Introduction The 19th Congress of the Austrian Sport Science Society (“Österreichische Sportwissenschaftliche Gesellschaft, ÖSG”), held in Innsbruck, Austria, centered on the theme of” Embracing Interdisciplinarity in Sport Science.” The idea of interdisciplinarity in sport science has been discussed for over three decades and stems from its position as a cross-sectional discipline integrating various natural and social sciences such as training science, sports medicine, biomechanics, sport pedagogy, sport psychology, sport sociology, and sport history. More recently, sports economy and sports management have also emerged as significant areas within sport science. Sports science is characterized by its strong practical relevance. It often focuses on applied research, where interdisciplinarity plays a critical role. Interdisciplinary work is a particularly important factor when approaching sport science from a problem-based perspective (Güllich & Krüger, 2022). Specifically, we argue that interdisciplinarity becomes crucial when we are trying to develop solutions for complex challenges in sport, the health sector, and society in general. For example, an interdisciplinary approach in sport science might merge aspects of psychology, physiology, and sociology with expertise of medical professionals to study and realize health promotion strategies. For the purpose of this editorial, we understand interdisciplinarity as a collaboration between individuals from different scientific disciplines but also from different professions with the goal of combining knowledge and methods to create new solutions for complex societal problems. This can range from the simple communication of ideas and experiences to mutual integration of concepts, methodologies, procedures, or data sharing (Zaiț et al., 2021). We think that sport scientists can and should take a leading role in such collaborations given their unique cross-disciplinary education related to human health, performance, and well-being. Leadership in interdisciplinary collaborations may be an opportunity for us as sport scientists to strengthen our profile and image in the society and to take responsibility in addressing societal challenges (Hottenrott et al., 2017). In preparation of this year’s ÖSG Congress in Innsbruck 2024, we tried to embrace this idea of interdisciplinarity in sport science. Before the event, we conducted an online survey across the DACH region (Germany, Austria, Switzerland) to identify current societal challenges that sport science should address and help with developing solutions. In parallel, we assessed the perceived importance of interdisciplinary work among sport scientists and related professions. Potential respondents to the survey were mainly contacted through the communication channels of the ÖSG and its equivalent associations in Germany (dvs) and Switzerland (SGS). Consequently, respondents included sport scientists as well as professionals from other fields who follow or are part of the activities of sport science associations. The findings of the survey were used in three different ways and will be described in this editorial: • to summarize the most frequently mentioned challenges and topics that sport science should address and help with developing solutions, • to develop an “Interdisciplinary Innovation Workshop” for the ÖSG Congress in Innsbruck 2024 where delegates transform the identified challenges into specific problems that can be solved, and • to compare the survey results with the content of the scientific abstracts submitted to the ÖSG Congress in Innsbruck 2024 and determine the alignment between the identified challenges and current research topics within the ÖSG community. The survey – Current challenges for sport science and beyond The survey responses were analyzed in MAXQDA 24 (VERBI software, 2021). The MAXQDA AI-Assist tool was used to suggest an initial coding scheme to group responses into categories. Two researchers refined the scheme into a final code set, independently coded the participants’ responses, and discussed mismatches to agree on the final code assignments. The survey yielded 176 responses, of which 85 were fully completed. Respondents (42% women) had a mean age of 40.2 years (± 13.8). Regarding their primary professional field, 34% identified as scientists working at a university, college, or research institution, 26% were healthcare professionals (e.g., physicians or therapists), 15% worked in the private sector including self-employment, 13% were students or educators, and 12% were either coaches, athletes, or employed within a sports federation. 91% reported that interdisciplinarity was a key component of their work. The most frequently mentioned challenges fell into the category of “prevention and rehabilitation” (34%), followed by “job profiles related to sport science and exercise therapy” (23%), “sport science mission for research and education” (11%), “broader societal issues” (5%), “structural development of organized and non-organized sports” (5%), “inclusion and integration through sports” (4%), “self-awareness and self-reflection” (3%), “technological progress” (2%), “financing” (2%), and “elite sports” (2%; orange bars in Figure 1). Coding was not possible for 5% of the answers. The workshop – Transforming challenges into specific problems Building on the findings of the survey, we collaborated with the ikivox collective (Nyon, France, https://ikivox.org/en/) to develop an “Interdisciplinary Innovation Workshop” held at the ÖSG Congress in Innsbruck 2024. With the help of ikivox who specialize in collective intelligence and collaborative design approaches, we designed a workshop with the following objectives: • to transform the identified challenges into specific problems that can be solved with innovative solutions • to experience interdisciplinary collaboration and new ways of working together • to position the Austrian Sport Science Society (ÖSG) as an enabler, bringing value to its members to improve exchange about sport science in Austria • to identify whether the teamwork could continue on some topics after the Congress with the support of the ÖSG Eventually, 42 Congress delegates signed up for the workshop and could choose to work on one of the following challenges: “physical inactivity at the work place”, “physical inactivity in children”, “image of sport science in society”, “role of exercise therapists in medical teams”, “influence of menstrual cycle on athletic performance”, “health awareness in society”, “inclusion of bodily disabled individuals as participants in public sport events”, and “integration of girls and women with migration background through sports”. This format of collaboration may provide a framework for future interdisciplinary initiatives within the ÖSG and beyond. The Congress abstracts – Comparing the identified challenges with actual research topics at the ÖSG Congress Having identified current challenges for sport science, it seemed of interest to compare those challenges with the content of the submitted scientific contributions to the ÖSG Congress in Innsbruck 2024. The Congress received 78 contributions including 60 regular abstracts, 12 Young Investigator Award submissions and 6 extended abstracts. Five section editors managed the peer-review process and drew on the expertise of 45 peer reviewers. Each contribution was evaluated and rated by two independent reviewers. Critical feedback of reviewers had to be addressed by the authors in revised abstract submissions. Following the revision round, 75 contributions were accepted for presentation at the Congress. The contributions spanned a wide range of research areas including “biomechanics, motor control & sports technology” (26% of abstracts), “sport psychology & pedagogy” (25%), “sports medicine, exercise therapy & public health” (20%), “sports physiology & exercise science” (16%), “sports sociology, economy & management” (14%). Of all contributions, 64 were presented orally and 11 as poster presentations while 65 abstracts were published in the Congress proceedings. When applying the same code set to the abstract submission, we found a remarkable similarity to the survey findings in that 34% of abstracts fell into the category of “prevention and rehabilitation” (blue bars in Figure 1). However, we also found clear mismatches: the content of the abstracts focused much more on “technological progress” (21% vs. 2% in survey), and “elite sports” (15% vs. 2% in survey). Further, while 23% of the survey respondents highlighted challenges in “job profiles related to sport science and exercise therapy”, none of the conference abstracts addressed this topic, indicating a gap between perceived challenges and ongoing research. Summary and outlook At this year’s ÖSG Congress in Innsbruck 2024, we tried to embrace interdisciplinarity in sport science by taking a problem-based approach to sport science. Based on a pre-Congress survey, we identified key challenges within sports and society in general that should be addressed by sport scientists. The most frequently mentioned challenges were related to the topic of “rehabilitation and prevention”, specifically physical inactivity in children and at the workplace. At the Congress, delegates participated in an “Interdisciplinary Innovation Workshop” to work on the identified challenges and transform them into more approachable and specific problems. Interestingly, the topic of “rehabilitation and prevention over the lifespan” was also dominant in a third of scientific contributions to the Congress, showing alignment between perceived challenges and research efforts in the ÖSG community. In contrast, the topics of “elite sports” and “technological progress” were highly represented in Congress abstracts but were not perceived as current challenges in the survey. In turn, more than 20% of survey respondents perceived challenges related to the job profile of sport science alumni and exercise therapists, which were not addressed by Congress abstracts. This potentially highlights the discrepancies between a discipline-based and problem-based applied approach to sport science: In many sub-disciplines of sport science, pushing the boundaries of human performance and health – often with the help of new technologies – remains an important and central basic science goal. However, there may be no apparent or immediate transfer to current challenges in society. From our perspective, both approaches to sport science are valuable as well as needed and we argue that interdisciplinary workshops and initiatives as organized at the ÖSG Congress in Innsbruck 2024 can help to facilitate the transfer of scientific findings from the sport science sub-disciplines to the solution of current challenges in society. The ÖSG plans to facilitate annual meetings of working groups formed at the innovation workshop to support ongoing work on the identified problems, fostering interdisciplinary collaboration, supporting activity within the society, and widening the impact of sport scientists in complex societal challenges. Author contributions JB, GR, KS, LSM, and MM were the section editors for the Congress abstracts. LR and MM conducted the pre-Congress survey and analyzed the responses as well as the Congress abstract content. LR wrote the first editorial draft. All authors edited and approved the final editorial version. References Güllich, A., & Krüger, M. (2022). Sport: Das Lehrbuch für das Sportstudium [Sport: The textbook for sports studies]. Springer Berlin Heidelberg. Hottenrott, K., Baldus, A., Braumann, K.-M., Hartmann-Tews, I., Holzweg, M., Kuhlmann, D., Seyfarth, A., Strauß, B., Sygusch, R., & Vogt, L. (2017). Memorandum Sportwissenschaft [Memorandum sports science]. German Journal of Exercise and Sport Research, 47(4), 287–293. https://doi.org/10.1007/s12662-017-0476-x Zaiț, A., Bratianu, C., Vătămănescu, E.-M., Andrei, A. G., & Horodnic, I. A. (2021). Interdisciplinarity: A complexity approach towards academic research. Systems Research and Behavioral Science, 38(3), 294–306. https://doi.org/10.1002/sres.2758

