The purpose of this study was to investigate whether eight weeks of aerobic high-intensity interval training with roller ski is effective in cross-country skiers. 10 male （age, 18.28 ± 2.1 years; height, 171.26 ...The purpose of this study was to investigate whether eight weeks of aerobic high-intensity interval training with roller ski is effective in cross-country skiers. 10 male （age, 18.28 ± 2.1 years; height, 171.26 ± 4.12 cm; weight 61.39 ± 6.28 kg） and 8 female （age, 16.05 ± 0.3 years; height, 158.3 ± 6.47 cm; weight, 49.34 ± 0.7 kg） junior cross country skiers completed the study. All skiers performed a 2 × 2-kin all-out uphill intervals with roller-skis, 3 times a week, in addition to their traditional training program. Measurements included VO2max （maximal oxygen uptake）, anaerobic power, and also for 2-km roller ski. All values were listed as pre-to post-test mean （± SD）, significant level, and percentage changes （%）. Pre-to post-testing changes in VO2max, anaerobic power, and also 2-kin roller ski performance were significantly higher during all post-test trials in all groups （P 〈 0.005）. With reference to the training effects found in our study, we suggest that the skiers should integrate the roller ski aerobic high-intensity interval uphill models in their training programs for improving performance.展开更多
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 eli...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.展开更多
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...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.展开更多
This study aimed to determine the appropriate nutritional intakes and dietary habits of high school-aged cross-country skiers and speed skaters. The subjects, all high school students from N Prefecture, included 18 ma...This study aimed to determine the appropriate nutritional intakes and dietary habits of high school-aged cross-country skiers and speed skaters. The subjects, all high school students from N Prefecture, included 18 male cross-country skiers, 5 male speed skaters, 10 female cross-country ski players and 4 female speed skaters. Physical measurements, food intake frequency survey results, bone mineral density and exercise stress test outcomes, and lactic acid measurements were evaluated. Female athletes in both sports had higher body fat percentages relative to the average range stated for female athletes. Male speed skaters had a significantly higher maximum oxygen in-take than that male cross-country skiers did. By contrast, this parameter did not differ significantly among female athletes. A negative correlation was observed between the fat free mass and muscle mass, and a positive correlation was observed among the body fat percentage, fat percentage, and fat mass. Both male and female athletes had protein intake ratios within the reference ranges. All athletes except male speed skaters had lipid energy ratios that were higher than the upper limit of the reference value. Both male and female athletes also reported carbohydrate energy ratios within the reference ranges, but had cereal energy ratios below the reference values. Athletes should pay attention to the ingestion of various nutrients to ensure a sufficient energy intake. Accordingly, adolescent athletes should consume daily meals containing a good balance of staple foods, main dishes, side dishes, milk and other dairy products, and fruits.展开更多
The Tour de Ski(TDS:6-9 sprint and distance races across 9-11 days)represents the most intense competition series of the cross-country(XC)ski season and is characterized by accumulated stress from consecutive days of ...The Tour de Ski(TDS:6-9 sprint and distance races across 9-11 days)represents the most intense competition series of the cross-country(XC)ski season and is characterized by accumulated stress from consecutive days of high-intensity(~85%-160% VO_(2max))racing,travel,cold temperatures and low to moderate altitude(500-1500 m above sea level).Here,nutritional strategies play a key supportive role for optimized health,recovery and performance.This narrative review aims to provide an evidence-based discussion on the energetic demands of the TDS and recommendations for nutritional strate-gies to optimize health and performance of XC skiers during and following the TDS.We highlight several challenges that may arise during the TDS,including the following:poor energy availability(EA)due to decreased appetite or a pressure to maintain a low body weight,suboptimal carbohydrate availability due to a failure to replenish muscle glycogen stores across consecutive-day racing and increased risk of illness due to a combination of factors,including high-intensity racing,poor nutrition,sleep,travel and hygiene.We encourage XC skiers to maintain optimal overall EA across the~1.5-week period,ensure high daily carbohydrate availability,as well as the use of strategies to maintain a healthy immune system.In addition,we include practical guidelines on the management of nutrition support prior to and during the TDS.We recognize that many nutritional questions remain unanswered both in the context of elite XC ski racing and specifically for extreme demands like the TDS that should be addressed in future investigations.展开更多
