Peak Force Research Articles

Effect of a multicomponent exercise program focused on multivariable fatigue improvement versus standard care for glenohumeral instability: MoveUS study protocol

BackgroundGlenohumeral instability is a highly prevalent pathology; however, there are problems in defining it. Traditionally, structural problems such as labral injury or bone loss in the glenoid cavity and/or humeral side were considered the main causes; but recently, it has been seen that motor control plays a very relevant role. This means that currently, there is a disparity of action protocols, and the treatment of this pathology is a great challenge.AimThe primary aim of this study is to evaluate the effectiveness of a supervised multicomponent therapeutic exercise program in reducing multivariable fatigue in patients with instability of the glenohumeral joint.MethodsA single-blind randomized controlled trial will be carried out, in which 108 adult patients who have suffered at least one episode of glenohumeral instability in the last year will be recruited by the Department of Traumatology and Rehabilitation of Axarquia Hospital (Málaga). Patients will be randomized to the intervention group, which will carry out a multicomponent therapeutic exercise program supervised by physiotherapists (MoveUS Program); or to the control group, which will receive the usual care. All subjects will be evaluated at baseline, mid-treatment, after the intervention, and three months later at the follow-up. In these evaluations, range of movement, maximum peak of isometric force, kinematic, physiological, and psychometric fatigue, return to activity, motor control, and number of recurrences will be assessed; as well as the quality of life measured through the Western Ontario Shoulder Instability Index, which will be the main outcome variable. A multivariate analysis will be performed through a statistical program to better determine the factors that could influence the results.DiscussionThis study aims to determine if therapeutic exercise supervised by physiotherapists is capable of reducing multivariable fatigue, reducing the number of recurrences, and improving quality of life; to be able to implement it in the future in public and private clinics since materials are available and physiotherapist have enough skills in the field of therapeutic exercise, so it is expected to be a quality tool in the approach to glenohumeral instability.RegistrationRegistry: ClinicalTrials.gov. Number: NCT05443295. Date: 01/07/2022.

Mechanical Behavior of 3D-Printed Zig-Zag Honeycomb Structures Made of BASF Ultrafuse 316L

The aim of this study is to determine the mechanical behavior of 2D honeycomb cellular structures with deformation initiators subject to quasi-static compression testing. Two different loading directions were studied: in-plane (IP) and out-of-plane (OP). The deformation initiators sought to stabilize the mechanical response by decreasing the initial peak force in the case of OP loading. The samples for testing were made using stainless steel 316L that was 3D-printed using material extrusion (MEX). The method enables fabrication of structures with high mechanical strength and ductility. The findings of the quasi-static compression testing showed that the additional deformation initiators were able to significantly reduce the orthotropy in the mechanical response of honeycomb cellular structures.

Study on Collision Dynamics Similarity of Thickness Distortion Model of Train Five-Hole Thin-Walled Structure

Full-scale train collision tests are rarely carried out because of high cost, but small-scale model tests have good economy and repeatability, providing a new research method for train crashworthiness design. The metal thin-walled tube is a commonly used energy-absorbing structure for trains. Its collision characteristics directly affect the impact resistance and collision behavior evolution process of trains. This paper studies the collision dynamics similarity of the small-scale model of a five-hole thin-walled energy-absorbing structure at the end of a high-speed train. Firstly, the dynamic mechanical behavior and governing equations of high-speed train collision were analyzed, and the applicable similarity criterion was derived by similarity transformation to develop a similarity scale model. According to the simulation, the energy absorption, peak force and other key responses of the full-scale prototype collision were analyzed. Then, the applicability of the thickness distortion scale model of the five-hole energy-absorbing structure in the high-speed train was proved by equation analysis and error analysis. The impact dynamic responses of the complete similarity model and the distortion similarity model were discussed. A correction program with collision deceleration as the dependent variable was proposed for the distortion similarity model, and the fitting relationship between the distortion factor and the correction factor was obtained. The results calculated by the proposed method prove that the peak force-deformation-energy absorption error of the thickness distortion similarity model in predicting the dynamic responses of the prototype collision is less than 8%, which means the thickness distortion scale model has good accuracy in the prediction of full-scale prototype collision dynamics responses.

