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Background The spinal nerve ligation (SNL) rat is well known as the most common rodent model of neuropathic pain without motor deficit. Researchers have performed analyses using only the von Frey and thermal withdrawal tests to evaluate pain intensity in the rat experimental model. However, these test are completely different from the neurological examinations performed clinically. We think that several behavioral reactions must be observed following SNL because the patients with neuropathic pain usually have impaired coordination of the motions of the right–left limbs and right–left joint motion differences. In this study, we attempted to clarify the pain behavioral reactions in SNL rat model as in patients. We used the Kinema-Tracer system for 3D kinematics gait analysis to identify new characteristic parameters of each joint movement and gait pattern. Results The effect of SNL on mechanical allodynia was a 47 ± 6.1% decrease in the withdrawal threshold during 1–8 weeks post-operation. Sagittal trajectories of the hip, knee and ankle markers in SNL rats showed a large sagittal fluctuation of each joint while walking. Top minus bottom height of the left hip and knee that represents instability during walking was significantly larger in the SNL than sham rats. Both-foot contact time, which is one of the gait characteristics, was significantly longer in the SNL versus sham rats: 1.9 ± 0.15 s vs. 1.03 ± 0.15 s at 4 weeks post-operation ( p  = 0.003). We also examined the circular phase time to evaluate coordination of the right and left hind-limbs. The ratio of the right/left circular time was 1.0 ± 0.08 in the sham rats and 0.62 ± 0.15 in the SNL rats at 4 weeks post-operation. Conclusions We revealed new quantitative parameters in an SNL rat model that are directly relevant to the neurological symptoms in patients with neuropathic pain, in whom the von Frey and thermal withdrawal tests are not used at all clinically. This new 3D analysis system can contribute to the analysis of pain intensity of SNL rats in detail similar to human patients’ reactions following neuropathic pain.

The aim of the present study was to determine the effects of breathing on the three - dimensional underwater stroke kinematics of front crawl swimming. Ten female competitive freestyle swimmers participated in the study. Each subject swam a number of front crawl trials of 25 m at a constant speed under breathing and breath-holding conditions. The underwater motion of each subject's right arm was filmed using two S-VHS cameras, operating at 60 Hz, which were positioned behind two underwater viewing windows. The spatial coordinates of selected points were calculated using the DLT procedure with 30 control points and after the digital filtering of the raw data with a cut-off frequency of 6 Hz, the hand's linear displacements and velocities were calculated. The results revealed that breathing caused significantly increases in the stroke duration (t9 = 2.764; p < 0.05), the backward hand displacement relative to the water (t9 = 2.471; p<0.05) and the lateral displacement of the hand in the X - axis during the downsweep (t9 = 2.638; p < 0.05). On the contrary, the peak backward hand velocity during the insweep (t9 = 2.368; p < 0.05) and the displacement of the hand during the push phase (t9 = -2.297; p < 0.05) were greatly reduced when breathing was involved. From the above, it was concluded that breathing action in front crawl swimming caused significant modifications in both the basic stroke parameters and the overall motor pattern were, possibly due to body roll during breathing. Key pointsThe breathing action increases the duration of the total underwater pull.The breathing action increases the absolute backward displacement of the hand.The breathing action caused significant modifications in the overall motor pattern, possibly due to body roll during breathing.

The aim of the present study was compare linear kinematics and energy changes of the barbell, along with the angular kinematics of the leg movement during the snatch technique, between male adolescent and adult weightlifters. Two S-VHS cameras operating at 60 fields per second recorded the heaviest lifts of 14 male adolescent and 9 adult top-level weightlifters under competitive conditions. The spatial co-ordinates of selected points on the body and the barbell were calculated using the direct linear transformation procedure. A low pass digital filter with 4 Hz cut-off frequency was used for the smoothing of raw co-ordinate data. The ''t''-test for independent samples was used for the statistical treatment of data. The results revealed that there were no significant differences between the adolescent and the adult weightlifters in the majority of the kinematic variables. However, adolescent weightlifters extended their knees significantly slower (t21 = 4.211, p < 0.05) during the 1st pull and their ankles during the 2nd pull (t21 = 2.440, p < 0.05) than the adult weightlifters did. Moreover, the average relative power output was significantly greater for the adult weightlifters during both the 1st (t21 = 2.303, p < 0.05) and the snd pull (t21 = 2.611, p < 0.05). These results indicate that the adolescent weightlifters were characterised from a high level of snatch technique and differentiated from the adults predominantly at the less powerful execution of the movement.