Purpose To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling(DP).Methods Thirty-three elite athletes in three track sections of FIS-WC races,with d...Purpose To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling(DP).Methods Thirty-three elite athletes in three track sections of FIS-WC races,with different slopes(2°,0°and−1.5°).Stereo vision capture system(50 Hz cameras)and 3D analysis were used to extract:kinematic parameters(center of gravity,veloc-ity);joint angles and angular velocities;energy(potential and kinetic)and energy recovery indices R% and R(t)during the entire DP cycle and within poling(R_(pol))and swing phase(R_(swi)).Results Average race velocity of the centre of gravity(V_(ave))significantly varied according to slopes(5.4,7.3 and 8.3 m/s).This correlated with differences in the angular velocities of the most relevant joints.Elbow flexion angular velocity in the early portion of poling phase was higher according to the slope variations(−137,−171 and−202 deg/s,for the slopes 2°,0°and−1.5°,respectively),indicating the possible modulation of muscular stretch shortening cycle(SSC).A similar trend was observed for shoulder angular velocity which increased during poling phase,and for knee extension velocity during swing phase,and for knee extension velocity during swing phase.R%decreased significantly for the−1.5°slope(32%and 24%vs.15%);R(t)was higher for the Rswi.Significant differences were observed in trunk-elbow,trunk-shoulder,trunk-knee and elbow-shoulder patterns for the−1.5°slope with respect to the others.Conclusions Despite the modest variation of the track’s slope,the effects on propulsion and recovery strategies were different.展开更多
Purpose The purpose of this study was to examine the effect of pole length on performance and technique selection during a simulated skating cross-country(XC)skiing competition on snow in female XC skiers.Methods Nine...Purpose The purpose of this study was to examine the effect of pole length on performance and technique selection during a simulated skating cross-country(XC)skiing competition on snow in female XC skiers.Methods Nine female XC skiers and biathletes(VO2max 63.6±6.2 mL/min/kg,age 22.9±3.5 years,body height 1.69±0.1 m and body mass 60.8±4.6 kg)completed two 5-km skating time-trail with maximal effort.The athletes had a minimum 4.5 h of rest between the two races,which were performed in a random order:one with self-selected poles(89.0%±0.6%of body height)and one with 7.5 cm increased pole length(94.0%±0.5%of body height).Speed in set terrain sections was determined and the selection of sub-technique was self-reported immediately after each race based on a detailed review of the entire track.Results Skiers performed on average 7.1±7.1 s(P=0.029)faster with the long poles,with this difference occurring during the first 200 m and in the uphill parts of the track,in which~5% more G3 and~5% fewer G2 sub-techniques were chosen(both P<0.05).The rating of perceived exertion was 1±0.9 point lower(P=0.04)and skiing technique was perceived to be~1.2±1.5 points better with long poles(P=0.038),while the physiological responses(i.e.,peak and average heart rate,and blood lactate concentration)did not differ between trials.Conclusion In conclusion,poles 7.5 cm longer than self-selected ones improved performance in skating,by enhancing speed in the initial phase(first 200 m)and in the uphill section of the track.In addition,the longer poles induced more use of the G3 skating sub-technique.展开更多
文摘The purpose of this study was to investigate whether eight weeks of aerobic high-intensity interval training with roller ski is effective in cross-country skiers. 10 male （age, 18.28 ± 2.1 years; height, 171.26 ± 4.12 cm; weight 61.39 ± 6.28 kg） and 8 female （age, 16.05 ± 0.3 years; height, 158.3 ± 6.47 cm; weight, 49.34 ± 0.7 kg） junior cross country skiers completed the study. All skiers performed a 2 × 2-kin all-out uphill intervals with roller-skis, 3 times a week, in addition to their traditional training program. Measurements included VO2max （maximal oxygen uptake）, anaerobic power, and also for 2-km roller ski. All values were listed as pre-to post-test mean （± SD）, significant level, and percentage changes （%）. Pre-to post-testing changes in VO2max, anaerobic power, and also 2-kin roller ski performance were significantly higher during all post-test trials in all groups （P 〈 0.005）. With reference to the training effects found in our study, we suggest that the skiers should integrate the roller ski aerobic high-intensity interval uphill models in their training programs for improving performance.
文摘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.
基金supported by a general collaborative grant for winter sport research provided through Mid Sweden University and the?stersund municipality(reference number:2018/1758-500584)。
文摘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.
文摘This study aimed to determine the appropriate nutritional intakes and dietary habits of high school-aged cross-country skiers and speed skaters. The subjects, all high school students from N Prefecture, included 18 male cross-country skiers, 5 male speed skaters, 10 female cross-country ski players and 4 female speed skaters. Physical measurements, food intake frequency survey results, bone mineral density and exercise stress test outcomes, and lactic acid measurements were evaluated. Female athletes in both sports had higher body fat percentages relative to the average range stated for female athletes. Male speed skaters had a significantly higher maximum oxygen in-take than that male cross-country skiers did. By contrast, this parameter did not differ significantly among female athletes. A negative correlation was observed between the fat free mass and muscle mass, and a positive correlation was observed among the body fat percentage, fat percentage, and fat mass. Both male and female athletes had protein intake ratios within the reference ranges. All athletes except male speed skaters had lipid energy ratios that were higher than the upper limit of the reference value. Both male and female athletes also reported carbohydrate energy ratios within the reference ranges, but had cereal energy ratios below the reference values. Athletes should pay attention to the ingestion of various nutrients to ensure a sufficient energy intake. Accordingly, adolescent athletes should consume daily meals containing a good balance of staple foods, main dishes, side dishes, milk and other dairy products, and fruits.
