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Alhammoud M, Girard O, Hansen C, Racinais S, Meyer F, Hautier CA, Morel B. Repeated practice runs during on-snow training do not generate any measurable neuromuscular alterations in elite alpine skiers. Front Sports Act Living 2022; 4:829195. [PMID: 35966108 PMCID: PMC9372580 DOI: 10.3389/fspor.2022.829195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 06/28/2022] [Indexed: 11/26/2022] Open
Abstract
Background Alpine skiers typically train using repeated practice runs requiring high bursts of muscle activity but there is little field-based evidence characterizing neuromuscular function across successive runs. Purpose To examine the impact of repeated ski runs on electromyographic activity (EMG) of the knee extensors and flexors in elite alpine skiers. Methods Nineteen national team alpine skiers were tested during regular ski training [Slalom (SL), Giant Slalom (GS), Super Giant Slalom and Downhill (Speed)] for a total of 39 training sessions. The surface EMG of the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF) and semimembranosus/semitendinosus (SMST) muscles was continuously recorded along with right knee and hip angles. The EMG root mean square signal was normalized to a maximal voluntary contraction (%MVC). The first and fourth runs of the training session were compared. Results There was no meaningful main effect of run on EMG relative activation time or mean power frequency beyond the skier's intrinsic variability. However, EMG activity of the vastii increased from the first to the fourth run in SL [VM, ~+3%MVC for IL and outside leg (OL), p = 0.035)], speed (VL, IL:+6%/OL:+11%, p = 0.015), and GS (VM, IL:0/OL:+7%, p < 0.001); the later with an interaction with leg (p < 0.001) due to a localized increase on the OL. The run time and turn time did not change from the first to the fourth run. There were no meaningful changes in angular velocities, amplitude of movement, or maximal and minimal angles. Conclusion Neuromuscular activity remains highly stable in elite skiers with low variability across four runs.
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Affiliation(s)
- Marine Alhammoud
- Aspetar–Orthopaedic and Sports Medicine Hospital, Doha, Qatar
- French Ski Federation, Annecy, France
- *Correspondence: Marine Alhammoud
| | - Olivier Girard
- School of Human Sciences (Exercise and Sport Science), The University of Western Australia, Crawley, WA, Australia
| | - Clint Hansen
- Department of Neurology, Christian-Albrechts-Universität zu Kiel Medizinische Fakultat, Kiel, Germany
| | | | - Frédéric Meyer
- Digital Signal Processing Group, Department of Informatics, University of Oslo, Oslo, Norway
| | - Christophe André Hautier
- Inter-University Laboratory of Human Movement Biology, University Claude Bernard Lyon 1, Lyon, France
| | - Baptiste Morel
- Inter-University Laboratory of Human Movement Biology (EA 7424), Savoie Mont Blanc University, Chambéry, France
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Park C, Kim B, Kim Y, Eum Y, Song H, Yoon D, Moon J, Han J. Carved Turn Control with Gate Vision Recognition of a Humanoid Robot for Giant Slalom Skiing on Ski Slopes. SENSORS 2022; 22:s22030816. [PMID: 35161561 PMCID: PMC8838643 DOI: 10.3390/s22030816] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/15/2022] [Accepted: 01/18/2022] [Indexed: 02/04/2023]
Abstract
The performance of humanoid robots is improving, owing in part to their participation in robot games such as the DARPA Robotics Challenge. Along with the 2018 Winter Olympics in Pyeongchang, a Skiing Robot Competition was held in which humanoid robots participated autonomously in a giant slalom alpine skiing competition. The robots were required to transit through many red or blue gates on the ski slope to reach the finish line. The course was relatively short at 100 m long and had an intermediate-level rating. A 1.23 m tall humanoid ski robot, ‘DIANA’, was developed for this skiing competition. As a humanoid robot that mimics humans, the goal was to descend the slope as fast as possible, so the robot was developed to perform a carved turn motion. The carved turn was difficult to balance compared to other turn methods. Therefore, ZMP control, which could secure the posture stability of the biped robot, was applied. Since skiing takes place outdoors, it was necessary to ensure recognition of the flags in various weather conditions. This was ensured using deep learning-based vision recognition. Thus, the performance of the humanoid robot DIANA was established using the carved turn in an experiment on an actual ski slope. The ultimate vision for humanoid robots is for them to naturally blend into human society and provide necessary services to people. Previously, there was no way for a full-sized humanoid robot to move on a snowy mountain. In this study, a humanoid robot that transcends this limitation was realized.
