Maximizing recovery time between knock-out races improves sprint cross-country skiing performance

Background:In a sprint cross-country(XC)ski competition,the difference in recovery times separating the first and the second semi-final(SF)heats from the final(F)may affect performance.The aim of the current study was to compare the effects of longer vs.shorter recovery periods prescribed between the 3 knock-out races of a simulated sprint XC ski competition involving a prologue(P),quarter-final(QF),SF,and F.Methods:Eleven well-trained XC ski athletes completed 2 simulated sprint XC ski competitions on a treadmill involving 4×883-m roller-ski bouts at a 4°incline using the gear 3 ski-skating sub-technique.The first 3 bouts were completed at a fixed speed(PFIX,QFFIX,and SFFIX)corresponding to~96%of each individual’s previously determined maximal effort.The final bout was performed as a self-paced sprint time trial(FSTT).Test conditions differed by the time durations prescribed between the QFFIX,SFFIX,and FSTT,which simulated real-world XC ski competition conditions using maximum(MAX-REC)or minimum(MIN-REC)recovery periods.Results:The FSTT was completed 5.4±5.5 s faster(p=0.009)during MAX-REC(179.2±18.1 s)compared to MIN-REC(184.6±20.0 s),and this was linked to a significantly higher power output(p=0.010)and total metabolic rate(p=0.009).The pre FSTT blood lactate(BLa)concentration was significantly lower during MAX-REC compared to MIN-REC(2.5±0.8 mmol/L vs.3.6±1.6 mmol/L,respectively;p=0.027),and the pre-to-post FSTT increase in BLa was greater(8.8±2.1 mmol/L vs.7.1±2.3 mmol/L,respectively;p=0.024).No other differences for MAX-REC vs.MIN-REC reached significance(p>0.05).Conclusion:Performance in a group of well-trained XC skiers is negatively affected when recovery times between sprint heats are minimized which,in competition conditions,would occur when selecting the last QF heat.This result is combined with a higher pre-race BLa concentration and a reduced rise in BLa concentration under shorter recovery conditions.These findings may help inform decision making when XC skiers are faced with selecting a QF heat within a sprint competition.

Differences between Cheeks and Dorsal Hands Skin Properties during Skiing in a Cold and Windy Environment

Background/Purpose: The skin protects against external factors and this skin function can be affected by environmental conditions, including low temperature, low humidity, and high altitude. Therefore, it is important to study the relationship between the environment and the skin. The purpose of this study is to determine how the skin barrier functions change at low temperatures. Methods: This study was performed at a Korean ski resort on January 2015 and evaluated 10 subjects skin condition during skiing. Skin properties were examined at 2 sites (cheeks and dorsal hands) and four time points (indoor;baseline, outdoor;after first skiing and after second skiing, indoor;after taking a shower). Results: The skin hydration on the cheek decreased after the second skiing session and the erythema decreased only after the first skiing while this value on dorsal hand was not changed by skiing. The brightness and yellowness of cheek skin increased and redness decreased therefore, skin color became pale during skiing. The extensibility of cheeks and dorsal hands decreased after skiing. We found positive correlation between skin temperature and redness (r2 = 0.707, p Conclusions: Low temperatures can affect human skin color so that the skin color becomes pale because capillary blood vessels shrink when skin is exposed to cold environment. The cheek skin tends to change easily than dorsal hand during ambient temperature change.

Establishment and Maintenance of Grass Skiing Resort Turf Based on Climatic Characteristics of Western Sichuan

In recent years, a new type of leisure sport—grass skiing, has been introduced from abroad. However, there is no standard design system for this type of turf. This paper, based on climatic characteristics of western Sichuan, introduced the requirements of the construction of grass skiing resort turf in western Sichuan as well as its maintenance management mode, and tried to explore the standard system of turf establishment and maintenance management of grass skiing resort in western Sichuan.

