Comparisons of the ski turn techniques of experienced and intermediate skiers

We compared selected kinematic variables for four different ski turn techniques performed by five experienced and five intermediate male skiers. The four ski turn techniques were the upstem turn, the downstem turn, the parallel turn and the parallel step turn. Each turn was divided into the initiation phase and the first and second steering phases. Most of the statistically significant differences (P < 0.05) between the two groups were found for the initiation phases of the four turns. Both the hip axis-hand axis angle and the edging angle of the uphill ski were significantly different between the two groups for the upstem turn at the beginning of the initiation phase. For the downstem turn, significant differences between the groups were found at the start of the initiation phase for the hip axis-hand axis angle, the shoulder axis-fall line angle, and the edging angle of the uphill ski. The standard deviation of the distance between the tips of the two skis over the second steering phase also differed significantly between the two groups. For the parallel step turn, significant differences were found at the start of the initiation phase for the edging angle of the downhill ski and the downhill ski to movement direction angle. Significant differences were also found for the edging angle of the downhill ski in the middle of the second steering phase and the shoulder axis to movement direction angle at the end of this phase. For the initiation phase of the parallel turn, significant differences were found for the timing of setting the ski pole, the uphill knee angle at the start of this phase and the range of the knee angle of the uphill leg from the start to the end of this phase. For this turn, significant differences between the two groups were also found for the edging angle of the downhill ski in the middle of the second steering phase and the shoulder axis to movement direction angle at the end of this phase. One of the reasons it was possible to identify a few significant differences only for the turns analysed, was the variability within the intermediate group: for most of the variables analysed, the standard deviation was much higher for the intermediate than for the experienced group.     

滑雪场安全问题探究

滑雪场是为消费者提供滑雪产品及服务的场所,滑雪者滑雪安全保障越来越受到消费者的关注。如何最大限度地保护滑雪者的人身安全,是滑雪场经营的首要问题。采用资料分析和实际调查相结合的方法,对滑雪场滑雪伤害产生的情形进行了追踪查证,并在调查基础上对滑雪的伤害类型及原因予以分类探究,提出了树立滑雪场安全经营理念,加强滑雪场规划的科学性论证,强化设备的日常保养和维护,规范滑雪器材的使用,建立完善的滑雪场安全设施标准等减少和防止滑雪伤害、提高滑雪安全的措施。     

Frequency and aetiology of injury in cross‐country skiing

A comparative analysis was carried out on 1263 injured downhill skiers and 85 cross‐country skiers with regard to risk of injury, diagnosis, localization and age distribution. While 48% of the injuries to crosscountry skiers involved the upper extremities, 77% of the injuries to downhill skiers involved lesions of the leg. Contusions accounted for 31.8% in the case of cross‐country skiers, while 37.8% of downhill skiers suffered distortions, 22.8% sustained torn ligaments and 22.2% suffered fractures.

A total of 57% of downhill skiers are under the age of thirty, while 87% of cross‐country skiers are at least 30 years of age. Female cross‐country skiers tend to suffer more injuries. The chief causes are falls on downhill slopes, but also on the level usually on icy or well‐trodden courses. Another course is the ski getting caught. Good equipment, a good state of fitness and preparation, protection against hypothermia, appropriate choice of cross‐country courses and cross‐country skiing lessons are ways of preventing injuries.     

Towards a methodology for comparing the effectiveness of different alpine ski waxes

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.     

Metabolic cost of level,uphill, and downhill running in highly cushioned shoes with carbon-fiber plates

