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1.
Recent experiments on the ski simulator produced ambiguous results and raised unanswered questions concerning the true nature of "novice" behavior and the occurrence of behavioral changes during learning. The aim of the present experiment was to analyze the evolving behavior of three beginners during six practice sessions on a ski simulator The position of the apparatus platform was recorded as time series and used for constructing dynamical models, including stiffness and damping functions. The results showed that novices tended to exploit a Rayleigh damping behavior during the first trials and then transition toward a van der Pol damping. These results replicate previous observations by Nourrit, Delignieres, Caillou, Deschamps, and Lauriot (2003) and suggest the transition to the expert behavior could arise early in practice, when the task is of moderate difficulty. The discussion focuses on the properties of the observed learning dynamics and proposes a global conceptualization for acquiring complex motor skills. 相似文献
2.
This study examines the effects of a self-controlled use of physical assistance devices on learning a complex motor skill (i.e., producing slalom-type movements on a ski simulator). Physical assistance was provided by ski poles. One group of learners (self-control) was provided with the poles whenever they requested them, whereas another (yoked) group had no influence on the pole/no-pole schedule. While there were no group differences during the practice phase (Days 1 and 2), clear group differences emerged in the retention test without poles (Day 3). The self-control group produced significantly larger amplitudes than the yoked group. These results extend previous findings by showing learning advantages of the self-controlled use of physical assistance devices in complex motor skill learning. 相似文献
3.
Thibault Deschamps Déborah Nourrit Nicolas Caillou Didier Delignières 《Journal of sports sciences》2013,31(9):867-874
The aim of this study was to assess the effect of stress on a previously acquired motor coordination. Following a longitudinal learning experiment, four participants performed oscillations on a ski simulator, either in normal or stressful conditions. The results showed that the amplitude of the oscillations decreased under stress, but no significant effect was seen regarding coordination, suggesting the strong resistance to stress of overlearned behaviour. Nevertheless, for one participant, a transient regression towards a former stage of learning was observed. This result was consistent with the regression hypothesis formulated by Fuchs (). 相似文献
4.
The aim of this study was to assess the effect of stress on a previously acquired motor coordination. Following a longitudinal learning experiment, four participants performed oscillations on a ski simulator, either in normal or stressful conditions. The results showed that the amplitude of the oscillations decreased under stress, but no significant effect was seen regarding coordination, suggesting the strong resistance to stress of overlearned behaviour. Nevertheless, for one participant, a transient regression towards a former stage of learning was observed. This result was consistent with the regression hypothesis formulated by Fuchs (1962). 相似文献
5.
文章运用文献资料法、逻辑分析法等研究方法,结合自身学习、探索与教学实践,以醉拳的基本特征、功能价值及技能训练要点为选题,从醉拳手法、步法、身法的特征及训练要点进行剖析。旨在分析醉拳的基本特征,为醉拳技能的训练提供科学的指导作用,也为运动员科学选材提供合理的理论参考,醉拳练习者在学习技术的同时,应进行客观和理智的分析,从而能真正理解醉拳的拳种内涵。 相似文献
6.
高山滑雪是具有显著北方特色的运动项目,是北方很多高校体育院系的必修课程,在教学中如何以先进的教育理念来指导教学已经成为滑雪教学改革的关键。利用教学实验法,通过“合作教学模式”开展高校高山滑雪技术教学。结果表明：合作教学模式应用于高校高山滑雪技术教学中是切实可行的,这种教学模式对于学生观察分析滑雪技术、提高学生技能的掌握、教学评价以及改善学生的学习态度等方面优于传统的教学模式,能够对学生起到“在合作中学习,在学习中合作”的作用。 相似文献
7.
Konstantin I. Matveev 《Sports Engineering》2017,20(4):293-298
This paper addresses sliding friction of a ski during steady horizontal gliding on snow. A simple mathematical theory accounting for both dry and wet friction is developed. The water film evolution along a ski is calculated with a lumped-element thermal model. An analytical solution is obtained for the ski friction force. Representative calculation results are demonstrated for a range of ski velocity, contact surface area fraction, snow temperature, and ski aspect ratio. 相似文献
8.
9.
随着新课标的实施,"好课"又成为了一个新问题.结合教学实践提出有可能是"好课"的必须具有"充分体现了学生的主体作用,促进了全体学生的全面发展,形成了良好的课堂学习氛围"的特征,同时指出要想上"好课"必须处理好健身与技能、继承与创新、面面俱到与亮点的关系. 相似文献
10.
11.
为减少我国大众滑雪伤害事故的发生,支持"3亿人参与冰雪"战略,采用数理统计法和案例分析法,研究近年大众滑雪伤害事故特征,结合案例论证滑雪场责任的法律基础、具体义务和过错类型。发现：大众滑雪伤害事故后果严重;案件属于侵权责任纠纷,责任认定较为简单;依据《侵权责任法》（2021年后为《民法典》）等法律,滑雪场有安全保障义务,具体可分为5类;司法实践中存在滑雪场担责比例偏高问题,"自甘风险"条款的确立可能加重该问题。建议：政府应强化监管和惩处力度;业界建立经验交流与赔偿协商机制;滑雪者应养成良好滑雪行为习惯;滑雪场应积极购买附高风险运动的意外伤害责任保险并提高额度。 相似文献
12.
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
13.