Introduction & Purpose The low friction coefficient of a ski on snow is due to the formation of a meltwater layer between the ski base and the snow surface. It is a widely accepted theory that the formation of this meltwater is due to frictional heating (Bowden & Hughes, 1939). The experimental evidence regarding the formation of frictional meltwater has been a challenging task. This is because meltwater is dynamically created and most likely refreezing immediately once the frictional heat input is terminated. Ambach & Mayr (1981) measured the change in capacitance of a probe to quantify the thickness of the meltwater layer. They reported a thickness of the meltwater layer of 4-20 µm during downhill skiing with sliding speeds up to 17 m/s and ambient temperatures of -5 °C and -10 °C. The reported thickness was put into question by Colbeck (1994). Strausky et al. (1998) used fluorescence spectroscopy to detect the meltwater layer. However, they concluded to have observed no water layer above their detection limit of 0.05 µm at speeds up to 0.1 m/s (an unrealistic speed of skiing). Hasler et al. (2021) used infrared imaging at a snow temperature of -4 °C, and gave evidence regarding meltwater formation by observing the temperature change of the snow surface after the ski passage. Furthermore, heat dissipation calculations made by Colbeck (1988), numerical modelling by Bäurle et al. (2007) and Makkonen & Tikanmäki (2014) suggest the thickness of the meltwater layer to be below 1 µm. Despite decades of research in the field of ski-snow tribology, the conclusive evidence regarding the formation of this meltwater layer and its detection are contentious. The complexity of the task of frictional meltwater detection is due to several influencing factors like small contact spots, low water layer thickness, short time intervals, high sliding speed of ski etc. In this regard, our purpose is to present an innovative approach for detecting the formation of frictional meltwater by applying a humidity indicator to the surface of snow and analysing the change in its color in response to contact with water. Methods Humidity indicators are chemicals that change their color in response to contact with water. As a humidity indicator we use crystal violet which is widely used as a dye in textile industry and for printers. The mechanism of color change of crystal violet involves a chemical reaction, resulting in the formation of a covalent bond between the central carbon atom and a hydroxyl ion (OH-). During ski-snow interaction, if the frictional heat generates a meltwater layer, the formed hydroxyl ions should undergo a direct chemical reaction with crystal violet resulting in a permanent color change of the chemical. The resulting change in color of the chemical from violet to blue is supposed to be a good indicator of the formation of frictional meltwater. The experiments were performed at the snow lab of the Research Center Snow, Ski and Alpine Sports at the University of Innsbruck (Austria) on a linear tribometer with 18 m sliding surface length (Hasler et al., 2016). A cross-country ski (Salomon LAB WC Equipe 10 Skate, 192 cm) was moved at a sliding speed of 15 m/s. The normal load was 430 N taking into account half the weight of the skier during XC skiing. On three different days we performed experiments with different snow temperatures. First day with snow temperature -1 °C, the next day with -3 °C and then on the third day with -5 °C. On each day, the gliding experiment was repeated on four snow tracks. The reason to select this range of temperatures was that we expected more frictional meltwater at higher temperatures. Crystal violet was sprayed over the snow surface using a pump sprayer. After spraying the chemical, a 30-minute break was applied to allow for any reaction with the surface. However, no change in the color of the chemical was observed. A digital camcorder (Sony FDR-AX53, video resolution 1920 x 1080, with frame rate of 50 Hz) was mounted close to the snow track to record the entire measurements. There was a manual white balance done before the start of video recording. During the entire measurements, there was no change in the camera settings and the lighting conditions did not change. Regular monitoring of the snow temperature was done using a PT1000 sensor (Nexensos W-EYK, Heraeus Holding GmbH, Germany) and an 18-bit data logger (Datataker DT80, ThermoFisher Scientific, United States). After the test, the images captured before, and after the runs were systematically analysed using a self-developed program in LABVIEW (National Instruments Corporation, Austin, Texas, USA). The objective was to detect meltwater caused by the frictional heating through the passage of the ski. With the presence of meltwater, crystal violet changes its color from violet to blue. To evaluate the color change, we separated the images into the three-color channels red, green and blue and calculated the intensity ratio red/blue. The decrease in the ratio indicates the presence of meltwater. For numerical evaluation of the data, we took a percentage change of the average ratios in the frames and then calculated the average for all ten runs. Results We observed a decrease in the red/blue ratio between the two images captured before and after the ski passage indicating the presence of more blue pixels. At snow temperature -1 °C, the average of the percentage decrease in ratio (red/blue) is -6.37% which is the highest as compared to -3.47% (at -3 °C) and -0.66% (at -5 °C). This shows that there is more pronounced color change at -1 °C, which gives an indication that the amount of frictional meltwater formed is highest at this temperature. Discussion The experimental results using the humidity indicator gave evidence for the generation of frictional meltwater. The frictional heat leads very probably to the formation of meltwater which in turn reacts with the crystal violet and changes its color. The change in color of the chemical from violet to blue was most pronounced at -1 °C (close to the melting point) as compared to lower temperatures (-3 °C and -5 °C). At constant frictional heat production, we expect most frictional meltwater at -1 °C because of the energy required is lowest to raise the snow temperature from -1 °C to the melting point of snow at 0 °C as compared to the other temperatures. The response of crystal violet in contact with the formed meltwater provides good evidence for unravelling and further understanding the mechanisms of ski-snow friction. This approach is useful for detecting the presence of meltwater but the amount or the thickness of the layer cannot be determined. Hence, the analysis is semiquantitative and requires more precise techniques like thermal imaging or measuring the dielectric properties of snow. Conclusion The goal of this work to detect the frictional meltwater using a humidity indicator was successfully achieved. These are the novel results providing experimental evidence of frictional meltwater. The present work provides a good basis to compare the amount of frictional meltwater formed at the three examined snow temperatures. Acknowledgement This work was supported by the Austrian Science Fund (FWF): [P36489-N]. References Ambach, W., & Mayr, B. (1981). Ski gliding and water film. Cold Regions Science and Technology, 5(1), 59-65. https://doi.org/10.1016/0165232X(81)90040-9 Bäurle, L., Kaempfer, T. U., Szabó, D., & Spencer, N. D. (2007). Sliding friction of polyethylene on snow and ice: Contact area and modeling. Cold Regions Science and Technology, 47(3), 276-289. https://doi.org/10.1016/j.coldregions.2006.10.005 Bowden, F. P., & Hughes, T. (1939). The mechanism of sliding on ice and snow. Proceedings of the Royal Society A. Mathematical and Physical Sciences, 172(949), 280-298. https://doi.org/10.1098/rspa.1939.0104 Colbeck, S.C. (1988). The kinetic friction of snow. Journal of Glaciology, 34(116),78-86. https://doi.org/10.1017/S0022143000009096 Colbeck, S.C. (1994). A review of the friction of snow skis. Journal of Sports Sciences, 12(3), 285-295. https://doi.org/10.1080/02640419408732174 Hasler, M., Jud, W., & Nachbauer, W. (2021). Snow temperature behind sliding skis as an indicator for frictional meltwater. Frontiers in Mechanical Engineering, 7, Article 738266. https://doi.org/10.3389/fmech.2021.738266 Hasler, M., Schindelwig, K., Mayr, B., Knoflach, C., Rohm, S., van Putten, J., & Nachbauer, W. (2016). A novel ski–snow tribometer and its precision. Tribology Letters, 63(3), 33. https://doi.org/10.1007/s11249-016-0719-2 Makkonen, L., & Tikanmäki, M. (2014). Modeling the friction of ice. Cold Regions Science and Technology, 102, 84-93. https://doi.org/10.1016/j.coldregions.2014.03.002 Strausky, H., Krenn, J. R., Leitner, A., & Aussenegg, F. R. (1998). Sliding plastics on ice: fluorescence spectroscopic studies on interfacial water layers in the μm thickness regime. Applied Physics B: Lasers & Optics, 66(5). https://doi.org/10.1007/s003400050442

