Contact Phase Research Articles

Thyme Essential Oil as a Potential Tool Against Common and Re-Emerging Foodborne Pathogens: Biocidal Effect on Bacterial Membrane Permeability.

Over the past decade, foodborne diseases have become a significant public health concern, affecting millions of people globally. Major pathogens like Salmonella spp., Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus contaminate food and cause several infections. This study investigates the potential of thyme essential oil (Thy-EO) as a natural antimicrobial agent against most common and re-emerging foodborne bacteria, including S. enterica, Yersinia enterocolitica, and L. monocytogenes. Preliminary tests provided qualitative evidence of Thy-EO's efficacy by evaluating its antibacterial activity through direct contact and vapor phase exposure. Then, the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were defined to quantitatively evaluate the bacteriostatic and bactericidal effects of Thy-EO, revealing a strong inhibitory effect against S. enterica, Y. enterocolitica and L. monocytogenes. Additionally, Thy-EO exerted rapid bactericidal kinetics characterized by the disruption of bacterial cell membrane integrity over time. Results highlight Thy-EO's potential as an alternative antimicrobial agent, demonstrating that treatment with Thy-EO significantly and irreversibly affects the growth of the tested foodborne pathogens.

Comprehensive assessment of lower limb alignment and forces during dance landings under fatigue

This study investigates the impact of fatigue on Lower Limb Alignment (LLA) and Ground Reaction Forces (GRF) during dance landings, intending to understand how fatigue-induced changes affect joint mechanics and stabilization in trained dancers. Thirty dancers (mean age: 23.4 years) with a minimum of three years of training in high-impact dance forms, such as ballet and contemporary dance, participated in the study. A within-subject experimental design assessed each participant’s landing mechanics before and after a fatigue-inducing protocol. Kinematic data were captured using a 3D motion capture system, while kinetic data were recorded with force plates. Joint angles at the hip, knee, and ankle were measured during the landing’s initial contact, peak force, and stabilization phases. Vertical and medial-lateral GRF and time to stabilization (TTS) were also analyzed pre- and post-fatigue. The fatigue protocol consisted of plyometric exercises and repetitive dance-specific movements designed to mimic the physical demands of a dance performance. Measurements were taken immediately after the fatigue protocol and at intervals of 15 min, 1 h, 24 h, and 48 h post-fatigue to assess both immediate and delayed effects of fatigue. Significant changes in joint angles were observed across all phases of the landing. Post-fatigue, hip and knee flexion increased significantly at initial contact (hip: +2.7°, knee: +3.6°, p < 0.05), reflecting compensatory adjustments for impact absorption. Ankle dorsiflexion also increased significantly during stabilization (+2.7°, p = 0.028). Vertical GRF increased across all phases post-fatigue (initial contact: +4.4 N/kg, p = 0.009), indicating a reduced ability to absorb impact forces efficiently. TTS was significantly prolonged at all post-fatigue intervals, particularly within the first 15 min post-exertion (+34 ms, p = 0.008), suggesting impaired neuromuscular control and balance.

A DEVICE-BASED (GAITON) SAGITTAL PLANE KINEMATICS ANALYSIS OF LOWER EXTREMITY JOINTS AMONG PATIENTS WITH KNEE OSTEOARTHRITIS – A METHODOLOGICAL APPROACH.

