Vertical Force Research Articles

EFFECT INITIAL FOOT POSITION HAS ON WEIGHT DISTRIBUTION SYMMETRY AND FORCE PRODUCTION DURING A SIT-TO-STAND TASK IN OLDER ADULTS

INTRODUCTION AND AIMS Transitioning from a seated position to standing is an important component to everyday living which can be affected by age-related muscle strength loss. Changing foot position has been found to affect a sit-to-stand transition in healthy younger populations however the effect it has on healthy older populations is unknown. The aim of this study was to provide clinicians with greater insight into the effect asymmetrical initial foot positions have on weight distribution symmetry and force production during a sit-to-stand transition in adults over 60 years of age. METHODS Three symmetrical and six asymmetrical initial foot positions were investigated on two separate testing sessions. The maximum vertical ground reaction forces collected from each foot placed on individual Kistler force platforms were used to calculate body weight symmetry percentage. RESULTS Body weight symmetry reduced when the dominant foot was moved posteriorly 1/3 and 2/3 participant’s foot length compared to the symmetrical positions (102-107%). When the non-dominant foot was moved posteriorly by 1/3 and 2/3 the participant’s foot length, body weight symmetry increased (99-102%) above the symmetrical positions. Maximum vertical ground reaction forces occurred (5.6-6.2N/kg) in the asymmetrical positions with the anterior foot positioned in neutral. CONCLUSIONS Asymmetrical foot positions which involved shifting one extremity posteriorly by 1/3 or 2/3 the participant’s foot length reduced transitional stability but increased force production. These results will help guide clinicians to scaffold progressions when prescribing sit-to-stand exercises to rehabilitate unilateral strength deficiencies within an older population.

Anterior-Posterior Center of Pressure Is Associated With Knee Extensor Moment During Landing After Anterior Cruciate Ligament Reconstruction.

A reduced knee extensor moment (KEM) in the involved limb and asymmetry in the KEM during landing tasks are observed after anterior cruciate ligament reconstruction (ACLR). There is limited information about the association of kinetic and kinematic parameters with the KEM during landing after ACLR. This study investigated the association of the anterior-posterior center of pressure (AP-COP) position, vertical ground reaction force (VGRF), and lower limb joint angles with the KEM during landing in female athletes following ACLR. Cross-sectional study. Twenty-two female athletes who underwent ACLR performed a drop vertical jump at 7.9 (1.7)months after surgery. We evaluated the KEM, AP-COP position, VGRF, and sagittal plane hip, knee, and ankle angles using a 3-dimensional motion analysis system with force plates. The peak KEM in the involved limb was significantly smaller than that in the uninvolved limb during landing (1.43 [0.33]N·m/kg/m vs 1.84 [0.41]Nm/kg/m, P = .001). The VGRF in the involved limb was significantly smaller than that in the uninvolved limb (11.9 [2.3]N/kg vs 14.6 [3.5]N/kg, P = .005). The limb symmetry index of the KEM was predicted by that of the VGRF (P < .001, R2 = .621, β = 0.800). The KEM was predicted by the AP-COP position in the involved limb (P = .015, R2 = .227, β = 0.513) and by the VGRF in the uninvolved limb (P = .018, R2 = .213, β = 0.500). No significant correlation was noted between the KEM and the lower limb joint angles. The AP-COP position and VGRF were associated with the KEM during landing. Evaluating the VGRF and AP-COP position, not the lower limb joint angles, may contribute to understanding the KEM during double-leg landing after ACLR in the clinical setting.

