of rotation of the knee, that is the axes of flexion-extension and longitudinal rotation. We compared 4 hypotheses on the correlation between the axis of flexion-extension and the femoral anatomy and 4 hypotheses on the correlation between the axis of longitudinal rotation and the tibial anatomy in 6 normal human knees. The methods used for the study were:. digitization by an electrogoniometer; computer reconstruction of motion and bone geometry, and an original geometrical interpolation to identify axes location. Our results suggest that: (a) the axis of flexion-extension lies in a cone spanned by the transepicondylar line and the so called FFc line;¹⁹ (b) the axis of longitudinal rotation can be represented by a line parallel to the tibial anatomical axis intersecting the flexion axis in a fixed point of the medial compartment.

With progress of modern technology, manually-propelled wheelchairs are still of importance for individuals with mobility impairments. The repeated wheelchair propulsion and strenuous daily activities cause high loads and thus injuries on the upper extremity joints. Over the past few years, a considerable number of studies have been made on biomechanical analysis of wheelchair propulsion and wheelchair-related activities. Thorough investigation of biomechanics during wheelchair propulsion enhances comprehension of mechanism of injuries and provides information to improve wheelchair design and fitting. Numerous investigations have been made to demonstrate factors which cause low effectiveness of force application and inefficiency of movements. Emphasis was also placed on developing analytical models to simulate wheelchair propulsion.

The reliable knowledge that model-based three-dimensional (3D) fluoroscopy can provide about in vivo joints kinematics is essential to diagnose orthopedic pathologies, develop new prosthesis, and evaluate clinical procedures. To exploit 3D fluoroscopy for the analysis of elbow kinematics, its use was evaluated considering a single model for the forearm or two different models for the ulna and radius. Active elbow flexion-extension and prono-supination motor tasks of a healthy male subject were acquired by means of fluoroscopy. The 3D bone models were automatically aligned to the relevant projections. The pose estimation algorithm sought the tangency condition of the projection rays with the model surface, minimizing a cost function and exploiting an adaptive distance map. Five iterative guided alignments were performed to avoid the final convergence to a local minimum. The results highlighted the critical alignment of the ulna/radius model, particularly when prono-supination is performed. From the physiological motion patterns and given the values of the cost function, 3D fluoroscopy was proven to be applicable to the analysis of the elbow kinematics when single bone models for the ulna and radius are used.

This study investigates upper limb movement and electromyography (EMG) signals during snatch under various loading conditions and discusses results from six lifting phases. Qualisys motion analysis and Noraxon EMG systems were used to record upper limb movement and muscle activity. When lifting heavy weights, the maximum shoulder flexion angle exceeded 180° in the rise phase and thus, was higher than when lifting lower weight categories. The deltoid and biceps muscles exhibited higher activity during this phase when lifting heavy weights. It can be inferred that the deltoid muscle is activated in this phase in order to maintain the shoulder in an abducted position, and to maintain hyperflexion of the biceps. Muscle activity of the deltoid and biceps in the second pull phase also increased significantly during heavy weight lifting. We infer that the effective use of these two muscles in the second pull phase would produce higher peak barbell vertical velocity, increasing the amount of weight can be lifted. Muscle activity for the latissimus dorsi during first pull showed a statistically significant increase when lifting heavy weights. This ability by the latissimus dorsi to generate higher velocities early in the concentric phase (downswing) possibly contributed to the improved final performance during heavy weight lifting.

Walking is daily physical activity and a common way of exercise during pregnancy, but morphological changes can modify the gait pattern. Biomechanical models can help in evaluating joint mechanical loads and kinetics and kinematics during gait, and provide patterns. This study aimed to describe the gait pattern during the second trimester of pregnancy and give an orientation for biomechanical modeling for pregnant women. The ankle and hip joints seem to be more overloaded, mainly in the sagittal and frontal planes, respectively. Results show that pregnant women have a similar walking pattern to the normal gait. This model construction was revealed to be appropriate for describing gait during the second trimester of pregnancy.

