Low Force Research Articles

Assessing age-related changes in brain activity during isometric upper and lower limb force control tasks.

Despite the widespread use of older adults (OA) as controls in movement disorder studies, the specific effects of aging on the neural control of upper and lower limb movements remain unclear. While functional MRI paradigms focusing on hand movements are widely used to investigate age-related brain changes, research on lower limb movements is limited due to technical challenges in an MRI environment. This study addressed this gap by examining both upper and lower limb movements in healthy young adults (YA) vs. OA. Sixteen YA and 20 OA, matched for sex, dominant side, and cognitive status, performed pinch grip and ankle dorsiflexion tasks, each requiring 15% of their maximum voluntary contraction. While both groups achieved the target force and exhibited similar force variability and accuracy, OA displayed distinct differences in force control dynamics, with a slower rate of force increase in the hand task and a greater rate of force decrease in the foot task. Imaging results revealed that OA exhibited more widespread activation, extending beyond brain regions typically involved in movement execution. In the hand task, OA showed increased activity in premotor and visuo-motor integration regions, as well as in the cerebellar hemispheres. During the foot task, OA engaged the cerebellar hemispheres more than YA. Collectively, results suggest that OA may recruit additional brain regions to manage motor tasks, possibly to achieve similar performance. Future longitudinal studies that track changes over time could help clarify if declines in motor performance lead to corresponding changes in brain activation.

The psychophysical assessments of tactile, temperature and electrical perception for implants with metal prosthetic surfaces.

The tactile function and thermal perception are two primary functions of oral structures. Implants without periodontal ligament and pulp might fail to sense the tactile and temperature change. This study aimed to investigate implants' tactile, thermal, and electrical perception by detailed psychophysical assessments. A total of forty-eight patients with single implant restoration were recruited. Mechanical (5 intensities), cold (4 temperatures), and electrical stimulation were respectively applied to implants and natural teeth, and the psychophysical results were recorded with a visual analog scale (VAS) and compared between implants and natural teeth. For tactile perception, at low and medium forces, implants were significantly poorer than natural teeth (P<0.01), but at the largest force, there were no significant differences (P >0.05). Regarding thermal perception, thermal changes on implants could be detected, although the signals were weaker when compared to natural teeth (P<0.01). Implants were less sensitive to electrical stimulation than natural teeth (P<0.01). Even though there is no periodontium and pulp, dental implants could perceive the mechanical, thermal, and electrical stimulation weakly.

Multimodal Characterization of Cortical Neuron Response to Permanent Magnetic Field Induced Nanomagnetic Force Maps.

Nanomagnetic forces deliver precise mechanical cues to biological systems through the remote pulling of magnetic nanoparticles under a permanent magnetic field. Cortical neurons respond to nanomagnetic forces with cytosolic calcium influx and event rate shifts. However, the underlying consequences of nanomagnetic force modulation on cortical neurons remain to be elucidated. Here, we integrate electrophysiological and optical recording modalities with nanomagnetic forces to characterize the in vitro functional response to mechanical cues. Neurons exposed to chitosan functionalized magnetic nanoparticles for 24 h and then exposed to magnetic fields capable of generating forces of 2-160 pN present elevated cytosolic calcium in neurons and a time-dynamic electrophysiological spike rate and magnitude response. Extracellular recordings with microelectrode arrays revealed a 2-8 pN force-specific increase in electrophysiological spiking with a trend in reduced activity following 2 min of continuous force exposure. Nanomagnetic forces in the 16-160 pN range produced increased electrophysiological activity and remained excited for up to 4 h under continuous stimulation before silencing. Furthermore, the neuronal response to nanomagnetic forces at 16-160 pN can be electrophysiologically mediated without calcium influx by altering the magnetic nanoparticle-neuron interactions. These results demonstrate that low pN nanomagnetic forces mediate neuronal function and suggest that magnetic nanoparticle interactions and force magnitudes can be harnessed to provoke different responses in cortical neurons.

Simulation and Analysis of Double Compound CAM Pusher Tool Changing Mechanism for NC Machine Tool

The core mechanism of existing CNC tool changers is typically a single composite cam swinging rod linkage. This setup has two main drawbacks: amplified vibration errors and high impact forces due to the swinging rod. To address these, this study focuses on CNC tool changers, specifically selecting the up-and-down motion follower and proposing a novel double composite cam push rod type mechanism. Solid modeling for both mechanisms was conducted using Creo and Matlab, and theoretical modeling of the contact forces for each follower type was completed. Comparative analysis shows the push rod follower exhibits lower contact forces than the swinging rod. Using the Adams platform, the dynamic characteristics of both mechanisms were analyzed, leading to an optimized design for the push rod type. An experimental model, scaled to 0.5, was built to compare experimental data with simulation results. The findings verify the accuracy of the models, supporting the feasibility of the push rod type tool changer.