BackgroundCompared to conventional racing shoes, Nike Vaporfly 4% running shoes reduce the metabolic cost of level treadmill running by 4%. The reduction is attributed to their lightweight, highly compliant, and resilient midsole foam and a midsole-embedded curved carbon-fiber plate. We investigated whether these shoes also could reduce the metabolic cost of moderate uphill (+3°) and downhill (–3°) grades. We tested the null hypothesis that, compared to conventional racing shoes, highly cushioned shoes with carbon-fiber plates would impart the same ～4% metabolic power (W/kg) savings during uphill and downhill running as they do during level running.MethodsAfter familiarization, 16 competitive male runners performed six 5-min trials (2 shoes × 3 grades) in 2 Nike marathon racing-shoe models (Streak 6 and Vaporfly 4%) on a level, uphill (+3°), and downhill (–3°) treadmill at 13 km/h (3.61 m/s). We measured submaximal oxygen uptake and carbon dioxide production during Minutes 4–5 and calculated metabolic power (W/kg) for each shoe model and grade combination.ResultsCompared to the conventional shoes (Streak 6), the metabolic power in the Vaporfly 4% shoes was 3.83% (level), 2.82% (uphill), and 2.70% (downhill) less (all p < 0.001). The percent of change in metabolic power for uphill running was less compared to level running (p = 0.04; effect size (ES) = 0.561) but was not statistically different between downhill and level running (p = 0.17; ES = 0.356).ConclusionOn a running course with uphill and downhill sections, the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall, compared to the savings on a perfectly level race course.     

Kinematic and postural characteristics of sprint running on sloping surfaces

The aim of this study was to identify the kinematic and postural characteristics associated with sprint running on uphill and downhill slopes of 3 degrees and on a horizontal surface. Eight male physical education students were filmed while sprinting maximally on an uphill-downhill platform under each of three conditions: (a) uphill at 3 degrees, (b) downhill at 3 degrees and (c) horizontal. Running speed, step rate, step length, step time, contact time, flight time and selected postural characteristics of the step cycle were analysed. Running speed was 9.2% faster (P < 0.05) during downhill and 3.0% slower (P < 0.05) during uphill compared with horizontal sprint running. During downhill and uphill sprint running, step length was the main contributor to the observed changes in running speed. It increased by 7.1% (P < 0.05) for downhill sprint running and was associated with significant changes in posture at touchdown and take-off. During uphill sprint running, step length decreased by 5.2% (P < 0.05), which was associated with significant changes in posture and reduced flight distance. Given the interaction between the acute changes in step length and posture when sprinting on a sloping surface, our findings suggest that such changes in posture may detract from the specificity of training on such surfaces. The chronic effects of training on such slopes on the kinematics and posture of horizontal sprint running are currently unclear.     

Effect of walking speed on lower extremity joint loading in graded ramp walking

Lower extremity joint loading during walking is strongly affected by the steepness of the slope and might cause pain and injuries in lower extremity joint structures. One feasible measure to reduce joint loading is the reduction of walking speed. Positive effects have been shown for level walking, but not for graded walking or hiking conditions. The aim of the study was to quantify the effect of walking speed (separated into the two components, step length and cadence) on the joint power of the hip, knee and ankle and to determine the knee joint forces in uphill and downhill walking. Ten participants walked up and down a ramp with step lengths of 0.46, 0.575 and 0.69 m and cadences of 80, 100 and 120 steps per minute. The ramp was equipped with a force platform and the locomotion was filmed with a 60 Hz video camera. Loading of the lower extremity joints was determined using inverse dynamics. A two-dimensional knee model was used to calculate forces in the knee structures during the stance phase. Walking speed affected lower extremity joint loading substantially and significantly. Change of step length caused much greater loading changes for all joints compared with change of cadence; the effects were more distinct in downhill than in uphill walking. The results indicate that lower extremity joint loading can be effectively controlled by varying step length and cadence during graded uphill and downhill walking. Hikers can avoid or reduce pain and injuries by reducing walking speed, particularly in downhill walking.     

Two critical psychological components of ski racing: Fun and feelings

The concepts of having fun and being aware of feeling states are presented as two critical factors in ski racing. First, the positive motivational characteristics of ‘fun’ are outlined. It is suggested that fun is not only a concept for young athletes but elite ones as well. Preliminary data based on a questionnaire, completed by the United States Alpine Ski Team and approximately 150 ski coaches, are presented. Second, the discussion on feelings refers to the mental programming of tactile sensations and determining one's emotional arousal (feeling state) prior to, and during, competition. Practical suggestions are made with regard to the psychological states and their effects on ski racing.     

