Kinematic Differences Research Articles

Three-dimensional scapular kinematics during commonly used rehabilitation exercises in patients 12 weeks after Reversed Shoulder Arthroplasty.

Reversed shoulder arthroplasty (rTSA) is often used to restore functionality in patients with joint arthropathy and dysfunctional rotator cuff. As rTSA changes the biomechanical properties of the shoulder, an altered movement pattern of arm and scapula is to be expected. Previous studies focused on changes of the scapulohumeral rhythm during functional elevation tasks. To our knowledge, no study exists examining scapular kinematics during rehabilitation exercises in a patient population with rTSA. Therefore, this study aimed to analyze 3-dimensional scapular kinematics during 3 commonly used rehabilitation exercises, 12 weeks after rTSA surgery. It was hypothesized that scapular kinematics would be different between the horizontal and the vertical plane. Secondly, differences in scapular kinematics in the vertical plane, between the open and closed chain were hypothesized. In this cross-sectional study, 48 patients (55 shoulders) aged 69 ± 7.4 years participated. Scapular kinematics in terms of anterior/posterior tilt, external/internal rotation and upward/downward rotation were registered during 3 rehabilitation exercises. Exercises varied based on the plane (horizontal or vertical) and the modality (closed or open chain). Data were analyzed using Statistical Parametric Mapping (SPM). Post-hoc pairwise analysis within SPM (SPM(t)) revealed no significant differences among the exercises regarding posterior tilt. During vertical plane exercises (Standing Wall Slide 120° (WS), Standing reach 120° (REACH)), the scapula was more upwardly rotated for most of the time (14.93% - 74.63%, p<0.001) than during the exercise in the horizontal plane (Seated Bench Slide (BS)). No statistically significant differences were found between the vertical open chain (REACH) and the vertical closed chain exercise (WS). For the internal /external rotation, significant differences were found between the horizontal (BS) and the vertical plane (WS, REACH) (0% - 100%, p<0.001), and between the open (REACH) and closed chain (WS) vertical exercises (3.0% - 91.5%, p<0.001), with more external rotation when performing the movement in the vertical plane, and in the closed chain compared to respectively the horizontal plane and the open chain. Scapular kinematics during rehabilitation exercises after rTSA differ, depending on the plane and modality of the exercise. Insight into the impact of changing the plane (horizontal /vertical), and training in open versus closed chain, may assist physical therapists in the choice of exercises.

Association between sperm DNA fragmentation index and recurrent pregnancy loss: results from 1485 participants undergoing fertility evaluation.

Several male factors have been reported to play a role in recurrent pregnancy loss (RPL). The aim of this study is to explore the relationship between semen parameters, sperm DNA fragmentation index (DFI) and RPL. A total of 1485 participants were recruited from a university hospital between April 2020 and August 2022. Six hundred and thirtyfour men from couples with RPL were assigned to the case group, while 851 men from couple without RPL who underwent fertile evaluation were assigned to the control group. Semen parameters including sperm DNA fragmentation, were assessed. No statistically significant differences in semen parameters, sperm kinematics and DFI were observed between the case group and the control group. A higher proportion of men in the case group had a DFI > 30% compared to those in the control group; however, this difference was not statistically significant. Restricted cubic spline analysis revealed no significant non-linear relationships between continuous DFI and risk of RPL. Our study indicates that there is no significant relationship between DFI and RPL risk. Further prospective studies are needed to explore the impact of DFI on fertility outcomes in couples experiencing RPL.

In vivo kinematics during step ascent: Changes to the knee associated with osteoarthritis

BackgroundStair climbing is a kinematically demanding activity, essential for maintaining independence and quality of life, yet is often impaired in patients with knee osteoarthritis (OA). The purpose of this study was to examine differences in kinematics of a step-up movement between participants with osteoarthritis and asymptomatic controls. MethodsThirty participants with end-stage OA awaiting total knee arthroplasty (TKA) and twenty-eight sex and age-similar asymptomatic participants were recruited. Participants performed a step-up task which was imaged via single-plane fluoroscopy. 3-dimensional prosthesis computer-aided design models were registered to the fluoroscopy, yielding in-vivo kinematic data. Kinematic variables of position, displacement, and rate-of-change in six degrees of freedom were compared between the two groups. ResultsOA knees exhibited significantly different kinematics to asymptomatic knees during step-up. Knees with OA demonstrated a reduced terminal extension angle, inferior translation and increased internal rotation throughout the movement compared to asymptomatic. OA participants exhibited more variability in kinematic parameters compared to asymptomatic controls, reflecting the heterogeneity within OA pathology. ConclusionThe findings of this study indicate that knee kinematics, particularly rotation, differ significantly between OA and asymptomatic knees during step-up. Optimising rotational profiles in OA knee management could help optimise patient function and inform rehabilitation and surgical protocols.