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 &lt; 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.

The Critical Influence of Wire Diameter and Bending for Orthodontic Wire Integration—New Insights for Maxillary Movements (In Vitro Study)

Background: Traditional methods for palatal expansion using fixed appliances often face limitations in comfort and aesthetics. In comparison, aligner therapy has limitations, particularly regarding maxillary expansion. The aim of this study is to examine the biomechanical properties regarding the wire diameter and bending of different stainless steel wires to evaluate their potential for incorporation into maxillary aligner therapy. Materials and Methods: Three rectangular stainless steel wires (0.016″ × 0.022″, 0.017″ × 0.025″, and 0.019″ × 0.025″) were tested for mechanical expansion forces in the intermolar region, comparing non-tooth-shaped bent wires (A groups) and tooth-shaped bent wires (B groups). Using a Z010 testing machine (ZwickRoell GmbH and Co. KG, Ulm, Germany), expansion forces were measured at 1 mm intervals over a 5 mm distance, with 15 samples analyzed per group. Statistical analyses included the Shapiro–Wilk test for normal distribution, the Mann–Whitney U test, which revealed significant results (U = 225, p &lt; 0.001), and the Kruskal–Wallis test, which indicated significance (H = 39.130; df = 2; p &lt; 0.001). Results: Tooth-shaped bent wires exhibited significantly lower expansion forces than non-tooth-shaped bent wires for all tested wire types. This difference was most notable in wires with larger transverse profiles (0.019″ × 0.025″), where the tooth-shaped bent wires displayed a marked reduction in mechanical load capacity. Specific force measurements for non-tooth-shaped wires ranged from 760.61 ± 79.51 mN at 1 mm of deformation to 2468.46 ± 66.27 mN at 5 mm of deformation, while tooth-shaped wires ranged from 116.80 ± 3.74 mN to 1979.49 ± 23.23 mN. Conclusions: These findings suggest that non-tooth-shaped bent wires offer a more efficient and uniform expansion potential for maxillary movements due to their stable elastic properties. Clinically, integrating non-tooth-shaped stainless steel wires into aligner therapy may provide a viable method for maxillary expansion, supporting both first- and second-order movements in orthodontic treatment. Further research is needed to explore the integration of such wires for effective maxillary expansion in aligner therapy.

Design, Development, and Characterization of Cross Beam Force Transducer for Low Force Measurement

Design, Development, and Characterization of Cross Beam Force Transducer for Low Force Measurement

Excess Molar Viscosities and Excess Molar Gibbs Energies of The Mixtures of Tire Pyrolytic Oil + Diesel Fuel at 293.15 K and 303.15 K

Diesel-like fuel mixtures are obtained by blending the pyrolytic oil obtained from the pyrolysis of tires and diesel fuel. The excess thermodynamic properties of blended fuel mixtures give a preliminary idea about the transport, storage and combustion properties of the fuel mixture. In this study, pyrolytic oil and diesel fuel were mixed in different proportions at temperatures of 293.15 K and 303.15 K and their excess molar properties were determined. A positive deviation was observed in the excess molar volume and excess molar Gibbs energy values of the two-component mixture, and a negative deviation was observed in the excess molar viscosity values. Volumetric expansion and flow rate of the mixture were found to be higher at 303.15 K. It has been observed that at low pyrolytic oil concentrations, dispersive and physical forces are dominant between molecules, while at high pyrolytic oil concentrations, π-π interactions are more dominant for the molecules.

Development and validation of a portable device for lab-free versatile nucleic acid extraction.

Nucleic acid testing (NAT) has revolutionized diagnostics by providing precise, rapid, and scalable detection methods for diverse biological samples. These recent advancements satisfy the increasing demand for on-site diagnostics, yet sample preparation remains a significant bottleneck for achieving highly sensitive diagnostic assays. There is an unmet need for compatible, efficient, and lab-free sample preparation for point-of-care NAT. To address this, we developed a portable, lab-free, and battery-powered device for extracting nucleic acids. We explored using low centrifugal forces with existing commercial chemistry, demonstrating excellent performance. We designed and tested a battery-powered device to enable lab-free extractions, and verified reagents stored out to 6 months, suggesting exceptional deployment capabilities. We evaluated our device, comparing our results against those from a benchtop centrifuge across three types of samples: HIV RNA in buffer, HIV RNA in plasma, and SARS-CoV-2 RNA in saliva. The portable device demonstrated excellent agreement with the benchtop centrifuge, indicating high reliability. By providing an effective on-site sample preparation solution, the widespread adoption of low centrifugal extractions will improve the sensitivity and reliability of NAT and will positively impact other point-of-care technologies such as next generation sequencing (NGS), biomarker detection, and environmental monitoring.