Aerodynamic drag in sports can be assessed using a multitude of methods such as wind tunnel tests, computational fluid dynamics simulations or field tests. All these methods are able to simulate specific situations in sports. The goal of this study was to describe a measurement system that assesses the aerodynamic properties of textile covered cylinders in a special situation: contrary to wind tunnel measurements, fabric-covered samples were moved in stationary air over a distance of up to 20 m at speeds from 5 to 20 ms(-1). The measurement system showed a precision better than 2%. The course of the drag coefficient over speed was very similar to comparison measurements in a wind tunnel, but the drag coefficient was lower by up to 18% with respect to the wind tunnel and the speed at which the drag crisis occurred in the wind tunnel was higher by up to 10 ms(-1). Reasons could be a higher turbulence intensity in our measurement setup or, more likely, that the motion of the sample was too short to build up a steady air flow as in wind tunnels. The limited duration of the experiment, however, maybe brings it closer to the reality in situations in sports where the athlete's posture and/or direction of motion change frequently or for some aspects of sports ball aerodynamics.

Modeling of ski friction requires an in-depth understanding of the ski-snow contact. For this aim, we imple-mented the Euler-Bernoulli beam equations for an embedded cross-country skating ski. Apparent contact area and pressure distribution were calculated from the ski's penetration depth using a hypoplastic force-penetration relation of snow. In a static validation experiment on an elastomer foundation, the difference between measured and calculated pressure of a loaded ski was below 5.1 kPa. For cross-country skis gliding on snow, the apparent contact area increased for increased normal load, softer snow, and decreased ski stiffness and camber. The pressure along the ski showed separated parts. The maximum pressure increased for increased normal load and harder snow. Overall, we observed an apparent contact area between 23.6 and 57.8% and a maximum pressure between 27.4 and 110.7 kPa. Concluding, a model for the ski-snow contact in straight gliding ski was developed. Apparent contact area and pressure distribution was affected by normal load, snow hardness, and ski stiffness and camber. Effects on the pressure should be considered in applications like ski construction, waxing, and modeling friction along the ski.

