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1.
Dirt absorption on the ski running surface — quantification and influence on the gliding ability 总被引：2，自引：2，他引：0
We propose a thesis that minimising dirt on the running surface of skis improves the surface glide. Waxing usually improves the gliding ability of skis in the short term. But how does waxing affect pollution absorption in the long term? In this study a number of skis with a transparent base and a white background were treated by steel scraping and with different glide waxes. The gliding ability of waxed and unwaxed skis, the sliding surface whiteness and the hydrophobicity were tested and documented. Tests were performed before and after the skis had been used for different distances. It was observed that all the waxed skis (regardless of the wax used) absorbed more dirt than unwaxed, and as a result all waxed skis lose their glide ability sooner than unwaxed (freshly scraped) skis in wet snow conditions. 相似文献
2.
The aim of this work is to develop a methodology for the glide testing of waxed skis at an indoor ski centre, using artificial
snow. Two skiers, one acting as a control with unwaxed skis, undertook the test runs over a 50-m course. Timing gates allowed
split times to be measured for a selection of waxes, as well as unwaxed skis. Five runs were conducted for each ski preparation,
interlaced with control runs. Unwaxed skis produced similar run times to waxed skis for the complete course, with measurements
showing their probable superiority over the first 10 m. A tentative interpretation involves the delay in forming a lubricating
meltwater film under waxed skis by comparison with unwaxed skis. Recommendations are made for future measurements, including
a longer course, close matching of skiers’ masses and ski sizes, all timing systems accurate to 0.001 s, a start 3 m above
the first timing gate and more effective methods of wax removal. 相似文献
3.
Esa Puukilainen Olli Ohtonen Teemu Lemmettylä Vesa Linnamo Björn Hemming Toni Laurila Salla Tapio Markku Räsänen Mikko Ritala Markku Leskelä 《Sports Engineering》2013,16(4):229-238
In this work, changes in the cross-country ski base properties resulting from stone grinding, skiing, waxing and re-stone grinding have been investigated. The surface topography, crystallinity, wettability and sliding properties of cross-country ski bases were recorded using a selection of measurement techniques: non-contact chromatic confocal microscopy, contact-type surface roughness analyser and scanning electron microscopy (topography), Raman spectroscopy (crystallinity), contact angle measurement (wettability) and a ski tester (sliding properties). The tested skis were used for 150 km and waxed 35 times. The ski base surface became smoother and the orientation and crystallisation of the base material increased. Wear decreased the hydrophobicity and increased the sliding friction. Even though re-grinding did not restore all of the ski base properties, re-grinding improved the wettability and sliding properties. The results help to optimise stone grinding interval to maintain the performance of the skis. 相似文献
4.
Modern treadmills allow cross-country skiers, biathletes and ski-orienteer’s to test their physical performance under laboratory
conditions using classical and freestyle techniques on roller skis. The differences in performance between tests are quite
small for elite athletes, and it is therefore of great importance to control the rolling resistance of the roller skis. Otherwise
different physiological tests cannot be accurately compared. This study shows that during a warm-up period of 30 min the coefficient
of rolling resistance (μ
R) decreases to about 60–65% and 70–75% of its initial value for freestyle and classical roller skis, respectively. Simultaneous
measurements of temperature and μ
R shows that stabilized rolling resistance corresponds to a certain running temperature for a given normal force on the roller
ski. Tests were also performed on the influence on μ
R of normal force, velocity and inclination. Normal forces produced significant influence on μ
R, while different velocities and inclinations of the treadmill only resulted in small changes in μ
R. 相似文献
5.