The motion of the skeletal estimated from skin attached marker-based motion capture(MOCAP) systems is known to be affected by significant bias caused by anatomical landmarks mislocation but especially by soft tissue artifacts (such as skin deformation and sliding, inertial effects and muscle contraction). As a consequence, the error associated with this bias can propagate to joint kinematics and kinetics data, particularly in small rodents. The purpose of this study was to perform a segmental kinematic analysis of the rat hindlimb during locomotion, using both global optimization as well as segmental optimization methods. Eight rats were evaluated for natural overground walking and motion of the right hindlimb was captured with an optoeletronic system while the animals walked in the track. Three-dimensional (3D) biomechanical analyses were carried out and hip, knee and ankle joint angular displacements and velocities were calculated. Comparison between both methods demonstrated that the magnitude of the kinematic error due to skin movement increases in the segmental optimization when compared with the global optimization method. The kinematic results assessed with the global optimization method matches more closely to the joint angles and ranges of motion calculated from bone-derived kinematics, being the knee and hip joints with more significant differences.

This study examined chronic, isolated posterior cruciate ligament (PCL) rupture patients, dividing them into symptomatic and asymptomatic groups according to whether they displayed obvious symptoms in daily activities. Each group comprised 10 patients while 10 healthy, young individuals were adopted as the control group. Using a three-dimensional motion analysis system and force plates, the gait patterns of the PCL-deficient patients were analyzed from both kinematics and kinetics perspectives to identify whether they differed from the control group and to compare symmetry between the injured and uninjured sides. The results showed that the symptomatic PCL-deficient group was closer to "normal", and the asymptomatic PCL-deficient group showed less knee extension moment and lower power absorption in the terminal stance than the control group. Additionally, the symptomatic PCL-deficient group appeared to have a relatively symmetric gait while the asymptomatic PCL-deficient group primarily showed an asymmetric gait also occurring in the terminal stance, including less joint moment and lower power absorption of the hip and knee, and lower vertical ground reaction force (GRF). Regarding the gait adaptations of the asymptomatic PCL-deficient group these compensation mechanisms are most likely to have been produced in order to assist in joint stabilization and reduce symptoms in joints.

The lack of awareness of the exact number of instantaneous centers of knee flexion/extension rotation leads to the presence in the market of total knee arthroplasty (TKA) femoral components designed under different hypotheses. Although single radius (SR) designs are thought to replicate the physiological behavior in a more realistic way, surgeons do not always agree about the veracity of their theoretical advantages with respect to the multiple radii components (J-curve (JC) design). Apart from clinical studies, up to now, any literature study biomechanically and exhaustively compares these two TKA solutions, thus a finite element analysis (FEA) has been carried out. In particular, two models were defined to analyze the performance of a SR design and a JC design with the same tibial component during gait cycle and squat motor task. Tibio-femoral kinematics and kinetics have been investigated comparing the resulting contact area between components, internal–external (IE) rotation, position and magnitude of the center of total forces due to contact pressure and polyethylene von Misses stresses. Results demonstrate that, for low demanding tasks, there are no significant differences between the two designs, however, during the squat motor task, some changes in contact force and increases in polyethylene stress were identified for the SR solution.

The objective of this study was to evaluate the effects of a semi-constrained artificial disc with upward instantaneous center of rotation (ICR) on the biomechanics of the cervical spine. A three-dimensional nonlinear finite element model of the lower cervical spine (C4–C7) was developed using computed tomography (CT) data. The FE model was validated by comparing it to previously published experimental results for flexion-extension, lateral bending and axial rotation movements. The validated model was then altered to include prosthesis at the C5–C6 level. A hybrid test protocol was used to investigate the effects of total disc replacement. The results of this study showed that this artificial disc can help maintain the same range of motion (ROM) and intradiscal pressure as the intact model for most loading conditions. We also found that loads on the facet joints increased dramatically at index level. The capsular ligaments were also found to transmit more tension during flexion at implanted level. Although the artificial disc with upward ICR was found to restore normal kinematics, and prevented increases in intradiscal pressure, it was also associated with an overloading of the facet joints and capsular ligaments leading to potentially undesirable outcomes in the long term.

The purpose of this study was to create a kinematic model of the knee joint with six degrees of freedom (DOF) and evaluate the effect of medial collateral ligament (MCL) and lateral collateral ligament (LCL) rupture on cartilage contact point distribution on the tibia during flexion. We hypothesized that collateral ligament contributions vary over six DOF of knee joint articulation and affect the cartilage contact point distribution during joint articulation. The ligament contributions and distribution of joint cartilage contact points cannot be fully assessed with simplified joint models or invasive experiments. Therefore, we developed a new model in which the tibia and femur centers of mass were determined from their surface geometry, and the displacement of the moving tibia was determined from the displacements of the attached ligaments. Compared to the intact knee, the tibia with the LCL removed had higher medial translation and lower valgus rotation. The tibia with the MCL removed had higher lateral translation and higher valgus rotation than the intact knee. At 0${}^{\circ }$, 30${}^{\circ }$, and 60${}^{\circ }$, the tibia with the LCL removed had more internal rotation than the intact knee. Understanding six DOF knee joint kinematics with integration of ligament contributions and cartilage contact positions is useful for the diagnosis of ligament injuries and the design of articulating surfaces for total arthroplasty.