Kinematics of Young Stellar Objects under Various Stellar Feedback

Based on the Gaia Data Release 3 and APOGEE data sets, we investigate the kinematic differences between young stellar objects (YSOs) and their parent clouds in five nearby star-forming regions. Overall, the one-dimensional velocity differences between Class II YSOs and their parent molecular cloud range from [0, 1.4] km s−1. In feedback environments dominated by outflows, massive stars, and supernova feedback, the corresponding velocity differences range from [0, 1.4], [0.1, 0.4], and [0.1, 1] km s−1, respectively. These results indicate that YSO kinematics are not significantly affected by these different types of feedback environments. Additionally, compared to the Class II YSOs, Class III YSOs have slightly larger velocities and dispersions.

X-Ray Fluoroscopy-Based Kinematic Analysis of Quadrupedal Locomotion in Slow and Fast Fatigue-Resistant Motor Neuron-Deleted Mice.

VAChT-Cre is a transgenic mouse line targeting slow-twitch fatigue-resistant and fast-twitch fatigue-resistant motor neurons that innervate oxidative type I and type IIa muscle fibers. To ablate these neurons, VAChT-Cre mice were crossbred with NSE-DTA mice, leading to the expression of diphtheria toxin A after Cre-mediated excision. The resulting VAChT-Cre;NSE-DTA mice exhibited motor deficits, abnormal locomotion, muscular atrophy, and tremor, making them a useful model for studying motor neuron physiology and pathology. In this study, we conducted a kinematic analysis to examine their abnormal locomotor phenotype. The quadrupedal walking of VAChT-Cre;NSE-DTA and control mice along a 500 mm acrylic tunnel was analyzed using an X-ray fluoroscopic system. Stride duration, stride length, footfall patterns, and limb and trunk kinematics were quantified and compared between the two groups. Our results demonstrated that VAChT-Cre;NSE-DTA mice walked more slowly than control mice (99.2 ± 43.5 mm/s vs. 120.5 ± 27.0 mm/s) and had a longer cycle duration (0.54 ± 0.19 s vs. 0.41 ± 0.09 s). In addition, the hindlimb was comparatively more flexed during the stance phase, the trunk was more rounded and humpbacked, and the cervix was lower in VAChT-Cre;NSE-DTA mice than in the control mice during locomotion. These characteristic differences in the gait kinematics might be attributed to a malfunctioning of the motor units with slow-twitch fatigue-resistant and fast-twitch fatigue-resistant types in VAChT-Cre;NSE-DTA mice. The basic description of the locomotor characteristics of this transgenic mouse line may serve as a basis for future comparative analyses.

Significant differences in knee kinematics of healthy subjects with high and low anterior tibial laxity