Skiing manufacturers depend on the development of new skis on trial and error cycles and extensive product testing. Simulation
tools, such as the finite element method, might be able to reduce the number of required testing cycles. However, computer
programs simulating a ski in the situation of a turn so far lack realistic ski–snow interaction models. The aim of this study
was to (a) implement a finite element simulation of a ski in a carved turn with an experimentally validated ski–snow interaction
model, and (b) comparison of the simulation results with instantaneous turn radii determined for an actual carved turn. A
quasi-static approach was chosen in which the ski–snow interaction was implemented as a boundary condition on the running
surface of the ski. A stepwise linear function was used to characterise the snow pressure resisting the penetration of the
ski. In a carved turn the rear section of the ski interacts with the groove that forms in the snow. Two effects were incorporated
in the simulation to model this situation: (a) the plasticity of the snow deformation, (b) the influence of the ski’s side-cut
on the formation and shape of this groove. The simulation results agreed well with experiments characterising snow penetration.
Implementation of the groove in the ski–snow interaction model allowed calculation of the instantaneous turn radii measured
in actual turns, but also caused significant numerical instability. The simulation contributes to the understanding of the
mechanical aspects of the ski–snow interaction in carved turns and can be used to evaluate new ski designs. 相似文献
6.
Bulge-disc type pressure sensors of diameter 6 mm were fitted as near as possible to the running edge of a modern carved ski.
The pressure signals were sampled at 30 Hz during long turns on snow, synchronously with signals from a geomagnetic compass
and a pressure pad in the ski boot. The pressure from the snow was found to be highly variable with a mean value of about
50 kPa and dynamic pressure spikes up to 300 kPa. With the outside leg, the snow contact width in the rear part of the ski
was found to be slightly wider, on average, than for the front part, as expected for a carving turn. Correlation within the
pressure sensor data showed that the rapid pressure fluctuations were probably not due to bumps or features on the snow; instead
they were probably caused by many small-scale collapses of the snow structure as the ski passed. 相似文献
7.
Participants in the sport of snow skiing devote considerable effort to reduce sliding friction of the ski. A large industry is devoted to providing products and ski preparation methods with claims of improved ski performance, sometimes at considerable expense. Despite this attention to the topic, there are very little data available to skiers that quantify the effect these products and methods have on reducing ski friction. Determining the coefficient of friction of a ski on snow presents a significant technical challenge. Our approach has been to develop a tribometer incorporating a series of proximity sensors to test commercially available ski equipment and waxes on natural snow. We developed a test protocol that significantly reduces the experimental noise associated with variable environmental conditions enabling us to differentiate the difference in friction between two pairs of skis with a resolution of 0.001. A large body of test data was acquired over a wide range of environmental conditions to quantify the effect of ski wax and base texturing treatments in terms of coefficient of friction in a way that is of practical use to skiers. An exercise physiology power model was used to estimate the ski race time difference that could be expected from changing the coefficient of friction. 相似文献
8.
Cross-country skiers use roller skis for their snow-free training with the aim of imitating skiing on snow. Also, exercise laboratories evaluate the biomechanics and physiology of cross-country skiing using roller skis on a treadmill. The roller skis on the market that are constructed for use in the classical style are equipped with a front and a back wheel, one of which has a ratchet to enable it to grip the surface when diagonal striding and kick double poling (static friction). The aim of this study was to investigate static friction coefficients (μS) of ratcheted wheel roller skis, and compare the results to the μS reported from skiing on snow with grip-waxed cross-country skis. Also, a new type of roller ski with a camber and adjustable grip function was evaluated. The results showed that ratcheted wheel roller skis, on a treadmill rubber mat and on dry and wet asphalt surfaces, reached μS values that were five to eight times greater than the values reported from on-snow skiing with grip-waxed cross-country skis. For the roller skis with a camber and adjustable grip function, the μs could be varied from no grip at all up to the level of the tested ratcheted wheel roller skis. 相似文献
9.
A new sensor for detecting ski bending and torsional deflection during an actual ski turn on the snow has been developed.