Morphological changes are associated to pregnancy, such as weight gain and increased volume of the trunk. The soft tissue artifact can also increase with these characteristics and affect the real joint kinematics. The main objective of this study was to understand the effect of using three different constraining sets in the lower limb joints, in the amount of soft tissue artifact (STA) of pregnant women, in order to obtain the most appropriated joint set to be used in gait and in this population. The ankle, knee and hip joints were modeled respectively with the following characteristics: (1) Universal–revolute–spherical (URS), (2) spherical–revolute–spherical (SRS) and (3) spherical–spherical–spherical (SSS). The six degrees of freedom (6DOF) model was used as the basis for comparison and considered the one with the highest error associated to the STA. In pregnant women, the URS model seems to affect more the kinematic variables when compared with the 6DOF model. Assuming that the kinematic error associated with pregnant women is increased due to the STA, the URS model may be affecting more the angular kinematics of the knee joint. SSS model seems to be more appropriated to analyze gait in second trimester pregnant women.

The most significant symptoms of autism are abnormal movement patterns that can lead to the decrease of life quality. The purpose of the study was to compare quantitatively the gait strategy of the typical subjects, children with classic high-functioning autism (HFA), and children with low-functioning autism (LFA). Secondly, the comparison and the evaluation of main changes of plantar pressure parameters between groups were presented. The evaluation was carried out on 18 children with HFA, 10 children with LFA, and 30 age-matched children as a control group. A six camera motion capture system, two force plates and a pedobarograph were used to measure gait kinematics, joint kinetics, and pressure distribution under foot during walking. The analysis shows significant differences between children with HFA, LFA, and typical children in velocity, cadence, and magnitude of plantar pressure distribution. The magnitude of plantar pressure was reduced in children with autism under all anatomical masks, which was caused by plano-valgus deformity. Differences were also observed in joint angles and moments during gait cycle. Some of the results can be a source of important information about gait patterns in autistic children. Any exercise treatment prescribed for autistic children should focus on changing the patterns of plantar pressure distribution, which would be similar to patterns of typical children. However, the exercise treatment cannot be generalized due to the high inter-subject variability in children with autism.

We developed a quantitative biomechanical analysis of the supine bridge exercise by combining biomechanical modeling with kinematic and kinetic measurements recorded with an optoelectronic motion capture system and a grid of force platforms embedded in the ground. The relevant joint angles and joint torques were determined accounting for three exercise variants: the distance L of the feet from upper back, the degree of pelvic elevation, and the change in shear ground reaction force intentionally induced by voluntary isometric knee-flexion/extension efforts. Contrary to the ankle and hip, the knee angle displays a nonmonotonic dependence on pelvic elevation. A voluntary isometric knee-flexion (knee-extension) effort enhances (reduces) the hip extensor torque when the hips are above the level of the ground. Progressive pelvic elevation and decrease in L gradually change the knee flexor torque into a knee extensor torque, while reducing the hip extensor torque, to reach a limit configuration where a knee extensor torque sustains the bridge position with a negligible contribution of the hip extensors. Moreover, in this configuration, a hip flexor torque is needed to counteract the hip extension thrust induced by a voluntary quadriceps effort across the closed kinetic chain constituted by the lower limbs and trunk.

