Competitive Cross-country Skiers Research Articles

The influence of race duration on oxygen demand, uptake and deficit in competitive cross-country skiers

PurposeTo measure oxygen demand, uptake, and deficits in competitive cross-country skiers during outdoor roller skiing at different competition durations, ranging from the endurance domain to the sprint domain.MethodsTen competitive cross-country skiers (6 males; V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{\ ext{V}}$$\\end{document}O2max 78 ± 3 and 4 females; V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{\ ext{V}}$$\\end{document}O2max 62 ± 3 mL∙kg−1∙min−1) raced time trials consisting of 1, 2, and 4 laps in a 1.6 km racecourse in a randomized order with 35 min recovery in-between. Oxygen uptake was measured using a wearable metabolic system while oxygen demand was estimated from kinematic data (GPS and IMU) and an athlete-specific model of skiing economy. Skiing economy and V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{\ ext{V}}$$\\end{document}O2max was established on a separate test day using six submaximal constant-load trials at different speeds and inclines, and one maximal-effort trial on a roller-skiing treadmill.ResultsAverage oxygen demand was 112 ± 8%, 103 ± 7% and 98 ± 7% of V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{\ ext{V}}$$\\end{document}O2max during the 1 (3:37 ± 0:20 m:ss), 2 (7:36 ± 0:38 m:ss) and 4 (15:43 ± 1:26 m:ss) lap time trials, respectively, and appeared to follow an inverse relationship with time-trial duration. Average oxygen uptake was unaffected by race length (86 ± 5%, 86 ± 5%, and 86 ± 7% of V˙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\dot{\ ext{V}}$$\\end{document}O2max, respectively). Accumulated oxygen deficit at the end of each time trial was 85 ± 13, 106 ± 32 and 158 ± 62 mL∙kg−1, while oxygen deficits per work bout was 23 ± 3, 18 ± 3 and 16 ± 3 mL∙kg−1 for the 1, 2, and 4-lap time trials, respectively.ConclusionElite cross-country skiers adjust their pacing strategies from attaining relatively small oxygen deficits per work bout in the endurance domain, to larger deficits in the sprint domain. This indicates a shift in strategy from prioritizing stable work-economy and rate-of-recovery in the endurance domain, to maximizing power output in the sprint domain.

Competitive Cross-Country Skiers Have Longer Time to Exhaustion Than Recreational Cross-Country Skiers During Intermittent Work Intervals Normalized to Their Maximal Aerobic Power.

To investigate differences in time to exhaustion (TTE), O2 uptake (V˙O2), and accumulated O2 deficit (O2def) between competitive and recreational cross-country (XC) skiers during an intermittent-interval protocol standardized for maximal aerobic power (MAP). Twelve competitive (maximal V˙O2 [V˙O2max]=76.5±3.8 mL·kg-1·min-1) and 10 recreational (V˙O2max=63.5±6.3 mL·kg-1·min-1) male XC skiers participated. All tests were performed on a rollerski treadmill in the V2 ski-skating technique. To quantify MAP and maximal accumulated oxygen deficit(MAOD), the skiers performed a steady-state submaximal test followed by a 1000-m time trial. After a 60-minute break, TTE, V˙O2, and accumulated O2def were measured during an intermittent-interval protocol (40-s work and 20-s recovery), which was individually tailored to 120% and 60% of each subject's MAP. During the 1000-m time trial, the competitive skiers had 21% (95% CI, 12%-30%) shorter finish time and 24% (95% CI, 14%-34%) higher MAP (all P < .01) than the recreational skiers. No difference was observed in relative exercise intensity (average power/MAP; P = .28), MAOD (P = .18), or fractional utilization of V˙O2max. During the intermittent-interval protocol, the competitive skiers had 34% (95% CI, 3%-65%) longer TTE (P = .03) and accumulated 61% (95% CI, 27%-95%) more O2def (P = .001) than the recreational skiers during work phases. Competitive XC skiers have longer TTE and accumulate more O2def than recreational XC skiers during an intermittent-interval protocol at similar intensity relative to MAP. This implies that performance in intermittent endurance sports is related to the ability to repeatedly recharge fractions of MAOD.