It consisted of bending and torsion sensors connected by light rigid beams. This structure was fixed to the upper surface
of a ski and passed through a tunnel in the central binding plate. The bending and torsion sensors were strain cells, designed
to reject strain orthogonal to the desired measurement direction. The calibration factor for each sensor was determined in
a jig, then the calibration of the overall sensor assembly was checked by static bending experiments and a free vibration
test. A data logger recorded the strain signals synchronously with other data such as the components of the earth’s magnetic
field measured by a sensor on the ski. The data set allowed reconstruction in software of the instantaneous shape, direction
and edge angle of the ski. The purpose of this paper is mainly to introduce the equipment used and methods developed. Tests
of the sensor performance are described. Results from a ski run on snow are presented to show how the various types of data
can be combined. A skilled ski athlete performed long turns with the ski at about 60 km/h on a groomed snow surface at Shiga
Kogen in Japan. The experiment on snow showed that the deformation of the ski was predominantly bending; torsional deflection,
although measurable, had only a small effect on the shape of the running edge. The ski edge adopted a symmetrical circular
bent shape with an unexpectedly small radius when on the outside, but was unconstrained, lightly loaded and nearly straight
when on the inside. 相似文献
10.
Fischer C Overney LS Fauve M Blanke O Rhyner H Herzog MH Bourban PE Månson JA 《Journal of sports sciences》2007,25(14):1567-1576
Flexural and torsional rigidity are important properties of skis. However, the flexural and torsional rigidity that lead to optimal performance remain to be established. In the present study, four pairs of slalom skis that differed in flexural and torsional rigidity were tested by advanced and expert skiers. Using a 10-item questionnaire, different aspects of the skis' performance were rated on a 9-point scale. For each pair of skis, physical measurements were compared with the ratings of the two groups of skiers. Correlations (Spearman) were then determined between (i) different mechanical properties of the skis (static and dynamic), (ii) subjective assessments of the participants, and (iii) properties of the skis and the participants' assessments. The latter showed that expert skiers rate the aspects of the skis more accurately than advanced skiers. Most importantly, expert skiers are particularly sensitive to torsion of the skis. These results suggest that such highly rated elements should be addressed in future ski designs. 相似文献
11.
Christian Fischer Leila S. Overney Mathieu Fauve Olaf Blanke Hansueli Rhyner Michael H. Herzog 《Journal of sports sciences》2013,31(14):1567-1576
Abstract Flexural and torsional rigidity are important properties of skis. However, the flexural and torsional rigidity that lead to optimal performance remain to be established. In the present study, four pairs of slalom skis that differed in flexural and torsional rigidity were tested by advanced and expert skiers. Using a 10-item questionnaire, different aspects of the skis' performance were rated on a 9-point scale. For each pair of skis, physical measurements were compared with the ratings of the two groups of skiers. Correlations (Spearman) were then determined between (i) different mechanical properties of the skis (static and dynamic), (ii) subjective assessments of the participants, and (iii) properties of the skis and the participants' assessments. The latter showed that expert skiers rate the aspects of the skis more accurately than advanced skiers. Most importantly, expert skiers are particularly sensitive to torsion of the skis. These results suggest that such highly rated elements should be addressed in future ski designs. 相似文献
12.
高校开展高山滑雪教学对培养大学生滑雪的兴趣、爱好,以及锻炼行的养成,达到娱乐与健身的目的具有重要作用。由于高校缺乏统一的高山滑雪教材,对开设的滑雪初级教学中存在的一些问题未能寞现有效的共性认识,严重制约了滑雪运动在高校的普及与发展。提出在高山滑雪初级教学中应注意使大学生了解高山滑雪板的结构与性能,学会选用不同类型的高山滑雪板;选择合适的高山滑雪鞋与固定器,固定器的强度要求指标控制在4～5kg为好;高山滑雪服与滑雪杖的选用时注重性价比等问题,探索提高冬季高山滑雪教学质量之策。 相似文献
13.
14.
Y. Hirano 《Sports Engineering》2006,9(4):221-228
Time differences between medalists at Olympic or World Cup alpine ski races are often less than 0.01 s. One factor that could
affect these small differences is the line taken between the numerous gates passed through while speeding down the ski slope.