BackgroundAnterior tibial laxity is considered to be a risk factor for knee injuries, including anterior cruciate ligament ruptures. The anterior cruciate ligament reconstruction also aims to restore anterior tibial laxity. While anterior tibial laxity is considered to be linked to dynamic knee stability, the mechanisms connecting anterior tibial laxity to these stability issues are not fully understood. The purpose of this study was to investigate the kinematic alterations between different anterior tibial laxity in healthy subjects. We hypothesized that anterior tibial laxity affects the anteroposterior tibial displacement during dynamic movements.MethodsThis study involved thirty-five healthy subjects. There were twenty males and fifteen females with an average age of 18.91 ± 0.78 years. Their knees were categorized into “Tight” (the smallest 50%) and “Lax” (the largest 50%) groups based on anterior tibial laxity measurements using a Kneelax3 arthrometer. Kinematic data were collected using a three-dimensional motion capture system when they performed level walking, upslope walking, and vertical jumping. The knee kinematics were recorded for statistical analysis. We used independent sample t-tests to analyze key kinematic differences between groups.ResultsThe “Lax” group exhibited increased posterior tibial translation during upslope walking (5.4 ± 2.22 mm at swing max flexion, p = 0.018) and vertical jumping (8.5 ± 2.78 mm at propulsion max flexion, p = 0.003; 7.6 ± 3.17 mm at landing max flexion, p = 0.019) than the “Tight” group. Significant differences in tibial internal rotation were observed during initial contact of the gait cycle of level walking (1.9° ± 0.95°, p = 0.049) and upslope walking (2.1° ± 1.03°, p = 0.041) in the “Lax” group compared to the “Tight” group. No significant differences in adduction/abduction or medial/lateral tibial translation were found between groups.ConclusionThe study revealed that high anterior tibial laxity resulted in increased posterior tibial translation and tibial internal rotation. High anterior tibial laxity resulted in dynamic instability of knees during motions, especially in high-demanding activities like upslope or vertical jumping. However, further research is needed to explore the clinical functional effects of knee laxity.

Comparison of In-Game Trunk and Upper Extremity Kinematics Between Fastballs, Breaking Balls, and Changeups in NCAA Division I Collegiate Baseball Pitchers.

Previous biomechanical analyses of baseball pitching report similar kinematics between pitch types. However, prior studies were conducted in a controlled laboratory environment. This study aimed to compare in-game trunk and upper extremity kinematics between fastballs, breaking balls, and changeups to determine whether there are kinematic differences that may affect performance as well as to provide new insights into potential risk factors for injury. It was hypothesized that there would be kinematic differences between pitch types. Descriptive laboratory study. A retrospective analysis was conducted of markerless motion capture data collected during National Collegiate Athletic Association Division I baseball games. Included were 34 pitchers who pitched at least 3 pitches of each type (fastball, breaking ball, changeup) during competition. A 1-way repeated-measures multivariate analysis of variance (MANOVA) was used to test differences between pitch types, and Bonferroni post hoc tests were used to test pairwise comparisons. The MANOVA revealed a significant effect of pitch type (P < .001), and follow-up univariate tests found a significant main effect of pitch type for 12 of the 15 kinematic variables analyzed. Post hoc Bonferroni tests revealed that maximum shoulder external rotation was significantly greater during fastballs than breaking balls. At foot contact, significantly less shoulder external rotation was seen during changeups compared with fastballs and breaking balls. At the time of ball release, changeups had significantly less trunk lean and less trunk flexion than fastballs and breaking balls, and fastballs had a significantly smaller arm slot angle than breaking balls and changeups. Collegiate baseball pitchers displayed numerous kinematic differences between pitch types during competitive play, some of which are known influencers of pitching kinetics. This study offers a novel perspective regarding kinematic differences between different pitch types during competition. These results are comparable to the findings of laboratory studies and provide valuable insights into potential injury mechanisms.

CLASH-VLT: Galaxy cluster MACS J0329–0211 and its surroundings using galaxies as kinematic tracers

Context. The study of substructure is an important step in determining how galaxy clusters form. Aims. We aim to gain new insights into the controversial dynamical status of MACS J0329–0211 (MACS0329), a massive cluster at z = 0.4503 ± 0.0003, through a new analysis using a large sample of member galaxies as kinematic tracers. Methods. Our analysis is based on extensive spectroscopic data for more than 1700 galaxies obtained with the VIMOS and MUSE spectrographs at the Very Large Telescope (VLT) in combination with B and RC Suprime-Cam photometry from the Subaru archive. According to our member selection procedure, we defined a sample of 430 MACS0329 galaxies within 6 Mpc, corresponding to approximately three times the virial radius. Results. We estimated the global velocity dispersion, σV841-36+26 km s−1, and present the velocity dispersion profile. We estimated a mass of M200 = (9.2 ± 1.5)×1014 M⊙ using 227 galaxies within R200 = (1.71 ± 0.07) Mpc, for which σV,200841-48+40 km s−1. The spatial distribution of the red galaxies traces a SE-NW elongated structure without signs of a velocity gradient. This structure likely originates from the main phase of cluster assembly. The distribution of the blue galaxies is less concentrated and more rounded, and it shows signs of substructure, all characteristics indicating a recent infall of groups from the field. We detected two loose clumps of blue galaxies in the south and southwest at a distance of ∼R200 from the cluster center. The strong spatial segregation among galaxy populations is not accompanied by a kinematical difference. Thanks to our extensive catalog of spectroscopic redshift, we were able to study galaxy systems that are intervening along the line of sight. We identified two foreground galaxy systems, GrG1 at z ∼ 0.31 and GrG2 at z ∼ 0.38, and one background system, GrG3 at z ∼ 0.47. We point out that the second brightest galaxy projected onto the MACS0329 core is in fact the dominant galaxy of the foreground group GrG2. MACS0329, GrG3, and two other systems detected using DESI DR9 photometric redshifts are close to each other, suggesting the presence of a large-scale structure. Conclusions. MACS0329 is close to a state of dynamical equilibrium despite being surrounded by a very rich environment. We emphasize that the use of an extensive spectroscopic redshift survey is essential to avoiding misinterpretation of structures projected along the line of sight.