Background: Gait assessment is an effective method for identifying functional limitations associated with knee Osteoarthritis and understanding the relationship between disease symptoms and gait quality. Objective: To evaluate the mean difference in the kinematics of lower extremity joints among patients with knee osteoarthritis. Methods: A total of 20 people living with Knee OA were recruited as of 25th September 2024 in this prospective cross-sectional design study. The eligible participants were conveniently recruited from the SRM physiotherapy OPD based on voluntary participation after signing the informed consent. Adult participants aged 18 years and above, both sexes and able to walk independently without mobility aids were recruited and the joint kinematics were measured using the GaitOn Software, 2-dimensional analysis, and sagittal kinematic parameters of stance phase. Results: The mean age of the patients was 53.6 ± 7.3, and the mean BMI was 29.1±4.6. The one sample t-test demonstrated a statistically significant difference between kinematic angles of the lower extremity joint in sagittal plane of population mean (reference value) and sample mean (measured by GaitOn); Initial contact phase (hip: mean diff -4.06, p<0.01, ankle: mean diff 34.1, p < 0.0001), Loading response (hip: mean diff -5.8. p <0.001, knee: mean diff 9.6, p < 0.001, ankle: mean diff 32.4, p < 0.001). Midstance (hip: mean diff 11.06, p <0.001, ankle: 31.4, p< 0.001). Terminal stance (hip: mean diff 28.3, p< 0.004, ankle: mean diff 31.4, p< 0.001) and Pre-swing (hip: mean diff 16.5, p< 0.001, ankle: mean diff 31.4, p< 0.001). Conclusions: The hip and ankle joints equally share knee kinematic compensations. By acknowledging the complex interactions between the hip, ankle, and knee joints, healthcare providers can develop more comprehensive and effective treatment plans for individuals with knee OA.

Locomotion and Postural Control in Young Adults with Autism Spectrum Disorders: A Novel Kinesiological Assessment.

Background/Objectives: The purposes of the present study were to assess gait by using a novel approach that plots two adjacent joint angles and the postural control in individuals with autism (ASD) and individuals with typical neurodevelopmental (TD). Methods: The surface electromyography (sEMG) activity was measured synchronously with the other variables. Twenty young adult men, 10 with TD and 10 with a diagnosis of ASD, took part in this study. Results: There was a significant difference between ASD and TD groups in the area described by the knee-ankle diagram (p < 0.05). The sEMG activity recorded from the lateral gastrocnemius (LG) during the contact phase of gait was significantly lower in the ASD group compared with the TD group (p < 0.05). The sEMG activity recorded in the different postural conditions showed differences in LG and tibialis anterior (TA) between the ASD and TD groups (p < 0.05). Conclusions: The knee-ankle diagram provided a sensitive and specific movement descriptor to differentiate individuals with ASD from individuals with TD. The reduced LG activation is responsible for the reduced area in the knee-ankle diagram and 'toe-walking' in individuals with ASD and represents the common denominator of an altered ankle strategy during locomotion and postural control.

Extraction and Separation of zirconium using Aliquat 336 from Egyptian black sand

A solvent extraction method has been employed to extract and separate zirconium from the nitric acid medium using 6% tri-caprylmethylammonium chloride (Aliquat 336) [CH3(CH2)7]3N+(CH3) Cl- dissolved in kerosene as diluent. The relevant factors controlling the extraction process of zirconium using Aliquat 336 were studied. These factors include Aliquat 336 concentration, A:O phase ratio, contact time and diluent type. More than 99.6% of Zr was extracted by 6% Aliquat 336 at contact time 10 minutes, phase ratio O:A (v: v) 2:1 and the diluent were kerosene. Third phase formation was studied and dissolving it by using decanol as modifier was also done. Stripping of zirconium from loaded Aliquat 336 has been carried out using 4M H2SO4 as an effective stripping agent. The feasibility of using Aliquat 336 for separation of zirconium was assisted by stripping studies. The loaded zirconium onto Aliquat 336 has been stripped by stripping efficiency 94.18% when using 4M H2SO4 as an efficient eluting agent at 10 minutes contact time and phase ratio O:A (v: v) 1:1.

Whole-body linear momentum control in two-foot running jumps in male basketball players

Running jumps that depart the ground from two feet require momenta redirection upward from initial momenta that are primarily horizontal. It is not known how each leg generates backward and upward impulses from ground reaction forces to satisfy this mechanical objective when jumping to maximize height. We examined whole-body linear momentum control strategies during these two-foot running jumps by uncovering the roles of each leg in impulse generation. 3D motion capture and force plates were used to record 14 male basketball players performing two-foot running jumps towards an adjustable basketball hoop. Total ground contact phase started from the first leg ground contact and ended at takeoff and was divided into center of mass descent and ascent subphases. During the total ground contact phase, all participants generated significantly more upward impulse with the first leg and ten participants generated significantly more backward impulse with the first leg compared to the second leg. During the descent subphase, all participants generated significantly more upward and backward impulses with the first leg. During the ascent subphase, all but one participant generated significantly more backward impulse with the second leg. In addition to group-level statistics, participant-specific strategies were described. Overall, this study revealed the fundamental whole-body momentum control strategies used in two-foot running jumps and supports future research into optimal jump techniques and training interventions that respect the need to satisfy the mechanical objectives of the movement.