The purpose of the present study was to determine the effect of two different sized hand paddles on the three-dimensional underwater stroke pattern of front crawl swimming at a fixed stroke rate. Nine male adolescent competitive freestyle swimmers participated in the study. Each subject swam a series of 25 m trials at a constant stroke rate, without and with hand paddles of two different cross sectional areas (small paddles: 116 cm(2), large paddles: 311 cm(2)). An acoustic metronome connected with a sound amplifier was used to help the subject keep the stroke rate constant. Stroke rate was calculated for each subject using the time for 3 complete right arm stroke cycles. The underwater motion of each subject's right arm was filmed using two S-VHS cameras, operating at 60 fields/s, which were located behind two underwater viewing windows. The spatial coordinates of selected points on the right arm and the hip were calculated using the DLT procedure with 30 control points and after the digital filtering of the raw data with a cut-off frequency of 6 Hz, the hand's linear displacements and velocities, as well as the mean swimming velocity, were calculated. Moreover, the displacement of the hip in the direction of propulsion, from the right hand's entry to the next entry of the same hand, was calculated in order to determine the stroke length. For the statistical treatment of the data the analysis of variance for dependent samples was used. The analysis of the data revealed that when hand paddles were worn, the stroke length (F(2,16)=10.329; P<0.05) and the mean swimming velocity (F(2),16=5.076; P<0.05) were significantly increased, while the temporal characteristics of the underwater stroke and the displacement of the hand were not significantly altered. On the other hand, the peak backward hand speeds during the insweep (F(2,16)=4.794; P<0.05) and the push phase (F(2,16)=5.827; P<0.05) were greatly reduced. These modifications were greater when large paddles were worn. From the results of the present study it was concluded that the movement pattern was not significantly modified when swimmers swam with hand paddles, at a constant stroke rate. However, large hand paddles caused a decrease in their hand velocities during the underwater stroke.

Background： Joint line （JL） is a very important factor for total knee arthroplasty （TKA） to restore. The objective of this study was to evaluate the early clinical and kinematic results of TKAs with posterior-stabilized （PS） or cruciate retaining （CR） implants in which the JL was elevated postoperatively. Methods： Data were collected from patients who underwent TKA in our department between April 2011 and April 2014. The patients were divided into two groups based on the prosthesis they received （PS or CR）. At 1-year postoperatively, clinical outcomes were evaluated by the American Knee Society （AKS） knee score, AKS function score, and patella score. In vivo kinematic analysis after TKA was performed on all patients and a previously validated three-dimensional to two-dimensional image registration technique was used to obtain the kinematic data. Anteroposterior （AP） translation of the medial and lateral femoral condyles, and axial rotation relative to the tibial plateau, were analyzed. The data were assessed using the Mann-Whitney test. Results： At time of follow-up, there were differences in the AKS knee scores （P = 0.005）, AKS function scores （P = 0.025）, patella scores （P = 0.015）, and postoperative range of motions （P = 0.004） between the PS group and the CR group. In the PS group, the magnitude of AP translation for the medial and lateral condyle was 4.9 ± 3.0 mm and 12.8 ± 3.3 mm, respectively. Axial rotation of the tibial component relative to the femoral component was 12.9 ± 4.5°. In the CR group, the magnitude of AP translation for the medial and lateral condyle was 4.3 ±3.5 mm and 7.9 ± 4.2 mm, respectively. The axial rotation was 6.7 ± 5.9°. There were statistically different between PS group and CR group in kinematics postoperatively. Conclusion： Our results demonstrate that postoperative JL elevation had more adverse effects on the clinical and kinematic outcomes ofCR TKAs than PS TKAs.

Quantifying angular joint kinematics of the upper body is a useful method for assessing upper limb function. Joint angles are commonly obtained via motion capture, tracking markers placed on anatomical landmarks. This method is associated with limitations including administrative burden, soft tissue artifacts, and intra- and inter-tester variability. An alternative method involves the tracking of rigid marker clusters affixed to body segments, calibrated relative to anatomical landmarks or known joint angles. The accuracy and reliability of applying this cluster method to the upper body has, however, not been comprehensively explored. Our objective was to compare three different upper body cluster models with an anatomical model, with respect to joint angles and reliability. Non-disabled participants performed two standardized functional upper limb tasks with anatomical and cluster markers applied concurrently. Joint angle curves obtained via the marker clusters with three different calibration methods were compared to those from an anatomical model, and between-session reliability was assessed for all models. The cluster models produced joint angle curves which were comparable to and highly correlated with those from the anatomical model, but exhibited notable offsets and differences in sensitivity for some degrees of freedom. Between-session reliability was comparable between all models, and good for most degrees of freedom. Overall, the cluster models produced reliable joint angles that, however, cannot be used interchangeably with anatomical model outputs to calculate kinematic metrics. Cluster models appear to be an adequate, and possibly advantageous alternative to anatomical models when the objective is to assess trends in movement behavior.