Vertical and Horizontal Force Measurements of a Double Crossed Loop

Vertical and Horizontal Force Measurements of a Double Crossed Loop

The influence of the number of loaded teeth on the distribution of occlusal vertical forces in onesided dental bridges with one distal cantilever

Aim: The paper aims to analyze the distribution of occlusal vertical forces on the abutment teeth in singlesided dental bridge constructions, in slightly shortened dental arches with one distal extension/cantilever, depending on the number of occlusal units. Materials and methods: In five mathematical models with a slightly shortened dental arch in the lower jaw, a single-sided dental bridge was constructed with 5 abutment teeth and one distal cantilever. A finite element method (FEM) was applied. Occlusal loading was done with simulated occlusal vertical forces of 0.5- 512N. Forces were applied on the occlusal surfaces of the teeth. The loading was done as follows: in Model 1 – on the distal cantilever, in Model 2 - on the distal cantilever and the distal abutment tooth, in Model 3 - on the distal cantilever and the two distal abutment teeth, in Model 4 - on the distal cantilever and the three distal abutment teeth, in Model 5 - on the distal cantilever and all abutment teeth. Distributed forces are measured at the level of the periodontal ligament (PDL). Results: The percentage comparison of distributed forces on the abutment teeth in the examined models 1, 2, 3, 4 and 5 indicates a different distribution of occlusal vertical forces between the models. The most even distribution of the percentage of occlusal vertical forces was observed in model 5, followed by Model 4 and Model 3, while the most unfavorable distribution was noted in model 1 and model 2. In all 5 models, the highest percentage of force is distributed on the distal abutment tooth, with the highest percentage noted in model 1. As the number of loaded teeth increases in models 2, 3, 4 and 5, the percentage of distributed force decreases with the lowest percentage of distributed forces found in model 5. There is a significant difference in the distributed forces percentage values on the distal abutment tooth in model 1 and model 5. In Model 1 it ranges from 92.39% to 148.45%, and for Model 5 from 38.09% to 48.02%. In Model 5 and model 4, the direction of the distributed force in all teeth aligns with the direction of the applied force, which means that the fixed construction in models 4 and 5 is the most stable. Conclusion: The percentage of distributed forces on the abutment teeth is in correlation with the number of teeth loaded. In order to achieve a well-balanced, single-sided dental bridge construction in slightly shortened dental arches with one distal cantilever, the occlusal load must be applied on at least three distal abutment teeth.

Optimal strategy of the asymmetric wave energy converter survival in extreme waves

Enhancing the survival performance of wave energy converters (WECs) in extreme wave conditions is crucial, and reducing wave loads is a key aspect of this. Placing the device underwater has been recognized as a beneficial strategy, yet the determination of the optimal submerged depth and the effects of varying wave conditions remain ambiguous. To address this, the study numerically analyzes the total forces in both horizontal and vertical directions, along with their harmonic components, across different wave configurations. A computational fluid dynamics method is employed to investigate a triangular-baffle bottom-shaped oscillating floater, which is known for its high energy conversion efficiency. The findings indicate that submerging the device to a depth equivalent to half the actual focused amplitude (1/2Ab) is the most effective strategy in the given sea state, offering superior wave force reduction vertically and robust performance horizontally. The analysis of harmonics reveals the significant contribution of high-order components to the total wave forces. Additionally, the study examines the impact of focused wave amplitudes and peak frequencies, showing that although force reductions are lessened in more extreme conditions, the optimal submerged depth of 1/2Ab still yields near 30% reduction in total vertical force and 22% in total horizontal force. This research provides theoretical insight that can guide the enhancement of WECs' survival capabilities in practical engineering applications.

Optimal design and experiment of bionic vacuum suckers with high attachment properties

A variety of bionic vacuum suckers with papillae structures of different parameters were developed to improve the attachment performance of vacuum suckers. The oral sucker of the suckermouth catfish served as the bionic prototype and bionic suckers were made by taking the diameter of papillae, the number of single rows of papillae, the center distance between adjacent rows of papillae, and the distance between the outermost row of papillae and the edge as influencing factors. The single-factor tests and response surface tests were carried out respectively with the growth rates of vertical and horizontal attachment forces as the response values. Twenty-five groups of bionic suckers and one group of standard suckers were fabricated and tested for attachment forces. The experimental results revealed that the bionic suckers had higher vertical and horizontal attachment forces than standard suckers and that their maximum growth rates for these forces were 5.16% and 59.87%, respectively. This suggested that the bionic suckers had better attachment performance. The significant orders of the factors affecting response values were established and their interaction was also analyzed. Besides, the optimal parameter combination of papillae structures of the bionic suckers with optimal vertical and horizontal attachment properties was obtained, respectively. Finally, the influence mechanism of papillae structures on the attachment properties of bionic suckers was analyzed. The studies can serve as a guide for the application of bionic suckers in agricultural production areas such as fruit picking and handling, and the improvement of attachment performance of associated machinery.