Cross-country skiers bounce to glide and slide uphill

Using almost every muscle in the body and with a low risk of injury, cross-country skiing has a reputation for being one of the healthiest sports, but the pastime is not without challenges. Coordinating all four limbs on a slippery surface can have its moments, and athletes have to manoeuvre themselves up hills while gliding across the snow. But how do cross-country skiers propel themselves as they glissade up gradients? Are they effectively running as they glide on one ski while stepping forward with the other, do they store bouncy energy in the Achilles tendon of the sliding leg in preparation for the next stride, and how do the calf muscles contribute? To find out, Øyvind Gløersen (SINTEF Digital, Norway), Amelie Werkhausen and Anders Lundervold (both from the Norwegian School of Sport Sciences, Norway) filmed 13 competitive cross-country skiers on roller skis as they propelled themselves uphill on a sloping treadmill while recording calf muscle activity to find out how the skiers use energy while gliding along.Recording the athletes manoeuvres with 12 cameras to reconstruct their movements as they roller skied on different inclines on the treadmill, the team saw the skiers kick off with one leg to swing it forward while gliding on the other, before touching down with the first leg to glide forward as the second leg kicked off, propelling the skier. Then, they analysed the complicated relationship between the calf muscle contraction and the Achilles tendon stretching to store energy as the skiers climbed and realised that the athletes’ movements were similar to those of runners. However, instead of bouncing into the air as they travelled forward, the skiers remained in contact with the treadmill, gliding forward on one ski. The researchers also realised that as the skiers prepared to push off with one leg, at the end of gliding on that ski, they contracted the calf muscles to store energy in the Achilles tendon, which is exactly what we do when preparing to jump. In addition, when the skiers propelled themselves up a steeper gradient, they contracted their calf muscles more to store a larger amount of energy in the Achilles tendon, to power the stronger kick they require.So, cross-country skiers effectively run, but instead of bouncing into the air like runners, they glide forward across the snow, while benefiting from the power of jumping to ski up gradients that other skiers would be happier to descend.

Cross-country skiers often experience respiratory symptoms during and after exercise but have a low prevalence of prolonged cough

BackgroundCross-country skiers train and compete during the winter for long periods of time in subfreezing conditions, which strains the airways and provokes respiratory symptoms. This study aimed to compare the...

A Systematic Review of the Effects of Strength and Power Training on Performance in Cross-Country Skiers.

To identify and evaluate current scientific literature concerning the effect of strength, power and speed training on relevant physiological and biomechanical characteristics and performance of competitive cross-country skiers (XCS), the databases Scopus and PubMed were searched systematically for original articles in peer-reviewed journals. Of the 599 studies retrieved, 12 met the inclusion criteria (i.e., assessment of outcome measures with relevance for XCS performance; involvement of traditional resistance training; application of external resistance to the body; intervention longer than 4 weeks; randomized controlled trial). The methodological rigor of each study was assessed using the PEDro scale, which were mostly poor-to-fair, with good methodological quality in only two articles. All of the strength/power/speed interventions improved 1RM (0.8-6.8 ES), but findings with respect to jump performance, ability to generate force rapidly and body composition were mixed. Interventions demonstrated moderate-to-high ES on XCS specific performance compared with control (mean ES = 0.56), but the pattern observed was not consistent. None of the interventions changed anaerobic capacity, while in most studies VO2max was either unchanged or increased. Work economy or efficiency was enhanced by most of the interventions. In conclusion, present research indicates that strength training improves general strength, with moderate effects on XCS performance, and inconclusive effects on work economy and VO2max/VO2peak. Strength training with high loads, explosive strength training, or sprint interval training seem to be promising tools for modern XCS training. Future investigations should include long-term (e.g., >6 months) strength training to allow sufficient time for increased strength and speed to influence actual XCS performance. Moreover, they should include both sexes, as well as upper- and lower-body muscles (trained separately and together) and employ free weights and core training. Methodological differences and limitations highlighted here may explain discrepancies in findings and should be taken into consideration in future research in this area.

Health problems in national team cross-country skiers over a competitive season: a 17-week prospective cohort study

ObjectiveFew long-term prospective studies have investigated health problems in elite competitive cross-country (XC) skiers. Hence, our objective was to compare the prevalence of health problems in national team XC skiers...

High training volume is associated with increased prevalence of non-allergic asthma in competitive cross-country skiers

BackgroundCross-country skiers have a high prevalence of asthma, but its phenotypes and association with success in competitions are not known.ObjectiveTo investigate, by means of a postal survey, the relative proportions...

Relationships Between Maximal Aerobic Speed, Lactate Threshold, and Double Poling Velocity at Lactate Threshold in Cross-Country Skiers.

