Ski Boots Research Articles

AStudy on Development and Analysis of Measurement System of Reaction Force from Snow Surface Using Compact Force Sensors for Private Ski Boots

AStudy on Development and Analysis of Measurement System of Reaction Force from Snow Surface Using Compact Force Sensors for Private Ski Boots

J1020102 関節の粘弾性特性に着目したアルペンスキー選手のスキル解析

We have studied the ski boots design based on the characteristic of the frame of the Japanese player experimentally to shorten finish time for the purpose of the improvement of the competition results of the alpine skiing player. However, understanding and the practicing of the technique to use the potential of the tool are important as well as modifying the design of the tool for shortening of the finish time. This paper focuses on the energy dissipation by the bending motion and the energy increase by the stretching motion at the change of turn, and clarify a turn technique to shorten the finish time. We analyzed the influence of energy balance during the joint movements on the finish time with posture analysis of the movie of world cup competitions by using a 3DCAD model. The results shows that shortening the finish time is achieved by reducing the number of bending motion and increasing the number of stretching motion while downhill. In addition, this paper shows that the joints motions of the skier during downhill can be estimated precisely by proposed analysis method using 3DCAD model.

J1020103 内傾角速度を向上するスキーブーツ用フットベッドの設計

J1020103 内傾角速度を向上するスキーブーツ用フットベッドの設計

Effect of the visco-elastic properties of thermoplastic polymers on the flexural and rebound behaviours of ski boots for alpine skiing

The flexural behaviour and elastic rebound are the main parameters that determine the global performance of a ski boot during skiing. These two parameters are related to the visco-elastic properties of the polymeric materials used. For this reason, the visco-elastic properties of the materials most utilized for the production of ski boots (polyurethanes and polyolefins) have been studied using dynamic mechanical thermal analysis in a temperature range between −30 °C and +50 °C. Also, the flexural and rebound behaviours of the boot have also been tested using specially designed test benches. The dynamic mechanical thermal analysis results and the flexural and rebound tests results were compared, and a significant effect of the visco-elastic properties on the flexural and rebound behaviour of ski boots was seen. Therefore, dynamic mechanical thermal analysis can be used in a knowledge-based design process of new ski boots in order to improve on-snow performances.

Flip-flop: a journey through globalisation's backroads

This book follows the global trail of one of the world’s most unremarkable and ubiquitous objects – flip-flops – from extraction of raw materials, to manufacture, distribution and consumption. Through this unique lens, Caroline Knowles takes a ground-level view of the lives and places of globalisation’s backroads, providing new insights that challenge contemporary accounts of globalisation. The book shows that globalisation along the flip-flop trail is a tangle of unstable, shifting and contingent connections, rather than an orderly product chain. Knowles examines this instability, exploring the complexities, personal topographies and skills with which people navigate global uncertainties. In doing so, Knowles provides new ways of thinking about globalisation from the vantage point of the shifting landscape crossed by a seemingly ordinary and everyday commodity. ‘Innovative, insightful, and by turns disturbing and inspiring. Caroline Knowles leads a journey through globalisation’s backroads that will inform and engage students and push professors to connect human experience and political economy.’ Professor Craig Calhoun, Director of the London School of Economics and Political Science ‘If you are invited to Davos, shiny shoes, high heels or ski boots may be in order. For understanding much of the rest of the world, Caroline Knowles shows, you think better with flip-flops.’ Ulf Hannerz, Emeritus Professor of Social Anthropology, Stockholm University