Objectives:In this study, we examined the practicability of deep learning-based 2D keypoint detection applied to regular skiing and injury situations (i.e., out-of-balance situations and fall situations) on an alpine ski racing track. Methods:We therefore created a regular skiing- and injury situation-specific dataset (hereinafter called "Injury Ski Dataset"), on which the state-of-the-art keypoint detection algorithms OpenPose, Mask-R-CNN, AlphaPose and DCPose were compared. The performance of each keypoint detector was evaluated by calculating the mean per joint position error (MPJPE) and the percentage of correct keypoints (PCK). Failure cases and common error patterns were further investigated by a visual analysis. Results:We observed the best results for regular skiing, with 81%-92% of all keypoints detected correctly at an MPJPE of 9 (2) to 14 (3) pixels. In injury situations, self-occlusions and rare poses became more likely, similar to occlusions due to snow spray and motion blur. As a result, the performance in out-of-balance situations decreased to 68%-80% (PCK), while in fall situations, only 35%-54% of all keypoints were detected correctly, with mean errors of 26-36 pixels. Among all algorithms, AlphaPose was the most robust and achieved the best results. Conclusions:PCK and MPJPE for regular skiing were in the range of manual annotation errors and can be considered low enough for further biomechanical analysis. For fall situations, keypoint detection should be further improved. Regarding the development of a deep learning tool for injury analysis in alpine skiing in the future, we propose to fine-tune a well-performing keypoint detector, such as AlphaPose, on a ski- and injury-specific dataset, such as ours.

Whilst studies of the wear of ski bases and wax coatings are available, few is known about the change of the snow due to sliding ski. In this study, ski-friction-induced changes of snow were investigated. The structure of the snow was scanned using X-ray computed tomography (CT) before and after 1, 10, and 20 recurring runs of a cross country ski at snow temperatures of-1.3,-10.7, and-19.1 degrees C. Concurrently, friction was measured. The volume fraction of ice as function of the vertical distance from the snow surface was derived from the CT data. Superficial snow was compacted and surface roughness was reduced by the ski passage. The volume fraction of ice in snow had maximum values of 0.58-0.93 at 0.02-0.3 mm below the snow surface. Below the depth of 1.0 mm, snow was not altered at all. Friction increased after the first run with subsequent runs at-1.3 degrees C and-10.7 degrees C whereas it decreased at-19.1 degrees C. In the first run of a ski, brittle deformation of the snow due to vertical force and ploughing was dominant. In the following runs, abrasive wear and/or melting appeared. Estimates for the available relative contact area varied between 0.02 and 0.27.