Optimizing generalized motor program and parameter learning 总被引：1，自引：0，他引：1
Two experiments examined generalized motor program (GMP) and parameter learning. Experiment 1 examined the effects of bandwidth knowledge of results (KR) about relative timing in constant and variable practice. The purpose was to determine if movement stability created by the bandwidth manipulation is associated with increased GMP learning and if bandwidth KR interacts with constant and variable practice. Participants were asked to depress four keys sequentially, using the same relative timing structure. Constant practice had one absolute timing requirement, whereas variable practice had three different absolute timing requirements. The results indicated that GMP learning was enhanced by constant practice (independent of the bandwidth KR condition) and by bandwidth KR, when variable practice was used. The findings suggest practice conditions (bandwidth KR, constant practice) that increase movement stability during practice enhance GMP learning. Parameter learning (during transfer), however, was enhanced by variable practice. Experiment 2 attempted to determine how constant and variable practice conditions could be combined to enhance both GMP and parameter learning. The results indicated that developing a stable GMP early in practice--by providing learners with constant practice early in practice--and refining parameter learning later in practice--by providing them with variable practice late in practice--were effective for both GMP and parameter learning. This suggests a hierarchy in the development of programmed actions with a stable GMP being a requisite for developing an effective and stable parameter rule. 相似文献
14.
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
15.
Victor Wennemar Wiltmann Hans-Christer Holmberg Pasi Pelttari Jussi Mikkola Keijo Häkkinen Olli Ohtonen 《European Journal of Sport Science》2016,16(8):1111-1120
The present study was designed to analyse and compare the kinetics and kinematics associated with three different starting strategies during classic cross-country ski racing. Inside a ski tunnel, 12 elite male skiers performed three sets of three 38?m starts. Each set included one start using: double poling only (DP), diagonal stride only (DIA) and freely chosen (FREE) (i.e. where subjects used the strategy or combination of strategies they felt was fastest) in random order. The first 18?m was performed on a series of force plates that measured horizontal and vertical forces followed by 20?m of a standard snow track. Additionally, cycle characteristics and joint angles were measured. DIA and FREE were faster over 38?m than DP (P?.01). Net horizontal impulse (taking into account both positive and negative impulses) 5–10?m after the start was lower during DP than during DIA and FREE (both P?<?.05). All subjects skied faster when using only DIA for the entire 38?m. Furthermore, the sum duration and frequency of propulsive contacts over the first 18?m was less in DP than DIA and FREE (P?相似文献
16.
Takeshi Yoneyama 《Sports Engineering》2018,21(4):277-282
The relation between the ski side-cut radius and deflection during a turn has been investigated. Using a model wherein the ski slides along a turn of a constant radius with an edging angle, it was found that the side-cut radius increases and the ski-deflection radius decreases as the edging angle increases. Even if additional deflection is necessary in the front part of the ski to form the turn groove, the side-cut radius is still the same in the groove. Owing to the constant side-cut radius of existing skis in the turn groove with a large edging angle, the top wide part of the ski causes an increase in skiing resistance. To reduce the skiing resistance, a prototype variable side-cut ski was fabricated, and test skiing was performed. Athletes felt more stable in the turn with the variable side-cut ski and found it easier to increase speed. 相似文献
17.
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. 相似文献
18.
高校大学生滑雪俱乐部组织与建设 总被引：1，自引：1，他引：0
论述了高校大学生滑雪俱乐部目标、宗旨和提高体育教学效果的作用。认为高校滑雪教学与户外俱乐部存在着传统的＂填鸭式＂体育教学思想占据统治地位,教学方式过于强调＂标准化＂而缺乏针对性,教学模式的＂计划供给式＂忽视学生的兴趣和需求,气候环境对教学的严重制约等问题;提出吸纳学员与教练员的选拔,滑雪俱乐部体育运动项目的确定与管理,宣传与发展规划等多方面积极构建高校大学生滑雪俱乐部并促进其长期的发展。 相似文献
19.
To determine the flight of a ski jumper it is essential to know what aerodynamic forces are acting on the ski jumper. However,
few data on this are available, especially for a V-style ski jumping flight. We have measured the aerodynamic forces during
the free flight phase for a V-style, as well as a parallel-style, ski jump by employing a full-size model in a wind tunnel.
The aerodynamic force data, (drag, lift and pitching moment) were obtained to create an aerodynamic database. These forces
are given in polynomial form as functions of the angle of attack, the body-ski (forward leaning) angle and the ski-opening
(V-style) angle. Using the polynomial form database is a convenient way of obtaining the aerodynamic forces. Moreover, the
wind tunnel was equipped with a ground effect plate to measure the aerodynamic forces during the landing phase. It was found
that the difference between the lift with and without the ground effect plate increases with the ski-opening angle. The longitudinal
stability in the pitching motion of a body-ski combination is also discussed on the basis of the pitching moment data. This
indicates that a stable pitching oscillation of the body-ski combination may arise around an equilibrium point in the angle
of attack, the trim angle of attack, during flight. 相似文献
20.
Six Danish male cross-country skiers were studied during the end-of-summer and winter seasons. Their maximal oxygen uptake was measured while running on a treadmill and using a ski ergometer incorporating the double-poling technique. Maximal oxygen uptake during treadmill running and double-poling was correlated with performance, expressed as a ranking score during 10 ski races. The tests were undertaken in September, December and April. Upper body maximal oxygen uptake increased 5.8% from September to December, decreasing to 2.3% above the September level in April. Upper body work output (2 min at maximal intensity) increased 11.8% from September to December (P less than 0.05). The relationship between upper body and leg maximal oxygen uptake--the upper body/leg ratio--was 89.4% in September. In four skiers, both treadmill and upper body tests were undertaken on each test occasion. The upper body/leg ratio changed from 87.7% in September to 95.7% in December. In April, the ratio was 91.0%. The maximal oxygen uptake measured using the ski ergometer during double-poling was significantly correlated with performance (P less than 0.05). It is concluded that the upper body ski ergometer can be used in the evaluation of elite cross-country skiers. 相似文献