Preparation of presulfided oil-soluble NiMo catalyst for slurry bed hydrocracking of vacuum residue

Here, a method is proposed for constructing presulfided oil-soluble NiMo catalysts using tetrathiomolybdate nickel ammonium as a precursor via a chelating ligand exchange strategy. Leveraging the close chemical bonding between Ni and Mo atoms, the NiMo catalyst can undergo in-situ self-sulfidation to generate active NiMoS sites and a composite structure of Ni3S2 and MoS2 nano phase in tight contact, thus exhibiting strong synergistic effects. The NiMo catalyst exhibited outstanding performance in hydrocracking of vacuum residue (VR) achieving a 64.7 wt% VR conversion while maintaining a coke yield of 0.51 wt%, as well as the excellent hydrogenation activity of polycyclic aromatic hydrocarbons. Combined with density functional theory calculations, it was further revealed that the presence of Ni reduces the energy barrier for H2 dissociation on MoS2, thereby enhancing the hydrogenation activity of the catalyst and its ability to suppress coke formation. This work validates the efficient bimetallic synergistic catalytic effect of presulfided oil-soluble NiMo catalysts in the slurry bed hydrocracking process.

Dynamic control simulation of a new joint model with energy recovery during walking, using magnetorheological fluids, for lower limb prosthesis

AbstractResearchers can now utilize new materials to create innovative models for lower limb prostheses and explore novel ways to use them for efficient dynamic control. To achieve user-friendliness, one area of research focuses on recovering and reusing kinetic walking energy for dynamic control. This paper proposes a new design for a magnetorheological (MR) valve, along with a rotary actuator which offers a dynamic control for a lower limb prosthesis. The design will allow the storage of the energy during heel and mid-foot contact phases and to utilize it during toe support to lift the foot off the ground and establish a balance for the lower limb prosthesis. The energy is transferred through a magnetorheological hydraulic circuit and stored using a pneumatic system. The speed of energy transfer is regulated by magnetorheological valves. A series of MR valve designs were proposed and evaluated experimentally, which allowed the identification of the most suitable variant in the targeted application context. The design of the lower limb prosthesis was simulated using SolidWorks, and its dynamic behavior was analyzed in ANSYS.

Small-scale roughness entraps water and controls underwater adhesion.

While controlling underwater adhesion is critical for designing biological adhesives and in improving the traction of tires, haptics, or adhesives for health monitoring devices, it is hindered by a lack of fundamental understanding of how the presence of trapped water impedes interfacial bonding. Here, by using well-characterized polycrystal diamond surfaces and soft, nonhysteretic, low-surface energy elastomers, we show a reduction in adhesion during approach and four times higher adhesion during retraction as compared to the thermodynamic work of adhesion. Our findings reveal how the loading phase of contact is governed by the entrapment of water by ultrasmall (10-nanometer-scale) surface features. In contrast, the same nanofeatures that reduce adhesion during approach serve to increase adhesion during separation. The explanation for this counterintuitive result lies in the incompressibility-inextensibility of trapped water and the work needed to deform the polymer around water pockets. Unlike the well-known viscoelastic contribution to adhesion, this science unlocks strategies for tailoring surface topography to enhance underwater adhesion.