Determining the shape of a flexible thread in the field of horizontal and vertical forces

In theoretical mechanics, the equilibrium of a flexible, inextensible thread is considered, to which the tension force of its ends and the distributed force of weight along the length of its arc are applied. An unsolved problem is finding the shape of the thread under the action of other distributed forces. This study has considered the equilibrium of a completely flexible thread, to which, in addition to this force, a transverse distributed force is applied. A sail serves as an example. Wind of equal intensity in the plane of the orthogonal section of the sail can be considered a distributed force. The sail can be cut into narrow strips with the same shape of the curves of the cross-section, which are equal to the cross-section of the sail as a whole. The theory of flexible thread is applied in the current study. The task is reduced to finding the curve of the cross-section of the sail. The object of research is the formation of a cylindrical surface from a flexible thread under the action of distributed forces applied to it. An important characteristic of the shape of a flexible thread is its curvature. Its dependence on the length of the arc was found and it was established that the found curve is a chain line (catenary). This is the feature of the current research and its distinguishing characteristics. The significance of the results stems from the derived analytical dependences, according to which the change in the ratio between the distributed forces acting on the flexible thread deforms it, but it retains the shape of the catenary. At the same time, the angle of deviation of its axis of symmetry from the vertical changes. In the absence of a horizontal distributed force and the presence of only a distributed force of weight, the axis of symmetry of the chain line is directed vertically – at an angle of 90° to the horizontal. If they are equal, this angle is 45°. Scope of application includes structures with stretched supporting wires, conveyor belts, flexible suspended ceilings, the shape of which can be calculated by using our results

Numerical analysis on tractor axle suspension for steering instability induced by bump disturbances

In Japan, small agricultural tractors without axle suspensions used on bumpy farm roads experience severe vibrations. Excessive vibrations often cause tyres to lose contact with the supporting ground or decrease the vertical tyre force such that the cornering force exceeds the static friction limit. The resulting bouncing and sliding motions induce steering instability, resulting in overturning accidents. This study investigated the effectiveness of axle suspension in alleviating bump disturbance-induced steering instability in small tractors. A step lane change test involving bump disturbances was newly proposed for the steering stability testing of small tractors. The numerical experiments compared four axle suspension structures: no-, front-, rear-, and full-suspensions. The results showed that bump disturbances induce steering instability in the no- and rear-suspension tractors. In contrast, the front- and full-suspension structures significantly improved the steering stability of the tractor by keeping the steering wheel in contact with the ground. The proposed testing method helped evaluate improvements in the steering stability brought about by increasing the ground contact of the steering wheel. Our results can aid in designing and testing suspension systems for small tractors.

Dynamic Load Analysis of Mine-Truck Using Multibody Dynamic Analysis Method

Abstract: Vehicle load distributed on front &amp; rear axle assembly during various working conditions is one of the most important factors influencing working performance and service life of drive axle assembly. The dynamic load on axle assembly is higher compared to the rated load because of variations in vehicle speed and road surface conditions. Early failure of structural components is caused because of higher dynamic reaction forces due to uneven road profiles. The dynamic load calculation of axle assembly is presented in this paper for a Mine-truck with various road conditions and vehicle speeds. The road load conditions consist of grade, bump &amp; path hole. Mine-truck with payload capacities of 63 Ton is considered for the study. The behaviour of vertical force is calculated for different vehicle speeds (3 - 12 km/hr.) of the machine on the front &amp; rear axle assembly during running conditions. Multi-body dynamic Analysis tool ADAMS is used for this study. ADAMS helps to study the dynamics of moving parts and load distribution throughout mechanical systems during motion. The Mine-truck3D model was created with the help of computer-aided design (CAD) software. Major units of Mine trucks are considered to prepare 3D models like Cabin-engine mass, Bucket, front axle assembly, rear Axle assembly &amp; tires. Multi-body vehicle models are prepared in simulation software ADAMS by importing 3D models prepared by computer-aided design (CAD) software. This provides guidelines for selecting dynamic load factors while designing structural parts of the vehicle.