The determination of the ‘quickest line’ is therefore critical to winning races. In this study the quickest lines are calculated
by direct optimal control theory which converts an optimal control problem into a parameter optimization problem that is solved
using a nonlinear programming method. Specifically, the problem is described in terms of an objective function in which state
and control variables are implicitly involved. The objective function is the time between the starting point and finishing
gate, while state variables are positions of the ski-skier systems on a ski slope, rotational angles of skis, velocities,
and rotational velocity at a discrete time, i.e., a node. The control variable at each node is the skier-controlled edging
angle between the ski sole and snow surface. Equations of motion of the ski-skier system on a ski slope are numerically satisfied
at the midpoint between neighbouring nodes, and the original problem is converted into a nonlinear programming problem with
equality and inequality constraints. The problem is solved by the sequential quadratic programming method in which numerical
calculations are carried out using the MATLAB Optimization Toolbox. Numerical calculations are presented to determine the
quickest lines of an uphill and a downhill ski turn with a starting point, first gate, and second gate (finish line) having
been successfully carried out. The quickest line through four gates could not be calculated due to numerical difficulty. Instead,
the descent line was respectively calculated for an uphill and downhill turn and simply added, giving a resultant time that
represents an upper bound. 相似文献
15.
A continuously waxed ski has been developed that releases a thin film of lubricant under the base of a ski. This replicates the melt water layer observed in snow skis which is caused by frictional and solar heating. The system is particularly effective on artificial (dry) slopes where skiers slide on plastic bristles rather than snow. Speeds comparable to those achieved on snow are achieved using this system and this improves the experience for the skier. Speed enhancements on plastic slopes of up to 50?% have been achieved using solutions of polyethylene glycol in water. There is speed enhancement of approximately 9?% on artificial snow and 2?% on fresh alpine snow. The latter value is highly significant as it can be the difference between winning a medal in ski competitions and finishing outside the top ten. In addition to the quantitative data, qualitative athlete perceptions were also recorded and show that a feel like snow can be achieved on artificial surfaces. Because the lubrication system is attached to the ski, it allows personal performance enhancement irrespective of a water misting system being in operation or not. The design complies with the equipment regulations of the skiing??s international governing body so it can be used in competition. 相似文献
16.
J P Clarys L Van Puymbroeck J Publie E Bollens J Cabri B De Witte 《Journal of sports sciences》1986,4(2):129-139
The purpose of this study was to examine whether differences in construction between the compact ski, the racing ski and the soft ski influence the behavioural and electromuscular responses of the user. Eight qualified male ski instructors performed two 'shuss' trials and three different basic turns. Six muscles (M. biceps femoris, M. gastrocnemius lateralis and medialis, M. rectus femoris, M. vastus lateralis and M. tibialis anterior) were studied, using a conventional but portable electromyographic (EMG) registration with telemetric synchronization, active electrodes and a six-channel portable data recorder. Muscle contractions were continuously registered and visualized in raw EMG form and linear envelopes. The differences between the mean rectified EMG data of dynamic contractions while skiing and the mean rectified EMG data of the maximal voluntary contraction were used in the primary analysis of data, from which the participation levels of the muscles investigated could be calculated for each type of ski. Based on this comparison, differences between the effects on muscle activity of the three types of skis were unimportant. In a second phase, the normalized linear envelopes of all subjects were graphically superimposed and averaged. This was performed for each muscle, for each movement, for each leg and for each ski tested. The EMG data were considered in combination with anthropometric values, with snow characteristics and with the velocity of skiing. This study showed systematic differences between the use of the racing, soft and compact ski. On average the soft ski showed the lowest muscle activity patterns and thus the most economical muscular efforts for all muscles investigated and within all movements. 相似文献
17.