Touch-down condition control for the bipedal spring-mass model in walking

Behaviors of animal bipedal locomotion can be described, in a simplified form, by the bipedal spring-mass model. The model provides predictive power, and helps us understand this complex dynamical behavior. In this paper, we analyzed a range of gaits generated by the bipedal spring-mass model during walking, and proposed a stabilizing touch-down condition for the swing leg. This policy is stabilizing against disturbances inside and outside the same energy level and requires only internal state information. In order to generalize the results to be independent of size and dimension of the system, we nondimensionalized the equations of motion for the bipedal spring-mass model. We presented the equilibrium gaits (a.k.a fixed point gaits) as a continuum on the walking state space showing how the different types of these gaits evolve and where they are located in the state space. Then, we showed the stability analysis of the proposed touch-down control policy for different energy levels and leg stiffness values. The results showed that the proposed touch-down control policy can stabilize towards all types of the symmetric equilibrium gaits. Moreover, we presented how the peak leg force changes within an energy level and as it varies due to the type of the gait since peak force is important as a measurement of injury or damage risk on a robot or animal. Finally, we presented simulations of the bipedal spring-mass model walking on level ground and rough terrain transitioning between different equilibrium gaits as the energy level of the system changes with respect to the ground height. The analysis in this paper is theoretical, and thus applicable to further our understanding of animal bipedal locomotion and the design and control of robotic systems like ATRIAS, Cassie, and Digit.

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.

Comparison of Vertical Jump Force–Time Metrics Between ACL-Injured and Healthy Semi-Professional Male and Female Soccer Players

Given the increasing use of innovative force plate systems in applied sports settings and the impact that anterior cruciate ligament (ACL) injuries have on team success, the purpose of the present study was to compare the lower-body neuromuscular performance characteristics of athletes who underwent ACL reconstruction (ACLR) and their non-injured counterparts (i.e., healthy controls). Forty-five male (thirteen injured) and twenty-six female (ten injured) semi-professional soccer players volunteered to participate in the present study. Each athlete performed three countermovement vertical jumps (CMJs) while standing on a uniaxial force plate system sampling at 1000 Hz. The injured athletes completed a nine-month recovery protocol and were screened 11–13 months post-ACLR. The dependent variables included the force–time metrics within both the eccentric and concentric phases of the CMJ. Independent t-tests or Mann–Whitney U-test were used to examine statistically significant (p < 0.05) differences in each variable (i.e., ACL-injured vs. healthy controls). The results revealed no significant between-group differences in any CMJ force–time metrics of interest (e.g., concentric peak force, eccentric mean power, countermovement depth) between ACL-injured and non-injured athletes, including inter-limb asymmetry measures (i.e., peak takeoff and landing force). Besides implying the effectiveness of the implemented rehabilitation protocol, these findings suggest that the CMJ may not present a sufficient neuromuscular performance stimulus needed to expose lower-limb asymmetries and strength and power deficiencies 11–13 months post-ACLR.

Mechanical behavior of composite pipe structures under compressive force and its prediction using different machine learning algorithms

Abstract Thanks to machine learning algorithms, the performance of composites with high energy absorption capacity can be predicted with high accuracy rates with a small number of data. The aim of this study is to experimentally and numerically determine the crushing performances of glass/epoxy composite pipe structures under compressive force and to predict their compression behavior with the help of different machine learning algorithms. In the study, the crushing performances of composite pipes (peak force (PF), peak force displacement (PFD), mean crushing force (MCF), specific energy absorption (SEA), and total inner energy (TIE)) were determined for different specimen thicknesses, specimen lengths, mesh sizes, numbers of integration points, diameters (D), and compression directions (axial and radial). Additionally, the maximum strength values of composite pipes under force were estimated with the help of Linear Regression (LR), K-Nearest Neighbors (KNN), and Artificial Neural Networks (ANN) machine learning algorithms. The data taken from the ANN algorithm were found to be more reliable in estimating the PF and TIE values, with an accuracy rate of 92 %. When determining the MCF value, it was found that the data obtained from the LR algorithm was more reliable than other algorithms, with an accuracy rate of 80 %.