Three-Rigid-Body-Particle Modeling and Optimization of Trajectory and Posture for Alpine Skiing

This paper presents a new study on modeling and optimization of trajectory and posture for the super-giant(SG)slalom of alpine skiing.It is the first time that a Three-Rigid-Body-Particle model based on rigorous derivations and stability analysis is established to represent skiers trajectory and posture characteristics,as it is more accurate than the single-rigid-body model which is commonly used in existing studies.In addition,the Radau pseudospectral method is applied to solve the trajectory and posture optimization problem in order to obtain better skiing trajectory,skiing posture,and some key kinematic parameters of skiers.Moreover,this paper analyzes the effects of different body types,minimum turning radii,and flexor and extensor strength of knees and hip joint on skiing performance.Finally,based on the findings of the study,some advice about how to improve the performance of the SG slalom in view of science and technology is given to skiers and coaches for reference.

Comparison and analysis of skiing injuries at ski resorts in Chongli,China and Japan

Purpose:The rapid development of winter sports requires investigation on injuries in Chongli district,Zhangjiakou city,one of the ski sites of the 2022 Winter Olympics.Careful evaluation is required to observe which injuries are caused under what circumstances,and then we can make corresponding preventive measures and recommendations based on the results.Methods:In this retrospective study,the data of injury cases at ski resorts in China(Chongli district)and Japan were analyzed to provide a reference for the ongoing injury prevention at ski resorts.We collected data on injuries at Wanlong and Fulong ski resorts in Chongli district during the 2017–2018 and 2018-2019 ski seasons.We referred to the skiing injury report issued in February 2020 of a nationwide ski safety statistical service–Japan Ski Safety Association.The causes of injury and specific injured body parts were analyzed based on the data of Chinese and Japanese ski resorts.Statistical significance has been calculated using the Chi-square test.Results:During the 2019–2020 ski season in Japanese ski resorts,the number of reported injuries per 10,000 skiers was 0.93,of which 457(17.3%)were over 50 years old,accounting for a large proportion of injuries,meanwhile in Chongli ski resort,the injury rate of skiers aged 50 and over was 7.1%.The knee joint(23.7%at Wanlong ski resort and 28.4%in Japanese ski resorts)was the most injured body part among Chongli and Japanese skiers.Among snowboarders,shoulder joint injury(17.7%in Japanese ski resorts)was the most common,and injury on hands and fingers(16.3%in Wanlong ski resorts)was the most common.Head injury rates are similar in Chongli,China and Japanese ski resorts(8.2%and 8.7%,respectively).Conclusion:Our analysis demonstrated that injury data recorded among young skiers was higher in Chinese ski resorts(Chongli district)than that in Japanese ski resorts,and elderly skiers made up a larger proportion of skiing injuries in Japanese resorts.Thus,according to our research,the protection of knee joints,shoulder joints,and hands and fingers should be taken seriously.It should pay attention to the teaching of ski poles(for finger protection),and use protective devices such as knee pads,helmets,etc.

Effects of Additional Rifle-Carriage Training on Physiological Markers and Roller-Skiing Performance in Well-Trained Biathletes

Purpose The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting a minimum of 12 weeks.Methods Seventeen well-trained biathletes(9 females,8 males)were assigned to an intervention(IG,n=10)or control(CG,n=7)group.Before(T1)and after(T2)the training intervention all participants performed,using treadmill roller-skiing,a submaximal test without the rifle on one day and two submaximal workloads and a maximal time trial(TT)with the rifle on a subsequent day.Between T1 and T2 all participants performed a minimum of 12 weeks of normal training,the only difference between groups being that IG performed more of their training sessions carrying the rifle.Results IG performed more training compared to CG(15.4±1.1 vs.11.2±2.6 h/week,P<0.05),including a higher amount of training with the rifle(3.1±0.6 vs.1.1±0.3 h/week,P<0.001).Speed at 4 mmol/L of blood lactate increased significantly for CG from T1 to T2(P=0.028),while only tended to increase for IG(P=0.058).Performance during the TT,VO2max and the aerobic metabolic rate increased significantly from T1 to T2,although the differences disappeared when including the speed at baseline as a covariate.Conclusion According to the present results,increasing training while carrying the rifle by 2 h/week does not appear to improve skiing performance in well-trained biathletes.In addition,physiological markers at submaximal and maximal intensities while carrying the rifle were not affected after the training intervention.