체감형 스키 시뮬레이터 개발을 위한 플루크보겐 동작의 운동역학적 비교

The purpose of this study was to compare pflugbogen's biomechanical characteristics between on the ski simulator and snowed ski slope to develop interactive ski simulator. Nine ski instructors(sex: male, age: <TEX>$29.6{\pm}5.4yrs$</TEX>, height: <TEX>$176.0{\pm}5.6cm$</TEX>, body mass: <TEX>$76.0{\pm}14.0kg$</TEX>) belong to Korean Ski Instructors Association participated in this research. 24 Infrared cameras for snowed ski slope experiment and 13 infrared camera for ski simulator experiment were installed near by path of pflugbogen. The participants did pflugbogen on the snowed ski slope and the ski simulator both. During the experiment, the participants weared motion capture suit with infrared reflective makers on it, and plantar pressure sensors in ski boots, so that ski motion and plantar pressure data were collected together. Displacement of COG(center of gravity) movements, trunk flexion/extension angle, adduction/abduction angle, and plantar pressure data were significantly different between on the simulator and ski slope. However, percentage of time of COG movement in the phases during medial/lateral and anterior/posterior movement were not significantly different. Findings indicate that the difference between two groups occurred because the ski simulator's drive mechanism is different from ski motion on the slope. In order to develop the ski simulator more interactively for pflugbogen, the ski simulator's drive mechanism need to be reflected 3D motion data of pflugbogen on the slope that were purposed in this research.

Effect of Ski Mountaineering Track on Foot Sole Loading Pattern

Ski mountaineering is becoming a popular sport. The ascending techniques (tracks) can be divided into 3 different groups: flat field, direct ascent, and traversing. This study examines the relationship between different mechanical loads on the foot and the 4 different mountaineering ascending techniques. All subjects used the same pair of ski boots and the same skis while performing the 4 different ascending techniques. An in-shoe dynamic pressure measuring system was used to measure the mechanical load on the foot soles of each ski mountaineer. The foot sole was divided into 6 anatomic sections to measure the different loads in each section. Thirteen men with an average age of 29 years were enrolled in the study. The results showed small, not significant differences in the mechanical foot load in the flat field or in the direct ascent. The average mechanical foot load was highest on the valley side foot while traversing (179 kPa to 117 kPa). The higher load forces were in the medial ball of the foot and the longitudinal aspect of the foot side closer to the hill. The higher impact placed on the valley side foot and the concentration of force placed on the medial ball of the valley side foot suggested the influence of the track on the load pattern of the foot sole. This higher impact may result in upward forces that affect the force distribution in the ankle and knee joints.

Flexion stiffness of a racing cross-country ski boot

For greater energy efficiency of sports footwear, mass needs to be minimized while preserving other favourable characteristics. In this article, an analysis of the flexion stiffness of the foot region, precisely its middle region, of a specific racing cross-country ski boot for the skating technique regarding its mass was performed. On the basis of a complex finite element model of the ski boot and an existing boot stiffness measuring set-up, flexion stiffness portions, mass portions and flexion stiffness/mass portion ratios were determined for individual boot components regarding the middle boot region. These values were determined for the shoe-upper with strengthening bands and shoelaces (altogether S-U), the sole, the midsole and the glue layer between. The S-U turned out to contribute a high flexion stiffness portion to the boot’s middle region’s flexion stiffness and also its flexion stiffness/mass portion ratio turned out to be the highest. The midsole and the sole present the highest potential for flexion stiffness/mass optimization due to their lowest flexion stiffness/mass ratios and highest mass portions. In order to increase the flexion stiffness/mass ratio of the middle boot region, the sole’s and the midsole’s size portions should be reduced, while the S-U’s size portion should be increased. Beside these findings, other suggestions in order to increase the flexion stiffness/mass ratio of the boot’s middle region are also given.

Evaluation of the mechanical behaviour of Telemark ski boots: Part I – materials characterization in use conditions

This study reports the first part of the analysis for the evaluation of the mechanical behaviour of ski boots by means of an integrated approach that considers polymeric materials characterization, in Part I, and numerical structural analysis, in Part II. In the present Part I, different techniques are adopted to characterize the mechanical behaviour of the polymeric materials used for ski boots, to define the elastic, visco-elastic, temperature and weathering-dependent characteristics. Experimental data provide fundamental information on mechanical response, in particular taking into account the effect of the environmental conditions, due to temperature variation, ultraviolet radiation and water absorption, which are correlated to the definition of reliability and durability of the materials. In more detail, experimental results from tensile tests and dynamic mechanical analysis are reported, evaluating mechanical response and chemical conformation of the polymers. Materials properties are correlated with the specific use conditions and boot structure, to be able to evaluate and preserve overall performances and general safety requirements of ski boots. This activity represents a reference procedure for the evaluation of the material mechanical behaviour that must be considered within the structural analysis.