The Computational Design of Corrugated Tube Lattice Structure with Negative Stiffness Property Under Axial Compression Load

Negative stiffness (NS) structures have singular mechanical properties and potential applications in various scenarios. A corrugated tube (CT) and an NS lattice structure (NLS) composed of CTs and connection plates are proposed. The mechanical properties of CT and NLS under axial compression are investigated by experiments and simulations. The deformation modes of CT and NLS are layer-by-layer folding of structural layers. The influences of geometric parameters on the compression performance of CT and NLS have been studied. Through a reasonable design of the thickness of upper and lower conical structures, CT and NLS can exhibit periodic changes in peak and valley forces during the compression process, resulting in significant NS behavior. In addition, the increase of CT’s number does not significantly affect the NS effect, and the load-carrying capacity of NLS increases significantly as the number of CT increases. The energy absorption (EA) and peak force values of NLS-[Formula: see text], NLS and NLS-[Formula: see text] are approximately 16, 9, and 4 times those of CT-3.0-0.6-f0.5, and the EA value of an NLS model is the sum of the EA values of its all CTs. In addition, the effects of geometric parameters on the mechanical properties of NLS are systematically investigated. With reasonable parameter values, NLS exhibits strong NS effect and excellent EA capacity.

Physical processes explaining the second force peak generated during a surge impact on a vertical wall

This paper presents an in-depth study of the impact of a surge on a vertical wall using incompressible and compressible RANS model simulations of a classical dam break experiment over a dry bed. The model allows access to the detailed flow structure and pressure field at any instant, which provides valuable complementary information to measurements. Our study focuses on the second force peak, which is often the largest one and for which the literature does not really provide a clear explanation. Before and after this peak, the pressure on the wall is governed by the flow kinematics in the area. Before the peak, an overpressure appears at the root of the reflected jet, corresponding to the violent interaction between the incoming surge and the run-down flow. At the peak instant, the situation suddenly changes due to the collapse of the reflected jet onto the incoming flow, trapping an air cavity. As in the classical case of direct wave impact on a wall with a trapped air pocket, this process generates an additional strong uniform pressure field in the air cavity, which propagates to the water and nearby boundaries due to the water confinement effect. This compressible effect, which varies depending on the capacity of air to escape the cavity, explains the formation of the second force peak. Finally, the 3D incompressible model provides a much more reliable estimate of the second force peak than the 2D incompressible model. This is likely due to the air escape phenomenon, which occurs when the experimental initial conditions are not perfectly 2D. Although it is unlikely that the 3D simulation perfectly reproduces the experimental flow, nevertheless, with more or less comparable air escape, the computation results appear consistent.

Smaller Formats of Volleyball Lead to Greater Improvements in Lower Limb Strength and Power, As Well As Reductions in Landing Forces: A Randomized Controlled Study in Girls.

The purpose of this study was to compare the adaptations in muscular strength, power, and landing forces of young female volleyball players enrolled in two experimental programs: one using smaller formats of the game (SFG) and the other using larger formats of the game (LFG), with a third group serving as a control. This study employed a randomized controlled design, with an 8-week intervention period and pre- and post-intervention evaluations. Fifty-six trained/developmental participants (age: 14.7 ± 0.5 years) voluntarily participated in this study. Each experimental group received additional training twice a week. The SFG group participated in 2v2 and 3v3 formats on smaller courts (covering 2/6 of the court's available zones) with a regular net, while the LFG group played in 4v4 and 5v5 formats on larger courts (covering 4/6 of the court's available zones). Assessments were conducted using force platforms and included the following tests: (i) isometric mid-thigh pull test (IMTP), measuring peak force; (ii) squat jump test (SJ), measuring peak force; (iii) countermovement jump test (CMJ), measuring peak power and landing force; and (iv) drop jump test (DJT), measuring the reactive strength index. Significant differences emerged post-intervention across all outcomes (p < 0.05). The SFG exhibited significantly greater IMTP peak force compared to both the LFG (p = 0.012) and control groups (p = 0.035). Additionally, the SFG showed significantly greater SJ peak force than the LFG (p = 0.036) and control groups (p = 0.023). Regarding CMJ peak power, significantly higher values were observed in the SFG compared to the LFG (p = 0.042) and control groups (p = 0.046). Moreover, the SFG had significantly lower CMJ peak landing force than both the LFG (p = 0.049) and control groups (p = 0.046). Finally, RSI was significantly higher in the SFG than in the LFG (p = 0.046) and control groups (p = 0.036). This study highlights the significant benefits of incorporating 2v2 and 3v3 SFG formats to enhance muscular strength, power, and landing forces in young female volleyball players, contrasting with less effective outcomes observed with 4v4 and 5v5 LFG formats, suggesting potential neuromuscular advantages crucial for improving volleyball performance.

