Ski Jumps Research Articles

Carving Out Spaces of Resistance: Remembering Women’s Ski Jumping, Gendered Spaces, and Built Environments at Canada Olympic Park, 1987–2019

This article examines the history of Canada Olympic Park (COP) as it transitioned from the Paskapoo Slopes to a venue for the Calgary 1988 Winter Olympic Games and how the site framed the fight for gender equality in the sport by women ski jumpers in Canada. Ski jumping is a sport that can be considered a “nature sport” as it is practiced in the open air while simultaneously relying on built environments. Understanding the COP ski jumping venue as a “sportscape” and a gendered landscape provides a unique opportunity to explore the tensions between land, air, and the body in this nature sport. Historical analysis of the XV Winter Olympic Games inventories held at the City of Calgary Archives is combined with autoethnographic reflections of my past experiences as a ski jumping athlete who trained at the COP ski jumping venue and plaintiff in the court case to get a women’s ski jumping event added to the 2010 Winter Olympic Games to frame my analysis. This paper argues that women ski jumpers at COP carved out spaces of resistance for themselves, shifted the gendered landscape of the ski jumps, and effected change across generations of women ski jumpers on and off the hill.

Estimation in jet deflection angle of deflector on the chutes

ABSTRACT Ski jumps are commonly used to discharge flow away from release structures into downstream rivers for energy dissipation. However, due to large intersection angles of jet and river flow or the jet impacting position unreasonable, the serious sour of riverbed or bank may occur, threatening the security of hydraulic structure. Hence, the impacting position and direction of jet from ski jump are pressing for research. For obtaining a controllable and desired outflow condition, adding rectangular tetrahedral deflector is a common and effective measure to change the flow direction. In this study, physical experiments and numerical simulation were conducted and the effect of the deflector contraction ratio on the flow deflection angle was revealed. The results indicate that the contraction ratio is a key parameter of the deflector, and a larger contraction ratio contributes to a larger jet deflection angle. Based on the data in the present and previous studies, a new empirical expression for estimating the deflection angle is proposed for rectangular tetrahedral deflector. By contrast with previous research, the calculated result from the expression presents a better agreement with the test data.

THE FEATURES OF SPORTS COMPLEX 'SUNKAR' MONITORING BY TERRESTRIAL LASER SCANNING

Abstract. The paper is aimed at the study of monitoring workflow in adverse observation conditions for sports structures. The application of terrestrial laser scanning for monitoring various objects is well-studied. However, the deployment of TLS for large sports structures is challenging. Such structures have huge sizes, complex geometry and need the control of particular elements. The monitoring gets complicated in the case when the structure is placed on a very steep slope, e.g., ski jumps or bobsleigh tracks. The subject of the presented study is the complex of ski jumps 'Sunkar' emplaced in Almaty, Republic of Kazakhstan. The monitoring network for the complex was created using a robotic total station. Due to the extreme sizes of the object (height 70 m, width 8 m, length over 100 m), TLS was accomplished from all points of the network to ensure the necessary density of point clouds and reliable georeferencing. The main observation parameters were the displacements of the ski jumps regarding the longitudinal axis. To retrieve the axis coordinates, the point cloud was sliced along the ski jump surface. The geometry of the longitudinal axis was simulated using spline functions. As an output, the suggested monitoring workflow is provided that ensures the quality of the necessary results.

XLength: Predicting Expected Ski Jump Length Shortly after Take-Off Using Deep Learning.