Swimming kinematics of rainbow trout behind a 3×5 cylinder array: a computationally driven experimental approach to understanding fish locomotion.

Fish in the wild often contend with complex flows that are produced by natural and artificial structures. Research into fish interactions with turbulence often investigates metrics such as turbulent kinetic energy (TKE) or fish positional location, with less focus on the specific interactions between vortex organization and body swimming kinematics. Here, we compared the swimming kinematics of rainbow trout (Oncorhynchus mykiss) holding station in flows produced by two different 3×5 cylinder arrays. We systematically utilized computational fluid dynamics to identify one array that produced a Kármán vortex street with high vortex periodicity (KVS array) and another that produced low periodicity, similar to a parallel vortex street (PVS array), both validated with particle image velocimetry. The only difference in swimming kinematics between cylinder arrays was an increased tail beat amplitude in the KVS array. In both cylinder arrays, the tail beat frequency decreased and snout amplitude increased compared with the freestream. The center of mass amplitude was greater in the PVS array than in only the freestream, however, suggesting some buffeting of the body by the fluid. Notably, we did not observe Kármán gaiting in the KVS array as in previous studies. We hypothesize that this is because (1) vorticity was dissipated in the region where fish held station or (2) vortices were in-line rather than staggered. These results are the first to quantify the kinematics and behavior of fishes swimming in the wake of multiple cylinder arrays, which has important implications for biomechanics, fluid dynamics and fisheries management.

Training in Roller Speed Skating: Proposal of Surface Electromyography and Kinematics Data for Educational Purposes in Junior and Senior Athletes.

Introduction: Roller skating shares biomechanical similarities with other sports, but specific studies on speed skaters are limited. Injuries, particularly to the groin, are frequent and related to acute and chronic muscle stress. Technology, particularly surface electromyography, can now be used to monitor performance and prevent injuries, especially those caused by muscular asymmetries. Such studies can be used to enhance training and for educational purposes. Materials and Methods: This pilot study was conducted on three subjects: two cadet-athletes and a novice, compared with the performance model of an elite athlete. Surface electromyography and kinematic analysis monitored the lower limb muscles during the propulsion and recovery phases of skating. Electrodes were placed on specific muscles, and triaxial accelerometers were used to detect kinematic differences and asymmetries. The results: Cadet 1 was closest to the elite athlete's performance model compared to Cadet 2, especially in kinematics and muscle efficiency. However, both cadets showed electromyographic differences compared to the elite athlete, with uneven muscle co-activations. The novice exhibited more oscillations and earlier propulsion compared to the elite athlete. Discussion: Using electromyography and kinematic analysis made it possible to identify differences between elite athletes, cadets, and novices. These observations provide useful data for developing personalized training and educational plans and preventing injuries related to muscle overload.

Probing CPT Invariance with Top Quarks at the LHC.

The first model-independent sensitivity to CPT violation in the top-quark sector is extracted from ATLAS and CMS measurements of the top and antitop kinematical mass difference. We find that the temporal component of a CPT-violating background field interacting with the top-quark vector current is restricted within the interval [-0.13,0.29] GeV at 95% confidence level.