Evaluation of the mechanical behaviour of Telemark ski boots: Part II – structural analysis

This work reports the evaluation of the mechanical behaviour of Telemark ski boots, by means of an integrated approach, considering polymeric material characterisation, reported in a previous study (Part I), and numerical structural analysis, reported in this study (Part II). Telemark boots entail a complex procedure for analysis of the mechanical response, with regard to both material assumption and overall structural behaviour, and represent a reference problem within sky footwear in consideration of this peculiar complexity. A visco-elastic constitutive model is formulated to describe the material mechanical response defined in accordance with experimental test performed. Solid models define the morphology of the ski boots and represent the basis for numerical modelling. Specific boundary conditions are assumed to mimic the binding effect. The numerical analysis leads to an interpretation of the global and local responses of a specific Telemark ski boot, considering material properties and structural conformation. The results provide valid information on the ski boot mechanical response, taking into account also the effects of temperature on material response and strain rate with regard to loading conditions. The evaluation of variations in shape and material of the different components can be performed representing a fundamental support for the design.

Effect of Knee Braces on Balance Ability Wearing Ski Boots (a pilot study)

In the literature it is mentioned that ski boots might decrease balance ability and this increases injury risk. The use of knee braces during skiing might help in knee stabilization and, therefore, improve balance ability. Eight female sport students participated in this study (age 24.88±2.1 years; BMI 21.6±1.97). Four knee supports were tested: the first (B1) was a soft knee sleeve with a reinforcement around the patella and two thin flexible metal bars for the lateral stabilization; the second (B2) was a neoprene sleeve with thin flexible metal bars for the lateral stabilization; the third (B3) was an elastic brace with double-joint metallic bars for the lateral stabilization, a reinforcement and a hole around the patella and fixation straps; the fourth (B4) was a massive knee brace with a more rigid structure ideated to return to sport after injury. The balance ability test was performed using the MFT-S3 Check System. The test was repeated five times, one without knee brace and one with each type of knee brace, in randomized order. Wearing the B3 a worsening in balance ability in comparison with the condition without brace was found. Wearing B2 the stability index (symmetry of the platform movement) in the anterior-posterior direction was significantly better than wearing the more cumbersome braces B3 and B4. No significant differences between the conditions were detected for the balance ability in the medio-lateral direction. From this pilot study it is possible to conclude that knee braces might influence balance ability wearing ski boots.

413 スキーシミュレータを用いたスキーブーツ設計の適合性評価(機械力学I)

413 スキーシミュレータを用いたスキーブーツ設計の適合性評価(機械力学I)

물리 모델 분석을 통한 상호 작용형 스키시뮬레이터 동작인식 시스템 개발

본 연구에서는 스키 시뮬레이터의 사용자 감응형 제어를 위한 물리모델과 동작인식 시스템의 개발되었으며, 스키 선수의 자세 변화에 따른 스키 슬로프 상에서의 거동과의 부합성 확보를 위하여 실제 현장 실험데이터의 회귀분석을 통해 동작인식 시스템에 사용될 파라미터 및 관계식을 도출하였다. 개발된 물리모델 기반 스키 동작 인식 시뮬레이터는 실시간으로 Kinect 장치를 사용하여 사용자의 관절별 질량을 분석하여, 정확한 체중심을 추정하고, 시뮬레이터 하드웨어에서 적용할 수 있도록 힘, 속도, 가속도에 대한 피드백을 전달하도록 구성되었다. 본 연구결과는 스키시뮬레이터의 인식모듈로 사용되었으며, 물리모델 기반 가상 스포츠 시뮬레이터 제작에 응용 할 수 있는 자료로 활용될 것이다.