PurposeTo investigate the relationships between maximal aerobic speed (MAS), lactate threshold in per cent of peak oxygen uptake (LT) and velocity at LT (LTv) in cross-country skiers. Secondly, we aimed to explore the fit of an equation previously used in cyclists and runners in a cohort of well-trained, competitive cross-country skiers for calculation of LTv. Thirdly, we aimed to investigate if a new LTv could still be calculated after a period of regular training only by providing a new MAS.MethodsNinety-five competitive cross-country skiers (65 males and 30 females) were tested for maximal oxygen uptake (VO2max), peak oxygen uptake in double poling (DP-VO2peak), oxygen cost of double poling (CDP), LT, and LTv. Thirty-five skiers volunteered to be tested 3 months later to evaluate potential changes in LT and LTv.ResultsVelocity at LT was mainly determined by MAS (r = 0.88, p < 0.01). LT did not show a significant impact on LTv. The product of MAS·LT precisely predicted LTv at baseline (r = 0.99, SEE = 2.4%), and by only measuring MAS, a new LTv could be accurately calculated (r = 0.92, SEE = 6.8%) 3 months later in a sub-set of the initial 95 skiers (n = 35).ConclusionThe results suggest that LT has minor impact on LTv in DP tested in a laboratory. LTv seemed to be predominantly determined by MAS, and we suggest to put more focus on MAS and less on LT and LTv in regular testing to evaluate aerobic performance capacity in DP.

The Effect of Different Periodization and Modes of Concurrent Strength and Endurance Training on Double Poling Performance and Body Composition in Adolescent Cross-Country Skiers.

The aim of the study was to compare the effects of different types and periodization of strength training on body composition and maximal aerobic performance in 10-week training period in adolescent XC skiers. Twenty-eight adolescent competitive cross-country skiers, including 10 females (age 17.9 ± 1.8 years; body mass 69.6 ± 9.7 kg; height 1.77 ± 0.1 m; training experience 8.6 ± 3.2 years) took part in this study. Pre-and post-intervention performance was measured with the incremental exercise test (Pmax) on a double poling ski ergometer. Changes in body composition were measured with DXA. In addition to regular endurance training, experimental group one (EXP1) performed maximal and explosive strength training two times per week, experimental group two (EXP2) performed maximal and explosive strength training 1–3 times per week, and the traditional (TRAD) group performed low intensity–high volume strength training 2 times per week. Increases in arm, trunk, and overall lean mass were found in TRAD (p < 0.05). Increases in arm lean-mass was found in EXP1 (p < 0.05), while no changes in body composition occurred in EXP2 (p ≥ 0.05). Pmax improved significantly in all groups (p < 0.05). Changes in body mass, overall and arm lean mass was related to changes in absolute performance (W; p < 0.05), while no relationships were found between changes in body composition parameters and relative performance (W/kg; p ≥ 0.05). In conclusion, different periodization of strength training led to similar improvements in double poling ergometer performance, but resulted in different changes in body composition (lean mass) in adolescent cross-country skiers.

Higher prevalence but later age at onset of asthma in cross-country skiers compared with general population.

Cross-country skiing causes strain in the airways because skiers train and compete in cold air. The aim of this survey was to investigate the prevalence and age at onset of asthma, asthma control, and use of asthma medication in Finnish competitive cross-country skiers. All cross-country skiers who were enrolled in the largest national competitions in winter 2019 (n=1282) were invited to the study via the Finnish Ski Association. A control group (n=1733) was matched for the responding skiers by age, gender, and region. The response rate was 27.4% (n=351) for skiers and 19.5% (n=338) for the controls. The prevalence of asthma was 25.9% in skiers and 9.2% in the controls (p<0.001). Median (IQR) age at first asthma-related symptoms was higher in skiers than in the controls (13.0 (8.25-16.0) vs. 8.0 (2.25-11.75) years, p<0.001), and the difference in asthma prevalence was evident only after the start of skiing career. Median (IQR) Asthma Control Test (ACT) score in skiers and controls with asthma was 22.0 (21-24) vs. 22.0 (19-24) (p=0.611), and 89.0% of skiers and 77.4% of controls had well-controlled asthma (ACT score ≥20). In skiers with asthma, 82.4% used regular inhaled corticosteroids (ICS), and 80.2% used bronchodilators. A fixed combination of ICS +long-acting β2-agonist was regularly used by 47.3% of the skiers and 22.6% of the controls with asthma (p=0.016). In conclusion, asthma prevalence is about 2.5 times higher, and age at onset of asthma is later in skiers compared with the controls. Asthma in cross-country skiers is mostly well controlled and on regular maintenance treatment.