Injury analysis may be one of the most beneficial applications of deep learning based human pose estimation. To facilitate further research on this topic, we provide an injury specific 2D dataset for alpine skiing, covering in total 533 images. We further propose a post processing routine, that combines rotational information with a simple kinematic model. We could improve detection results in fall situations by up to 21% regarding the PCK@0.2 metric.

OBJECTIVES:Ski boots are designed to transfer forces from skier to ski. This transfer is among others affected by the flexion stiffness (FS) and so effects safety and skiing performance. Previous studies have used devices with prosthetic legs to evaluate FS, however, influencing factors like the foot and lower leg shape or individual buckle closure are not considered. The purpose of the study was to (i) develop a device to measure the individual flexion stiffness (IFS) of ski boots worn by skiers, to (ii) determine the repeatability of the measurement, and to (iii) compare the IFS with the nominal flex index of the manufacturers. METHODS:21 subjects were tested twice to assess repeatability. The IFS of 135 subjects were measured on ski slopes and compared with the nominal flex indices. RESULTS:Repeated measurements revealed a correlation rp of 0.98 (p<0.001) and a relative standard error of SEMrel=3.0%. The correlation between IFS and nominal flex index was moderate with rs=0.64 (p<0.001). Post hoc analysis showed no statistical differences between flex index 80 and 90 (p=0.29) and flex index 100 and 110 (p=0.60). CONCLUSION:The determination of IFS was sufficiently repeatable. Considerable differences were found between IFS and the nominal flex indices of the manufacturers. The introduction of a measurement standard may improve the comparability among the manufacturers. Our method is not suitable as standardization method due to the measurements with subjects. However, the data collected may provide a valuable baseline for a future standardization.

Objectives: In winter terrain parks special airbags are used for skiers and snowboarders to practice jumps and achieve safe landings. However, in 2010 two skiers landed at the end of oval airbags. One suffered fatal, the other severe, injuries. The aim of this study was to identify parameters that lead to jumping over the airbag and to suggest preventive measures. Design: Simulation study. Methods: For the calculation of the flight distance the equation of motion was solved for the jumper's approach and flight phase. Measured data of five jumps into an airbag employed in a similar geometry and conditions as in the second accident case were used to validate the simulation and to measure typical takeoff velocities. The effect of approach and takeoff parameters on the flight distance for oval and flat airbags was analyzed with the simulations. Results: In both accident cases a too long approach led to a too high takeoff speed, which was the cause for landing at the end of the oval airbags. The effect of flight distance is considerably more sensitive to approach and takeoff parameters with oval versus flat airbags. Conclusions: Three measures are recommended to prevent jumping over an airbag. An approach corridor with top and lateral fences has to be set up and the approach should be steep. Flat airbags are preferable to oval airbags. Airbags should be equipped with a heightening at the end. (C) 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Objectives: Since the polymeric materials commonly used for ski boots feature viscoelastic properties, the results of ski boot flexion tests are expected to be influenced by flexion velocity. Devices testing at all skiing specific ankle angular velocities are currently not available. Therefore, the aims of this study were to (i) develop a system allowing the testing of ski boots at high ankle angular velocities, (ii) quantify the effect of ankle angular velocity on viscoelasticity and (iii) determine the repeatability of the system. Design and Method: A test bench and a lower limb prosthesis were developed to determine tibia angle and applied torque. To assess the effect of angular velocity, two pairs of ski boots were tested at 5 degrees/s, 50 degrees/s, 75 degrees/s and 100 degrees/s. To assess stiffness variation and measurement repeatability, ten different used ski boots of different manufacturers were tested twice. Results: Four ski boot flexion stiffness parameters and two energy dissipation factors were reported. The repeatability of the stiffness and the energy dissipation parameters was better than 4% and 3%, respectively. Stiffnesses and dissipation factors increased with increasing angular velocity. Conclusion: In the present study a reliable system facilitating the testing of ski boots at velocities of up to 100 degrees/s was developed. To comprehensively characterise the viscoelastic properties of ski boots, we propose to report four ski boot stiffness parameters and two energy dissipation factors. An ankle angular velocity above 50 degrees/s was recommended to perform mechanical tests of ski boots if employed in slalom-like skiing. (C) 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Slalom skiers hit flex poles whereby an impulse is transferred from the skier to the flex pole. Each such impact leads to a speed reduction of the skier, which is clearly greater for relatively lighter skiers than it is for relatively heavier skiers. Additionally, there is an injury risk for the skier caused by the impact and the risk for breakage of the flex pole. For a detailed analysis of causes and consequences of this impact, three-dimensional finite element models were developed for flex poles and a pendulum impactor. The finite element models were validated by comparing data of experiments with the pendulum impactor and simulations. The comparisons included flex-pole motion, flex-pole speed, whiplash measure, pendulum impulse loss and cross-sectional deformed oval shapes. The differences of the comparisons were less than 3% for the first four parameters. The comparison of the cross-sectional deformed oval shapes' behavior agreed well. With the new validated finite element model, the influence of factors such as flex-pole diameter, wall thickness, length and material properties on the transferred impulse and the mechanical loadability of the flex pole can be systematically analyzed. With this knowledge, specifications for flex poles can be adapted to improve fairness at slalom races and reduce the injury risk and the danger of damaging the upright pole.