With tracking systems becoming more widespread in sports research and regular training and competitions, more data are available for sports analytics and performance prediction. We analyzed 2523 ski jumps from 205 athletes on five venues. For every jump, the dataset includes the 3D trajectory, 3D velocity, skis' orientation, and metadata such as wind, starting gate, and ski jumping hill data. Using this dataset, we aimed to predict the expected jump length (xLength) inspired by the expected goals metric in soccer (xG). We evaluate the performance of a fully connected neural network, a convolutional neural network (CNN), a long short-term memory (LSTM), and a ResNet architecture to estimate the xLength. For the prediction of the jump length one second after take-off, we achieve a mean absolute error (MAE) of 5.3 m for the generalization to new athletes and an MAE of 5.9 m for the generalization to new ski jumping hills using ResNet architectures. Additionally, we investigated the influence of the input time after the take-off on the predictions' accuracy. As expected, the MAE becomes smaller with longer inputs. Due to the real-time transmission of the sensor's data, xLength can be updated during the flight phase and used in live TV broadcasting. xLength could also be used as an analysis tool for experts to quantify the quality of the take-off and flight phases.

Experimental Validation of Real-Time Ski Jumping Tracking System Based on Wearable Sensors.

For sports scientists and coaches, its crucial to have reliable tracking systems to improve athletes. Therefore, this study aimed to examine the validity of a wearable real-time tracking system (WRRTS) for the quantification of ski jumping. The tracking system consists of wearable trackers attached to the ski bindings of the athletes and fixed antennas next to the jumping hill. To determine the accuracy and precision of the WRRTS, four athletes of the German A or B National Team performed 35 measured ski jumps. The WRRTS was used to measure the 3D positions and ski angles during the jump. The measurements are compared with camera measurements for the in-flight parameters and the official video distance for the jumping distance to assess their accuracy. We statistically evaluated the different methods using Bland–Altman plots. We thereby find a mean absolute error of for the jumping distance, for the in-flight positions, and °, and ° for the camera projected pitch and V-style opening angle, respectively. We show the validity of the presented WRRTS to measure the investigated parameters. Thus, the system can be used as a tracking system during training and competitions for coaches and sports scientists. The real-time feature of the tracking system enables usage during live TV broadcasting.

Jumping Towards the Future

Between the late nineteenth and the mid-twentieth century numerous ski-jumping towers were built all across Sweden. This accumulation of large, monumental sporting facilities occurred even though ski jumping never attracted large numbers of practitioners. The building of such towers in the southern and central parts of Sweden, where snowy winters are far from guaranteed, is of particular interest. Today, most of the ski-jumping towers in the southern half of Sweden have been torn down, but they have left a hidden and forgotten material heritage. This paper examines the abandoned places of ski jumping, where fragmented material remains give witness to a phenomenon that once was of central importance in shaping and expressing ideals and social identities in the modernization of Sweden. The ski jumps became arenas for a new and spectacular sport that drew large crowds, but they also became landmarks and monuments of progress and prosperity in the new modern age.

Performance Analysis in Ski Jumping with a Differential Global Navigation Satellite System and Video-Based Pose Estimation.

This study investigated the explanatory power of a sensor fusion of two complementary methods to explain performance and its underlying mechanisms in ski jumping. A differential Global Navigation Satellite System (dGNSS) and a markerless video-based pose estimation system (PosEst) were used to measure the kinematics and kinetics from the start of the in-run to the landing. The study had two aims; firstly, the agreement between the two methods was assessed using 16 jumps by athletes of national level from 5 before the take-off to 20 after, where the methods had spatial overlap. The comparison revealed a good agreement from 5 after the take-off, within the uncertainty of the dGNSS (± ). The second part of the study served as a proof of concept of the sensor fusion application, by showcasing the type of performance analysis the systems allows. Two ski jumps by the same ski jumper, with comparable external conditions, were chosen for the case study. The dGNSS was used to analyse the in-run and flight phase, while the PosEst system was used to analyse the take-off and the early flight phase. The proof-of-concept study showed that the methods are suitable to track the kinematic and kinetic characteristics that determine performance in ski jumping and their usability in both research and practice.