Using anthropometry-based scaling to predict responses across sex in reclined frontal impact sled tests

Objective Field data studies have suggested greater injury risk in motor vehicle crashes for females compared to males. Data on female responses may provide more insight into these sex-based differences in injury risk, but few sled tests have been conducted with female subjects, with most cases being of either small or obese anthropometries. Since numerous sled tests have been conducted using mid-size male post mortem human subjects, anthropometry-based scaling of mid-size male responses is a potential approach to leverage this mid-size male data for a broader range of applicability. This study aimed to determine if scaling to predict female responses from male responses is suitable for a reclined condition and evaluate the effectiveness of varying anthropometry-based scaling techniques in predicting female responses from male responses. Methods Data from frontal impact sled tests conducted on four mid-size male and three mid-size female post mortem human subjects in a reclined posture were used. Geometric scaling using dimensional analysis (equal stress-equal velocity approach) was then implemented on the male data to test the effect various scale factors had on predicting female response. These scaling factors were based on mass, stature, torso height, torso volume, and torso volume at torso height. Results Predictions results varied, with lap belt force and forward excursions of bony landmarks yielding high overall prediction scores and vertical excursions of bony landmarks yielding lower overall prediction scores. Generally, the unscaled responses also yielded high prediction scores, and while scaling offered an improvement to the overall prediction score, this suggested that anthropometry-based differences may not fully explain male-female differences in reclined occupant response. Torso volume yielded the highest overall prediction score for the greatest number of responses, but the anthropometry measure that yielded the highest average overall prediction score across all responses varied. Conclusions Marginal differences in the predictive capabilities of the different anthropometry-based measures were found, but, in general, anthropometry was not able to fully explain differences in the responses observed between sex. Overall, this study highlighted the need for further whole body sled tests with mid-size female PMHS to further investigate male-female differences in occupant kinematics.

Analysing trunk and arm motion in volleyball jump serve: a comparison of straight line and diagonal line techniques

ABSTRACT This study aimed to clarify the disparities in trunk rotation and attack arm movement and their effect on hand kinematics adjustments between straight-line (SL) and diagonal-line (DL) volleyball jump serves. Thirteen male professional volleyball players (age 21.53 ± 5.39 years, height 1.95 ± 0.06 m, body mass 86.48 ± 11.63 kg, experience 8.61 ± 3.47 years) performed SL and DL jump serve, with three-dimensional coordinate data captured using a motion capture system (200 hz). Paired t-test and statistical parametric mapping examined kinematic differences between the two serving directions. At ball contact (BC), the speed of the attack arm hand was significantly faster in DL (16.99 ± 1.36 m/s) compared to SL (16.37 ± 1.53 m/s), whereas the face angle was significantly smaller in DL (1.98 ± 11.75°) than in SL (17.60 ± 17.98°). Forward rotation angles of the pelvic and upper torso at BC were significantly greater in DL (28.47 ± 10.89°; 21.30 ± 10.25°) than in SL (18.27 ± 12.46°; 9.09 ± 14.41°). During the arm swing phase, the pelvic’s forward rotation angles in DL were significantly greater than in SL at 42–72% spiking motion, and the upper torso’s angles were significantly greater at 49–58% spiking motion. These findings underscore the importance of adjusting pelvic and upper torso rotations to control the hand’s face angle when serving in the diagonal line.

Turtle Girdles: Comparing the Relationships Between Environment and Behavior on Forelimb Function in Loggerhead Sea Turtles (Caretta caretta) and River Cooters (Pseudemys concinna).

Locomotion in water and on land impose dramatically different demands, yet many animals successfully move in both environments. Most turtle species perform both aquatic and terrestrial locomotion but vary in how they use their limbs. Freshwater turtles use anteroposterior movements of the limbs during walking and swimming with contralateral fore- and hindlimbs moving in synchrony. In contrast, sea turtles swim primarily with "powerstroke" movements, characterized by synchronous forelimb motions while the hindlimbs act as rudders. High-speed video has been used to study powerstroking, but pectoral girdle movements and long-axis rotation (LAR) of the humerus are likely both key components to turtle locomotor function and cannot be quantified from external video. Here, we used XROMM to measure pectoral girdle and humeral movements in a sea turtle (loggerhead, Caretta caretta) compared to the freshwater river cooter (Pseudemys concinna) during terrestrial and aquatic locomotion. The largest difference among species was in yaw of the pectoral girdle during swimming, with loggerheads showing almost no yaw during powerstroking whereas pectoral girdle yaw in the cooter during rowing was over 30°. The magnitude of humeral LAR was greatest during loggerhead powerstroking and the temporal pattern of supination and pronation was opposite from that of cooters. We hypothesize that these kinematic differences are driven by differences in how the limbs are used to power propulsion. Rotations at the glenoid drive the overall patterns of movement in freshwater turtles, whereas glenohumeral LAR in loggerheads is used to direct the position and orientation of the elbow, which is the joint that determines the orientation of the thrust-generating structure (the flipper) in loggerheads.