In skiing the skier-flex pole impact causes a deflection and rotation of the flex pole and a speed loss of the skier. The purpose of the present study was to investigate the effects of skier and pole parameters on time loss, pole deflection, and pole damage speed caused by the skier-pole impact in slalom. Validated finite element models were used for the simulation of the impact. Skier mass, speed and impact height and pole mass, bending stiffness, diameter, and wall thickness were analyzed. Time loss was assessed for seven pole impacts by a simple simulation model of a skier schussing down an inclined plane. From the skier parameters, impact height followed by impact speed showed the highest effect on the skier-pole impulse. The impulse increased with increasing pole mass whereas the effect of bending stiffness was negligible. Time loss could be reduced by lowering the pole mass. However, lowering of pole diameter or wall thickness increased pole deflection enhancing injury risk due to the whiplash effect. Additionally, the reduction of wall thickness decreased pole damage speed with the disadvantage of higher risk of pole fractures. Overall, lowering pole mass for the current impact speeds in World Cup slalom races requires additional investigation. In children and youth races with lower impact speeds than in World Cup races, a pole mass reduction would be possible.

In Europe and North America, approximately 150 fatalities occur as a result of avalanches every year. However, it is unclear whether certain shovel shapes are more effective than others in snow removal during avalanche victim recovery. The objective was to determine the performance parameters with a developed standardized test using different shovel shapes and to determine sex-specific differences. Hence, several parameters were determined for clearing the snow from a snow filled box (15 men, 14 women). A flat (F) and a deep (D) shovel blade with the shaft connected straight (S) or in clearing mode (C) were used for the investigation of the shovel shapes FS, DC and the subsequent use of DC&DS. Mean snow mass shifted per unit time increased significantly from 1.50 kg/s with FS to 1.71 kg/s (14%) with DS and further to 1.79 kg/s (4%) with DC&DS for all participants. Snow mass shifted per unit time was 44% higher (p < 0.05) for men than for women. In excavation operations, the sex-specific physical performance should be taken into account. The results were limited to barely binding snow, because only with this snow did the tests show a high reliability.

Friction between skis and snow was studied in a variety of field and laboratory measurements. Whilst field tests have the drawback of changing conditions, in laboratory tests sport-specific sample sizes and speeds could not be measured up to now. Hence, a novel linear tribometer was developed allowing studies with whole skis at sport-specific speeds. The precision of the tribometer was better than 2.2 %. The dominant cause for the imprecision was the variability of the single snow tracks at lower speed, whilst at higher speeds also the determination of normal and friction force and speed became relevant. The precision is high enough for discriminating differences needed for the analysis of different ski and snow conditions and the study of friction processes.