Special issue on winter sports

In all forms of winter sports the equipment is of central importance. The equipment is needed to protect the athlete from adverse environmental conditions and to provide safety and comfort. Moreover, in a majority of winter sports the equipment facilitates a specific form of locomotion: gliding on the snow or ice. Gliding allows for much higher speeds than other, more typical forms of human locomotion, such as walking or running. It is thus the equipment that makes most forms of winter sport the highly dynamic sports that are so appealing to many of us. Much research has been and continues to be carried out in improving the safety and performance of winter sports athletes through better designed equipment. It is, therefore, perhaps not a surprise that our call for papers for a special issue on winter sports in the journal Sports Engineering resulted in an overwhelming response. Nineteen manuscripts were submitted of which 11 were found suitable for the journal. Eight of these could be included in this special edition, and others were distributed throughout volume 17. This editorial provides a brief overview of all accepted papers. Protection against injury has always been a primary field of interest for researchers and engineers working on winter sports. Two papers submitted for this special issue specifically address injury prevention. A white paper by Michel and colleagues presents current concepts for wrist protectors in snowboarding and discusses the need for an industry standard. This paper represents a position statement of the International Task Force on Wrist Protectors in Snowboarding of the International Society for Skiing Safety (ISSS). Another review paper by Senner et al. focuses on knee injuries in recreational alpine skiing and discusses what modifications of the ski-binding-boot system might offer an opportunity for reducing the risk of injury. The authors specifically consider the implications that the development of mechatronic bindings may have for injury prevention in skiing discussing three different types. Speed is an important determinant for athlete performance, which places a premium on optimising gliding friction and air drag. Several studies included in this special issue address friction phenomena. Puukilainen et al. used a variety of measurement devices that are currently used in the industry to characterise the surface properties of skis. They document changes in the topography, crystallinity and wettability of the skis’ running surface and in the skis’ sliding properties due to ski use, waxing and stone grinding. Bardal and Reid investigated how air drag depends on the permeability of alpine skiing apparel. Contrary to common belief, they found a weak dependence implying that increasing apparel permeability may have only a marginal effect on the speed of alpine skiers. Lozowski and colleagues investigated the friction between speed skate blades and ice by developing a sophisticated model that incorporates various interaction processes. To the best of our knowledge, this is the first model for speed skate-ice interaction that considers inclined skate blades. The studies by Swaren et al. and Petrone et al. investigated the deformation properties of cross country ski poles and alpine ski boots, respectively. Both of these topics are important for the performance and the comfort of the athletes participating in these sports. P. Federolf (&) Norwegian School of Sport Sciences, P.O. Box 4014, Ulleval Stadion, 0806 Oslo, Norway e-mail: peter.federolf@nih.no

Technical possibilities for optimising the ski-binding-boot functional unit to reduce knee injuries in recreational alpine skiing

This review study focuses on knee injuries in recreational alpine skiing. The objectives of this study were (1) to provide selected knowledge derived from current and past knee injury epidemiology; (2) to outline the most important knee injury mechanisms; and (3) to review and discuss how modifications of the skiing equipment might alleviate the risk of knee injuries. This review represents the essence of a comprehensive research report and considers the content of more than 230 scientific papers, further “grey literature”, patents, international standards and other publications. Knee injuries are the most frequent injuries in alpine skiing and their incidence rate remained high despite a decline of the incidence of other skiing injuries in recent years. Women have a higher knee injury risk, but age and tiredness appear not to be significant factors. Apart from the commonly described injury mechanisms “phantom foot” and “boot-induced anterior drawer” other more sophisticated injury categorisations are given. The ski radius, the ski length and the standing height on the ski may be relevant ski parameters. For the binding, the release mechanisms in different mechanical degrees of freedom, the impact tolerance and the maintenance frequency are discussed. In the ski boot, the height of the upper, the boot liner, the shaft stiffness, and the position on the ski may play a role. The biggest challenge, but probably also the biggest opportunity for a reduction of knee injury rates seems to be the development of a mechatronic binding. The current strategies to develop these types of bindings are explained and illustrated by one example. Some of the possible parameters which may be essential for the necessary control algorithms are described. Finally, considerations regarding the strategic and operational implication of the analysed technical measures are given.