Об учете особенностей геомеханических процессов при геомониторинге устойчивости конструкций спортивных объектов в предгорной местности

The article discusses the issues of taking into account the features of the geomechanical state of the rock massif in the complex conditions of foothill area to solve the actual scientific and practical problem of studying the negative effects of geomechanical processes on the stability of structures and safety of sports facilities of national and international importance. It was noted that one of the main reasons for the increase cases of deformation in engineering objects is insufficient study of processes of development of dynamics of surface soils shift and change in the physical and mechanical properties of rocks. In this regard, an analysis was carried out of engineering and geological features of the rock massif on the territory of the international complex of ski jumps "Sunkar". It was established the development of geomechanical processes on the territory of the object, leading to deformation of the base and structures of the ski jumps, which determines the need for high-precision geomonitoring measurements.

Flow Pressure Behavior Downstream of Ski Jumps

Ski jump spillways are frequently implemented to dissipate energy from high-speed flows. The general feature of this structure is to transform the spillway flow into a free jet up to a location where the impact of the jet creates a plunge pool, representing an area for potential erosion phenomena. In the present investigation, several tests with different ski jump bucket angles are executed numerically by means of the OpenFOAM® digital library, taking advantage of the Reynolds-averaged Navier–Stokes equations (RANS) approach. The results are compared to those obtained experimentally by other authors as related to the jet length and shape, obtaining physical insights into the jet characteristics. Particular attention is given to the maximum pressure head at the tailwater. Simple equations are proposed to predict the maximum dynamic pressure head acting on the tailwater, as dependent upon the Froude number, and the maximum pressure head on the bucket. Results of this study provide useful suggestions for the design of ski jump spillways in dam construction.

Creating a node connection for scaffolding and studying its stress-strain state by means of a full-scale test

The article presents the results of the analysis of the stress-strain state of the developed jointing node of construction scaffolding (spatial rod temporary structures), since nodal connections are often the weakest elements of such temporary structures. The analysis of the stress-strain state of the node was performed on the basis of a full-scale experiment. The study revealed the most stressed zones in the node structure, as well as the causes of node destruction. Nodes are well known to be the weakest elements of scaffolding. It often happens that structural elements are more stable than the connections between them. Mobile spatial rod structures are very popular in construction at the present time. These structures are used for the construction of ski jumps, stands, stages and scaffolding. They are also used as support scaffolding to support the formwork of floorings. Therefore, the development of new nodal solutions, increasing the bearing capacity of nodal joints and studying their stress-strain state under various loads is a very important task.

Numerical Investigation of Ski Jump Hydraulics

AbstractThe hydraulics of ski jumps is an issue of utmost importance in dam construction, the former being in practice the only existing solution as related to the dissipation of energy from high-s...

The attitude of state authorities to the development of physical culture in the Second Polish Republic

Physical culture in the Second Polish Republic has taken an important place in the politics of the state. It included physical education, physical recreation along with active forms of tourism, mass sports, high-performance sport and military adoption related programmatically with physical education. The state played a significant role in popularizing sport. They developed, among others infrastructure, building mountain hostels, ski jumps, indoor swimming pools, local playgrounds and modern large stadiums. A great contribution to the development of physical culture in pre-war Poland was made by institutions, unions and sports associations. The purpose of the article is to outline the attitude of state authorities to physical culture during the interwar period. The text has a problem layout, I present the state's policy in financial, organizational and legal terms.

Simulation of take-off angle of a ski jump energy dissipater

Ski jumps has been widely used in water conservancy and hydropower engineering with its simple structure and high energy dissipation. The jet trajectory is a key factor to directly determine the scour location, which are the significant index of hydraulic design. Actually, the take-off angle of jet flow is different from the geometrical take-off angle. Reasonable take-off angle would be quite important for calculation method of horizontal length of jet flow. The object of this work is based on the research of three take-off angels of upper and lower jet trajectories with different outlets (geometrical take-off angle, virtual take-off angle, and computational take-off angle), and provides actual calculation method for horizontal length of ski jumps. On the basis of theoretical analysis and numerical simulation, the main contents and methods of this research report includes: 1) analyzing affective analysis of virtual take-off angles of both the lower and upper jet trajectories, establishing virtual take-off angles of both the lower and upper jet trajectories equations with hydraulic and structure parameters and etc; 2) analyzing by comparing virtual take-off angles of both the lower and upper jet trajectories with different outlets of flip bucket (including circular, triangle, etc.); 3) providing horizontal length of jet flow of ski jumps calculation method with take-off angles of upper and lower jet trajectories.