小肠过表达Ski蛋白对扭体小鼠的抑炎镇痛作用

目的 研究小肠过表达鸟类癌基因(virus sloan-kettering institute, v-ski)的细胞内同源物(Ski)蛋白对醋酸致扭体小鼠的抑炎镇痛作用。方法 选取8周龄雄性ICR小鼠,给予腹腔注射现配的0.7%醋酸溶液(0.1 mL/10 g)诱发扭体反应。实验小鼠分为假手术(sham)组、醋酸(acetic acid)组、醋酸(acetic acid)+布洛芬(ibuprofen)组、醋酸(acetic acid)+腺病毒空质粒(ad-EGFP)组、醋酸(acetic acid)+腺病毒ski质粒(ad-ski)-1组、醋酸(acetic acid)+腺病毒ski质粒(ad-ski)-2组和醋酸(acetic acid)+柳氮磺胺吡啶(sulfasalazine)组,每组10只。观察并记录第1次扭体出现的潜伏期,同时记录15 min内的扭体次数。获取标记的小肠组织,鉴定腺病毒转染效果,检测促炎因子、疼痛生物标志物的蛋白表达量,进一步分析核转录因子-κB(NF-κB)通路蛋白表达及其与Ski蛋白的结合情况。结果 腹腔注射ad-ski腺病毒后,小肠成功过表达Ski蛋白。过表达的Ski蛋白延长了小鼠发生扭体的潜伏期,同时减少了扭体反应的频率,与布洛芬的效果相当(P>0.05)。与醋酸组比较,过表达的Ski蛋白显著抑制了促炎因子和疼痛生物标志物的蛋白表达(P<0.05)。而且NF-κB p65与Ski有复合物形成。结论过表达Ski蛋白对醋酸引起的炎性疼痛有抑炎镇痛作用,且与Ski调节NF-κB信号通路有关。

Sierpiński图和Sierpiński金字塔上的一些费马型指标

本文中我们给出一些费马型指标的结果,包括费马偏心距、费马半径和费马直径.我们使用编码的组合方法确定了Sierpiński图和Sierpiński金字塔的费马半径和费马直径.通过归一化Sierpiński图上的距离,我们给出了Sierpiński金字塔的平均费马偏心距的精确值并由此得到关于Sierpiński图的渐近公式.

广义Sierpiński网络的全控制数

设G=(V,E)为一个无孤立点的图.如果一个双值函数f:V→{0,1}对任意点v∈V,均有f(N(v))≥1成立,则称f为图G的一个全控制函数.图G的全控制数定义为γt(G)=min{f(V)|f为图G的一个全控制函数}.该文应用数学归纳法和分类讨论法,得到了以路P_(m)、圈C_(m)、完全图K_(m)为基图的广义Sierpiński网络的全控制数.

基于BP神经网络的金属材料翘曲图像捕捉及参数调整

热板翘曲缺陷是影响成品质量和生产进度的重要原因,以往采用的人工修正、有限元预测、在线监测均未取得良好的效果。因此,本文开发一套基于BP神经网络的翘曲自动化控制策略。首先采用机器视觉技术对翘曲程度进行定量化测量,利用现场数据建立预测翘曲值的BP神经网络模型,并验证模型的性能。其次根据神经网络模型,结合生产规程和实际数据制定翘曲自动化控制策略,完成对SKI值的修正,以得到最小程度的翘曲。经过测试,该策略满足生产现场的实际需求,可以为后续自动化控制系统的开发提供依据。