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Affiliation(s)
- Cheonyu Park
- Department of Convergence Robot System, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si 15588, Gyeonggi-do, Korea; (C.P.); (B.K.); (Y.K.); (Y.E.)
| | - Baekseok Kim
- Department of Convergence Robot System, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si 15588, Gyeonggi-do, Korea; (C.P.); (B.K.); (Y.K.); (Y.E.)
| | - Yitaek Kim
- Department of Convergence Robot System, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si 15588, Gyeonggi-do, Korea; (C.P.); (B.K.); (Y.K.); (Y.E.)
| | - Younseal Eum
- Department of Convergence Robot System, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si 15588, Gyeonggi-do, Korea; (C.P.); (B.K.); (Y.K.); (Y.E.)
| | - Hyunjong Song
- Department of Mechanical and Aerospace Engineering, New York University, New York, NY 10003, USA;
| | - Dongkuk Yoon
- ERICA IUCF, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si 15588, Gyeonggi-do, Korea;
| | - Jeongin Moon
- Sports Engineering Laboratory, Department of Physical Education, Seoul National University, 1 Gwanak-ro 38-gil, Gwanak-gu, Seoul 08732, Korea;
| | - Jeakweon Han
- Department of Robotics, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan-si 15588, Gyeonggi-do, Korea
- Correspondence: ; Tel.: +82-31-400-5292
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Gosselin P, Truong J, Chapdelaine C, Guilbert JS, St-Pierre É, Trahan X, Lussier Desbiens A. Effect of edged snow contact on the vibration of alpine skis. SPORTS ENGINEERING 2021. [DOI: 10.1007/s12283-021-00363-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Yoneyama T, Kagawa H, Tatsuno D, Kitade M, Osada K, Shigehara S. Effect of flexural stiffness distribution of a ski on the ski–snow contact pressure in a carved turn. SPORTS ENGINEERING 2021. [DOI: 10.1007/s12283-020-00339-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Reid RC, Haugen P, Gilgien M, Kipp RW, Smith GA. Alpine Ski Motion Characteristics in Slalom. Front Sports Act Living 2020; 2:25. [PMID: 33345019 PMCID: PMC7739813 DOI: 10.3389/fspor.2020.00025] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 03/04/2020] [Indexed: 11/13/2022] Open
Abstract
Important insight into ski function, and ultimately skier technique and tactics, can be gained by studying how measured ski trajectories compare to predictions based on theoretical models of ski-snow interaction mechanics. The aim of this investigation was to use a 3D kinematic data set collected on highly-skilled skiers during slalom race simulations to quantify ski motion characteristics and to compare these measures with theoretical predictions based primarily on ski geometrical characteristics. For slalom turns on moderate steepness (19°), ski edging angles reached maximum values of 65.7 ± 1.7° and 71.0 ± 1.9° for 10 and 13 m gate spacings. Turn radii reached minimum values of 3.96 ± 0.23 and 4.94 ± 0.59 m for the 10 and 13 m courses. These values were in good agreement with theoretical predictions by Howe (2001) of turn radius based on edging angle. Other results of the study support recent developments in understanding of the role which the ski shovel plays in groove formation during carving, and also point to the need for further study of how ski geometrical and physical characteristics interact to determine the ski's trajectory, particularly at low edge angles. These results have important implications for understanding the consequences that ski design can have for skier technique and tactics in competitive slalom skiing.
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Affiliation(s)
- Robert C Reid
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.,Alpine Skiing, Norwegian Ski Federation, Oslo, Norway
| | - Per Haugen
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Matthias Gilgien
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.,Alpine Skiing, Norwegian Ski Federation, Oslo, Norway
| | - Ronald W Kipp
- Independent Researcher, Squaw Valley, CA, United States
| | - Gerald Allen Smith
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.,Colorado Mesa University, Grand Junction, CO, United States
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Spörri J, Kröll J, Gilgien M, Müller E. Sidecut radius and the mechanics of turning-equipment designed to reduce risk of severe traumatic knee injuries in alpine giant slalom ski racing. Br J Sports Med 2016; 50:14-9. [PMID: 26702014 PMCID: PMC4717421 DOI: 10.1136/bjsports-2015-095737] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND There is limited empirical knowledge about the effect of ski geometry, particularly in the context of injury prevention in alpine ski racing. We investigated the effect of sidecut radius on biomechanical variables related to the mechanics of turning. METHODS During a field experiment, six European Cup level athletes skied on three different pairs of giant slalom (GS) skis varying in sidecut radii (30 m, 35 m and 40 m). Using a video-based three-dimensional (3D) kinematic system, a 22-point body segment model of the athletes was reconstructed in 3D, and the variables ground reaction force, centre of mass (COM) speed, COM turn radius, ski turn radius, edge angle, fore/aft position and skid angle were calculated. RESULTS While steering out of the fall line after gate passage, ground reaction force significantly differed between the 30 m and 40 m skis and between the 35 m and 40 m skis. These differences were mainly explainable by larger COM turn radii when skiing on the 40 m ski. During the same turn phase, significant differences in ski turn radius also were found, but there were no differences in edge angle, fore/aft position and skid angle. SUMMARY The sidecut-induced reduction in ground reaction force and the sidecut-induced increase in centre of mass and ski turn radius observed in this study provides indirect evidence of reduced self-steering of the ski. Self-steering plays a central role in the mechanism of anterior cruciate ligament rupture in alpine ski racing.
