Jumping Towards the Future Ljunge, Magnus O.
Journal of contemporary archaeology (Online),
01/2021, Volume:
8, Issue:
1
Journal Article
Peer reviewed
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.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In view of the inability to directly and accurately obtain an athlete’s aerodynamic force during the take-off phase through the wind tunnel test, the athlete’s aerodynamic force and surrounding flow ...field form under different take-off postures are obtained through numerical simulation research, and the effects of different take-off modes on the aerodynamic characteristics during take-off in ski jumping are discussed. The multi-body system composed of the athlete and skis was selected as the research object. By using a partially averaged Navier–Stokes (PANS) turbulence model and a 3D numerical simulation of computational fluid dynamics (CFD), the aerodynamic characteristics of the athlete under different take-off postures were predicted. The take-off modes include the knee-push-hip (KPH) mode and hip-drive-knee (HDK) mode, and the hip joint angle of the HDK mode is significantly greater than that of the KPH mode. First, the aerodynamic force ratio of the athlete’s torso and legs is obviously large. Although the aerodynamic forces of arms themselves are not obvious, they have a great impact on the overall aerodynamic characteristics of the athlete, so the posture of the arms cannot be ignored. The total drag and moment of the HDK mode are significantly higher than that of the KPH mode, and the lift-to-drag ratio of the HDK mode is significantly lower than that of the KPH mode. At first, the total lift of the HDK mode is higher than that of the KPH mode, but in the last attitude, the total lift of the HDK mode does not rise but fall, and finally, the total lift of the HDK mode is lower than that of the KPH mode. The aerodynamic characteristics change dramatically during the take-off phase, and the aerodynamic characteristics of the two take-off modes are quite different, and these changes and differences are difficult to observe during real training and at the competition site. The KPH mode has an obvious aerodynamic advantage over the HDK mode. During the take-off process, the athlete should increase the force generated by the knee joint extension and appropriately reduce the speed of the hip joint extension, control the using force order of the lower limb joints, and push the hip joint extension by the knee joint extension in order to avoid issues, such as the hip joint angle being too large, the hip joint extension angle being too fast, the center of gravity being too far back, and other problems. Studying the aerodynamic characteristics during the take-off phase provides valuable insights for athletes to achieve favorable flight postures after take-off, offering scientific guidance to improve their training strategies and enhance their competitive performance.
Abstract Three-dimensional analysis of the entire sequence in ski jumping is recommended when studying the kinematics or evaluating performance. Camera-based systems which allow three-dimensional ...kinematics measurement are complex to set-up and require extensive post-processing, usually limiting ski jumping analyses to small numbers of jumps. In this study, a simple method using a wearable inertial sensors-based system is described to measure the orientation of the lower-body segments (sacrum, thighs, shanks) and skis during the entire jump sequence. This new method combines the fusion of inertial signals and biomechanical constraints of ski jumping. Its performance was evaluated in terms of validity and sensitivity to different performances based on 22 athletes monitored during daily training. The validity of the method was assessed by comparing the inclination of the ski and the slope at landing point and reported an error of −0.2±4.8°. The validity was also assessed by comparison of characteristic angles obtained with the proposed system and reference values in the literature; the differences were smaller than 6° for 75% of the angles and smaller than 15° for 90% of the angles. The sensitivity to different performances was evaluated by comparing the angles between two groups of athletes with different jump lengths and by assessing the association between angles and jump lengths. The differences of technique observed between athletes and the associations with jumps length agreed with the literature. In conclusion, these results suggest that this system is a promising tool for a generalization of three-dimensional kinematics analysis in ski jumping.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This study was conceived to bring a new orientation in the ski jumping training process addressing psychomotor quality, especially to its component - rapid force. The fast force education requires a ...new approach of the training process according to the technical components specificity and related to the individual particularities. The rapid force manifestation in symbiosis with de second phases in ski jumping and the takeoff movement ensures a fast entry into the flight phase with an optimal trajectory under a right timing. The research was conducted on young athletes - three components of the national ski jumping team aged 13-14 years - and targeted the rapid force as physical component. After applying the bi-cycle planned of rapid force development methodology, the results obtained provide more confidence in the effectiveness of the training and a positive prognosis regarding the results to be obtained in this field.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Aero/hydrodynamics plays a vital role in speed sports (athletes, athletes’ outfits, sports balls, sports equipment, etc.). Sports balls (spherical - golf, cricket, tennis, soccer, baseball, softball, ...etc. and oval shape - rugby, American football, Australian football), sports garments (swimsuits, ski jumping & alpine skiing suits, cycling skin suits, skating suits) are affected by aerodynamic and hydrodynamic behavior of fluids (air and liquids). The aero/hydrodynamics dictates the curved flight path of a soccer, tennis, cricket, baseball or golf ball and the course of a surfboard and sailboat through water. It affects speed, motion (position and placement) and ultimately athlete’s performance. Ignoring the effect of aerodynamic and hydrodynamics, it is almost impossible to achieve the desired success in any competitive speed sports. Due to stiff competition, the outcome of most sports aero/hydrodynamics research work undertaken by commercial organizations as well as individual sports teams/organizations are kept in-house, and scant information is available in the public domain. The RMIT University’s Sports Aerodynamics Research Group has been active in aerodynamics and hydrodynamics research related to some popular speed sports. This paper highlights some research work on sports aerodynamics and hydrodynamics undertaken at RMIT University
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article looks at how psychological variables such as passion, perceived performance, affect, worries and working alliance are associated with athlete burnout and illness and injuries among ...junior athletes in sport. A sample of 356 junior elite athletes from different sports such as cross country skiing, biathlon, Nordic combined, shooting, ice-hockey, ice-skating, ski jumping, alpine skiing, cycling, track and field, football, orienteering, handball, football and volleyball participated in the investigation. Our results show that harmonic passion, perceived performance, positive and negative affect, worry and working alliance are uniquely associated with athlete burnout, whereas sex, perceived performance and working alliance uniquely are associated with illness and injuries. The results are discussed in regard of applied implications and possible future research.