The introduction of low cost optical 3D motion tracking sensors provides new options for effective quantification of motor dysfunction. The present study aimed to evaluate the Kinect V2 sensor against a gold standard motion capture system with respect to accuracy of tracked landmark movements and accuracy and repeatability of derived clinical parameters. Nineteen healthy subjects were concurrently recorded with a Kinect V2 sensor and an optical motion tracking system (Vicon). Six different movement tasks were recorded with 3D full-body kinematics from both systems. Tasks included walking in different conditions, balance and adaptive postural control. After temporal and spatial alignment, agreement of movements signals was described by Pearson's correlation coefficient and signal to noise ratios per dimension. From these movement signals, 45 clinical parameters were calculated, including ranges of motions, torso sway, movement velocities and cadence. Accuracy of parameters was described as absolute agreement, consistency agreement and limits of agreement. Intra-session reliability of 3 to 5 measurement repetitions was described as repeatability coefficient and standard error of measurement for each system. Accuracy of Kinect V2 landmark movements was moderate to excellent and depended on movement dimension, landmark location and performed task. Signal to noise ratio provided information about Kinect V2 landmark stability and indicated larger noise behaviour in feet and ankles. Most of the derived clinical parameters showed good to excellent absolute agreement (30 parameters showed ICC(3,1) > 0.7) and consistency (38 parameters showed r > 0.7) between both systems. Given that this system is low-cost, portable and does not require any sensors to be attached to the body, it could provide numerous advantages when compared to established marker- or wearable sensor based system. The Kinect V2 has the potential to be used as a reliable and valid clinical measurement tool.

As one of the most common failure forms of discontinuity-controlled rock slopes, wedge failure is likely to occur in a wide range of geologic and geometric conditions. In this study, the wedge failure of rock slopes and the movement and disaster processes after failure are investigated using 3D discontinuous deformation analysis (DDA). Compared with the analytical solutions derived from a typical rock wedge model, the performance of the original 3D DDA for analyzing the wedge stability under different geometrical and physical parameters is presented. The deficiency of the joint contact model in 3D DDA under critical state is improved. The improved 3D DDA is used to simulate a rock slope subjected to wedge failure in Tibet Autonomous Region, and the failure of the dangerous rock masses and movement of the formed blocks under different discontinuity cutting are discussed. The improved 3D DDA has high accuracy in calculating wedge critical stability and sliding after failure. The actual wedge slope presents sliding failure along the intersection line of structural planes, and tensile and shear failure and downward dislocations can be observed among blocks. The lateral deviation and deflection of wedge blocks occur constantly, showing 3D kinematic characteristics. With the increase of secondary discontinuities, the influence range of sub-blocks due to wedge failure becomes larger, constituting the geological disaster of the G318 national road. 3D DDA can evaluate wedge stability and analyze kinematic characteristics of wedge blocks, which lay a foundation for formulating disaster prevention countermeasures and reducing human casualties.

This contribution is concerned with joint angle calculation based on inertial measurement data in the context of human motion analysis. Unlike most robotic devices, the human body lacks even surfaces and right angles. Therefore, we focus on methods that avoid assuming certain orientations in which the sensors are mounted with respect to the body segments. After a review of available methods that may cope with this challenge, we present a set of new methods for: (1) joint axis and position identification; and (2) flexion/extension joint angle measurement. In particular, we propose methods that use only gyroscopes and accelerometers and, therefore, do not rely on a homogeneous magnetic field. We provide results from gait trials of a transfemoral amputee in which we compare the inertial measurement unit (IMU)-based methods to an optical 3D motion capture system. Unlike most authors, we place the optical markers on anatomical landmarks instead of attaching them to the IMUs. Root mean square errors of the knee flexion/extension angles are found to be less than 1° on the prosthesis and about 3° on the human leg. For the plantar/dorsiflexion of the ankle, both deviations are about 1°.

Two-dimensional video analysis systems (2DVAS) are commonly used by clinicians and researchers to determine angles during running. The aim of this systematic review (PROSPERO: CRD42022322798) was to synthesize the literature on the criterion validity and reliability of 2DVAS for measuring angles during running compared to three-dimensional motion analysis systems (3DMAS). We searched for articles on MEDLINE/Pubmed, EMBASE, SciELO, and LILACS up to October/2022. We included studies that evaluated the validity of 2DVAS (when compared to 3DMAS) and/or the reliability of 2DVAS measurements of lower limb and trunk angles during running. Qualitative and quantitative analyses were performed. Seven hundred and five studies were found and 17 were included. Ten studies analysed criterion validity between 2DVAS and 3DMAS and the results ranged from poor to excellent, with most of the parameters assessed presenting poor or moderate validity. Inter-rater reliability of 2DVAS was assessed in nine studies and most of the parameters investigated had good to excellent reliability. Intra-rater reliability (between-day processing) of angular running parameters – investigated in ten studies – was considered excellent for most of the parameters analysed. Inter-session reliability was assessed in three studies and was defined as good or excellent for most of the variables assessed. 2DVAS is a reliable method for measuring joint angles during running. However, the validity of 2DVAS compared to 3DMAS ranges from low to moderate for most running parameters. Therefore, based on the available evidence, caution should be taken when applying 2DVAS, particularly for frontal and transverse plane angles.