Three km Track Time Trial Performance Changes after HIIT in Competitive Cross-Country Skiers

Background: Limited research surrounding sex differences in fatigue and performance after high intensity interval training (HIIT) exists in the field setting. While lab-based protocols provide a controlled environment, physiological mechanisms of fatigue and performance response in competitive athletes are best measured by time-trial (TT). Few studies, however, have investigated fatigue in TT performance while controlling for the menstrual cycle (MC). Objective: The study investigated the influence of sex and MC phase on 3km track TT performance after a HIIT session in Competitive Cross Country (XC) skiers. Methods: A quasi-experimental design was employed and athletes over the age of 16 years (30F, 9M), were recruited from across Canada and completed 3 days of testing/training: a 3km track TT on Day 1 and Day 3; and a HIIT session (4-8x, 800m) on Day 2. MC phase was verified by ovulation testing and salivary hormone samples; athletes were classified as either “Low Hormone” or “High Hormone” for analysis. Results: An overall improvement in performance from pre- to post-HIIT TTs occurred (p&lt;0.01). No significant differences in TT performance after HIIT were observed between sexes (p=0.16) or MC phase (p=0.26). Conclusion: These results indicate that competitive XC skiers will likely experience an improvement in TT performance after a bout of HIIT. Coaches and athletes should plan their workouts prior to testing accordingly to maximize TT performance. These results also suggest that no special adjustments need to be considered for differences in performance after HIIT between sexes and MC phase, although further studies with a greater sample size and repeated testing are warranted.

The Effects of Sub-Technique and Pole Length on Classic Roller Skiing Performance and Physiological Responses at Steep Uphill Inclination.

The aims of this study were to compare performance with physiological and perceptual responses on steep uphill inclines between double poling and diagonal stride and to investigate the effects of pole length when double poling. Eight male, competitive cross-country skiers (22 ± 1.1 yrs, peak oxygen uptake (VO2peak) in the diagonal stride: 69.4 ± 5.5 ml·kg-1·min-1) performed four identical tests, one in the diagonal stride, and three in double poling with different pole lengths (self-selected, self-selected -5 cm and self-selected +10 cm). Each test was conducted at a fixed speed (10 km/h), with inclination rising by 1%, starting with 7%, each until voluntary exhaustion. VO2peak, the heart rate, blood lactate concentration, and the rating of perceived exertion were determined for each pole length in each test. The peak heart rate (p < 0.001) and VO2peak (p = 0.004) were significantly higher in the diagonal stride test compared with double poling with all pole lengths. Time to exhaustion (TTE) differed significantly between all four conditions (all p < 0.001), with the following order from the shortest to the longest TTE: short poles, normal poles and long poles in double poling, and the diagonal stride. Consequently, a significantly higher slope inclination was reached (p < 0.001) using the diagonal stride (17%) than for double poling with long poles (14%), normal (13%) and short (13%) poles. The current study showed better performance and higher VO2peak in the diagonal stride compared to double poling in steep uphill terrain, demonstrating the superiority of the diagonal stride for uphill skiing. However, in double poling, skiers achieved improved performance due to greater skiing efficiency when using long poles, compared to normal and short poles.

Differences in pacing pattern and sub-technique selection between young and adult competitive cross-country skiers.

The present study describes differences in pacing patterns and sub-technique selection in young compared to adult competitive cross-country skiers. Eleven young male skiers (YOS) (14.4±0.5years, O2peak 63.9±2.8mL∙kg-1 ∙min-1 ) and eight adult male skiers (ADS) (22.6±4.3years, O2peak 77.4±4.4mL∙kg-1 ∙min-1 ) performed a free technique rollerski time trial (TT) over a distance of 4.3km (YOS) and 13.1km (ADS) to simulate normal racing distances. A GNSS/IMU system was used to track position, speed, and classify sub-techniques. Skiing economy and O2peak were measured on an additional day to calculate the relative oxygen demand ( O2dem ) in 13 segments of the TT. YOS were slower than ADS in all types of terrain (mean speed difference of 13%), with differences for uphills of 19%, undulating terrain of 11% and downhills of 8% (all P<.05). The mean relative O2dem tended to be higher for YOS compared to ADS (120% vs 112% of O2peak , P=.09), and the difference was more pronounced in the initial four segments of the race (130% vs 110% of O2peak , P<.01). YOS used more of the sub-technique Gear 2 (23±7 vs 14±4%), less Gear 3 (36±7 vs 45±5%), and had more frequent transitions between sub-techniques (18±2 vs 15±3km-1 ) (all P<.05) than ADS. Over an age-related distance, young skiers tend to exhibit higher mean exercise intensity than adult elite skiers, with a more pronounced positive pacing pattern. Differences in physical ability affect speed and sub-technique selections, implying a need for differentiating technical training for different ages and levels.