Combined Pullout Tests And Wave Overtopping Simulations On Three Species-Rich Grass Covered Dikes In The Netherlands

Grass cover erosion by wave overtopping is a major failure mechanism for earthen dikes. Grass cover erosion resistance (represented by the critical velocity, Uc) can be assessed using full-scale, destructive tests with the wave overtopping simulator (WOS) in combination with the erosion model ‘cumulative overload method’ (COM). Although these tests provide valuable information, they are relatively expensive and time consuming. Therefore, a small-scale grass pullout test (GPT), which translates the vertical pullout force of a grass sod to a Uc, may be an attractive alternative. In this paper, based on comparative testing with the WOS and GPT on three species-rich grass covers on dikes in the Netherlands, we assess the correspondence between the Uc obtained with the WOS and GPT for species-rich grass covers. Ultimately, by also including historical tests, we aim to get more insight into the suitability of the GPT for quantitative erodibility assessment of grass covers in general. During testing with the WOS, no failure was observed for the tested grass cover sections. Therefore only a lower bound of the Uc could be derived. Results indicate that the estimated Uc with the GPT is around the lower bound values obtained with the WOS. This is in line with previous tests on conventional grass covers, for which the GPT provides a more conservative estimate of the Uc than the WOS. Adaptations in the translation from pullout force to Uc may correct for the negative bias and hence improve the reliability of the GPT for quantitative erodibility assessment. Several suggestions to adapt the GPT in future work are provided in this paper. These adaptations should be tested and validated for conventional as well as species-rich grass covers to guarantee the general applicability of the method.

Nonsurgical synergistic full-arch vertical intrusion treatment of bimaxillary protruded hyperdivergent skeletal Class II malocclusion using aligners.

A bone-borne full-arch vertical control strategy using miniscrews was deployed with aligners to treat a case of skeletal hyperdivergent Class II malocclusion with bimaxillary protrusion. Miniscrews were inserted in the posterior buccal and palatal regions and the anterior buccal region of the maxilla to distribute vertical intrusive force through the upper arch by anchoring vertical elastics from the miniscrews to the aligners. Synergetic lower anterior intrusion was completed using bilateral posterior miniscrews to counteract the extrusive force generated. Substantial full upper arch and lower anterior vertical intrusion was achieved. In conjunction with en masse anterior-posterior retraction, synergetic posterior and anterior vertical intrusion facilitated counterclockwise rotation of the mandible, creating significant esthetic improvement. Anterior vertical elastics also provided flaring of the anterior teeth, reducing the side effect of lingual tipping from en masse retraction, while successfully controlling overbite and incisor torque during space closure. The bone-borne full-arch vertical intrusion strategy can work well with aligners to address hyperdivergent skeletal Class II malocclusion with bimaxillary protrusion.

The phenomenon of anticipation in fencing. An applicability approach.

The aim of the study was to determine the structure of muscular activity and ground reaction forces during the preparatory period and the execution of a fencing lunge at the opponent's torso. The analysis focused on the correlations between three phases of a fencing technical action in the context of factors of temporal anticipation. Six female épée fencers from the Polish National Fencing Team participated in the study. The research tools included electromyography (EMG), ground reaction force (GRF) platforms, and the OptiTrack motion capture system. The fencers performed the lunge three times in response to visual cues from the coach. By integrating the testing system, the EMG signal indices of the fencers' upper and lower limbs and the vertical force values of the fencers' front and rear leg muscles were obtained simultaneously. The results of the study demonstrated the key role of five muscles: BICEPS BRACHII, LAT TRICEPS, EXTCARP RAD, BICEPS FEMORIS and MED GAS in influencing the speed of lunge execution. In addition, a significant correlation was found between the EMG signal of the gastrocnemius muscle of the rear leg and the movement time (MT) phase of the lunge execution. The anticipatory activation of the EMG signal in relation to the vertical force waveforms generated by the ground forces response platform in the 15-30 ms interval was demonstrated. Finally, the importance of the preparatory period for the effectiveness of the fencing lunge was highlighted based on the phenomenon of anticipation.

