Fall Height Research Articles

Traumatic spinal cord injuries due to falls from trees in a tertiary rehabilitation center: a retrospective analysis of causes and outcomes

Aims: Falls from heights are a major cause of spinal cord injury. In developing countries such as Turkey, where fruit picking from trees is an important part of the agricultural economy, falls from trees are common. This study aims to comprehensively analyze the causes and consequences of spinal cord injuries due to falls from trees. Methods: This retrospective study reviewed cases of spinal cord injury resulting from falls from trees, treated at a tertiary rehabilitation center between March 2020 and November 2023. Data encompassed demographics (age, gender, occupation, education), spinal injury specifics (level, severity), additional injuries, tree fall details (type of tree, height of fall, cause of fall, safety precautions), and treatment details (surgery need, hospital stay duration). The patients who fell from trees were divided into two groups: those who fell from walnut trees and those who fell from other trees, and statistical analyses were performed accordingly. Results: Among the 49 patients falling from trees, the mean age was 52.3 ± 13.4 years, with 73.5% being male, 32 patients (%65.3) had graduated from primary or secondary school. No safety precautions were taken by any participants. Paraplegia (%87.8) and complete spinal cord injuries (57.1%) were common. Additional injuries occurred in %61.2 of cases. In terms of fall causes, the most common was branch breakage (%57.1), while walnut trees accounted for %44.9 of falls. There was a significant difference in education levels between the group that fell from walnut trees and the group that fell from other trees (p:0.028). Falls from walnut trees resulted in higher fall heights, complete injury rates, and longer hospital stays (p:0.003, p:0.047, p: 0.010). Conclusion: This study found that spinal cord injuries from falls often lead to additional injuries, with none of the patients taking safety precautions. This study found that walnut trees were the most common cause of spinal cord injury from falling trees. This study highlights the need for improved safety precautions and educational interventions.

Optimal design of deep stormwater drainage tunnels to address urban flooding in Korea

Deep stormwater drainage tunnels play a crucial role in mitigating severe urban flooding in Korea, particularly as climate change leads to more extreme weather events. These tunnels typically consist of an entrance reservoir, a circular reinforced concrete culvert with a flat slope, a downstream reservoir, and an outlet to a nearby river. In this system, the flow within the circular culvert is driven solely by the momentum of free-falling stormwater runoff. However, concerns have emerged within the Korean water resources engineering community about the drainage capacity of these tunnels, even with a substantial fall height of approximately 30 m. Intensified localized rainfall, the abrupt transition from flood waves to pressurized flow within the circular culvert, and trapped air pockets can also pose significant challenges to the tunnel’s drainage efficiency. Conventional design methods often fail to optimize the culvert’s diameter and spatial configuration, leading to suboptimal performance. In response, this study utilizes 3D numerical simulations with the interFoam solver from the OpenFOAM toolbox to address these issues. The results indicate that smaller culvert diameters—provided they do not exceed the maximum permissible flow velocity—enhance drainage capacity by reducing the impact of shock waves and stabilizing flow. These findings challenge the prevailing design practice in Korea, which holds that larger culverts inherently offer superior drainage capacity. Moreover, the simulations suggest that as culvert diameters increase, the size of trapped air pockets grows, further reducing efficiency. Although air chambers can help mitigate the retarding effects of trapped air pockets, their effectiveness diminishes if positioned near the origin of shock waves, where they risk being filled with stormwater. Based on these insights, several key recommendations are proposed: First, the design of deep stormwater tunnels should prioritize minimizing the extent of trapped air pockets, even when air chambers are used. Second, the current focus on detention capacity in design practices should be reevaluated, as excessive detention capacity may exacerbate air pocket formation. Finally, modifying the inlet channel to induce spiral flow within the entrance reservoir could reduce impulsive forces, lower maintenance costs related to armoring rocks at the reservoir bottom, and stabilize flow more quickly, thereby enhancing overall drainage capacity.