Comments to my works, written by myself

In the mid-1980s, Anatolii AlekseevichKaratsubamade, for himself, a chronological collection of xerocopies of his papers in four volumes provided with hand-written comments.2 The present paper is compiled from fragments of these records (in fact, a diary): some of Karatsuba’s comments are cited completely, while some others, only partially (compilers’ explanations are given in footnotes; the omitted lines are replaced by asterisks and the omitted words are replaced by dots). In 1990–2000, Karatsuba supplemented some comments with brief remarks on the further development of their topics (here, these more recent remarks are set in oblique type). From 1954 to 1959, Anatolii Karatsuba studied at the Mechanics and Mathematics Faculty, Lomonosov Moscow State University. His first scientific advisor was Andrei Nikolaevich Kolmogorov; under his supervision, Karatsuba wrote his third-year term paper entitled “On variations of functions of two variables” and fourth-year term paper “Experiments with automata.” On “Experiments with automata,” Karatsuba’s first published paper was based, with which the present comments begin. Karatsuba often recalled his student years, his teachers and advisors, professors at Moscow State University. He remembered ski jaunts organized for students by Kolmogorov, who kept 20 pairs of skis and 20 pairs of ski boots at his dacha for this purpose, as well as more than 20 pairs of slippers and cups for subsequent tea with students. Karatsuba’s daily record of November 19, 1985, reads: “Listening to Kathleen Ferrier3 (Schumann in German), remembered Komarovka4, Pavel Sergeevich5, and Andrei Nikolaevich6, their musical concerts after skis. Extraordinary atmosphere, incomparable with anything (and, apparently, will never recur). Different time, different attitude to science. Rare pragmatism and careerism.” Having chosen number theory as the main direction of his research, Karatsuba received PhD (Candidate of Science) degree in 1962; his thesis was entitled Rational Trigonometric Sums of a Special Form and Their Applications (the thesis advisor was Nikolai Mikhailovich Korobov). In 1966, Karatsuba presented his Doctor of Science thesis entitled Method of Trigonometric Sums and Mean-Value Theorems and took the position of researcher at Steklov Mathematical Institute, Russian Academy of Sciences (MIAN), which was headed by Ivan Matveevich Vinogradov at that time. Karatsuba always admired the scientific achievements of Vinogradov. In [1], he wrote about Vinogradov: “He solved Goldbach’s problem, which has resisted all efforts of scientists during centuries, and Vinogradov’s method of trigonometric sums has drastically changed the character of analytic number theory and opened a new era in this classical area of mathematics”. In the same paper, he wrote: “Using a few mathematical notions and facts, he penetrates the essence of problems so deeply that this enables him both to create an apparatus necessary for solving the problem and to solve it.”

The effect of boot stiffness on field and laboratory flexural behavior of alpine ski boots

The aim of this work was to study the effect of boot stiffness on the field and laboratory flexural behavior of alpine ski boots. Ski boots have a direct influence on performance, safety, and comfort of alpine skiers. Despite their technological evolution during a number of years, the parameters used in the evaluation of boot stiffness are not yet standardized and still require a shared engineering approach to achieve common quantitative definitions to be used either in boot classification or in boot selection for the different users. This work reports the boot flexion angles between shell and cuff and between cuff and tibia, collected during slalom tests on three boots with different nominal Flex Index. The laboratory data collected on the same boots under conventional cyclic bending tests are reported and compared with the field data for the development of a new test method more representative of the field behavior. As a result, clear definitions of Flex Index and of boot stiffness are introduced: boot stiffness had a clear effect on both the field and the laboratory flexural behavior of boots.