Bilateral symmetry assessment of healthy forearm kinematics using 4D-CT

Advanced stage distal radio-ulnar joint (DRUJ) injury may warrant radius corrective osteotomy or arthroplasty. These procedures aim to restore geometry, function and kinematics and could benefit from preoperative planning where the contralateral forearm is typically used as reference. Natural variations regarding geometry and function between forearms are known but kinematic differences are not. This work aimed to quantify bilateral differences in forearm kinematics. Consequently, 4D-CT data of ten healthy volunteers was acquired, imaging motion of both forearm joints. Segmentation and registration of the radius and ulna bones resulted in a 3D representation of forearm rotation. Subsequently, the forearm rotation axis, radius translation along the ulna and radius rotation around its own inertial axis were calculated. The rotation axis of the right arm was mirrored to set up a comparison with the left arm. All other differences were calculated directly. The mean angle and distance between forearm rotation axes were 0.6° and 0.8 mm. The mean difference in radius translation along the ulna was 0.9 mm. On average, radius rotation around the radius’ inertial axis differed 2.6°, between forearms. This study’s findings can benefit DRUJ surgery preoperative planning and postoperative kinematic evaluation.Level of evidence: IV.

The Biomechanical differences in maximum snatch weight between elite and sub-elite weightlifters: A one-dimensional statistical parameter mapping study

Background: Current research primarily relies on discrete data collected at specific time points to analyze the weightlifting process, often overlooking the impact of continuous temporal changes on athletic performance. Purpose: This study aimed to quantitatively analyze the one-dimensional kinematic patterns of maximum snatch weight actions in elite and sub-elite weightlifters using statistical parameter mapping (SPM). It explores kinematic differences in snatch actions between elite and sub-elite weightlifters, which assists in summarizing the technical characteristics of elite athletes. Methods: Two cameras recorded three successful maximum snatch attempts of 10 elite and 10 sub-elite weightlifters at the World Weightlifting Championships and Chinese Olympic selection competitions. Simi Motion 10.2 was used for kinematic analysis. SPM was employed for comparative analysis of snatch kinematics among different levels of weightlifters, and independent sample t-tests were used for phase duration proportions. Results: Elite weightlifters showed significant advantages in multiple movement phases: smaller knee joint angles in M1 phase (p &lt; 0.001, 35.82%–78.45%) and M3 phases (p = 0.047, 17.47%–24.74%; p = 0.036, 30.92%–49.38%; p = 0.040, 50.93%–65.85%); lower vertical body center of gravity (COG) height in M1 phase (p = 0.019, 0.00%–51.08%), M3 phase (p = 0.046, 48.27%–100.00%), and M5 phase (p = 0.045, 38.49%–59.54%); closer displacement between barbell COG and body COG in M1 phase (p = 0.006, 0%–38.18%; p = 0.048, 43.91%–48.94%) and M2 phase (p = 0.026, 0%–100%); greater barbell acceleration in M5 phase (p &lt; 0.001, 0%–94.61%); and slower barbell descent speed in M6 phase (p = 0.001, 0%–30.58%; p = 0.046, 44.57%–51.37%; p = 0.048, 67.16%–72.41%). Moreover, elite weightlifters exhibited significantly higher phase duration proportions in M1 phase (p = 0.034, d = 1.03) than sub-elite weightlifters. Conclusion: Elite weightlifters demonstrated longer distance and time exerting work on the barbell in M1 phase, less energy consumption in barbell ascent in M2 phase, and greater upward power gain for the barbell in M1 and M3 phases. They showed faster squat-to-barbell catching speed in M4 phase and excellent braking and precise squat-to-barbell catching capabilities in M5 and M6 phases.