INVESTIGATION OF IMPACT PERFORMANCE OF CYLINDER CORRUGATED SANDWICH STRUCTURES WITH DIFFERENT GEOMETRIC CONFIGURATIONS

The aim of this study is to numerically investigate and compare the impact performance of CFRP composite cylinder sandwich structures with five different geometric configurations. The impact performances and damage types of composite cylinder structures for different core configurations were determined. The impact analyses were performed in LS DYNA finite element program using MAT-54 material model with Progressive damage analysis based on the combination of Hashin damage criterion, Cohesive zone model and Bilinear traction-separation law. Among the five different specimens in the study, the highest peak force (PF) value of 1.88 kN was obtained at impact point P2 of the Trapeozidal sandwich structure. The lowest value was obtained at P1 impact point in Triangular sandwich structure with 0.62 kN. The highest and lowest energy absorption efficiency occurred in the Triangular structure, 78% and 38% respectively. The PF value at P2 point is higher than P1. The effect of core support on PF is very important. Since point P1 is not supported by the core, it is determined that the deformation is larger than P2.

Phase-field modeling of interfacial fracture in quasicrystal composites

Quasicrystals (QCs) have been used as a particle reinforcement phase in polymer or metal matrix composites to enhance the material strength, hardness and wear resistance while maintaining the lightweight advantages of the composites. In this paper, a phase-field fracture model (PFM) is proposed to predict crack propagation and interfacial debonding in QC composites. The phase-field and interface-field variables are introduced to regularize the cracks and interfaces in the composites, respectively. An equivalent critical energy release rate is introduced to characterize the influence of the interface on crack propagation. The present model is numerically implemented in Comsol Multiphysics based on the Weak Form PDE module. Several numerical examples are simulated to demonstrate the ability of the proposed model to predict crack propagation and interfacial failure of QC composites and to analyze the influence of QC reinforcement phase on fracture behaviors of QC composites. Numerical results indicate that the interface significantly influences the crack propagation paths, and the phason elastic field has a remarkable influence on the peak force and failure displacement in the fracture test of QC composites. The developed phase-field model and numeral implementation approach provide a convenient tool for predicting interfacial failure and assessing the safety of QC composites in engineering.

Dynamic behaviour and failure mechanism of bamboo scrimber panels under single and repeated impacts: Experimental tests

Bamboo scrimber, as a renewable and sustainable material engineered from bamboo, is inevitably subjected to impact loadings in engineering applications. To study the dynamic behaviour and failure mechanism of bamboo scrimber panels under low-velocity impact, a series of drop hammer impact tests were conducted on 36 panels. The peak force, deformation and energy absorption of bamboo scrimber panels were obtained and analysed. The influence of impact energy, impactor shape and impact angle on the dynamic behaviour of panels was quantitatively characterised. Besides, based on test observations and microscopic views, the failure mechanism of bamboo scrimber panels under different impact types was revealed, including the energy absorption mechanism through fibre fracture, fibre debonding, fibre pull-out and matrix failure. Test results showed that with increasing impact energy, the peak force of panels impacted by the spherical and flat impactors increased, while that of panels impacted by the wedge impactor did not vary significantly. The deformation and energy absorption of panels also increased with increasing impact energy. Notably, the impactor shape obviously influenced the dynamic behaviour of panels, causing a higher peak force of panels impacted by the flat impactor and a larger deformation of panels impacted by the wedge impactor. The failure mechanism of panels depended highly on the impact energy and the impactor shape. Finally, a comparative study of single versus repeated impacts revealed that the deformation of bamboo scrimber panels under repeated impacts was less than that of panels under a single impact when the same amount of energy was imposed to the panel. This study provided a basis for the use of bamboo scrimber to resist impact loadings.

Interlayer toughening effect of graphene oxide and polydopamine modified kevlar fiber on the carbon fiber panel/plastic honeycomb sandwich structure

This study examines the performance of modified Kevlar fiber-reinforced carbon fiber/plastic honeycomb panels. Graphene oxide (GO) is successfully grafted onto the Kevlar fiber surface using polydopamine (PDA) as a binding medium. The combined effect of GO and PDA's secondary functionalization significantly improves bonding strength. The toughened samples exhibit markedly higher peak force and energy absorption compared to the untoughened ones. Specifically, the PDA-GO-2 toughened specimen shows the best performance, with peak force and energy absorption increased by 70.9% and 109.4%, respectively. Kevlar fibers and resin form a complex "compound and rounded structure" at the edge of the honeycomb core. This structure enhances the bonding strength between the carbon fiber-reinforced polymer (CFRP) panel and the polypropylene (PP) honeycomb core. Furthermore, the PDA and GO treatment improves the fibers' wettability, tensile strength, surface roughness, and specific surface area, facilitating better mechanical interlocking between the fiber and resin. GO enhances the contact between epoxy resin and fibers by facilitating covalent and hydrogen bond interactions, resulting in a tighter transition interface that improves the interfacial adhesion strength between the fibers and the resin.