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Affiliation(s)
- Jörg Spörri
- Department of Sport Science and Kinesiology, University of Salzburg, Hallein-Rif, Austria
| | - Josef Kröll
- Department of Sport Science and Kinesiology, University of Salzburg, Hallein-Rif, Austria
| | - Matthias Gilgien
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Erich Müller
- Department of Sport Science and Kinesiology, University of Salzburg, Hallein-Rif, Austria
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Mössner M, Heinrich D, Schindelwig K, Kaps P, Schretter H, Nachbauer W. Modeling the ski-snow contact in skiing turns using a hypoplastic vs an elastic force-penetration relation. Scand J Med Sci Sports 2013; 24:577-85. [PMID: 23289971 DOI: 10.1111/sms.12035] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2012] [Indexed: 11/30/2022]
Abstract
A ski-snow interaction model is presented. The force between ski and snow is decomposed into a penetration force normal to the snow surface, a shear force parallel to it, and friction. The purpose of this study was to investigate the benefits of a hypoplastic vs an elastic contact for penetration in the simulation of skiing turns. To reduce the number of influencing factors, a sledge equipped with skis was considered. A forward dynamic simulation model for the sledge was implemented. For the evaluation of both contact models, the deviation between simulated trajectories and experimental track data was computed for turns of 67 and 42 m. Maximum deviations for these turns were 0.44 and 0.14 m for the hypoplastic contact, and 0.6 and 7.5 m for the elastic contact, respectively. In the hypoplastic contact, the penetration depth of the ski's afterbody maintained nearly the same value as the part under maximum load, whereas it decreased in the elastic contact. Because the shear force is proportional to the penetration depth, the hypoplastic contact resulted in a higher shearing resistance. By replacing the sledge with a skier model, one may investigate more complex skier actions, skiing performance, or accident-prone skiing maneuvers.
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Affiliation(s)
- M Mössner
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
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A parameter optimization method to determine ski stiffness properties from ski deformation data. J Appl Biomech 2011; 27:81-6. [PMID: 21451186 DOI: 10.1123/jab.27.1.81] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The deformation of skis and the contact pressure between skis and snow are crucial factors for carved turns in alpine skiing. The purpose of the current study was to develop and to evaluate an optimization method to determine the bending and torsional stiffness that lead to a given bending and torsional deflection of the ski. Euler-Bernoulli beam theory and classical torsion theory were applied to model the deformation of the ski. Bending and torsional stiffness were approximated as linear combinations of B-splines. To compute the unknown coefficients, a parameter optimization problem was formulated and successfully solved by multiple shooting and least squares data fitting. The proposed optimization method was evaluated based on ski stiffness data and ski deformation data taken from a recently published simulation study. The ski deformation data were used as input data to the optimization method. The optimization method was capable of successfully reproducing the shape of the original bending and torsional stiffness data of the ski with a root mean square error below 1 N m2. In conclusion, the proposed computational method offers the possibility to calculate ski stiffness properties with respect to a given ski deformation.
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Abstract
Kinaesthesia and Methods for its Assessment: Literature Review
In this review measurement techniques used for kinaesthetic sense assessment are presented. Kinaesthesia is an important part of human movement control and provides us with better understanding of specific movement system adaptations to fatigue, training and injury. Additionally, decreased kinaesthesia can be an injury predisposing factor, which stresses the necessity for its assessment in sports injury prevention programs. First, terminology and functional concept of kinaesthesia is presented in relation to other related concepts like proprioception and sensory-motor function. For better understanding, basic underlying neurological backgrounds are discussed in chapter two, encompassing peripheral sensory fields as well as the basics of the central processing. Additionally, factors affecting kinaesthesia and its adaptations to training are presented. Functional aspects are discussed, supporting the role of assessment of kinaesthesia in sports and rehabilitation. In the third chapter, a proposal for measuring methods classification is given. In the final chapter, different measuring protocols and their modifications are presented. Due to their usefulness in sports and injury prevention, methods for measuring sense of joint position, movement onset and active tracking are discussed in more detail. Possibilities and examples of their application to sports and sports injury rehabilitation settings are presented. Some basic guidelines are given of how to use these methods in training or for screening kinaesthesia.
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