自由式滑雪空中技巧项目女子技术发展趋势的研究

自由式滑雪空中技巧项目是我国近年来发展起来的项目 ,在国家冬季项目管理中心的支持下 ,特别是女子项目在我国得到了极快发展。本课题根据第 19届冬奥会本项目比赛的情况 ,展望第 2 0届冬奥会女子空中技术比赛可能使用的最难动作问题 。

Biomechanical analysis of the "running" vs. "conventional" diagonal stride uphill techniques as performed by elite cross-country skiers

Purpose:This study aimed to compare biomechanical aspects of a novel"running"diagonal stride(DSRUN)with"conventional"diagonal stride(DSCONV)skiing techniques performed at high speed.Methods:Ten elite Italian male junior cross-country skiers skied on a treadmill at 10 km/h and at a 10°incline utilizing both variants of the diagonal stride technique.The 3-dimensional kinematics of the body,poles,and roller skis;the force exerted through the poles and foot plantar surfaces;and the angular motion of the leg joints were determined.Results:Compared to DSCONV,DSRUN demonstrated shorter cycle times(1.05±0.05 s vs.0.75±0.03 s(mean±SD),p<0.001)due to a shorter rolling phase(0.40±0.04 s vs.0.09±0.04 s,p<0.001);greater force applied perpendicularly to the roller skis when they had stopped rolling forward(413±190 N vs.890±170 N,p<0.001),with peak force being attained earlier;prolonged knee extension,with a greater range of motion during the roller ski-stop phase(28°±40 vs.16°±3°,p=0.00014);and more pronounced hip and knee flexion during most of the forward leg swing.The mechanical work performed against friction during rolling was significantly less with DSRUN than with DSCONV(0.04±0.01 J/m/kg vs.0.10±0.02 J/m/kg,p<0.001).Conclusion:Our findings demonstrate that DSRUN is characterize by more rapid propulsion,earlier leg extension,and a greater range of motion of knee joint extension than DSCONV-Further investigations,preferably on snow,should reveal whether DSRUN results in higher acceleration and/or higher peak speed.

清胰化积方下调Ski表达抗胰腺癌生长实验研究

目的探讨清胰化积方(Qingyi Huaji Formula,QYHJ)是否通过下调Ski表达抑制胰腺肿瘤的生长。方法采用Real-time PCR和Western blot对QYHJ治疗后21天人胰腺癌裸小鼠皮下移植瘤Ski mRNA和蛋白表达进行检测;通过慢病毒介导的RNA干扰技术建立Ski低表达人胰腺癌细胞系,并通过建立裸小鼠皮下移植瘤,评价Ski不同表达肿瘤对QYHJ治疗反应性是否存在差异。结果 QYHJ治疗后,人胰腺癌SW1990皮下移植瘤Ski mRNA和蛋白表达与未用QYHJ治疗组比较分别下降了39.6%和41.3%(均P<0.05);建立了Ski低表达SW1990细胞系(SW1990/Ski RNAi)和阴性干扰细胞系(SW1990/con RNAi),其Ski mRNA和蛋白表达量分别是亲代细胞的105%、123%和46%、30%(均P<0.05);SW1990细胞和SW1990/con RNAi细胞皮下移植瘤应用QYHJ治疗后其瘤重抑制率分别为29.6%和32.2%,但SW1990/RNAi细胞组其瘤重抑制率为16.0%～17.8%(均P<0.05)。结论 Ski下调增加了人胰腺癌细胞对QYHJ治疗的敏感性,Ski为QYHJ治疗胰腺癌一个重要作用靶点,其不同表达介导了胰腺癌细胞对QYHJ治疗的反应性差异。