Investigation of MoSe2 filled MAO Coating on TC6 alloy- tribological and corrosion characterization of multiple interface structure

To enhance the tribological properties and corrosion resistance of titanium alloys, this study proposes a novel tribological interface structure combining micro-arc oxidation ceramic coatings with MoSe2. Comprehensive analysis using X-ray diffractometry, profilometry, energy-dispersive spectroscopy, and scanning electron microscopy was conducted to evaluate the tribological characteristics of this structure under dry friction and liquid lubrication conditions. Electrochemical experiments assessed the corrosion resistance of the structure. The results indicated that under 3 N-2.5 cm/s, oil lubrication, the structure exhibited the best friction-reducing and lubricating performance, with the friction coefficient reduced by 75 %. The synergistic interaction between the low shear force MoSe2 particles and the TiO2-rich ceramic coating formed a lubricating layer on the surface, thereby achieving reduced friction and enhanced wear resistance. Additionally, this structure demonstrated excellent corrosion resistance. This study provides valuable insights for integrating micro-arc oxidation with new materials in engineering applications.

CMIP6 Models Underestimate Arctic Sea Ice Loss during the Early Twentieth-Century Warming, despite Simulating Large Low-Frequency Sea Ice Variability

Abstract The variability of Arctic sea ice extent (SIE) on interannual and multidecadal time scales is examined in 29 models with historical forcing participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6) and in twentieth-century sea ice reconstructions. Results show that during the historical period with low external forcing (1850–1919), CMIP6 models display relatively good agreement in their representation of interannual sea ice variability (IVSIE) but exhibit pronounced intermodel spread in multidecadal sea ice variability (MVSIE), which is overestimated with respect to sea ice reconstructions and is dominated by model uncertainty in sea ice simulation in the subpolar North Atlantic. We find that this is associated with differences in models’ sensitivity to Northern Hemispheric sea surface temperatures (SSTs). Additionally, we show that while CMIP6 models are generally capable of simulating multidecadal changes in Arctic sea ice from the mid-twentieth century to present day, they tend to underestimate the observed sea ice decline during the early twentieth-century warming (ETCW; 1915–45). These results suggest the need for an improved characterization of the sea ice response to multidecadal climate variability in order to address the sources of model bias and reduce the uncertainty in future projections arising from intermodel spread. Significance Statement The credibility of Arctic sea ice predictions depends on whether climate models are capable of reproducing changes in the past climate, including patterns of sea ice variability which can mask or amplify the response to global warming. This study aims to better understand how latest-generation global climate models simulate interannual and multidecadal variability of Arctic sea ice relative to available observations. We find that models differ in their representation of multidecadal sea ice variability, which is overall larger than in observations. Additionally, models underestimate the sea ice decline during the period of observed warming between 1915 and 1945. Our results suggest that, to achieve better predictions of Arctic sea ice, the realism of low-frequency sea ice variability in models should be improved.

Optimal drag-based collision avoidance: Balancing miss distance and orbital decay

The increasing number of objects in Low Earth Orbit makes active collision avoidance imperative for satellites operating in this region. For satellites non equipped with propulsion systems, the collision risk can be mitigated by exploiting the active modulation of aerodynamic forces through the ballistic coefficient. This article proposes a novel and high-fidelity optimal control approach for collision avoidance via aerodynamic drag modulation for an unpropelled SmallSat. Central to this approach is a cost function that jointly maximizes the miss distance while minimizing orbital decay during the maneuver. Moreover, the proposed approach has been rigorously tested through its application to the real-world scenario of the SOURCE satellite, slated for launch in 2025. For the satellite under investigation and a maneuver altitude of 350km, an in-track separation distance of around 22km can be accomplished within a warning time of 24h, which is large enough to conclude that the collision was successfully avoided. As a downside, however, this results in an additional loss in the semi-major axis of 165m and thus a reduced lifetime of the satellite. This balance between separation distance and additional loss in altitude can be flexibly adjusted by the user, which is demonstrated extensively in the article by means of a parameter study. Compared to the widespread use of chemical propulsion systems, this strategy naturally demands longer warning times due to the significantly lower available forces, and also radial offsets to the potential collision object cannot be in this case. Nevertheless, it offers a very promising alternative for active collision avoidance, especially for low-altitude applications.