J.P. Clarys L. van Puymbroeck J. Publie E. Bollens J. Cabri B. de Witte 《Journal of sports sciences》2013,31(2):129-139
The purpose of this study was to examine whether differences in construction between the compact ski, the racing ski and the soft ski influence the behavioural and electromuscular responses of the user. Eight qualified male ski instructors performed two ‘shuss’ trials and three different basic turns. Six muscles (M. biceps femoris, M. gastrocnemius lateralis and medialis, M. rectus femoris, M. vastus lateralis and M. tibialis anterior) were studied, using a conventional but portable electromyographic (EMG) registration with telemetric synchronization, active electrodes and a six‐channel portable data recorder. Muscle contractions were continuously registered and visualized in raw EMG form and linear envelopes. The differences between the mean rectified EMG data of dynamic contractions while skiing and the mean rectified EMG data of the maximal voluntary contraction were used in the primary analysis of data, from which the participation levels of the muscles investigated could be calculated for each type of ski. Based on this comparison, differences between the effects on muscle activity of the three types of skis were unimportant. In a second phase, the normalized linear envelopes of all subjects were graphically superimposed and averaged. This was performed for each muscle, for each movement, for each leg and for each ski tested. The EMG data were considered in combination with anthropometric values, with snow characteristics and with the velocity of skiing. This study showed systematic differences between the use of the racing, soft and compact ski. On average the soft ski showed the lowest muscle activity patterns and thus the most economical muscular efforts for all muscles investigated and within all movements. 相似文献
18.
ABSTRACTThis study aimed to explore the plantar loading variables between habitual rearfoot strike (RFS) and non-rearfoot strike (NRFS) during running. 78 healthy males participated in this study (41 RFS, 37 NRFS). In-shoe pressure sensors were used to measure plantar loading while the participants were running on a 15 m indoor runway with their preferred foot strike pattern (FSP) at 12.0 ± 5% km/h. Results indicate that force and pressure parameters were much higher in the rearfoot and midfoot regions during RFS running and relatively greater in forefoot region during NRFS running. However, compared with NRFS running, the contact area, maximum force and force-time-integrals during RFS running on total foot were 21.44% (P < 0.001, ES = 2.29), 13.99% (P = 0.006, ES = 0.64) and 21.27% (P < 0.001, ES = 0.85) higher, respectively. Total foot peak pressure and pressure-time-integral between two FSPs were similar. Higher loads in the rearfoot region may transmit to the knee joint and result in patellofemoral joint injuries. NRFS runners’ higher loads in forefoot seem to be ralated to metatarsal stress fractures and compensatory damage to the Achilles tendon. Therefore, runners should choose proper FSPs according to their unique physical conditions. 相似文献
19.
A robot that simulates a number of human leg joint motions during carved turns has been developed. Each leg had six degrees
of freedom like those of human athletes. An on-board computer controlled the sequence of joint angles in an open-loop mode
during skiing on an artificial grass slope. The relations among joint motions, reacting forces and turn trajectory were investigated
by programming various motions of the robot. At first, the effect of basic joint motions, such as abduction–adduction and
flexion–extension of the hip, knee and ankle joints were investigated. Then the sequence of a top athlete’s joint motions,
measured in a separate study, was applied to investigate its effect on the ski turn. The human-inspired programme produced
a more even force balance between the skis and also a higher-quality turn. The requirements for a successful physical model
of a human skier are discussed. 相似文献
20.
雪蜡作为雪上项目必备辅助材料,无论是在世界顶尖的滑雪比赛,还是在日常休闲的滑雪运动中均发挥着不菲的价值。运动科学的相关研究表明,雪蜡使用的合理性和精准性已成为赢得比赛的重要因素;及时引进、吸收相关科学研究成果已成为提高雪上项目的运动表现和预防损伤的关键因素之一。雪蜡的产生源自偶然的发现,并逐步渗透人们的生活。在当今滑雪比赛中,不同的雪蜡以及打蜡方式会对雪上项目的竞技表现产生巨大影响;氟化物和石蜡的混合物所制成的滑雪蜡是目前最常用的雪蜡,但纳米科技在雪蜡中的介入为运动表现的提高提供了潜在的可能;雪板滑行的本质为底板在水膜层上的运动,通过打蜡可使水膜的厚度最佳化,但同时也应留意蜡质、温度和雪质等因素对雪板运行的影响。 相似文献