The Modified Reactive Strength Index Is a Valid Measure of Lower-Body Explosiveness in Male and Female High School Athletes.

Witte, BC, Schouten, TC, Westphal, JA, VanZile, AW, Jones, DD, Widenhoefer, TL, Dobbs, WC, Jagim, AR, Luedke, JA, and Almonroeder, TG. The modified reactive strength index is a valid measure of lower-body explosiveness in male and female high school athletes. J Strength Cond Res 38(8): 1428-1432, 2024-The modified reactive strength index (mRSI) is a commonly used metric to quantify lower-body explosiveness during countermovement jump (CMJ) performance. However, few studies have attempted to examine its validity as a measure of explosiveness, particularly among high school athletes. The purpose of this study was to examine the validity of the mRSI as a measure of lower-body explosiveness among a relatively large sample of male and female high school athletes from various sports. As part of this study, male ( n = 132) and female ( n = 43) high school athletes performed CMJs, while ground reaction forces were recorded using a force platform. The vertical ground reaction force data collected during the CMJs were used to derive the following variables: peak force (PF), peak power, time to PF, time to take-off, peak rate of force development, and the mRSI. Principal component analysis was applied and reduced these variables into 2 components related to "force" and "speed." The mRSI loaded on both the force (loading = 0.82) and speed (loading = -0.46) components, indicating that it incorporates elements of both force and speed, although it loaded more strongly on the force component than the speed component. The observed pattern of cross-loading suggests that the mRSI is generally a valid measure of lower-body explosiveness for male and female high school athletes.

Residual Effects of Same Day Lower Extremity Strength Training on Countermovement Jump Performance in Collegiate Women Athletes.

Balancing of strength programming intensity with sport demands is necessary to avoid excessive workloads that could inhibit performance. To expand previous jump height focused literature, this study evaluated whether countermovement jump (CMJ) movement strategies, including eccentric characteristics, might reveal CMJ execution strategy shifts to achieve similar afternoon CMJ height following a morning resistance training session (RTS). Fifteen collegiate women's soccer and volleyball athletes (18-24 years, 73.6 ± 8.4 kg, 1.74 ± 0.19 m) participating in an offseason RTS completed five CMJs during two afternoon sessions (48 h apart), one 4-6 h post morning RTS, and one on a rest day. The RTS consisted of 2 sets of 10 repetitions at 70-80% 1RM for the back squat, the front squat, and the forward lunge. Vertical ground reaction forces were recorded from which 13 outcome measures describing elements of the eccentric and concentric CMJ phases were computed. No significant differences in jump height (p = 0.427, d = 0.17) or outcome measures (p = 0.091-0.777, d = -0.07-0.21) between sessions with exception of a significant concentric phase time decrease (p = 0.026, d = 0.23) following the RTS were identified. Given the magnitude of the mean concentric phase time change (0.01 s), the result likely has limited practical meaning. As these results confirm previous CMJ height literature, practitioners have further evidence that a morning RTS does not interfere or enhance afternoon CMJ performance in athletic women.

Observe, Practice, and Improve? Enhancing Sidestep Cutting Execution in Talented Female Soccer Players: A Four-Week Intervention Program With Video Instruction.