Experimental and numerical analysis of the fluid flow behavior of a tank corner impacting a water surface

The interaction of a tank impacting a water surface is an extremely complex nonlinear multiphase flow phenomenon. In this study, experiments and numerical simulations are used to systematically investigate the flow physics and load characteristics of a tank corner impacting a water surface. Free surface flow at different fall heights (200–800 mm) and inclination angles (0°–15°) was obtained through free fall experiments. The volume of fluids method and overset grid technology were used to simulate the water impact process of a three-dimensional structure accurately. For typical bubble flows, the numerical and experimental results agree well. On the basis of the three-dimensional flow characteristics and pressure distribution, flow behaviors, such as fluid climbing, corrugation disturbances, and air cavity effects, are analyzed. Bubble flow has a significant effect on the behavior mode of the impact load. In particular, the bubbles at the upper wall play a key role in the load characteristics at different locations. In addition, the influences of corrugations inside the tank's corner and the impact velocity on fluid flow were investigated. These results provide beneficial references for an in-depth understanding of the fluid flow and load characteristics between a tank and fluid.

MEASUREMENT OF WATER DISCHARGE OF SAKARTEMEN RIVER TO IDENTIFY POTENTIAL OF MICRO HYDRO POWER PLANT IN FAKFAK REGENCY

Fakfak Regency, West Papua Province is one of the oldest regencies in Papua. However, electricity problems are still a scourge that has not yet been resolved properly. So far, the mainstay of power plants in Fakfak Regency is the Diesel Power Plant (PLTD) which is highly dependent on the supply of Fuel Oil (BBM) and the reliability of the Diesel Engine. In fact, Fuel Oil (BBM) is one of the natural resources that cannot be renewed. For this reason, it is necessary to conduct a study on New Renewable Energy (EBT) that has the potential to be developed in Fakfak Regency. There are several rivers that have the potential to be developed as Micro Hydro Power Plants (PLTMH) in Fakfak Regency. The existence of Micro Hydro Power Plants (PLTMH) in Fakfak Regency is one of the real solutions to the power outages that still often occur in Fakfak Regency. Through this study, it is hoped that there will be a mapping of the energy potential that can be produced by several rivers in Fakfak Regency if used as Micro Hydro Power Plants (PLTMH). In addition, the potential of Micro Hydro Power Plant (PLTMH) will support the transition of power plants in Fakfak Regency. Another objective is to support environmental conservation efforts (nature and culture) and increase community participation in the management of existing natural resources, thus providing economic benefits to the local community. The research was conducted through surveys and direct measurements where the measurement results will be calculated to determine the potential river flow discharge and the potential for power generation. The results of the measurements and calculations obtained an average discharge of the Sakartemen River of 3.1m3/second which based on the measurement of the effective fall height (Heff) of the flow was obtained at 4 m. With these results, it can be estimated that the electrical power generated is 104,260 kW.

Multiple Self-Powered Sensor-Integrated Mobile Manipulator for Intelligent Environment Detection.

A multiple self-powered sensor-integrated mobile manipulator (MSIMM) system was proposed to address challenges in existing exploration devices, such as the need for a constant energy supply, limited variety of sensed information, and difficult human-computer interfaces. The MSIMM system integrates triboelectric nanogenerator (TENG)-based self-powered sensors, a bionic manipulator, and wireless gesture control, enhancing sensor data usability through machine learning. Specifically, the system includes a tracked vehicle platform carrying the manipulator and electronics, including a storage battery and a microcontroller unit (MCU). An integrated sensor glove and terminal application (APP) enable intuitive manipulator control, improving human-computer interaction. The system responds to and analyzes various environmental stimuli, including the droplet and fall height, temperature, pressure, material type, angles, angular velocity direction, and acceleration amplitude and direction. The manipulator, fabricated using 3D printing technology, integrates multiple sensors that generate electrical signals through the triboelectric effect of mechanical motion. These signals are classified using convolutional neural networks for accurate environmental monitoring. Our database shows signal recognition and classification accuracy exceeding 94%, with specific accuracies of 100% for pressure sensors, 99.55% for angle sensors, and 98.66, 95.91, 96.27, and 94.13% for material, droplet, temperature, and acceleration sensors, respectively.