Study on Impact Load Mitigation for High-Speed Water Entry Projectiles Using Aluminum Foam Buffering Structure

Abstract This paper investigated the fluid-solid coupling nonlinear problem of water entry by a high-speed projectile, considering cavitation, air cushion effect, and water vapor generated by the high-speed relative motion between the projectile and the fluid. To this end, a sandwich structure containing aluminum foam attached piston was studied and designed. The numerical simulation of the entry process was analyzed by LS-DYNA. The results show that the sandwich structure reduces the peak impact load. 87.47% reduction in peak force during water entry and aluminum foam has good cushioning effect.

The association between foot morphology and foot loading during gait

The perceived association between foot type and injury risk has inspired the development of many foot typing methods. The purpose of this study was to determine how well different foot typing methods explained variations in regional foot loading in asymptomatic adults during gait, while considering age, sex, and walking speed as covariates. Six methods were used to determine foot type in 92 asymptomatic adults. An insole pressure sensor system measured peak force and force-time integral during treadmill walking at a self-selected pace. The foot was divided into nine regions and the association between foot type and foot loading was analyzed using generalized estimating equations (GEE) while accounting for the covariates. Over an average of 250 steps per individual, the results demonstrated variability in the association between regional foot loading and foot type. Specifically, Arch Index and X-Ray Arch Type correlated with hindfoot and midfoot loading, while Foot Posture Index correlated with medial midfoot, forefoot, and toe loading. Calcaneal Pitch and Meary’s Angle correlated with medial hindfoot, midfoot, and forefoot loading, while Varus/valgus angle correlated with loading in the forefoot and toes. The location and direction of associations were generally similar for Calcaneal Pitch, Meary’s Angle, and X-Ray Arch Type, and opposite of Arch Index. The analyses demonstrated that walking speed, age, and sex were all important factors that affected the relationship between plantar loading and foot type. Specific foot type methods correlate better with loading in specific foot regions, potentially making them better to evaluate injury risk in those regions.

Posterior Shoulder Stability Depends on Acromial Anatomy: A Cadaveric, Biomechanical Study

Failure rates in the management of recurrent posterior shoulder instability remain a concern. Cadaveric studies have established that posterior capsulolabral tears, glenoid retroversion, and posterior glenoid bone loss result in increased posterior humeral head translation in the setting of a posteriorly directed force. A high and flat acromion has recently been associated with posterior instability. Therefore, the purpose of this study was to evaluate a potential stabilizing effect of the acromion against posterior humeral head displacement. Eight fresh-frozen human cadaveric shoulders were biomechanically tested in a shoulder simulator in the load-and-shift and Jerk test positions. Prior to testing, CT scans were performed to measure native glenoid width, glenoid retroversion, posterior acromial coverage (PAC), sagittal acromial tilt (SAT) and posterior acromial height (PAH). Each specimen underwent four testing conditions using pre-planned and 3D printed cutting and reduction guides: (1) Intact joint, native acromion; (2) Intact joint, severe acromial malalignment (SAT 69°, PAC 47°, PAH 26mm); (3) Intact joint, moderate acromial malalignment (SAT 59°, PAC 57°, PAH 20mm); (4) Intact joint, corrected acromial alignment (SAT 48°, PAC 70°, PAH 11mm). The degree of acromial malalignment and acromial reorientation was chosen based on a previous study that defined acromial anatomy in patients with posterior instability. The humeral head was translated posteriorly until reaching either (1) a peak force of 150N or (2) a maximum posterior displacement of 50% of the glenoid width. Forces (N), displacement (mm) and acromiohumeral contact pressures (kPA) were simultaneously recorded. The force needed to displace the humeral head by 50% of the glenoid width decreased between 23% and 60% in moderate to severe acromial malalignment (high and flat acromion) and increased up to 122% following surgical correction of acromial alignment (low and steep acromion) when compared to the native condition. Correction of acromial alignment significantly increased stability compared to all other scenarios after ≥5% of displacement (p<0.05 for all comparisons). Furthermore, it increased acromiohumeral contact pressures compared with severe malalignment in 30° flexion and with moderate and severe acromial malalignment in 60° flexion (p<0.05 for all comparisons). The acromion acts as a mechanical buttress to posterior humeral head displacement. Surgical correction of acromial malalignment cannot only effectively restore but increase glenohumeral joint stability. Future studies are needed to define the quantitative relevance of the different factors contributing to posterior shoulder instability and assist in defining the optimal amount of correction needed in an individual situation.