Ski在大鼠活化星形胶质细胞中表达的变化

目的:探究Ski在大鼠正常及活化星形胶质细胞中的表达及随时间变化的规律。方法:提取大鼠大脑皮质,分离星形胶质细胞,体外培养。采用LPS刺激和细胞划痕损伤2种方法活化星形胶质细胞,均采用Western blot法检测各个时点2种活化星形胶质细胞中Ski和胶质纤维酸性蛋白(GFAP)蛋白表达情况,利用间接免疫荧光法检测Ski蛋白在星形胶质细胞中的表达定位。结果:GFAP蛋白在星形胶质细胞中固有表达,LPS活化和划痕损伤后表达均上调。Ski在正常星形胶质细胞中呈低表达状态,1 mg/L LPS活化星形胶质细胞后,Ski表达开始增加,4 d时表达量最高(P<0.05),6 d时开始下降,但仍高于未活化组;细胞划痕损伤后Ski蛋白表达情况与上述情况高度一致。Ski在正常及LPS活化6 d星形胶质细胞中表达主要集中在胞核,LPS活化后2和4 d时在胞质中出现明确的Ski表达。结论:Ski蛋白表达于星形胶质细胞,并在活化星形胶质细胞中表达上调。由此,我们推测Ski蛋白可能调控星形胶质细胞的活化、增殖等过程。

沉默ski基因对大鼠星形胶质细胞迁移的影响

目的研究ski基因在大鼠星形胶质细胞迁移过程中的作用。方法分离大鼠脑皮质星形胶质细胞,体外培养。合成ski基因和阴性对照小干扰片段。设置ski-siRNA转染组、阴性对照组和空白对照组。采用脂质体法将特异性针对ski基因的siRNA和阴性对照siRNA转入大鼠星形胶质细胞。采用Western blotting检测各组ski蛋白的表达水平;采用Transwell细胞迁移实验和细胞划痕实验检测ski-siRNA转染后星形胶质细胞迁移能力的变化。结果与空白对照组和阴性对照组比较,ski-siRNA转染组细胞内ski蛋白的相对表达水平显著降低(F=132.957,P<0.001)。Transwell细胞迁移实验发现,ski-siRNA转染组每孔迁移细胞数少于空白对照组和阴性对照组(F>47.197,P<0.05)。细胞划痕实验显示,转染组细胞1~5 d的划痕愈合率均明显低于对照组(F>69.187,P<0.01)。结论沉默ski基因能显著抑制星形胶质细胞的迁移能力,ski可能参与星形胶质细胞的转移过程,进而调控胶质瘢痕的形成。

脂多糖对大鼠星形胶质细胞Ski蛋白表达的影响

目的探讨内毒素脂多糖对大鼠星形胶质细胞ski蛋白表达规律及胞定位的影响。方法新生3 d内Sprague-Dawley大鼠,取大脑皮质分离星形胶质细胞,体外培养。采用0μg/ml、0.001μg/ml、0.01μg/ml、0.1μg/ml、1μg/ml、10μg/ml、100μg/ml脂多糖诱导6 h;采用0.1μg/ml脂多糖诱导0 d、2 d、4 d、6 d、8 d。Western blotting法检测星形胶质细胞中ski蛋白的表达,间接免疫荧光双标法检测ski在星形胶质细胞中的定位。结果 0.1μg/ml脂多糖诱导下,ski蛋白表达最高(F=46.656,P<0.001)。0.1μg/ml脂多糖诱导4 d时最高,6 d时逐渐降低。在无脂多糖诱导及脂多糖诱导6 d时,ski蛋白主要表达于细胞核;脂多糖诱导2 d、4 d时,细胞质中出现ski表达。结论脂多糖可诱导星形胶质细胞ski蛋白表达,可能参与炎症反应。