The rolling resistance of skis used in roller skiing competitions should resemble the gliding resistance of cross-country skis to allow specific training and moving patterns for cross-country skiing and to guarantee equal opportunities for athletes in roller ski races. Therefore, the purpose of this work was to develop a portable rolling resistance meter to precisely measure the rolling resistance of roller skis. Measurements were based on recordings of the angular deceleration of a flywheel due to the rolling resistance between a roller ski’s wheel and the flywheel’s steel surface. Rolling resistance coefficients of four roller ski types ranged between 0.019 and 0.025. Measurements of the rolling resistance coefficient showed a precision of 1.26%. Substantial rolling resistance coefficient variations (10%) were observed for wheels of the same type. Furthermore, the rolling resistance coefficient was found to be negatively correlated with normal load or ambient temperature. The proposed rolling resistance meter is appropriate to determine the rolling resistance coefficient of roller skis’ wheels precisely.

After falls, skiers or snowboarders often slide on the slope and may collide with obstacles. Thus, the skier's friction on snow is an important factor to reduce incidence and severity of impact injuries. The purpose of this study was to measure snow friction of different fabrics of ski garments with respect to roughness, speed, and contact pressure. Three types of fabrics were investigated: a commercially available ski overall, a smooth downhill racing suit, and a dimpled downhill racing suit. Friction was measured for fabrics taped on a short ski using a linear tribometer. The fabrics' roughness was determined by focus variation microscopy. Friction coefficients were between 0.19 and 0.48. Roughness, friction coefficient, and friction force were highest for the dimpled race suit. The friction force of the fabrics was higher for the higher contact pressure than for the lower one at all speeds. It was concluded that the main friction mechanism for the fabrics was dry friction. Only the fabric with the roughest surface showed friction coefficients, which were high enough to sufficiently decelerate a sliding skier on beginner and intermediate slopes.

The purpose of this study was to analyze the effect of the surface structure on the friction between steel and snow. On a linear tribometer positioned inside a cold laboratory, four steel skis with different running surfaces were tested over a wide range of velocity, snow temperature and normal force. The surface roughness was measured with a focus variation microscope. The friction tests showed that the surface roughness had a major effect on friction between steel and snow, with higher friction for smooth surfaces than for rough ones. The effect was particularly strong for temperatures close to the melting point, where the friction strongly increased for smooth surfaces. The degree of dependence was affected by the gliding speed, leading to two different kinds of velocity-dependent friction curves. Increased adhesion and wet friction due to an increase in contact area were interpreted as cause for the higher friction of smooth surfaces.

The temperature of snow under skating skis was studied with infrared sensors at four positions and three different velocities. To have an indication of causes and consequences of the heating the friction coefficient with a linear tribometer and the pressure distribution were measured as well. The friction increased with velocity. The highest temperature increase was measured 440mm from the ski end at the highest velocity of 10 m/s. Temperature increase at position 1550mm was independent of velocity. Friction coefficient, pressure distribution and temperature measurements showed a high reliability and allowed to create a model to explain the temperature profile along the ski.

The influence of important parameters on the flight trajectory for jumps in downhill W orld C up races was investigated. To quantify the impact injury risk at landing, the parameter equivalent landing height ( ELH ) was introduced, which considered a variable slope inclination during the landing movement. Altogether, 145 runs at four different jumps in W orld C up races and trainings were recorded and analyzed. A simulation model was developed to predict the flight phase of the skier. Drag and lift areas were selected by parameter identification to fit the simulation trajectory to the two‐dimensional data from the video analysis. The maximum values of the ELH which can be absorbed with muscle force was taken from the study of M inetti et al. for elite female and male ski racers. A sensitivity analysis based on the four jumps showed that ELH is mainly influenced by takeoff angle, takeoff speed, and the steepness of the landing surface. With the help of the developed simulation software, it should be possible to predict the ELH for jumps in advance. In case of an excessive ELH , improvements can be made by changing the takeoff inclination or the approach speed.

The purpose of this study was to analyze the kinetic friction of different combinations of snowboard base structures and waxes. On a linear tribometer in a cold lab 3 snowboards with 3 different base structures were first waxed with a training wax. Then the friction coefficient was assessed at 2 m/s, 5 m/s and 8 m/s. Subsequently the boards were prepared with a racing finish and the friction coefficient of the boards was measured again.The effects of base structure and wax on the kinetic friction on snow appear to be strongly interdependent. A wax that takes effect on one board at given conditions must not be working on a board with different base structure. In addition there is a strong influence of the sliding speed. Optimization of race equipment must not only consider the interdependency of base structure and wax but also the relevant competition speed. (C) 2014 Published by Elsevier Ltd.