Forecasting open-pit slope runout distances

Geotechnical engineers are routinely tasked with advising suitable stand-off distances below high-risk sections of slopes in open-pit mines that are identified to have potential to deform or collapse. Accurate prediction of failed material runout can mean the difference between continuous safe mining and unwanted high-potential incidents that result in loss of production, equipment damage, injury, or loss of life. This paper updates previous empirical relationships presented by the authors for estimating the volume and runout distance of excavated slope failures, in an open-pit mine operation, using slope geometry as the primary predictor. Cases are sourced from varying slope geometries (fall heights up to 385 m, slope angles up to 80°) and a range of commodities (iron ore, coal, nickel, gold, copper, boron, and limestone), excavated in sedimentary, banded-sedimentary, epithermal, and copper-porphyry deposits, across all six inhabited continents. Analysis of these cases identified positive correlations between slope height and runout distance, and slope height and failed material volume. In general, negative correlations were identified between Fahrböschung angle and slope height, and Fahrböschung angle and failed material volume; however, significant scatter is observed in these datasets. A definitive relationship could not be derived comparing Fahrböschung angle with failed material runout. Slope angle was also found to be a poor indicator of runout. Of the parameters analysed, slope height (i.e., fall height) was found to be the simplest and best predictor of runout distance. This paper presents new charts for predicting failed material runout distance for rock slopes. Relationships are defined for structurally and rock-mass driven slope failure mechanisms at average, 75%, and 95% prediction intervals.

Designing Corrugated Board Properties to Mitigate Puncturing Impacts Occurring in E‐Commerce or Other Demanding Parcel Handling Distribution Chains

ABSTRACTThe growth of e‐commerce trade has led to more parcel shipments, causing an increase in corrugated board box packaging. Individually shipped boxes often sustain more damage, like crushing or puncturing, compared to pallet‐transported boxes. In contrast to the known relationships between containerboard properties and box compressive strength, there is no standard method for designing corrugated board against puncturing, which can result in damages, customer dissatisfaction and costly returns. A hole is typically seen as a severe compromise to package integrity, whereas some crushed boxes can be acceptable for nonfragile items. Addressing this, this research has focused on developing design equations linking containerboard and corrugated board properties to resistance against puncturing. These equations give the energy loss of an impacting object that would cause a hole and define the energy absorbance limit of the material. The equations enable material design aimed at minimizing puncturing risks based on specific distribution chain conditions, like fall heights and velocities.

Genomic prediction of regional-scale performance in switchgrass (Panicum virgatum) by accounting for genotype-by-environment variation and yield surrogate traits.

Switchgrass is a potential crop for bioenergy or carbon capture schemes, but further yield improvements through selective breeding are needed to encourage commercialization. To identify promising switchgrass germplasm for future breeding efforts, we conducted multisite and multitrait genomic prediction with a diversity panel of 630 genotypes from 4 switchgrass subpopulations (Gulf, Midwest, Coastal, and Texas), which were measured for spaced plant biomass yield across 10 sites. Our study focused on the use of genomic prediction to share information among traits and environments. Specifically, we evaluated the predictive ability of cross-validation (CV) schemes using only genetic data and the training set (cross-validation 1: CV1), a subset of the sites (cross-validation 2: CV2), and/or with 2 yield surrogates (flowering time and fall plant height). We found that genotype-by-environment interactions were largely due to the north-south distribution of sites. The genetic correlations between the yield surrogates and the biomass yield were generally positive (mean height r = 0.85; mean flowering time r = 0.45) and did not vary due to subpopulation or growing region (North, Middle, or South). Genomic prediction models had CV predictive abilities of -0.02 for individuals using only genetic data (CV1), but 0.55, 0.69, 0.76, 0.81, and 0.84 for individuals with biomass performance data from 1, 2, 3, 4, and 5 sites included in the training data (CV2), respectively. To simulate a resource-limited breeding program, we determined the predictive ability of models provided with the following: 1 site observation of flowering time (0.39); 1 site observation of flowering time and fall height (0.51); 1 site observation of fall height (0.52); 1 site observation of biomass (0.55); and 5 site observations of biomass yield (0.84). The ability to share information at a regional scale is very encouraging, but further research is required to accurately translate spaced plant biomass to commercial-scale sward biomass performance.