Countermovement Jump and Isometric Strength Test-Retest Reliability in English Premier League Academy Football Players.

To examine the test-retest reliability of countermovement jump (CMJ) and isometric strength testing measures in elite-level under-18 and under-23 academy football players. A total of 36 players performed 3 maximal CMJs and isometric abductor (IABS), adductor (IADS), and posterior chain (IPCS) strength tests on 2 separate test days using dual force plates (CMJ and IPCS) and a portable strength testing device (IABS and IADS). Relative (intraclass correlation coefficient) and absolute (coefficient of variation, standard error of the measurement, and minimal detectable change [MDC%]) reliabilities for 34 CMJ, 10 IABS, 10 IADS, and 11 IPCS measures were analyzed using between-sessionsbest, mean, and within-session methods. For all methods, relative reliability was good to excellent for all CMJ and all IADS measures and poor to good for all IABS and IPCS measures. Absolute reliability was good (ie,coefficient of variation < 10%) for 27 (best) and 28 (mean) CMJ variables and for 6 (IABS and IADS) and 2 (IPCS) isometric measures. Commonly used CMJ measures (jump height, eccentric duration, and flight-time:contraction-time ratio) had good to excellent relative reliability and an MDC% range of 14.6% to 23.7%. Likewise, commonly used isometric peak force measures for IABS, IADS, and IPCS had good to excellent relative reliability and an MDC% range of 22.2% to 26.4%. Commonly used CMJ and isometric strength measures had good test-retest reliability but might be limited by their MDC%. Rate-of-force-development measures (for all isometric tests) and impulse measures (IPCS) are limited by poor relative and absolute reliability and high MDC%. MDC% statistics should be considered in the context of typical responsiveness.

Effects of flywheel resistance training on countermovement jump performance and vastus lateralis muscle stiffness: A controlled study

ABSTRACT This study aimed to investigate the effects of an 8-week resistance training using flywheel (FW) device on countermovement jump (CMJ) performance and resting stiffness of the vastus lateralis (VL) muscle. Physically active adults were randomly assigned to a training intervention group (T; n = 18) and a control group (C; n = 13), which received no intervention. Jump performance variables and ultrasound-assessed resting VL shear modulus were measured before and after the intervention. Analysis of covariance revealed statistically significant group differences in jump height (T = +9%; C = -3%), rate of force development (T = +32%; C = +4%), peak power (T = +9%; C = -1%), and peak force (T = +7%; C = -1%). Jump performance improved only in the training group (all CMJ variables p < 0.05). Conversely, no significant changes within groups were observed in the resting shear wave modulus results (p > 0.05). VL stiffness decreased in the training group (−4%) and increased in the control group (+6%). Our results suggest that resistance training using FW device with individually allocated high-load FW inertia induces significant improvements in jump performance, which are not underpinned by changes in VL muscle stiffness.

Impact Risk Assessment of Gravity-Based Foundation of Offshore Wind Turbine Under Tsunamis

As an important renewable engineering structure, offshore wind turbine foundation is threatened by tsunami bore. A three-dimensional numerical model of dam-break wave tsunami is established and validated based on computational fluid dynamics to study the impacting effects of gravity-based foundation (GBF) of offshore wind turbines under tsunamis. The impacting process of the small, middle, and large tsunami on the GBF is numerically simulated, and the load effects characteristics of the GBF of the wind turbine at different stages of the tsunami impact process are analyzed. The research results show that the GBF is subjected to two peak impact forces under tsunami-impacting action. The tsunami bore has a frontal impact on the GBF, and the force peak of the flow direction is the largest, which has the greatest impact on the foundation of the wind turbine. Specifically, the middle tsunami exerts a maximum frontal impact force of 16.8[Formula: see text]N, with a peak dynamic pressure of 678.2 Pa, and a maximum base moment of 1.24[Formula: see text]N[Formula: see text]⋅[Formula: see text]m. Besides, the variation on the base moment in the incident flow direction of the incoming is larger than that in the transverse direction. The research provides valuable insights into the tsunami-resistant GBF, offering recommendations and guidelines for ensuring the long-term stability of offshore wind turbines in tsunami-prone regions.