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.

Applied forces with high vs. low resuscitation table during neonatal ventilation: a randomized crossover manikin study.

In a neonatal manikin model, the lower force applied during positive pressure ventilation with the resuscitation table at the operator's navel may be a desirable goal, but the clinical validations should be assessed in further studies. clinicaltrial.gov NCT06254651. • Apnoea and bradycardia may occur more frequently when higher forces are exerted during face mask ventilation in preterm infants immediately after birth • As the quality of the ventilation may be influenced by procedure-related factors such as the position of the patient, we hypothesized that the height of the resuscitation table could influence the applied forces during the procedure. • In a neonatal manikin model, the lower force applied during face mask ventilation with the resuscitation table at the operator's navel may be a desirable goal. • Further studies in a clinical setting are warranted.

Effect of carbon black properties on cut and chip wear of natural rubber

The effect of carbon black colloidal properties on cut and chip wear of natural rubber compounds is investigated across a wide range of applied impact normal forces using an Instrumented Cut and Chip Analyzer (ICCA). The objective of the study is to determine the basic fatigue and fracture mechanisms that drive cut and chip wear. Natural rubber compounds reinforced with eight different carbon blacks varying in structure and surface area are studied. The loading of the carbon blacks in the rubber compounds is fixed at 50 parts per hundred rubber (phr). The cut and chip performance strongly correlates to both the carbon black morphological properties and the resulting compound mechanical and fracture properties. The cut and chip performance also depends on the applied impact normal force level. At low forces, high structure carbon blacks result in compounds which are stiffer and deflect less under the applied impact normal forces and minimize cut and chip wear. At high forces, low structure carbon black compounds, which are softer and more readily able to crystallize under force-controlled deflection, minimize cut and chip wear. It is argued that at low applied impact normal forces, the cut and chip behavior is dominated by a force-controlled fatigue crack growth mechanism which transitions to a critical tearing energy dominated mechanism at high applied impact normal forces. It is therefore important to understand the severity of application to select optimum compound properties such as the carbon black type to minimize cut and chip wear in application.

Influence of insulating and conducting walls on magnetohydodynamic flow in a suddenly expanded channel: A numerical study

ABSTRACT In this study, we conducted numerical simulations using the robust code AnuPravaha. The code’s performance was rigorously validated by benchmarking it against a range of standard cases, including Shercliff and Hunt’s cases. The same AnuPravaha code is used to identify the effect of conduction and insulating walls on a suddenly expanded channel for low Hartmann number ranging from 10–100 and Reynolds number ranging from 100–500. The results finding indicate that at a low Hartmann number Ha ≤ 40, the effect on the flow profile remains negligible. As the Hartmann number increases Ha > 40, it generates a more crescent-shaped profile, reducing the centerline flow velocity and increasing it near the side walls. It is also observed that variations in pressure drop are minimal within the low Hartmann number range of Ha = 10–30 but become very significant for a higher Hartmann number (Ha > 30). For a change in Hartmann number from Ha = 20 to Ha = 40, the pressure drop rises by 212% and at Hartmann number from Ha = 50 to Ha = 100, it increases by 284% indicating an amplification effect on the magnetic field at a higher Hartmann number. The pressure drop achieved in Insulating walls is far lesser than the conduction walls as insulating walls don’t allow any current-wall interaction. It is found that by using insulating walls the average pressure drop is reduced by about 94%. At a fixed Reynolds number, insulating walls yield higher outlet velocities than conduction walls due to lower Lorentz force resistance which modifies the volumetric heating effects. Increasing Hartmann number reduces the velocity difference between both types of walls.

Biomechanical Insights in Ancient Greek Combat Sports: A Static Analysis of Selected Pottery Depictions