The aim of the current investigation was to examine the effects of high- and low-cut basketball-specific footwear, in relation to minimalist and conventional athletic footwear, on the kinetics and three-dimensional (3D) kinematics of sport-specific basketball movements. Ten males performed run and 45${}^{\circ }$ cut movements, whilst wearing low-cut, high-cut, minimalist and conventional athletic footwear. 3D kinematics of the lower extremities were measured using an eight-camera motion analysis system, alongside the vertical rate of loading, which was obtained using an embedded force platform. Footwear differences in 3D kinematic and loading rate parameters were examined using 4 (footwear) $\times 2$ (movement), repeated measures ANOVA. The results showed that loading rate was significantly larger in the minimalist footwear ($\mathrm{\text{run}}=239.45$ and $\mathrm{\text{cut}}=221.94$BW/s), in relation to the low-cut ($\mathrm{\text{run}}=144.02$ and $\mathrm{\text{cut}}=216.58$BW/s), high-cut ($\mathrm{\text{run}}=163.83$ and $\mathrm{\text{cut}}=192.11$BW/s) and conventional ($\mathrm{\text{run}}=140.32$ and $\mathrm{\text{cut}}=170.83$BW/s) conditions. In addition, it was also revealed during the run movement that peak angles of eversion were reduced significantly when wearing the high-cut ($-11.14^{\circ }$) footwear, compared to the low-cut $(-13.71^{\circ })$, minimalist $(-13.13^{\circ })$ and conventional $(-13.75^{\circ })$ conditions. The findings from the current investigation indicate that from an injury prevention context, conventional athletic footwear may be most appropriate for basketball players who are susceptible to chronic impact-related injuries, and high-cut footwear may be most suitable for players who require additional medial/lateral ankle stability.

Single crouch walking gait (SCWG) is one of the main walking gaits when one of the legs is injured. However, the research on movement biomechanical characteristics (MBC) of lower extremity in SCWG has not been reported. So, the aim of this study is to analyze kinematics and main muscle fatigue damages of lower extremity in SCWG. Gaits data were collected with functional assessment biomechanics (FAB) system which applies the real-time wireless gait phase detection system, the movement function relations of joints of lower extremity were obtained by fitting the collected data in normal walking gait (NWG) and SCWG with Fourier series, the fitted movement functions were input to 3D human musculoskeletal model as driving functions for human movement to analyze the differences of MBC between SCWG and NWG. Finally, the muscle contractions were used to evaluate muscle fatigue damage. Compared with NWG, the result shows that the movement range of the joint angles of lower extremity are reduced in SCWG, the change law of hip internal/external rotation angle (IERA) has a significant difference, and the change laws of other joint angles are similarly between SCWG and NWG. The muscle contractions of Gluteus maximum (GMAX) 2, Gluteus meddle (GMED) 1, GMED2, Iliacus (ILI), Rectus femoris (RFEM), Soleus (SOL), Gastrocnemius (GAS) and Vastus lateralis (VLAT) are significantly larger in SCWG than in NWG (except GlutMed2 which is about 20–40% and VLAT which is about 63.8–76.1% of gait cycle), namely, these muscles easily cause muscle damages in SCWG. The contraction change of Adductor magnus (AMAG) is dispersed, so AMAG is prone to muscle fatigue in SCWG. The study results will fill in the gaps in the MBC of lower extremity in SCWG and provide data for Rehabilitation Medical Technology (RMT) and development of rehabilitation equipment of lower extremity.

In this study, a multidirectional posture and motion evaluation tool system using a camera-based vision system was developed. By installing a camera on the top, back, left, and front of the system, kinematical information of the participant was collected and analyzed on the sagittal, coronal, and transverse planes. A dedicated color light-emitting diode (LED) marker was developed for increasing recognition rate of marker. Based on LabVIEW, images collected from four cameras were printed on one screen, and the detection angle of each marker was calculated using the cosine second law. To evaluate the performance of this system, a motion analysis experiment was performed on 20 office workers in Jeonju area. The reliability was measured using POFOMO, Dartfish and the results were compared. The comparison results indicate that the concurrent validities of the two results for the knee angle, left shoulder, and right shoulder were highly correlated as $r=0.967$, 0.988, and 0.991, respectively. Because the POFOMO image analysis tool in the present system reduces the analysis time and involves a simpler measurement procedure than that of Dartfish, this system can be used as an effective device for measuring the posture alignment of the human body.