Lower limb joint angles and ground reaction forces in forefoot strike and rearfoot strike runners during overground downhill and uphill running

This study investigated the normal and parallel ground reaction forces during downhill and uphill running in habitual forefoot strike and habitual rearfoot strike (RFS) runners. Fifteen habitual forefoot strike and 15 habitual RFS recreational male runners ran at 3 m/s ± 5% during level, uphill and downhill overground running on a ramp mounted at 6° and 9°. Results showed that forefoot strike runners had no visible impact peak in all running conditions, while the impact peaks only decreased during the uphill conditions in RFS runners. Active peaks decreased during the downhill conditions in forefoot strike runners while active loading rates increased during downhill conditions in RFS runners. Compared to the level condition, parallel braking peaks were larger during downhill conditions and parallel propulsive peaks were larger during uphill conditions. Combined with previous biomechanics studies, our findings suggest that forefoot strike running may be an effective strategy to reduce impacts, especially during downhill running. These findings may have further implications towards injury management and prevention.     

滑行经济性测评方法和技术特征的研究进展

系统梳理国外相关文献,探究滑行经济性测评方法的演进发展和影响经济性水平的主要技术特征发现:随着场地至实验室测试条件的转变,滑行经济性测评的效度和信度得以不断提升,目前已形成一套规范严谨的测评方法。上下肢协同的用力模式和“低频长幅”的周期步态是反映SE水平的主要技术表征;不同地形条件下,存在着SE更强的优选技术,适度延长撑杖时间和增大雪板方位角是提高上坡能量利用效率的关键;轻质雪板仅在陡坡地形表现出经济性的优势;长杖对改善SE有潜在的作用,但机理仍有较大分歧。未来SE研究可从实验室环境迁移至户外训练和比赛场地,由单一因素分析转向“技术-地形-装备”的复合影响因素探索,由基础性研究逐渐过渡至干预实验以及高水平竞技迁移等应用性研究。     

Biomechanical determinants of cross-country skiing performance: A systematic review

ABSTRACT

Cross-country skiing is a complex endurance sport requiring technical skills, in addition to considerable physiological and tactical abilities. This review aims to identify biomechanical factors that influence the performance of cross-country skiers. Four electronic databases were searched systematically for original articles in peer-reviewed journals addressing the relationship between biomechanical factors (including kinematics, kinetics, and muscle activation) and performance while skiing on snow or roller skiing. Of the 46 articles included, 22 focused exclusively on the classical technique, 18 on the skating technique, and six on both. The indicators of performance were: results from actual or simulated races (9 articles); speed on specific tracts (6 articles); maximal or peak speed (11 articles); skiing economy or efficiency (11 articles); and grouping on the basis of performance or level of skill (12 articles). The main findings were that i) cycle length, most often considered as a major determinant of skiing speed, is also related to skiing economy and level of performance; ii) higher cycle rate related with maximal speed capacity, while self-selected cycle rate improves skiing economy at sub-maximal speeds; iii) cross-country skiing performance appears to be improved by joint, whole-body, ski, and pole kinematics that promote forward propulsion while minimizing unnecessary movement.     

Social Support and Recovery from Sport Injury: Elite Skiers Share Their Experiences

Abstract

Research suggests that social support can be an important coping resource for athletes recovering from sport injury. Few studies have investigated this claim, however: To address this gap in the literature, 10 elite downhill skiers who had recovered from serious sport injuries were interviewed about the sources of stress associated with injury and the role of social support in recovery from sport injury. This paper presents the social support findings that emerged from this research¹. Content analyses of the social support data revealed that the skiers needed various types of emotional, informational, and tangible support from the occurance of injury through the return to full activity. Members of the treatment team, the ski team, and the skiers' home support networks provided social support throughout these phases. In general, the skiers were satisfied with the support received, indicating that it reduced distress and kept them motivated throughout recovery. The findings from this research have implications for the design of sport injury interventions.     