A two-way coupled fluid–structure interaction method for predicting the slamming loads and structural responses on a stiffened wedge

Ships navigating through rough seas are subjected to slamming loads from waves, which can lead to structural damage and maritime accidents. The wedge model is commonly employed to investigate slamming loads and structural responses. While a stiffened wedge closely resembles a real ship hull plate, incorporating it into fluid–structure interaction simulations presents challenges. This paper proposes a two-way coupled fluid–structure interaction method to examine slamming loads and structural responses of a free fall non-prismatic stiffened steel wedge. Hydrodynamic loads are determined through Reynolds-averaged Navier–Stokes computations using OpenFOAM, while structural responses are predicted using the finite element analysis (FEA) software Calculix. To achieve two-way coupling between computational fluid dynamics and FEA simulations, a coupling library for partitioned multi-physics simulations, preCICE, is introduced. The computed impact pressure and stress align well with available experimental data. Various free fall heights are investigated in the numerical simulations. The results indicate that elastic deformation mitigates impact pressure, while the presence of transverse ribs enhances the rigidity of the flexible plate. The duration of pressure and the peak slamming pressure exhibit an inverse correlation. Greater free fall heights result in shorter pressure duration times, and smaller free fall heights may reduce rise time. Three-dimensional effects cause pressure to decrease along the midpoint of the plate toward both sides. Additionally, structural stress in the central area exceeds that in the areas on both sides at the same height. In conclusion, the proposed two-way coupled model proves suitable for accurately and efficiently computing hydroelastic slamming on flexible wedges.

Granular Scaling Approach to Landslide Runout.

A main objective in landslide research is to predict how far they will travel. Landslides are complex, and a complete understanding in principle requires accounting for numerous parameters. Here we engender a simplification by investigating the maximum landslide runout using granular laboratory experiments and a scaling analysis. We find that correctly accounting for the fall height and grain size distribution not only yields an improved correlation of normalized runout, but also quantitatively unites laboratory and field data. In particular, we find that the mobility of landslides increases with the square root of the fall height and with the skewness of the grain size distribution.

Multi-scale microstructural construction in ultralight graphene aerogels enables super elasticity and unprecedented durability for impact protection materials

Ultralight graphene aerogels have gained extensive recognition in the impact protection field. However, attaining both elasticity and durability at low material density is challenging due to their intrinsic conflicts. Inspired by the mantis ootheca, we present a simultaneous improvement in the elasticity, durability, and density restrictions of ultralight graphene aerogels via constructing a multiscale honeycomb microstructure (MHM) within the graphene skeleton. This approach enables resulting graphene aerogel to achieve a strength per unit volume of 284.6 cm3 mg−1, the ability to recover its shape within 10 ms after an impact at 3.569 m/s, and maintain 97.2 % of its sample height after 20,000 cycles at 90 % strain. The operand analyses and calculation results reveal that the MHM structure facilitates this aerogel’s dual-stage stress transfer pathway. Initially, the macroscale honeycomb structure (millimeter-scale) of the graphene aerogels bear and transmit stress to the surrounding regions, followed by the microscale honeycomb structure (micron-scale) deformation to convert stress kinetic energy into elastic potential energy. This two-stage stress transition mechanism of the MHM structure can effectively mitigate excessive local stress and suppress strain localization, thus providing remarkable elasticity and durability. Ultimately, the obtained graphene aerogel demonstrates promising applications as a fall height detection device and impact protective material.