Kinematic differences in forehand serve-receiving techniques of the male tennis players at low and high-speed serves

The purpose of this study was to compare the joint, racket, and ball kinematics between the different levels of male tennis players in tennis serve-return at slow and high serve speeds. Thirty male tennis players were divided into an advanced group (n = 15) and an intermediate group (n = 15) based on skill level. The advanced group and intermediate group matched shake hand-grip players performed serve-receive test at the different serve speeds. Kinematic data were collected on the trunk, upper limbs, racket and ball to compare the differences between the advanced and intermediate groups at different serve speeds. At both serve speeds, the AG has faster racket speed and ball speed, and is closer to the baseline placement (p<0.05). It is characterized by a faster trunk turn, greater speed with the shoulder joint forward and outward and greater angle of wrist flexion and extension during the stroke (p<0.05), and greater speed with the forearm inward and internal rotation during the follow-through swing, at the same time, there is a difference in the angle of the racket to the ground between the advanced group and an intermediate group(p<0.05). Elbow internal rotation and abduction angular velocity in the backswing phase, Timing of peak racket resultant velocity and Wrist extension in the stroke phase, and shoulder and elbow joint activities in the follow-through phase were significantly correlated with the ball speed of the return. With faster serve speeds, higher quality serve-receive can be achieved by shortening the duration of the backswing lifting the upper arm and rotating the forearm inward quickly, accelerating the speed of movement of wrist joints at the impact phase, adjusting the speed of shoulder adduction and elbow internal rotation to complete the follow-through swing. These findings help to improve elite players’ serve-receive skills at faster serve speed.

Self-selected speed provides more accurate human gait kinematics and spatiotemporal parameters than overground simulated speed on a treadmill: a cross-sectional study

BackgroundWalking speed, a key element of gait analysis, is essential for evaluating the biomechanics of the musculoskeletal system and is typically assessed on flat surfaces, such as walkways or treadmills. While many authors have compared the differences and similarities between treadmill and overground walking, no studies have yet investigated the differences between treadmill gait analysis at self-selected speed (SS) and overground simulated speed (OS). The hypothesis is that accurate kinematic measurements depend on selecting the correct gait speed; however, a mismatch between the perceived comfortable treadmill speed and actual overground speed may affect the accuracy of treadmill gait analyses. This study aimed to assess treadmill gait in healthy young adults by comparing the SS with the OS. The objectives were to determine whether participants could match SS with OS on a treadmill, examine sex differences in gait kinematics and spatiotemporal parameters (KSP) at different speeds, and identify which speed better reflects natural gait kinematics.MethodsA total of 60 healthy men and 70 healthy women, aged 22–35 years, participated in this cross-sectional study to investigate the gait kinematics and spatiotemporal differences between the SS and OS. Student’s t-test, Bonferroni adjustment, Cohen’s effect size, and quadratic regression were employed to analyse differences across walking speeds and groups.ResultsA discrepancy between OS and SS was observed in 66.4% of the participants. Our findings revealed that the adjusted R² values for KSP at SS were consistently greater than those at OS, suggesting that SS offers a more robust and accurate representation of gait kinematics, whereas OS is less reliable.ConclusionsThese findings underscore the importance of individualized speed selection in gait analysis, as it significantly impacts the accuracy of kinematic and spatiotemporal measurements. This insight is pivotal for clinicians and researchers to develop more effective rehabilitation strategies and comprehensively understand gait dynamics.

Alterations to the Kinetic Chain Sequence After a Shoulder Injury in Throwing Athletes.