Body Posture Stability in Ski Boots Under Conditions of Unstable Supporting Surface

The authors attempted to determine whether: (1) there are differences in stability between the conditions of standing in ski boots and barefoot, (2) the type of surface affects stability, and, (3) the level of stability differs between the frontal and sagittal planes. The study included 35 young male recreational skiers aged 20.71 ±0.63 years. Measurements of stability were taken by means of a Libra seesaw balance board. The conditions of soft surface were created by attaching an inflated cushion to the board. The experiment was carried out on both rigid and soft surface for both movement planes and two different conditions: maintaining the seesaw balance board in the horizontal position and performance of a particular balancing task. All the tests were performed with visual feedback. Restricted ankle joint mobility that results from wearing ski boots caused a reduction of stability in studied subjects, particularly in the sagittal plane. The differences found in the study were likely to be caused by the difficulty the beginners experienced in re-organizing muscular coordination in hip joint strategy and effectively using mechanical support of ski boots that reduces lower limb muscle tone. The use of the soft surface improved stability exhibited by the subjects in the frontal plane without compromising the stability in the sagittal plane. The soft surface might have contributed to a reduction in excessive corrective movements, thus improving stability in studied subjects. The aim of this study was to determine the effect of limitation of foot mobility and disturbances in afferent information from the plantar mechanoreceptors due to wearing ski boots on the level of postural stability in beginner skiers under conditions of the unstable support surface.

Differences in V1 and V2 ski skating techniques described by accelerometers

The aims of the study were to describe the differences between the ski skating techniques V1 and V2 and evaluate reproducibility in complex cyclic hip movements measured by accelerometers. Fourteen elite senior male cross-country skiers rollerskied twice for 1 min (V1 and V2) at 4° inclination and 3 m/s. Tests were repeated after 20 min and again 4 months later. Five triaxial accelerometers were attached to the subject's hip (os sacrum), poles, and ski boots. Post-processing included transforming to an approximately global coordinate system, normalization for cycle time, double integration for displacement, and revealing temporal patterns. Different acceleration patterns between techniques and large correlation coefficients (Pearson's r = 0.6-0.9) between repeated trials were seen for most parameters. In V2, the hip was lowered [-10.9 (1.2) cm], whereas in V1, the hip was elevated [4.8 (1.5) cm] during the pole thrust. In conclusion, V2 but not V1 showed similarities to double poling in the way that potential energy is gained between poling strokes and transferred to propulsion during the poling action. Elite skiers reproduce their own individual patterns. One triaxial accelerometer on the lower back can distinguish techniques and might be useful in field research as well as in providing individual feedback on daily technique training.

Microclimate in ski boots – Temperature, relative humidity, and water absorption

Ski boot quality is determined by mechanical properties and comfort. Comfort is strongly affected by cold feet. The purpose of this study was to determine the microclimate in ski boots. Climate chamber tests with five male subjects and field tests with two male subjects were conducted. Temperature and relative humidity were measured using four sensors placed on the foot and one on the liner. Absorbed water in liners and socks was measured with a precision balance. The subjects gave subjective ratings for comfort. The toe sensor temperature dropped below 20 °C at an ambient temperature of 0 °C, −10 °C, and −20 °C. Relative humidity values at the foot were as high as 78% in the climate chamber and 93% in the field. Water absorption in socks and liners ranged from 4 to 10 g in the climate chamber and 19 to 45.5 g in the field. The results reveal the importance of keeping the feet and in particular the toes warm during skiing. One possible improvement may be to construct the liner so that sweat and melted snow are kept as far away as possible from the foot. Liner material with high water absorption capacity and hydrophobic socks were suggested to prevent wet feet.