The effect of safety modifications on head kinematics experienced during common skills in women’s artistic gymnastics

ABSTRACT The objective of this study was to evaluate the effect of skill modifications on head motion experienced during women’s artistic gymnastics skills. Nine gymnasts (four beginner and five advanced) completed three trials of up to 24 skill progressions, each consisting of a skill and two progressive safety modifications. Gymnasts were instrumented with mouthpiece sensors embedded with an accelerometer and gyroscope collecting motion data at 200, 300, and 500 Hz during each skill performance. Peak-to-peak linear and rotational kinematics during contact phases and peak rotational kinematics during non-contact phases were computed. A mixed-effects model was used to compare differences in modification status nested within skill categories. Timer skills (i.e. drills that simulate performance of a gymnastics skill) resulted in the highest median ΔLA and ΔRA of all skill categories, and 132 skill performances exceeded 10 g ΔLA during a contact phase. Modifications were associated with significant reductions in head kinematics during contact phases of timers, floor skills, bar releases, and vault skills. Gymnasts can be exposed to direct and indirect head accelerations at magnitudes consistent with other youth contact sports, and common safety modifications may be effective at reducing head motion during contact and non-contact phases of gymnastics skills.

Evolution, sedimentation and thermal state of the emerging pro‐glacial lakes at Witenwasserengletscher, Switzerland

AbstractAs glaciers retreat worldwide, local basal depressions are exposed where new pro‐glacial lakes are forming. Although the formation of such new lakes has been mapped widely, the impact of their interaction with the glacier on sediment dynamics and the thermal state is rarely studied. At the example of Witenwasserengletscher, Switzerland, we use historic aerial imagery and a bathymetric survey to investigate in detail the interaction of glacier retreat, lake formation and sedimentation. Three lakes have emerged since the mid‐1990s with mean depths between 1.25 and 6 m. The deepest lake lost contact to the ice in 2009 with a delta forming from mobilized sub‐glacial sediment. Phases of direct contact of the glacier with the lakes are found to increase terminus retreat and affect the thermal state and sedimentation. In summer, lake water temperatures in these small ice‐contact lakes stay close to 0°C, whereas the disconnected eastern lake shows temperatures consistently over 6°C. Temperature profiles from 2021 show that after losing ice contact, warm sediment‐rich glacial water forms an underflow that is breaking through the summertime stratification with warm water over cold water. In this case, density stratification is dominated by suspended sediment rather than temperature. Sedimentation shows a high multiannual variability and is dependent on a multitude of factors, ultimately on the routing of glacial streams. These tend to migrate towards the centre of the valley as the glacier retreats. Our study shows that during deglaciation lake evolution, sediment redistribution and the thermal state are highly dynamic and pro‐glacial lakes strongly affect the sediment evolution and may thereby impact on the ecosystem in pro‐glacial streams.

An Analytical Adhesion Model for Elastic Contact Electrification

Abstract Contact electrification is a universal phenomenon that commonly occurs in almost every solid–solid contact pair. The tribo-charges deposited on two surfaces by contact electrification can significantly affect adhesion; however, contact electrification is often overlooked in the study of adhesive contact. Here, we develop an analytical model to investigate electroadhesion during the contact phase between two initially uncharged dielectric surfaces, namely, an elastic parabolic surface and a rigid flat. A system of nonlinear equations is derived to describe the relationship between the indentation, normal load, radius of contact area, and radius of the charged zone using the Barthel–Maugis–Dugdale model (Barthel, 1999, “Modelling the Adhesion of Spheres: When the Form of the Interaction Is Complex, Colloids. Surf., A., 149, pp. 99105.). The analytical results show good agreement with the numerical results of the full self-consistent contact model. When contact electrification leads to a higher tribo-charge density and a larger charged zone, it has a greater impact on the normal traction, interfacial gap, force-approach curves, jump-out, and dissipated energy. The analytical model developed in this study serves as the foundation for advances in rough surface electroadhesive contact and electroadhesion testing, and it sheds light on the usage of adhesive joints in ultra-high vacuum environments and outer space, where contact electrification has a significant impact.

Experimental and finite element analysis of surface asperity geometry during the running-in phase of rolling contact

This paper presents the experimental and finite element analysis of surface asperity geometry during the running-in phase of rolling contact. Previous research efforts typically relied on simulating various shapes of asperity geometry to elucidate rough surface characteristics. However, this approximation did not accurately represent the actual surface asperities. In this study, a rolling contact rig was fabricated, and periodic surface scans were utilized to track the deformation of roller surface asperities. The experimental findings reveal a notable 69% reduction in surface roughness throughout the running-in phase, alongside showcasing the deformation of asperity geometry. Subsequently, a simulation model is developed using data derived from these experiments. Stress analysis conducted on individual and multiple asperities illustrates a decrease in contact stress over time, indicating a transition in contact behavior from plastic to elastic. Furthermore, simulations involving multiple asperities demonstrate an expansion in contact length as roughness diminishes with increasing cycles. Initially, only the highest peaks of asperities make contact, resulting in elevated contact stress. However, as rolling cycles progress, a greater number of asperities come into contact, leading to a more uniform distribution of load. Notably, the more prominent asperities endure significant contact stress and deformation compared to their smaller counterparts.