Potensi Pembangkit Listrik Berbasis Energi Air Mikrohindro Bendungan Di Banten

Banten Province has a number of dams that have the potential to be developed as micro hydro-based renewable energy centers. Micro hydro is a technology that utilizes water flow to produce electricity on a small scale, ideal for areas with abundant water resources. The dam in Banten, which was originally built for irrigation, flood control and raw water supply, can be optimized to produce environmentally friendly electrical energy. This research uses literature study methods and secondary data analysis to evaluate the potential of dams in Banten as a micro hydro renewable energy center. The data used includes official reports, scientific publications, and data from government agencies. The analysis includes evaluation of flow capacity and water fall height, as well as the environmental impact of implementing micro hydro technology. The research results show that several dams in Banten have adequate flow capacity and water fall height to support micro hydro installations. The environmental impact of micro hydro installations can be minimized by implementing existing best practices. Micro hydro development in Banten dams can reduce dependence on fossil energy and support the national renewable energy mix target. This research recommends the development of supportive policies and the participation of local communities to realize this potential. In this way, the dam in Banten can be transformed into a renewable energy center that contributes significantly to energy security and environmental sustainability in Indonesia.

Air drag controls the runout of small laboratory landslides.

Laboratory granular landslides are smaller-scale, simplified, yet well-controlled versions of larger and often tragic natural landslides. Using systematic experiments and scaling analysis, we quantify the influence of grain size, fall height, and landslide volume on runout distance. We also determine the minimum landslide size required to observe this scaling, which we find is set by a combination of air drag, grain size, and fall height.

Construction and analysis of a mechanical model for viscoelasticity and plasticity in potato

AbstractThe aim of this paper is to develop a precise collision model of potatoes falling onto a separation sieve to assess their damage characteristics. A viscoelastic‐plastic mechanics model is created by integrating the collision process with the potato soil separation device. Test factors include fall height, potato mass, fall direction, and varieties. Potato deformation and damage volume serve as evaluation indices in single‐factor tests to explore their relationships with these factors. The model analyzes the collision loading and unloading process, studying relationships between parameters and test factors, examining the potato collision damage mechanism. Predictive equations for potato damage volume based on fall height, potato mass, and plasticity ratio λp are derived: V1 = 1606λp–537, V2 = 4751λp–2087, and V3 = 12617λp–5303. This study provides a theoretical foundation for analyzing potato collision damage and offers technical references for optimizing potato harvesting machinery.Practical applicationsDamage resulting from the mechanical harvesting process significantly impacts the quality and economic worth of the tubers. Currently, research on constructing a mechanical model of potatoes, treating them as viscoelastic plastic bodies, and integrating the collision process with potato soil separation devices is limited. Thus, the objective of this paper is to investigate the correlation between various test factors and potato damage via drop tests, and to establish a viscoelastic–plastic mechanical model. Additionally, the study further explored the correlation between model parameters and tuber damage, resulting in the establishment of a mathematical model for predicting the extent of damage. This study provides a theoretical basis for an in‐depth analysis of the collision damage mechanism of potato, and a technical reference for the design and optimization of potato harvesting machinery.

Kinetic Comparison between Drop Jumps and Horizontal Drop Jumps in Elite Jumpers and Sprinters

Previous research addressed the spatiotemporal variables of the drop jump (DJ) versus the horizontal drop jump (HDJ). This study compared the kinetic variables of the DJ versus the HDJ in elite jumpers and sprinters. In a single session, sixteen elite jumpers and sprinters performed two DJ attempts with three different fall heights (0.30 m, 0.40 m, and 0.50 m), and after 2 h, performed two HDJ attempts from the same fall heights (0.30 m, 0.40 m, and 0.50 m). Kinetic variables: eccentric ground reaction forces (GRFE) and concentric ground reaction forces; eccentric impulse (PE) and concentric impulse (PC); peak power in the concentric phase; and rate of force decrease (RFDe) were measured using a research-grade force plate. The Wilcoxon test was used to compare the vertical and anteroposterior axes. GRFE was significantly higher (p ≤ 0.05) in the DJ vs the HDJ with large effect sizes. The PE (p ≤ 0.006) and PC (p = 0.002) were significantly lower in the DJ than in the HDJ. The RFDe was also significantly lower in the DJ at 0.30 m vs. the HDJ at 0.30 m (p = 0.002). In summary, elite jumpers and sprinters may benefit from incorporating both the DJ and the HDJ into their training regimens, with the DJ being particularly advantageous for enhancing power metrics and RFDe.