Kinetic chain (KC) sequencing is essential for efficient energy translation through the body in overhead-throwing sports. A sequencing breakdown can result in injuries to the throwing shoulder and thus the management of athlete recovery in an attempt to minimize the impact on both training and performance. To determine kinematic differences in KC sequencing, imperative for the prevention and rehabilitation of a shoulder injury, during maximal throwing in overhead athletes with and without a shoulder injury. Controlled laboratory study. Kinematic data were collected and analyzed for 36 male overhead athletes with (symptomatic) and without (asymptomatic) a shoulder injury (18 participants per group) during maximal overhead-throwing trials using 3-dimensional motion analysis (100 Hz). Peak angular velocities and associated timing of the throwing shoulder, throwing elbow, thorax, pelvis, lead hip, and rear hip were calculated to determine the KC sequence in both groups. Kinematic data were compared using independent t tests, and relationships between variables were assessed using the Pearson correlation coefficient (both P < .05). The KC sequence in overhead athletes with or without a shoulder injury was the same, except for peak elbow extension and shoulder flexion angular velocities. These angular velocities occurred simultaneously in asymptomatic throwers (both 0.17 % before ball release [BR]) but sequentially in symptomatic throwers (0.06 % before BR and 0.67 % after BR, respectively). No differences were evident in stride length (m) or resultant ball velocity (m/s) between the groups, despite differences in key joint angular velocities across KC segments (P range, <.001-.035). Relationships between resultant ball velocity and all key joint angular velocities were evident for symptomatic but not asymptomatic throwers (P range, <.001-.026). Our study demonstrated that overhead athletes, regardless of their shoulder injury history, had similar KC sequencing across the lower limb and lumbopelvic-hip complex segments before differences in the timing of peak elbow extension and shoulder flexion angular velocities of the throwing arm approaching BR. Further research investigating muscle activity changes and technique parameters during overhead throwing may present explanations as to how we can ensure that the KC sequence is not altered as a result of an injury. This study provides a new perspective on the KC and how an injury may not change the sequence itself in overhead-throwing performance.

An in vivo three-dimensional, kinematics study of the cervical vertebrae under physiological loads in patients with cervical spondylosis

Background ContextStudies of in vivo kinematic differences between healthy individuals and those with cervical spondylosis (CS) have been reported, but only movements under non-physiological loads have been investigated. Differences in the in vivo, cervical kinematics between healthy individuals and those with CS are unknown. PurposeTo investigate the in vivo, cervical kinematics of patients with CS under physiological loads. Study DesignThis was a retrospective, case-controlled study that used three-dimensional (3D) to 3D registration techniques combined with conical beam computed tomography (CBCT) to investigate the cervical kinematics of patients with CS. Patient SampleTwenty individuals diagnosed with CS were selected for study participation and matched with 20 participants who did not have CS and were in good health. Outcome MeasuresPfirrmann grading,intervertebral range of motion(ROM), kinematics and cross-sectional area of posterior neck muscles(CAPNM). MethodsAll study participants underwent seven CBCT scans of their cervical vertebrae. The 3D segmental motion features of the vertebra in vivo were calculated using 3D-to-3D volume registration to overlay images of the vertebra at each functional position. The 3D range of motion (ROM) of each cervical segment was expressed with six degrees of freedom using Euler angles and translated onto a coordinate system. A kinematic subgroup analysis was conducted based on the severity of symptoms within the CS group, and differences in muscle volume between the CS and control groups were also evaluated. Project supported by the National Natural Science Foundation of China (Grant No. 81960408,82260445), Training plan for academic and technical leaders of major disciplines in Jiangxi Province(Grant No.20204BCJL22047), Clinical Cultivation Project of The First Affiliated Hospital of Nanchang University (Grant No.YFYLCYJPY 20220203).The authors declare no conflict of interest in preparing this article. ResultsThe CS group exhibited noticeable reductions in the primary rotational ROMs of left-right rotation at C4-C5, C5-C6, C6-C7, C4-C7, and C1-C7 compared to the controls. During left-right bending, there were no significant differences in the primary ROMs, coupled translations, or rotations between the two groups. However, compared to controls, the CS group had significantly lower primary ROMs for C4 C7, C1-C7 and C5-C6 during flexion-extension. During left-right rotation, the primary rotations and coupled lateral bending at C6-C7 were significantly increased in the mild CS group compared to the moderate CS group. In the mild CS group, the primary ROM of the C4-C5 and C5-C6 during flexion-extension was significantly greater than that of the moderate CS group. ConclusionsFor the first time, the in vivo 3D kinematics of the cervical spine during head movement under physiological load in CS individuals have been adequately described and compared with healthy cervical vertebrae, which can be used as a reference point for future studies. The application of CBCT helps to obtain accurate and precise movement information of CS patients and effectively enhance the evaluation results obtained from imaging information.