Background: Though ancient Greece preserves many pictures of combat sports, there is limited research in terms of biomechanical analysis of their sports. This research aimed to investigate the Pankration postures of ancient Greek athletics, expecting to bridge the gap between historical sports practices and contemporary biomechanical applications. Methods: This study employed computer vision (OpenPose) to analyze two images, one as readiness and another as kicking postures, from ancient Greek Pankration by constructing a static multi-segmental model. Using Newton’s Laws, the models simulated the postures as presented in historical depictions, estimated joint forces and moments, and calculated weight distribution and ground reaction forces for these postures. Results: For the readiness posture, it was found that the right hind leg experienced significant forces, with the highest moment at the knee joint, while the ankle and hip joints showed similar slightly lower moments. The front leg encountered lower forces and moments. For the kick posture, the supporting leg experienced the highest moment at the knee, while the kicking leg showed minimal moments at the ankle, knee, and hip. Conclusions: The static analysis provided quantitative estimates of joint forces and moments in the depicted Pankration postures, suggesting that these postures were biomechanically effective for their intended functions in combat. While the analysis cannot confirm whether ancient athletes deliberately applied biomechanical principles, the results highlight the potential of biomechanical modeling to enhance our understanding of ancient sports practices. The research demonstrates the possible benefits of integrating static analysis with historical elements to study the physical demands and techniques of ancient combat sports.

Inovasi Transportasi Modern: Pemanfaatan Medan Elektromagnetik pada Kereta Maglev dan Kendaraan Listrik

The introduction of electromagnetic devices into modern transportation has revolutionized mobility and enabled more rapid, efficient, and reliable solutions. This study examines the use of electromagnetic devices in Maglev and listrik (EV) keretas. Utilizing magnetic levitasi, EV uses electromagnetic principles to propel its hemat energy, whereas Maglev achieves high-speed transportation with low force. This study identifies key technologies, their benefits, and challenges in implementing the system in question. It also examines the system's global impact on energy consumption and environmental degradation. All of this indicates that more extensive innovation and investment in electromagnetic transportation can speed up transitions to ramah lingkungan mobility.

Autoantibodies immuno-mechanically modulate platelet contractile force and bleeding risk

Altered mechanotransduction has been proposed as a putative mechanism for disease pathophysiology, yet evidence remains scarce. Here we introduce a concept we call single cell immuno-mechanical modulation, which links immunology, integrin biology, cellular mechanics, and disease pathophysiology and symptomology. Using a micropatterned hydrogel-laden coverslip compatible with standard fluorescence microscopy, we conduct a clinical mechanobiology study, specifically focusing on immune thrombocytopenia (ITP), an autoantibody-mediated platelet disorder that currently lacks a reliable biomarker for bleeding risk. We discover that in pediatric ITP patients (n = 53), low single platelet contraction force alone is a “physics-based” biomarker of bleeding (92.3% sensitivity, 90% specificity). Mechanistically, autoantibodies and monoclonal antibodies drive increases and decreases of cell force by stabilizing integrins in different conformations depending on the targeted epitope. Hence, immuno-mechanical modulation demonstrates how antibodies may pathologically alter mechanotransduction to cause clinical symptoms and this phenomenon can be leveraged to control cellular mechanics for research, diagnostic, and therapeutic purposes.

Effect of kinematics on ground reaction force during single-leg jump landing in children: a causal decomposition approach in jumpers and non-jumpers.

The interaction between joint kinematics and kinetics is usually assessed by linear correlation analysis, which does not imply causality. Understanding the causal links between these variables may help develop landing interventions to improve technique and create joint-specific strengthening programs to reduce reaction forces and injury risk. Therefore, the aim of this study was to analyze the causal interaction between lower limb sagittal kinematics and vertical ground reaction force (VGRF) during single-leg jump landing in children who are jumpers (volleyball and gymnastics) and non-jumpers, using the causal empirical decomposition method. Our hypothesis is that children who participate in jumping sports, compared to those who do not, employ a different joint strategy to regulate ground reaction forces during landing, particularly at the ankle level. Two groups were compared: the jumpers group (n = 14) and the non-jumpers (control group, n = 11). The causal interaction between sagittal kinematics and VGRF was assessed using ensemble empirical mode decomposition (EEMD) and time series instantaneous phase dependence in bi-directional causality. The relative causal strength (RCS) between the time series was quantified as the relative ratio of absolute cause strength between kinematics and VGRF. A significant interaction between joint and group was found for RCS (p = 0.035, η 2 p = 0.14). The post-hoc analysis showed the jumpers group had higher ankle-to-VGRF RCS than the control group (p = 0.017, d = 1.03), while in the control group the hip-to-VGRF RCS was higher than the ankle-to-VGRF RCS (p = 0.004, d = 0.91). Based on the causal decomposition approach, our results indicate that practicing jumping sports increases the causal effect of ankle kinematics on ground reaction forces in children. While non-jumper children rely more on the hip to modulate reaction forces, jumper children differ from non-jumpers by their greater use of the ankle joint. These findings could be used to develop specific training programs to improve landing techniques according to practice level, potentially helping to reduce the risk of injury in both athletes and non-athletes.