Accident data show that lower limb is one of the most frequently injured body parts for cyclists in vehicle collisions. However, studies of cyclist lower limb injuries and protection are still sparse. Therefore, the purpose of this study is to investigate the kinematics and injury mechanism of cyclist lower limb in vehicle-to-bicycle collisions considering different impact boundary conditions. To achieve this, the finite element (FE) modeling approach and an FE human body lower limb model with detailed muscles were employed, and impact boundary conditions with different vehicle front-end shapes and cycling postures were considered. Predictions of lower limb kinematics, knee ligament elongation and bending moment of upper and lower leg were used for analysis. The simulation results show that cycling posture has a significant influence on cyclist lower limb kinematics and injury risk, lateral bending toward the direction of vehicle or vehicle moving combining with lateral shearing is the main mechanism for cyclist knee ligament injuries, and injuries to long bones of cyclist leg in vehicle impacts could form lateral bending at both directions. The findings suggest that the influence of cycling posture and distinct difference in injury mechanism between cyclist and pedestrian should be considered in the assessment of vehicle safety design for cyclist lower limb protection.

Although ankle robotic control has emerged as a critical component of robot-interactive gait training (RIGT), no study has investigated the neurophysiological and biomechanical effects on ankle muscle activity and joint angle kinematics in healthy adults and participants with brain damage, including stroke and cerebral palsy (CP). This study compared the effects of RIGT, with and without ankle control actuator, on ankle muscle activity and joint angle kinematics in healthy adults and participants with brain damage. Ten patients ($\mathrm{\text{healthy}}=4$, left hemiparetic $\mathrm{\text{stroke}}=3$, $\mathrm{\text{CP}}=3$) underwent standardized surface electromyography (EMG) neurophysiological and kinematics biomechanical tests under the RIGT with and without ankle control actuator conditions. Outcome measures included the EMG amplitudes of the tibialis anterior and gastrocnemius muscle activity, and ankle movement angles recorded with a two-axis digital inclinometer. Descriptive statistical analysis demonstrated that RIGT with ankle control actuator showed superior effects on EMG (30%) and kinematics angles (25%) than RIGT without ankle control actuator. Our results provided novel, promising clinical evidence that RIGT with ankle control actuator can more effectively improve the neurophysiological EMG data and ankle dorsiflexion and plantarflexion movements than RIGT without ankle control actuator in participants with stroke and CP.

Patients with adhesive capsulitis (AC) demonstrate limited shoulder movement, often accompanied by pain. Common treatment methods include pain medication, and continuous passive movement (CPM). However, it is sometimes difficult to improve the reduction of pain and movement using a CPM intervention because the patient’s interest is diminished. In this study, we developed an innovative deep learning-based smartphone application (Funrehab exercise game (FEG)) to provide accurate kinematics movement and motivation as well as high-intensity and repetitive movements using deep learning. We compared the effects of CPM and FEG on brain activity and shoulder range of motion in patients with AC. Sixteen patients (males, $n=5$; females, $n=11$; mean age, $50.3\pm 3.3$ years) with acute AC were randomized into either CPM group or FEG group 4 days/week for 2 weeks. The outcome measures were shoulder abduction kinematics movement and electroencephalography (EEG) brain activity (bilateral prefrontal, bilateral sensorimotor cortex, and somatosensory association cortex) during the intervention. The analysis of variance (ANOVA) test was performed at $P<0.05$, and the analysis demonstrated that FEG showed superior effects on shoulder abduction kinematics and brain $\alpha$ and $\beta$-wave activations compared to CPM. Our results provide a novel and promising clinical evidence that FEG can more effectively improve neurophysiological EEG data and shoulder abduction movements than CPM in patients with AC.

Studies have shown that rehabilitation training with the unaffected side guiding affected side is more consistent with the natural movement pattern of human upper limb compared with unilateral rehabilitation training, which is conducive to improve rehabilitation effect of the affected limb motor function. In this paper, a bilateral end-effector upper limb rehabilitation robot (BEULRR) based on two modern commercial manipulators is developed first, then the kinematics, reachability, and dexterity analysis of BEULRR are performed, respectively. Finally, a bilateral symmetric training protocol with the unaffected side guiding the affected side is proposed and evaluated through healthy human subject experiment testing based on BEULRR. The simulation results show that the developed BEULRR could perform spatial rehabilitation training and its rehabilitation training workspace can fully cover the physiological workspace of human upper limb. The preliminary experiment results from the healthy human subject show that the BEULRR system could provide reliable bilateral symmetric training protocol. These simulation and experiment results demonstrated that the developed BEULRR system could be used in bilateral rehabilitation training application, and also show that the BEULRR system has the potential to be applied to clinical rehabilitation training in the further step. In the close future, the proposed BEULRR and bilateral symmetric training protocol are planned to be applied in elderly volunteers and patients with upper limb motor dysfunction for further evaluating.