Body Mass and Foot-dominance Disparities in the Foot Plantar Pressure Parameters of Older Women.

To examine the effects of foot dominance and body mass on foot plantar pressures in older women of regular, overweight, and obese weights. 96 female adults were divided into regular-weight group (68.30 ± 4.19 yr), overweight group (69.88 ± 3.76 yr), and obesity group (68.47 ± 3.67 yr) based on their body mass index scores. Footscan® plantar pressure test system was used to assess the dynamic plantar pressures, and parameters were collected from risk analysis, foot axis analysis, single foot timing analysis, and pressure analysis. (1) The local risks of lateral forefoot and midfoot, the minimum and maximum subtalar joint angles, the flexibility of subtalar joint, foot flat phase, as well as the average pressures on toes, metatarsals,, midfoot, and lateral heel, with the peak pressures on toe 2-5, metatarsal 2, metatarsal 5, midfoot, and lateral heel had significant within-subject differences. (2) The phases of initial contact and foot flat, the average pressures on toe 2-5, metatarsals, midfoot, and heels, with the peak pressures on metatarsal 1-4, midfoot, and heels exhibited significant between-subjects differences. (3) There was an interaction effect of foot dominance and body mass index on the flexibility of subtalar joint. The non-dominant foot works better for stability, especially when touching on and off the ground. The dominant foot works better for propulsion but is more susceptible to pain, injury, and falls. For obese older women, the forefoot and midfoot are primarily responsible for maintaining stability, but the lateral midfoot and hindfoot are more prone to pain and discomfort.

ANALYSIS OF THE SPATIO-TEMPORAL CHARACTERISTICS OF THE TECHNIQUE OF KICKING WITH THE LEFT FOOT TO THE SIDE FROM THE LEFT-HANDED STANCE OF HIGHLY SKILLED ATHLETES SPECIALISING IN HAND-TO-HAND COMBAT

The relevance of the research topic. A wide arsenal of technical actions and a wide range of potential conflict situations that regularly occur in the course of martial arts determine the peculiarities of operations, actions and mechanisms for their improvement. The aim of the research was to analyse the indicators of the spatial-temporal structure of the technique of a kick with the left foot to the side from the left- handed stand performed by highly skilled sportsmen. Research methods: analysis of literature sources, video recording and biomechanical video computer analysis using the optoelectronic system "Qualisys", methods of mathematical statistics. Results. The movement of the biolinks of the athletes' body during the phase of preparing for the impact is from 0.03 m to 0.25 m. During the kicking phase, the values of the average velocities of the right ankle and right knee joints are 4.23 m·s-1 and 2.26 m·s -1 respectively. Conclusions. The execution of a blow is effective from the point of view of biomechanical analysis, and the indicators of the kinematic structure of movements during the execution of this blow can be used both as a reference sample of sports technique and for the development of model characteristics of movements based on them. The values of the average velocities of the shoulder, elbow, and carpal joints of the right hand during the walking phase are 0.50 m·s-1, 1.10 m·s-1, and 0.95 m·s-1, respectively. The average speed of the shoulder joint of the left hand is 0.69 m·s-1, the left elbow joint - 0.97 m·s-1, and the left carpal joint - 2.03 m·s-1. Such high indicators of the average speeds of the hand joints during the walking phase indicate swinging movements to increase the force of the impact due to the use of inertial forces. The movement of the biolinks of the athletes' body during the walking phase ranges from 0.08 m to 0.63 m. The values of the indicators of the joints of the upper limbs during the two support phases when performing a left leg kick to the side from the left stance are: right shoulder joint - 0.65 m·s-1, left shoulder joint -0.52 m·s-1, right elbow joint – 2.73 m·s-1, left elbow joint – 1.71 m·s-1, right and left carpal joints – 1.84 m·s-1. In the two-support phase, the movement of the studied body points of the athletes is in the range from 0.08 m to 0.56 m. The values of the average velocities of the studied body points of the athletes during the contact phase when performing a left leg kick to the side from the left stance range from 0.23 m s- 1 to 2.53 m·s-1, and the displacement of the same points during this phase is from 0.02 m to 0.20 m