Analysis of Characteristics of Bamboo Water Wheels 6 Bamboo Plate with Height Variations of Water Attacking the Blade

A waterwheel is a mechanical device in the form of a wheel with blades (bucket or vane) around the edges which are placed on the shaft. horizontally. The waterwheel is a simple tool whose purpose is to convert motion energy into electrical energy. In the design of the waterwheel, the type and dimensions of the waterwheel depend on the location of the wheel, the height of the water fall and the available water capacity. So that in order to obtain optimal efficiency, the design of a waterwheel that operates at a particular location will have a speciLic design, both in the form of type and dimensions that are different from other locations. The purpose of this study was to determine the maximum power, maximum torque and maximum efLiciency that produced a bamboo water wheel with 6 bamboo plate blades. In this study, the data produced is experimental data with the height of the water hitting the blades of 15 cm, 20 cm, 25 cm, 30 cm, and 35 cm and the number of blades is 6 pieces. The results obtained, the maximum power is 7.61 and is found in the variation of water height hitting 15 cm, the maximum torque is 3.71 and there is a variation in water height hitting 15 cm and the maximum efLiciency that can be produced by the bamboo water wheel is 47.67% and found in variations in water height that hit the blade 15 cm.

Spine Injuries Sustained After Falls While Crossing the U.S.-Mexico Border.

This study is to report the demographics, incidence, and patterns of spinal injuries associated with border crossings resulting from a fall from a significant height. A retrospective cohort study was performed at a Level I trauma center from January 2016 to December 2021 to identify all patients who fell from a significant height while traversing the U.S.-Mexico border and were subsequently admitted. A total of 448 patients were identified. Of the 448 patients, 117 (26.2%) had spine injuries and 39 (33.3%) underwent operative fixation. Females had a significantly higher incidence of spine injuries (60% vs. 40%; p < 0.00330). Patients with a spine fracture fell from a higher median fall height (6.1 vs. 4.6 m; p < 0.001), which resulted in longer median length of stay (LOS; 12 vs. 7 days; p < 0.001), greater median Injury Severity Score (ISS; 20 vs. 9; p < 0.001), and greater relative risk (RR) of ISS >15 (RR = 3.2; p < 0.001). Patients with operative spine injuries had significantly longer median intensive care unit (ICU) LOS than patients with non-operative spine injuries (4 vs. 2 days; p < 0.001). Patients with spinal cord injuries and ISS >15 sustained falls from a higher distance (median 6.1 vs. 5.5 m) and had a longer length of ICU stay (median 3 vs. 0 days). All patients with operative spine injuries had an ISS >15 relative to 50% of patients with non-operative spine injuries (median ISS 20 vs. 15; p < 0.001). Patients with spine trauma requiring surgery had a higher incidence of head (RR = 3.5; p 0.0353) and chest injuries (RR = 6.0; p = 0.0238), but a lower incidence of lower extremity injuries (RR = 0.5; p < 0.001). Thoracolumbar injuries occurred in 68.4% of all patients with spine injuries. Patients with operative spine injuries had a higher incidence of burst fracture (RR = 15.5; p < 0.001) and flexion-distraction injury (RR = 25.7; p = 0.0257). All patients with non-operative spine injuries had American Spinal Injury Association (ASIA) D or E presentations, and patients with operative spine injuries had a higher incidence of spinal cord injury: ASIA D or lower at time of presentation (RR = 6.3; p < 0.001). Falls from walls in border crossings result in significant injuries to the head, spine, long bones, and body, resulting in polytrauma casualties. Falls from higher height were associated with a higher frequency and severity of spinal injuries, greater ISS, and longer ICU length of stay. Operative spine injuries, compared with non-operative spine injuries, had longer ICU length of stay, greater ISS, and different fracture morphology. Spine surgeons and neurocritical care teams should be prepared to care for injuries associated with falls from height in this unique population.