不同地形越野滑雪自由滑行技术的运用

越野滑雪运动员根据滑雪场地不同地形的需要,熟练运用最合理的滑行技术可以减小雪板与雪地之间的摩擦力和空气阻力,达到以最小的体能代价获得最佳运动速度的目的。分析越野滑雪运动员在不同滑道地形自由滑行技术的特点,探讨运动员在各种地形中使用自由滑行技术的合理性,并在训练中针对平原——缓上坡——缓下坡——陡上坡等地势变化的具体情况,培养运动员合理运用自由滑行技术,使越野滑雪运动员取得更优异的运动成绩。     

大众滑雪安全与体育休闲旅游的协调发展

随着滑雪体育休闲旅游的日益升温,参与的人数和损伤人数均呈上升趋势,大众滑雪者意外伤害事故的不断发生,使旅游安全成为滑雪产业发展的制约因素。通过文献资料法、问卷调查法、实地考察法、数理统计分析法等分析大众滑雪运动损伤的原因。结果表明:每个滑雪场所都会发生大众滑雪者人群的安全事故,自我防范意识较差、思想上对运动损伤不够重视是诱发意外事故的主要原因;意外伤害事故所引发的滑雪安全问题,会导致游客对滑雪丧失兴趣,降低滑雪爱好者的滑雪旅游出行率,滑雪安全问题会对滑雪休闲旅游产业链条的发展产生不良影响。滑雪场所要加强安全意识,建立自己的滑雪俱乐部或与上述滑雪俱乐部合作,积极引导与组织大众滑雪者参与滑雪运动,提高大众滑雪的安全度;滑雪爱好者应增强预防观念,提高个人保护能力,提高个人技术,从而避免或减少大众滑雪者事故的发生。     

Energy cost and kinematics of level,uphill and downhill running: fatigue-induced changes after a mountain ultramarathon

This study aimed to determine whether the fatigue induced by a mountain ultramarathon (MUM) led to changes in energy cost and kinematic during level and graded running. Pre- and post-race, 14 ultratrail runners ran on a level, uphill (5%) and downhill (5%) treadmill at 10 km · h^?1. Kinematic data were acquired using a photocell system. Post-race, the downhill energy cost increased by 13.1% (P < 0.001). No change was noted in level and uphill running. Duty factor and stride frequency were increased, whereas swing time, cycle time and stride length were decreased in all conditions (P < 0.05). Contact time was increased and the rate of force generation was decreased only in the uphill and downhill conditions (P < 0.05). Positive correlations were observed between performance time and the pre- to post-changes in the energy cost of level (r = 0.52, P = 0.04) and uphill running (r = 0.50, P = 0.04). MUM-induced fatigue resulted in physiological and spatiotemporal changes, though the response to fatigue varied considerably between running conditions. These changes resulted in a significant increment only in the downhill energy cost. Incorporating downhill locomotion in the training programmes of ultratrailers may help to improve performance-related physiological and biomechanical parameters.     

济南市大众滑雪运动开展现状调查与分析

采用文献资料法、问卷调查法、访谈法和逻辑分析法等,通过济南市滑雪场和滑雪人群的深入调查分析,目前济南市开展大众滑雪运动的现状和影响发展的各种因素,发现济南市大众滑雪运动发展速度较快,但还存在滑雪费用高、滑雪道难度小、器材陈旧,大众滑雪教练整体水平低等问题,因此还需要政府以及各部门的支持帮助,推动济南市大众滑雪的可持续发展。     

Emotional responses during repeated sprint intervals performed on level,downhill and uphill surfaces

The purpose of this study was to test emotional responses during sprint intervals performed on a level, down and up surface. Fifty trained participants performed a maximal effort during a 60-m sprint and 10 repetitions of 60 m running sprints on a level, down and up surface on a 5.9% slope. Running speeds, emotional responses and heart rate were measured. Self-selected speeds were correlated with the rating of perceived exertion, the affective balance, the desire to stop and the resources needed for the task in all conditions whereas the pleasure, the desire to continue and the capacity to realise the task were correlated with speeds only during level and uphill running. Mean values of emotional parameters were significantly different (P < 0.05) during running on a flat surface, downhill and uphill. When the gradient of running surface is changed, the pattern of emotional responses was just translated, i.e. most of the slope between the evolution of emotional parameters and the repetitions were not significantly different whereas Y-intercepts were different.

Consented effort is highly correlated with the resources needed for the task (P < 0.001, r² = 0.72). We propose that the difference in the resources needed for the task between level, downhill and uphill running (F _{2, 1499} = 166.5, P < 0.001, Eta² = 0.18) is the most important key that explains our results.     