Physical modeling of erosion in low height structures with ski jumps

La erosion local aguas abajo de estructuras hidraulicas puede comprometer la seguridad de las mismas. En el caso de obras con estructura terminal tipo salto de esqui hay vastos estudios e investigaciones disponibles que proponen formulaciones teorico-experimentales para estimar la maxima profundidad de erosion. Sin embargo, las incertidumbres que aun existen en este tipo de fenomenos llevan a la necesidad de abordarlos mediante tecnicas experimentales detalladas. En este trabajo se presenta un estudio experimental de erosion local aguas abajo de estructuras hidraulicas de baja altura con salto de esqui, donde la descarga se hace sobre un rio de gravas; se comparan los resultados experimentales con los de formulas empiricas que aparecen en el estado del arte, validando el grado de aplicabilidad de las mismas.

Development of an inertial motion capture system for kinematic analysis of ski jumping

In this research, a fully automatic inertial motion capture system for the determination and analysis of kinematic motion parameters in ski jumping was developed. Two databases were created for the implementation of the measurement system: one basic database acquired in a laboratory setting and one database acquired during a summer ski jump season on an actual ski jumping slope. First, the former database was used to set up the fundamental data processing method. Next, this method was extended to derive jump kinematics for motion analysis in the larger summer jumping data set. Data analysis showed that the determined body kinematics varied largely in heading angle due to variances in the magnetic field near the top of the ski jumping hill. Therefore, a novel method for the additional compensation of magnetic disturbances was added to the processing framework. The resulting system output data indicated that the final body orientations, joint positions and joint angles were of good and meaningful accuracy. The enhanced inertial capture system consequently constitutes a reliable and very accurate tool to evaluate ski jumps from inertial sensor data under high data comparability and repeatability within different athletes and capture sessions.

How Do World-Class Nordic Combined Athletes Differ From Specialized Cross-Country Skiers and Ski Jumpers in Sport-Specific Capacity and Training Characteristics?

To compare sport-specific laboratory capacities and the annual training of world-class Nordic combined (NC) athletes with specialized ski jumpers (SJ) and cross-country (XC) skiers. Five world-class athletes from each sports discipline were compared. Ski jump imitations were performed on a 3-dimensional force plate in NC athletes and SJ, whereas XC skiing characteristics were obtained from submaximal and maximal roller ski skating on a treadmill in NC athletes and XC skiers. In addition, anthropometrics and annual training characteristics were determined. NC athletes demonstrated 9% higher body mass and showed 17% lower vertical speed in the ski jump imitation than SJ (all P < .05). NC athletes had 12% lower body mass and showed 10% lower peak treadmill speed and 12% lower body-mass-normalized peak oxygen uptake than XC skiers (all P < .05). NC athletes performed half the number of ski-jumping-specific sessions and outdoor ski jumps compared with SJ. NC athletes performed 31% less endurance training, mainly caused by lower amounts of low- and moderate-intensity training in the classical technique, whereas high-intensity strength and speed training and endurance training in the skating technique did not differ substantially from XC skiers. To simultaneously optimize endurance, explosive, and technical capacities in 2 different disciplines, world-class NC athletes train approximately two-thirds of the XC skier's endurance training volume and perform one-half of the ski-jump-specific training compared with SJ. Still, the various laboratory capacities differed only 10-17% compared with SJ and XC skiers.