Preliminary design of micro hydro power plant in Enim river, Plakat village

The utilization of renewable energy in meeting electricity needs in Indonesia continues to be carried out, including by utilizing river flow as a source of electrical energy for the community. Micro hydro power plants are one type of power plant that utilizes river flow as a source of energy that is widely used in Indonesia, especially for people in rural areas who have difficulty in accessing the electricity grid and spread throughout Indonesia. One of the rivers in South Sumatra Province, Indonesia that has the potential to be developed as a micro hydro power plant is the Enim River located in Plakat Village. This research was conducted to obtain an estimate of the amount of energy that can be generated from the Enim River. In the methodology, the data needed to calculate the amount of energy produced includes effective the effective fall height data, identification of the intake channel, forebay and penstock pipe obtained from direct observation and then the calculation of water power that can be generated by the Enim River tributary in Plakat Village. In the calculation results, the micro hydro design in Plakat Village, Enim River is as follows: 184 m pipe dimensions, minimum pipe thickness of 0.5 m, effective energy height of 26.1 m, and output power of 35.88 kW.

Spatiotemporal variables comparison between drop jump and horizontal drop jump in elite jumpers and sprinters.

General expectations speculated that there are differences between drop jump (DJ) and horizontal drop jump (HDJ) exercises. While these criteria may be valid, we have yet to find a report that explores these differences in competitive level athletes. The study aimed to compare spatiotemporal variables in the drop jump (DJ) vs. the horizontal drop jump (HDJ) in elite jumpers and sprinters. Sixteen international-level male athletes performed two DJ attempts at different fall heights 0.3, 0.4, and 0.5 m (DJ30, DJ40, and DJ50), and after 2 h, they performed two HDJ attempts (HDJ30, HDJ40, HDJ50). All jumps were performed on a Kistler force plate. The variables analyzed were ground contact time (GCT), flight time (FT), eccentric phase time, concentric phase time, and time to peak concentric force. The GCT was found to be significantly shorter in DJ vs. HDJ (Z = 4.980; p = 0.0001; ES = 3.11). FT was significantly lower in DJ30 versus HDJ30 (Z = 4.845; p = 0.0001, d = 3.79), but significantly higher in DJ40 vs. HDJ40 (Z = 4.437; p ≤ 0.0001, d = 3.70) and in DJ50 vs. HDJ50 (Z = 4.549; p ≤ 0.0001, d = 4.72). It is concluded that the HDJ requires more time for force production, that the eccentric component requires more time than the concentric and that it is not recommended to use the HDJ over the DJ for reactive purposes. This is the first study that comprehensively compare the differences between DJ and HDJ, which will assist coaches and researchers in the design of future training strategies.

Falls from height in children: epidemiology and outcome.

Childhood injury is one of the leading causes of death globally, with falls being the sixth leading cause. This study aimed to examine the demographics, patterns of injury and temporal risk factors for falls from height above 3 m in Singapore. This is a retrospective study conducted on patients who presented after a fall to a paediatric emergency department at a tertiary hospital between January 2011 and July 2017. Electronic medical records were reviewed to extract demographics and data on the patterns of injuries. Criteria for inclusion were patients under 18 years of age and the occurrence of fall from a height of 3 m or above. A total of 149 children met the inclusion criteria. The median age was 10 years and 69.1% were boys. Death occurred in two (1.3%) cases; 84 (56.4%) were admitted and survived. Of those admitted, five (3.4%) required care in the intensive care unit and 11 (7.4%) required surgery. Falls occurred mostly at homes or residential buildings (n = 59, 39.6%). The two cases of mortality were due to falls from windows at homes. Twenty (33.9%) children fell from windows at homes, with two requiring admission to the intensive care unit. Our study shows that falls from windows of homes are an important cause of mortality. Height of fall was also an important predictor of morbidity that led to a higher level of hospitalisation care. Preventive measures should be implemented to ensure safety in high-rise residential buildings to prevent paediatric falls from heights.