Calibration to Differentiate Power Output by the Manual Wheelchair User from the Pushrim-Activated Power-Assisted Wheel on a Force-Instrumented Computer-Controlled Wheelchair Ergometer

To examine the biomechanical demands of manual wheelchair propulsion, it is crucial to determine the wheelchair user’s (WCU) force for propulsion technique parameter calculation. When using a pushrim-activated power-assisted wheelchair (PAPAW) on a wheelchair ergometer, a combined propulsion force from the WCU and PAPAW is exerted. To understand PAPAW’s assistance and distinguish the WCU’s force application from the force exerted by the PAPAW, both propulsion components must be assessed separately. In this study, a calibration of the PAPAW on an ergometer was developed to achieve this separation. The calibration consists of five steps: (I) Collecting data on force and velocity measured from the ergometer, along with electrical current and velocity from the PAPAW. (II) Synchronizing the velocity signals of the wheelchair ergometer and PAPAW using cross-correlation. (III) Calibrating the PAPAW’s electromotors to convert electrical current (mA) to force (N). A product-specific motor constant of 0.30, provided an average ICC of 0.563, indicating a moderate agreement between the raw ergometer data (N) and the motor constant-converted drive-rim (PAPAW) data (from mA to N). (IV) Subtracting the PAPAW’s force signal from the ergometer’s measured force to isolate forces generated by the WCU. (V) Using markerless motion capture to determine and validate the phase of hand contact with the handrim. This technical note provides an example of PAPAW calibration for researchers and clinicians. It emphasizes the importance of integrating this calibration into the development of PAPAW devices to reveal the complex interaction between PAPAW and WCU during wheelchair propulsion.

A contact sensor-free framework for ground reaction force observation in heavy-legged robots considering unknown loads

As a direct response to robot movements and load distributions, the ground reaction force (GRF) is pivotal for heavy-legged robot (HLR) applications. This study presents a technical framework for GRF monitoring in an electric cylinder-driven HLR, eliminating the need for information on body motion, load distributions, and measured servo outputs. Traditional joint space-based dynamics are extended to include servo currents, compensating for the influence of unknown servo outputs. An essential contribution is incorporating the impact of floating bases and unknown loads into a virtual spatial force (VSF) applied to the HLR hip joint. The VSF is obtained through the nonlinear disturbance observer when the HLR is in a stable contact phase. Subsequently, a high-order GRF observer (HOGO), compensated with VSF, enables GRF observations without the pre-acquired body movement and load distribution data. In contrast to conventional GRF observations, the proposed framework could determine virtual payloads acting on the hip joint while ensuring precise GRF monitoring without requiring supplementary sensors. The GRF observations of the proposed framework are experimentally superior to those of the conventional methods with unknown HLR body motion and load information.

The Impact of Induced Acceleration Perturbations in Selected Phases of the Gait Cycle on Kinematic and Kinetic Parameters

Background: The prevalence of falls among the older population underscores the imperative of comprehending human adaptations to gait perturbations. Dual-belt treadmills offer a controlled setting for such investigations. The purpose of this study was to examine the effect of the acceleration of one belt of the treadmill during three different phases of the gait cycle on kinematic and kinetic parameters and relate these changes to unperturbed gait. Methods: Twenty-one healthy young females walked on a treadmill in a virtual environment, in which five unexpected perturbations were applied to the left belt at the Initial Contact (IC), Mid Stance (MS), and Pre-Swing (PS) phase of the gait cycle. Data from the undisturbed gait and the first disturbance of each trial were extracted for analysis. Results: All perturbations significantly affected the gait pattern, mainly by decreasing the knee extension angle. The perturbation in the IC phase had the most significant effect, resulting in a 248.48% increase in knee flexion torque. The perturbation in the MS phase mainly affected plantar flexion torque, increasing it by 118.18%, while perturbation in the PS phase primarily increased the hip extension torque by 73.02%. Conclusions: The presence of perturbations in the IC and PS phases caused the most aggressive and significant changes in gait parameters.