Development of an Automated Motion Evaluation System from Wearable Sensor Devices for Ski Jumping

We developed a system for the automatic evaluation of ski jumps on the base of machine learning algorithms. In several capture sessions during summer jump season, motions of four junior ski jumpers were captured by inertial sensors over the complete jump, from the start of the in-run to the end of the outrun phase. Additionally, style points were collected from an experienced judge to serve as ground truth and control data for the machine learning algorithms. All jumps were randomly separated into a training and a test database. Next, we determined kinematic factors such as body segment orientation and body joint position and segmented every jump into its main motion phases on the base of the raw sensor data. Specific motion characteristics that influence the performance and length of a jump were then used to create machine style knowledge from the training database in compliance to the official scoring guidelines. In a last step, we computed the similarity of every jump within the test database to the trained knowledge on a ski jump's style parameters and evaluated the presence or absence of jump errors. Results showed that the computed error annotations conform largely to the human-based judging scores. Adding automatic score measures to the algorithm in future, this method might be an important step towards better measurability and objectivity of performance-oriented sports in form of a mobile competition evaluation system.

Concurrent Development of Endurance Capacity and Explosiveness: Training Characteristics of World-Class Nordic-Combined Athletes.

Performing at an elite level in Nordic combined (NC) requires both the explosiveness required for ski jumping performance and the endurance capacity required for cross-country skiing. To describe the characteristics of world-class NC athletes' training and determine how endurance and non-endurance (ie, strength, power, and ski jumping) training is periodized. Annual training characteristics and the periodization of endurance and non-endurance training were determined by analyzing the training diaries of 6 world-class NC athletes. Of 846 ± 72 annual training hours, 540 ± 37 h were endurance training, with 88.6% being low-, 5.9% moderate-, and 5.5% high-intensity training. While training frequency remained relatively constant, the total training volume was reduced from the general preparatory to the competition phase, primarily due to less low- and moderate-intensity training (P < .05). A total of 236 ± 55 h/y were spent as non-endurance training, including 211 ± 44 h of power and ski-jump-specific training (908 ± 165 ski jumps and ski-jump imitations). The proportion of non-endurance training increased significantly toward the competition phase (P < .05). World-class NC athletes reduce the volume of low- and moderate-intensity endurance training toward the competition phase, followed by an increase in the relative contribution of power and ski-jump training. These data provide novel insight on how successful athletes execute their training and may facilitate more-precise coaching of future athletes in this sport. In addition, this information is of high relevance for the training organization of other sports that require optimization of 2 fundamentally different physical capacities.

Deflector Effect on Chute Flow

Jet deflection and energy dissipation of ski jumps guarantee the safety of hydraulic structures. Deflectors on spillways and bottom outlets are mostly complex constructions. The aim of this study is to find simple-shaped deflectors allowing for jet deflection into the tailwater, thereby characterizing the parameters of the trajectory under different approach flow conditions. The test program included eight right-angled tetrahedrons and two vertical plate deflectors. A systematic variation of the approach flow depth and Froude number, in combination with different deflector alignments, resulted in basic principles for deflector design. To study scale effects caused by viscosity and surface tension, three symmetric deflectors were tested as a model family at different approach flow depths. The results indicate the importance of the approach flow Froude number and the relative deflector height on the jet trajectory. The relevant jet parameters, including the deflection angle, the maximum jet elevation, and the jet impact onto the tailwater channel, are specified.

Deflector-jets affected by pre-aerated approach flow

Jets generated at chute ends move a potential scour zone away from the dam, and dissipate flow energy to reduce the scour. Usually, so-called flip buckets or ski jumps are provided to generate jets, yet they are rarely issued by deflectors. The application of a theoretical mass point parabola is limited to predict the jet features, because effects related to the take-off angle and the disintegration process affect the jet air transport and trajectories. This research discusses the effect of pre-aeration of the approach chute flow on the jet features. A comparison with a former study indicates that mainly the upper jet portion is affected, that the black water jet core becomes shorter, and that the air transport increases. Although the lower trajectory is less affected and thus remains more coherent, the small effect of pre-aeration is sufficient to reduce the total jet throw length, so that pre-aerated jets tend to be shorter as compared with black-water approach flow jets, in agreement with prototype observations.