Nordic combined (NC) is an Olympic winter-sport performed as a ski jumping (SJ) event followed by a cross-country (XC) pursuit race employing the skating style.
To elucidate the associations between ...sport-specific laboratory capacities and SJ, XC skiing, and overall NC performance in a world-cup NC event.
Twelve international world-cup NC athletes from 8 nations performed laboratory testing one day prior to participating in a world-cup NC event. Squat jumps and SJ imitations (IMIT) were performed on a three-dimensional force plate, whereas XC skiing-specific physiological characteristics were obtained from roller ski skating tests on a treadmill and an all-out double poling (DP) test. Finally, body composition was measured. Laboratory capacities were correlated against performance in SJ, 10-km XC skiing, and overall NC in the world-cup event. Multiple regression analysis was used to determine the best suited laboratory variables for predicting performance.
Vertical IMIT velocity together with body-mass provided the best prediction for SJ performance (r2 = 0.70, p<0.01), while body-mass-normalized Formula: see text and DP power provided the best prediction for XC performance (r2 = 0.68, p<0.05). Body-mass-normalized Formula: see text was the only significant correlate with overall NC performance (r2 = 0.43, p<0.05) in this competition.
Overall, the concurrent development of Formula: see text, upper-body power, and SJ-specific vertical jump capacity while minimizing body-mass within the BMI limit set by FIS should be considered in the seasonal training of NC athletes.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
With the campaign for women's participation in international and Olympic ski jumping as a practical case, sport's potential for recognition of individual rights is explored. In line with Honneth's ...influential ethical theory, recognition of rights refers to a mutual recognition between persons of each other as rational and responsible agents with an equal right to take part in the public formation and development of their community or practice. The argument is that women ski jumpers were entitled to compete as they had actual and/or potential capabilities and skills to contribute in the public formation and development of their sport. Their exclusion was a violation of individual rights. At a more general level, sport is discussed as a sphere for recognition of rights. It is argued that the basic principles of equal opportunity to take part and to perform make sport a particularly clear and potent sphere for such recognition, and also for the identification of rights violations. In sport, rights, or the violation of rights, are demonstrated in concrete and embodied ways. It is concluded that struggles for recognition and individual rights are a continuous process in sport as in most other human institutions and practices.
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BFBNIB, FSPLJ, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This study uses inertial sensors to measure ski jumper kinematics and joint dynamics, which was until now only a part of simulation studies. For subsequent calculation of dynamics in the joints, a ...link-segment model was developed. The model relies on the recursive Newton-Euler inverse dynamics. This approach allowed the calculation of the ground reaction force at take-off. For the model validation, four ski jumpers from the National Nordic center performed a simulated jump in a laboratory environment on a force platform; in total, 20 jumps were recorded. The results fit well to the reference system, presenting small errors in the mean and standard deviation and small root-mean-square errors. The error is under 12% of the reference value. For field tests, six jumpers participated in the study; in total, 28 jumps were recorded. All of the measured forces and moments were within the range of prior simulated studies. The proposed system was able to indirectly provide the values of forces and moments in the joints of the ski-jumpers' body segments, as well as the ground reaction force during the in-run and take-off phases in comparison to the force platform installed on the table. Kinematics assessment and estimation of dynamics parameters can be applied to jumps from any ski jumping hill.
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Abstract The purpose of this study was to investigate the effects of posture of a ski jumper on aerodynamic characteristics during the take-off using computational fluid dynamics (CFD). The CFD ...method adopted for this study was based on Large–Eddy Simulation. Body surface data were obtained by 3-D laser scanning of an active ski jumper. Based on video analysis of the actual take-off movement, two sets of motion data were generated (world-class jumper A and less-experienced jumper B). The inlet flow velocity that corresponds to the in-run velocity in actual ski jumping was set to 23.23 m/s in the CFD. The aerodynamic force, flow velocity, and vortexes for each model were compared between models. The total drag force acting upon jumper A was lower than that acting upon jumper B through the whole movement. Regarding the total lift force, although jumper A's total lift force was less in the in-run posture, it became greater than that of jumper B at the end of the movement. In the latter half of the movement, low air-speed domain expansion was observed at the model's back. This domain of jumper B was larger. There were two symmetric vortexes in the wake of jumper A, but the disordered vortexes were observed behind the jumper B. In the case of jumper A, these two distinct vortexes generated by the arms produced a downwash flow in the wake. It is considered that the positioning of the arms in a very low position strongly influences the flow structure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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