Impact of specialized fatigue and backhand smash on the ankle biomechanics of female badminton players

During fatigued conditions, badminton players may experience adverse effects on their ankle joints during smash landings. In addition, the risk of ankle injury may vary with different landing strategies. This study aimed to investigate the influence of sport-specific fatigue factors and two backhand smash actions on ankle biomechanical indices. Thirteen female badminton players (age: 21.2 ± 1.9 years; height: 167.1 ± 4.1 cm; weight: 57.3 ± 5.1 kg; BMI: 20.54 ± 1.57 kg/m2) participated in this study. An 8-camera Vicon motion capture system and three Kistler force platforms were used to collect kinematic and kinetic data before and after fatigue for backhand rear-court jump smash (BRJS) and backhand lateral jump smash (BLJS). A 2 × 2 repeated measures analysis of variance was employed to analyze the effects of these smash landing actions and fatigue factors on ankle biomechanical parameters. Fatigue significantly affected the ankle-joint plantarflexion and inversion angles at the initial contact (IC) phase (p < 0.05), with both angles increasing substantially post-fatigue. From a kinetic perspective, fatigue considerably influenced the peak plantarflexion and peak inversion moments at the ankle joint, which resulted in a decrease the former and an increase in the latter after fatigue. The two smash landing actions demonstrated different landing strategies, and significant main effects were observed on the ankle plantarflexion angle, inversion angle, peak dorsiflexion/plantarflexion moment, peak inversion/eversion moment, and peak internal rotation moment (p < 0.05). The BLJS landing had a much greater landing inversion angle, peak inversion moment, and peak internal rotation moment compared with BRJS landing. The interaction effects of fatigue and smash actions significantly affected the muscle force of the peroneus longus (PL), with a more pronounced decrease in the force of the PL muscle post-fatigue in the BLJS action(post-hoc < 0.05). This study demonstrated that fatigue and smash actions, specifically BRJS and BLJS, significantly affect ankle biomechanical parameters. After fatigue, both actions showed a notable increase in IC plantarflexion and inversion angles and peak inversion moments, which may elevate the risk of lateral ankle sprains. Compared with BRJS, BLJS poses a higher risk of lateral ankle sprains after fatigue.

Altered gait patterns during arch important development period in children with persistent obesity: An experimental longitudinal study

BackgroundObesity can cause structural changes and functional adjustments in growing children’s feet. However, there is a lack of continuous observation of changes in feet in children with persistent obesity during important developmental periods. This makes it challenging to provide precise preventive measures. ObjectiveThis study aimed to investigate the effects of persistent obesity on gait patterns in children at an important stage in the formation of a robust foot arch. MethodsThe Footscan® plantar pressure system was used for 3 checks over two years. A total of 372 children aged 7–8 years participated in the study, and gait data from 33 children who maintained normal weight and 26 children with persistent obesity were finally selected. Repeated measures ANOVA or Friedman’s test were used for longitudinal comparisons. Independent-Sample t-tests or the Mann-Whitney-Wilcoxon tests were used for cross-sectional comparisons. ResultsDuring the important period of development, children with persistent obesity did not exhibit a significant decrease in the arch index and had significantly higher values than the normal group in the third check. The persistently obese children showed increased load accumulation in the lateral rearfoot, first metatarsophalangeal joints, and the great toe regions. Children with persistent obesity had significantly greater medial-lateral displacements in the initial contact phase and forefoot contact phase than normal children in the first check. These differences diminished between the second and third checks. SignificancePersistent obesity during an important period of foot development leads to slow or abnormal development of arch structure and affects foot loading patterns with heel inverted and forefoot everted. Additionally, the development of gait stability is not limited by persistent obesity.