Nijmeijer, EM, Kempe, M, Elferink-Gemser, MT, and Benjaminse A. Observe, practice and improve? Enhancing sidestep cutting (SSC) execution in talented female soccer players: A four-week intervention program with video instruction. J Strength Cond Res 38(8): e430-e439, 2024-Implicit learning has the potential to improve movement execution and reduce injury risk. Previous research showed beneficial effects of short-term interventions with implicit learning in male athletes. However, research on long-term interventions in female athletes is lacking. The aim of this study was to examine the effects of a 4-week intervention with video instruction on movement execution of SSC, a task that is highly related with anterior cruciate ligament (ACL) injury risk, in female athletes. Twenty talented adolescent female soccer players were part of the control (CTRL, n = 10) or video instruction (VIDEO, n = 10) group. All subjects practiced 4 weeks and received general task instructions. In addition, the VIDEO group received expert video instruction during practice. Lower extremity kinematics and kinetics and vertical ground reaction force of SSC were examined during baseline, immediate post, and 1-week retention tests. After nonlinear registration, differences between each subject and the expert she had seen were determined. These differences were analyzed with SPM1D 2-way ANOVA. No interaction effects between time and group were found ( p > 0.05). Main effects of time were found in the frontal plane. In particular, smaller deviations of subjects compared with the seen expert of the knee adduction ( p = 0.005, 97.9-100% stance phase [SP]) and hip abduction ( p = 0.005, 11.5-13.8% SP) and adduction ( p < 0.001, 33.4-87.7% SP) moments were found in immediate post compared with baseline. These frontal plane short-term improvements, replicating earlier findings in both sexes, may lower ACL injury risk. The large observed interindividual differences over time may have concealed the long-term effects of video instruction at the group level.

Carsim-based simulation study on the performances of raised speed deceleration facilities under different profiles

Objective Studying the optimal profile shape and size of deceleration facilities suitable for low-speed environment roads under different speed control intervals. Methods Simulation modeling of deceleration facilities with various profile shapes and sizes and for vehicles in different speed intervals was performed using the vehicle dynamics simulation software Carsim. The height jumped by a vehicle’s wheels, the vertical force on the wheels, and the vertical acceleration of the vehicle were used as indicators of ride comfort and operational stability for the various deceleration facility profiles. Results stability and comfort were related to the contour of the deceleration facility. Vertical forces were positively related to vehicle jump height, but the jump heights of vehicles passing through deceleration mounds with different planes at the same speed were not significantly different with increasing height. When the vehicle is traveling slowly, the vertical impact force on the vehicle is not significantly related to the speed loss of the vehicle. Conclusions Within the speed range of 20–60 km/h and profile heights of 3–10.5 cm, the effectiveness ratings of circular high width and parabolic were basically at level 2 and level 3, but the circular high width had a more stable jump height and was the best profile form, followed by sinusoidal and parabolic, then isosceles trapezoidal, and lastly conventional speed bumps.

The association of range of motion, lower limb strength, and load during jump landings in professional ballet dancers

This study aimed to investigate the associations between peak plantarflexion ankle joint moments and vertical ground reaction forces (vGRF) during jump landings, and static ankle dorsiflexion range of motion (ROM), three-dimensional ankle excursions, and lower extremity strength in professional ballet dancers. Twenty-seven professional ballet dancers volunteered to participate (men = 14, women = 13). Participants attended one data collection session to measure dorsiflexion ROM and isometric lower extremity strength. Two further sessions were used to establish ankle mechanics and vGRFs during countermovement jump landings in seven foot positions, via a seven-camera motion capture system and piezoelectric force platform. Two linear mixed-effects models were used to investigate associations between the target variables and strength, dorsiflexion ROM, and ankle excursions. Dancer identification, sex, and foot position were entered as random effects. Model fit, when considered independent of random effects, was generally poor with the predictor variables explaining little of the variance of peak plantarflexion ankle joint moments (R2 = 0.02) or vGRF (R2 = 0.01). Model fit improved when random effects were considered (R2 = 0.65 & 0.34). Frontal plane ankle excursion was the only predictor variable with a significant negative association with peak plantarflexion ankle joint moments (p = .016), although coefficient estimates were small. Strength, static ankle dorsiflexion ROM, and three-dimensional ankle excursions are poor predictors of load experienced at a joint and system level in professional ballet dancers. Differences between individuals, sex, and foot position may be better indicators of the load experienced during jump landings.