文摘The Tour de Ski(TDS:6-9 sprint and distance races across 9-11 days)represents the most intense competition series of the cross-country(XC)ski season and is characterized by accumulated stress from consecutive days of high-intensity(~85%-160% VO_(2max))racing,travel,cold temperatures and low to moderate altitude(500-1500 m above sea level).Here,nutritional strategies play a key supportive role for optimized health,recovery and performance.This narrative review aims to provide an evidence-based discussion on the energetic demands of the TDS and recommendations for nutritional strate-gies to optimize health and performance of XC skiers during and following the TDS.We highlight several challenges that may arise during the TDS,including the following:poor energy availability(EA)due to decreased appetite or a pressure to maintain a low body weight,suboptimal carbohydrate availability due to a failure to replenish muscle glycogen stores across consecutive-day racing and increased risk of illness due to a combination of factors,including high-intensity racing,poor nutrition,sleep,travel and hygiene.We encourage XC skiers to maintain optimal overall EA across the~1.5-week period,ensure high daily carbohydrate availability,as well as the use of strategies to maintain a healthy immune system.In addition,we include practical guidelines on the management of nutrition support prior to and during the TDS.We recognize that many nutritional questions remain unanswered both in the context of elite XC ski racing and specifically for extreme demands like the TDS that should be addressed in future investigations.
文摘Purpose To analyze the inter-limb coordination patterns and energy recovery of elite cross-country skiers performing double poling(DP).Methods Thirty-three elite athletes in three track sections of FIS-WC races,with different slopes(2°,0°and−1.5°).Stereo vision capture system(50 Hz cameras)and 3D analysis were used to extract:kinematic parameters(center of gravity,veloc-ity);joint angles and angular velocities;energy(potential and kinetic)and energy recovery indices R% and R(t)during the entire DP cycle and within poling(R_(pol))and swing phase(R_(swi)).Results Average race velocity of the centre of gravity(V_(ave))significantly varied according to slopes(5.4,7.3 and 8.3 m/s).This correlated with differences in the angular velocities of the most relevant joints.Elbow flexion angular velocity in the early portion of poling phase was higher according to the slope variations(−137,−171 and−202 deg/s,for the slopes 2°,0°and−1.5°,respectively),indicating the possible modulation of muscular stretch shortening cycle(SSC).A similar trend was observed for shoulder angular velocity which increased during poling phase,and for knee extension velocity during swing phase,and for knee extension velocity during swing phase.R%decreased significantly for the−1.5°slope(32%and 24%vs.15%);R(t)was higher for the Rswi.Significant differences were observed in trunk-elbow,trunk-shoulder,trunk-knee and elbow-shoulder patterns for the−1.5°slope with respect to the others.Conclusions Despite the modest variation of the track’s slope,the effects on propulsion and recovery strategies were different.
文摘Purpose The purpose of this study was to examine the effect of pole length on performance and technique selection during a simulated skating cross-country(XC)skiing competition on snow in female XC skiers.Methods Nine female XC skiers and biathletes(VO2max 63.6±6.2 mL/min/kg,age 22.9±3.5 years,body height 1.69±0.1 m and body mass 60.8±4.6 kg)completed two 5-km skating time-trail with maximal effort.The athletes had a minimum 4.5 h of rest between the two races,which were performed in a random order:one with self-selected poles(89.0%±0.6%of body height)and one with 7.5 cm increased pole length(94.0%±0.5%of body height).Speed in set terrain sections was determined and the selection of sub-technique was self-reported immediately after each race based on a detailed review of the entire track.Results Skiers performed on average 7.1±7.1 s(P=0.029)faster with the long poles,with this difference occurring during the first 200 m and in the uphill parts of the track,in which~5% more G3 and~5% fewer G2 sub-techniques were chosen(both P<0.05).The rating of perceived exertion was 1±0.9 point lower(P=0.04)and skiing technique was perceived to be~1.2±1.5 points better with long poles(P=0.038),while the physiological responses(i.e.,peak and average heart rate,and blood lactate concentration)did not differ between trials.Conclusion In conclusion,poles 7.5 cm longer than self-selected ones improved performance in skating,by enhancing speed in the initial phase(first 200 m)and in the uphill section of the track.In addition,the longer poles induced more use of the G3 skating sub-technique.