Ski对脂多糖诱导大鼠星形胶质细胞炎症因子释放的影响

目的探讨Ski对激活星形胶质细胞炎症因子分泌的影响。方法从3日龄Sprague-Dawley大鼠大脑皮质分离星形胶质细胞,分为空白对照组、阴性对照组、siRNA组,siRNA组沉默Ski基因。48 h后,采用Western blotting和免疫荧光染色检测Ski表达;再以脂多糖激活星形胶质细胞24 h。ELISA检测各组细胞中肿瘤坏死因子-α(TNF-α)和白细胞介素-1β(IL-1β)的浓度。结果 siRNA组Ski蛋白表达显著降低(P<0.001);激活后,TNF-α、IL-1β浓度显著减少(P<0.001)。结论 Ski可能参与星形胶质细胞炎症反应。

HPV-16 E6 siRNA与hIL-24基因联合诱导人宫颈癌Ca Ski细胞的凋亡

目的:观察HPV-16 E6 siRNA与hIL-24基因体外共转染,联合诱导人宫颈癌Ca Ski细胞凋亡的效应。方法:HPV-16 E6 siRNA与hIL-24基因的质粒载体分别以单独或联合的方式转染人宫颈癌Ca Ski细胞,随后利用RT-PCR技术检测细胞中HPV-16 E6癌基因的mRNA水平变化;Western blot分析细胞中抑癌蛋白p53水平的变化;流式细胞技术分析细胞凋亡情况。结果:经HPV-16 E6 siRNA和hIL-24转染后细胞后HPV E6癌基因的mRNA水平均下降,其中联合转染组显著下降(P<0.05);抑癌蛋白p53水平均增高,其中联合转染组显著增高,细胞凋亡率均升高,其中联合转染组显著升高(P<0.05)。结论:HPV-16 E6 siRNA与hIL-24基因分别转染宫颈癌Ca Ski细胞后,均能抑制Ca Ski细胞中HPV-16 E6癌基因的表达,使抑癌蛋白p53恢复活性,诱导宫颈癌Ca Ski细胞凋亡;两者联合则具有协同效应,能显著提高肿瘤细胞凋亡率。

C-ski和Smad3在大鼠皮肤成纤维细胞辐射性损伤中的变化及意义

目的研究C-ski和Smad3在大鼠皮肤成纤维细胞辐射性损伤中的变化和意义。方法软X线照射诱导大鼠皮肤成纤维细胞辐射性损伤,Western blot和RT-PCR观察C-ski、Smad3蛋白和mRNA水平的变化,EMSA检测Smad3转录活性的变化。结果辐射后2h,C-ski、Smad3蛋白和mRNA水平、Smad3转录活性无显著变化,4h开始,C-ski表达逐渐下降,Smad3表达和转录活性逐渐升高,在8h分别达到峰谷和峰顶。结论C-ski和Smad3参与大鼠皮肤成纤维细胞辐射性损伤的病理过程,辐射后C-ski下降,Smad3升高,并导致Smad3转录活性增强,细胞增殖受抑,凋亡增加。

沉默ski基因对大鼠星形胶质细胞活化增殖及Cyclin D1表达的影响

目的研究ski基因对大鼠星形胶质细胞增殖的影响及其分子机制。方法分离3日龄Sprague-Dawley大鼠脑皮质星形胶质细胞,体外培养。合成ski和阴性对照小干扰片段。设置ski-si RNA组、阴性对照组和空白对照组,采用脂质体法将特异性针对ski基因的si RNA和阴性对照si RNA转入ski-si RNA组、阴性对照组星形胶质细胞中。Western blotting分析ski、胶质纤维酸性蛋白(GFAP)和Cyclin D1蛋白表达;CCK8法检测星形胶质细胞增殖活力;流式细胞仪检测细胞周期。结果 ski-si RNA组星形胶质细胞ski蛋白表达明显降低(F=38.611,P<0.01),GFAP(F=7.547,P<0.05)和Cyclin D1蛋白(F=3.901,P<0.05)表达降低;培养12 h后,ski-si RNA组增殖活力明显降低(F>30.507,P<0.01),G1期细胞比例明显增加,S期明显减少(F>48.425,P<0.01)。结论沉默ski基因可能通过下调Cyclin D1表达,抑制星形胶质细胞增殖。