Knee angular displacement and extensor muscle activity in telemark skiing and in ski-specific strength exercises

Much of the training of competitive telemark skiers is performed as dry-land exercises. The specificity of these exercises is important for optimizing the training effect. Our aim here was to study the activation of the knee extensor musculature and knee angular displacement during competitive telemark skiing and during dry-land strength training exercises to determine the specificity of the latter. Specificity was analysed with respect to angular amplitude, angular velocity, muscle action and electromyographic (EMG) activity. Five male telemark skiers of national and international standard volunteered to participate in the study, which consisted of two parts: (1) skiing a telemark ski course and (2) specific dry-land strength training exercises for telemark skiing (telemark jumps and barbell squats). The angular displacement of the right knee joint was recorded with an electrogoniometer. A tape pressure sensor was used to measure pressure between the sole of the foot and the bottom of the right ski boot. Electromyographic activity in the right vastus lateralis was recorded with surface electrodes. The EMG activity recorded during maximum countermovement jumps was used to normalize the EMG activity during telemark skiing, telemark jumps and barbell squats. The results showed that knee angular displacement during telemark skiing and dry-land telemark jumps had four distinct phases: a flexion (F1) and extension (E1) phase during the thrust phase of the outside ski/leg in the turn/jump and a flexion (F2) and extension (E2) phase when the leg was on the inside of the turn/jump. The vastus lateralis muscle was activated during F1 and E1 in the thrust phase during telemark skiing and telemark jumps. The overall net knee angular amplitude was significantly greater (P<0.05) for telemark jumps than for telemark skiing. Barbell squats showed a knee angular amplitude significantly greater than that in telemark skiing (P<0.05). The mean knee angular velocity of the F1 and E1 phases during telemark skiing was about 0.47 rad?·?s^?1; during barbell squats, it was about 1.22 rad?·?s^?1. The angular velocity during telemark jumps was 2.34 and 1.59 rad?·?s^?1 in the F1 and E1 phase, respectively. The normalized activation level of the EMG bursts during telemark skiing, telemark jumps and barbell squats was 70–80%. In conclusion, the muscle action and level of activation in the vastus lateralis during the F1 and E1 phases were similar during telemark skiing and dry-land exercises. However, the dry-land exercises showed a larger knee extension and flexion amplitude and angular velocity compared with telemark skiing. It appears that an adjustment of knee angular velocity during barbell squats and an adjustment of knee angle amplitude during both telemark jumps and barbell squats will improve specificity during training.     

黑龙江省滑雪场所设施情况的调查

滑雪旅游已经成为黑龙江省支柱性产业,研究黑龙江省滑雪场地的布局与设施情况,对促进龙江滑雪旅游产业的健康、可持续发展具有重要作用。采用问卷调查法、文献资料法、访谈法和数理统计法等研究方法,抽取黑龙江省60家滑雪场所进行调查与分析,结果表明只有少部分滑雪场的索道、雪道、雪具等配备较合理,大部分雪场的医疗救护、环保以及雪道质量有待完善和提高,大多数雪场周边遍布村屯,外部环境较差,行车极不方便。     

不同方式跑台运动对去卵巢小鼠破骨细胞分化及相关调节因子的影响

目的:以去卵巢小鼠模拟妇女绝经后骨质疏松症状,对比研究上、下坡跑台运动对去卵巢小鼠破骨细胞分化及相关调节因子的影响.方法:64只8周龄C57 BL/6雌性小鼠随机分为4组:假手术安静组(SHAM),去卵巢安静组(OVX),去卵巢上坡跑组(OVX +UP),去卵巢下坡跑组(OVX +DOWN).结果:与SHAM组相比,OVX组小鼠干细胞向巨噬细胞分化的能力、巨噬细胞向破骨细胞分化的能力均显著增强;骨组织RANKL、M-CSF和RANK的基因表达显著增加,而OPG的基因表达显著降低.与OVX组相比,两运动组小鼠破骨细胞的分化得到了较好的抑制.结论:跑台运动可有效抑制小鼠去卵巢后破骨细胞的大量分化,从而有利于预防骨质疏松症的发生,且下坡跑运动比上坡跑运动更有效.