Pacing and predictors of performance during cross-country skiing races:A systematic review

Background: Cross-country skiing(XCS) racing, a popular international winter sport, is complex and challenging from physical, technical, and tactical perspectives. Despite the vast amount of research focusing on this sport, no review has yet addressed the pacing strategies of elite XCS racers or the factors that influence their performance. The aim was to review the scientific literature in an attempt to determine the effects of pacing strategy on the performance of elite XCS racers.Methods: Four electronic databases were searched using relevant subject headings and keywords. Only original research articles published in peerreviewed journals and the English language and addressing performance, biomechanics, physiology, and anthropometry of XCS racers were reviewed.Results: All 27 included articles applied correlative designs to study the effectiveness of different pacing strategies. None of the articles involved the use of an experimental design. Furthermore, potential changes in external conditions(e.g., weather, ski properties) were not taken into consideration. A comparable number of studies focused on the skating or classical technique. In most cases, positive pacing was observed, with certain indications that higher-level athletes and those with more endurance and strength utilized a more even pacing strategy. The ability to achieve and maintain a long cycle length on all types of terrain was an important determinant of performance in all of the included studies, which was not the case for cycle rate. In general, uphill performance was closely related to overall race performance, with uphill performance being most closely correlated to the success of female skiers and performance on flat terrain being more important for male skiers. Moreover, pacing was coupled to the selection and distribution of technique during a race, with faster skiers employing more double poling and kick double poling,less diagonal stride, and more V2(double dance) than V1(single dance) skating across a race.Conclusion: We propose that skiers at all levels can improve their performance with more specific training in techniques(i.e., maintaining long cycles without compromising cycle rate and selecting appropriate techniques) in combination with training for endurance and more strength. Furthermore, we would advise less experienced skiers and/or those with lower levels of performance to apply a more even pacing strategy rather than a positive one(i.e., starting the race too fast).

The influence of physiobiomechanical parameters,technical aspects of shooting,and psychophysiological factors on biathlon performance:A review

The biathlon, an Olympic sporting discipline that combines cross-country skiing with rifle marksmanship, entails considerable physiological demands, as well as fine motor control while shooting after intense exercise and under mental pressure. Although much of our knowledge about cross-country skiing is probably also applicable to the biathlon, carrying the rifle and shooting under stress make this discipline somewhat unique. The present review summarizes and examines the scientific literature related to biathlon performance, with a focus on physiological and biomechanical factors and shooting technique, as well as psychophysiological aspects of shooting performance. We conclude with suggestions for future research designed to extend our knowledge about the biathlon, which is presently quite limited.

极简鞋与坡度对跑步时垂直刚度和下肢刚度的影响（英文）

目的:采用运动学数据描述和比较传统跑鞋和极简鞋在下坡、平坡和上坡跑步时对垂直刚度和下肢刚度的影响。方法:受试者为14名男性业余跑步者(年龄23.4±4.4岁,身高177.5±5.2 cm,体重69.5±5.3 kg)。要求一周内完成2次测试,每次测试时,受试者以10 km/h的速度在跑步机上进行7组(每组5 min)跑步,组间有5 min坐式休息。每组试验在-8%(下坡)到+8%(上坡)的范围内随机选择不同的坡度跑步。在每组试验中,要求所有受试者穿极简鞋跑步(5 min),随后再穿传统跑鞋跑步(5 min),以确保每个坡度各有一次随机平衡条件下的两种鞋对比试验。采用光电测试系统和高速摄像机采集运动学数据,计算出垂直刚度和下肢刚度。结果:在不同坡度跑时,极简鞋组的下肢压缩、触地时间和质心垂直位移均明显小于传统跑鞋组。随着倾斜角度增加,两组鞋的步频均显著增大。运动学分析显示,在相似的坡度跑时,极简鞋组的下肢刚度高于传统鞋组,在垂直刚度上两组鞋并无差异,但均会随着坡度的增加而增加。结论:不同的鞋和(或)坡度能对跑步时垂直刚度和下肢刚度产生不同影响。本研究采用两种刚度的测量方法,为理解不同条件下跑步的生物力学适应提供了独特视角。同时,通过量化各种刚度能进一步加深理解跑步者的训练、运动表现和损伤。

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.

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.

Methodological Guidelines Designed to Improve the Quality of Research on Cross-Country Skiing

Cross-country(XC)ski races involve a variety of formats,two different techniques and tracks with highly variable topography and environmental conditions.In addition,XC skiing is a major component of both Nordic combined and biathlon competi-tions.Research in this area,both in the laboratory and field,encounters certain difficulties that may reduce the reliability and validity of the data obtained,as well as complicate comparisons between studies.Here,13 international experts propose specific guidelines designed to enhance the quality of research and publications on XC skiing,as well as on the biathlon and Nordic combined skiing.We consider biomechanical(kinematic,kinetic and neuromuscular)and physiological methodology(at the systemic and/or muscle level),providing recommendations for standardization/control of the experimental setup.We describe the types of measuring equipment and technology that are most suitable in this context.Moreover,we also deal with certain aspects of nomenclature of the classical and skating sub-techniques.In addition to enhancing the quality of stud-ies on XC skiing,Nordic combined and biathlon,our guidelines should also be of value for sport scientists and coaches in other disciplines where physiological and/or biomechanical measurements are performed in the laboratory and/or outdoors.

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.

Monitoring the Performance of Alpine Skiers with Inertial Motion Units: Practical and Methodological Considerations

Although reliable feedback is crucial to improving the performance of competitive alpine skiers,the coach’s eye may not be sensitive enough to detect small,but highly significant“mistakes”.Monitoring of the performance of alpine ski racers by inertial motion units(IMU)has proven to be of value in this context and here we summarize practical and methodological aspects of this approach.Methodologically,the IMUs employed should combine high sampling frequencies with minimal signal drift.The sensors should be positioned to sense the movement of the bones in a given body segment while being pro-tected as much as possible against impact with the ski gates.The data obtained,often synchronized with input from Global Satellite Navigation Systems(GNSS),are usually refined utilizing advanced biomechanical models and other computerized approaches.In practice,the combination of inertial sensors and GNSS allows accurate monitoring of skiing kinematics(technique)and the movement of the skier’s center-of-mass,also allowing analysis of both whole-body vibrations(WBV)and loss of mechanical energy.Presentation of the findings to coaches and athletes can be facilitated by synchronizing them with video recordings.Recent advances in IMU technology,including miniaturization,wireless communication,direct stor-age of data in the cloud,and processing with artificial intelligence may allow these sensors,in-combination with GNSS,to become real-time virtual alpine ski coaches,perhaps the next step in the development of this sport.