Experimental and numerical investigation of fairing countermeasure for tsunami forces on three different types of bridge superstructure

By extending Wu et al. (2023)'s research of reducing tsunami loads on bridge decks through fairings and openings, this study aims to optimize fairing designs for three typical bridge superstructures, i.e., T-girders, Single-box girders, and Multi-box girders, and assess the effectiveness of fairings in mitigating hydrodynamic forces from extreme waves. A comprehensive methodology including both experimental testing and numerical simulations is adopted and the load reduction capabilities of fairings for bridge girders is evaluated, where an active machine learning model is utilized to identify the optimal fairing configurations for each bridge type. Key findings include: (a) Well-designed fairings can substantially reduce both horizontal and vertical wave loads, simultaneously avoiding potential structural damages from openings; (b) Under the investigated tsunami bore wave conditions, as the incident tsunami bore wave height increases, the horizontal and vertical forces acting on the fairing structures significantly increase, highlighting the importance of considering these loads in the fairing design; and (c) For the studied three bridge deck structures with the same width and height dimensions, the observed variations in the optimal fairing configurations are minimal, indicating a feasible potential for the standardized implementation of fairing in practical engineering.

Estimation of Vertical Ground Reaction Force during Single-leg Landing Using Two-dimensional Video Images and Pose Estimation Artificial Intelligence.

Assessment of the vertical ground reaction force (VGRF) during landing tasks is crucial for physical therapy in sports. The purpose of this study was to determine whether the VGRF during a single-leg landing can be estimated from a two-dimensional (2D) video image and pose estimation artificial intelligence (AI). Eighteen healthy male participants (age: 23.0 ± 1.6 years) performed a single-leg landing task from a 30-cm height. The VGRF was measured using a force plate and estimated using center of mass (COM) position data from a 2D video image with pose estimation AI (2D-AI) and three-dimensional optical motion capture (3D-Mocap). The measured and estimated peak VGRFs were compared using a paired t-test and Pearson's correlation coefficient. The absolute errors of the peak VGRF were also compared between the two estimations. No significant difference in the peak VGRF was found between the force plate measured VGRF and the 2D-AI or 3D-Mocap estimated VGRF (force plate: 3.37 ± 0.42 body weight [BW], 2D-AI: 3.32 ± 0.42 BW, 3D-Mocap: 3.50 ± 0.42 BW). There was no significant difference in the absolute error of the peak VGRF between the 2D-AI and 3D-Mocap estimations (2D-AI: 0.20 ± 0.16 BW, 3D-Mocap: 0.13 ± 0.09 BW, P = 0.163). The measured peak VGRF was significantly correlated with the estimated peak by 2D-AI (R = 0.835, P <0.001). The results of this study indicate that peak VGRF estimation using 2D video images and pose estimation AI is useful for the clinical assessment of single-leg landing.

Effects of key parameters of hybrid cable-stayed suspension bridge on the fatigue resistance of side hangers in bonding zones

Hybrid cable-stayed suspension bridges (HCSBs) have excellent mechanical and spanning capacities. However, their hangers in the bonding zones experience high cyclic stresses, and their fatigue failure jeopardize HCSB safety. This study adopted a HCSB finite element model and applied the influence line method to assess the effects of the following six factors on the stress amplitudes of side hangers: ratio of hanger force to vertical force in the stay cable in the bonding zone, relative stiffness of the main beam in the bonding zone, number of hangers in the bonding zone, arrangement pattern of stay cables and hangers, suspension-to-span ratio, and number of auxiliary piers. The exemplary HCSB had asymmetric span arrangement and a main span of 1400 m. Nodal loads were imposed on the main beam in the entire bridge to obtain the influence lines of each hanger and identify the most unfavorable hanger. The values of the above six parameters of the model varied to obtain the new influence lines of each hanger and identify the most unfavorable hanger in the new reasonably completed state. The stress amplitudes of the hangers thus obtained ware compared with those in the original model, reflecting the effects of these six factors on the stress amplitudes in the most unfavorable hanger. Based on the above, the cyclic stress amplitudes of the side hangers were reduced by installing additional stay cables with optimization of their arrangement pattern and relative cross-sectional areas. The results are considered instrumental in improving the fatigue resistance of HCSBs hangers under realistic bridge engineering scenarios.