The Prevalence of Asthma and Respiratory Symptoms among Cross-Country Skiers in Early Adolescence

Objective To determine the prevalence of asthma and respiratory symptoms among Swedish cross-country skiers in early adolescence in comparison to a population-based reference group of similar ages. Methods A postal questionnaire on asthma, asthma medication, allergy, respiratory symptoms, and physical activity was distributed to Swedish competitive cross-country skiers aged 12–15 years (n = 331) and a population-based reference group (n = 1000). The level of asthma control was measured by the Asthma Control Test. Results The response rate was 27% (n = 87) among skiers and 29% (n = 292) in the reference group. The prevalence of self-reported asthma (physician-diagnosed asthma and use of asthma medication in the last 12 months) and the prevalence of reported wheezing during the last 12 months were 23% and 25%, respectively, among skiers, which were significantly higher than the values reported in the reference group (12% and 14%). Skiers exercised more hours/week than the reference group. Among adolescents with self-reported asthma, neither the usage of asthma medications nor the level of asthma control according to the Asthma Control Test differed between skiers and the reference group. Conclusions Adolescent competitive cross-country skiers have an increased prevalence of respiratory symptoms and asthma compared to nonskiers.

INJURY INCIDENCE IN COMPETITIVE CROSS-COUNTRY SKIERS: A PROSPECTIVE COHORT STUDY

Endurance sports, including cross-country skiing, require long hours of repetitive training potentially increasing the chance of injury, yet injury incidence and risk factors for adult cross-country skiers remain relatively unexplored. Data for elite adult north American competitive cross-country skiers is unexplored. A 12 month prospective surveillance study was undertaken to calculate the injury incidence and exposure of cross-country skiers. Injuries by anatomic location and mechanism of injury were calculated. Further, the relationships between new injury and the participant's demographics and physical assessment parameters were examined. The aims of this study were to determine the injury incidence and any risk factors for injury in elite adult north American cross-country skiers. Elite cross-country skiers (35 men, 36 women) self-reported demographics, injury history, and injury and training surveillance monthly over 12 months. t-tests compared the mean number of injuries per individual, per 1,000 training/exposure hours between anatomic regions, type of injuries, and seasons. Spearman's correlation analyses tested the relationship between new injury and Movement Competency Screen (MCS) score, past injury, total training time, and running training time. To determine if new injury could be predicted from any demographic data, intake physical measures, or, monthly injury, training and racing data, a regression model was developed. Overall, 58% of participants (18 men, 23 women) completed the study, and reported 3.81 injuries per 1,000 training/exposure hours. Over 12-months, lower extremity injury incidence (2.13) was higher than upper extremity (0.46) and trunk injury incidence (0.22) (p < 0.05). Non-traumatic/overuse injury incidence (2.76) was higher than acute injury incidence (1.05) (p < .05). Non-ski-season injury incidence (5.25) was not statistically higher than ski-season injury incidence (2.27) (p = 0.07). New injuries were positively correlated with previous injury (p < 0.05), but not with any other variables (p > 0.05). In this year-long monthly survey of injuries and training load in elite adult north American cross-country skiers, new injuries were positively correlated with previous injury. Lower extremity, and non-traumatic/overuse injuries had the highest incidence rates. There was no significant correlation between new injuries and physical assessment parameters or training load. Level 3, Prospective Longitudinal Cohort Study.

The effect of exhaustive exercise on the choice of technique and physiological response in classical roller skiing.

The aim of this study was to investigate the effect of exhaustive exercise on technique preference and the accompanying physiological response during classic skiing at constant workload, but with varying incline-speed combinations. Seven male competitive cross-country skiers performed four tests, each lasting 23min, at constant 200W workload roller skiing on a treadmill using classic style, three in unfatigued state, and one after exhaustion. The incline and speed combination (that determined the 200W) were altered each minute during the tests. The athletes were allowed to change sub-technique at free will. Physiological variables and cycle rate were recorded continuously as well as the incline-speed combinations at which the sub-technique was changed. Exhaustive exercise did not (or hardly) affect cycle rate and choice of technique. The physiological response was most prominent in slight incline-high speed conditions, independent of exercise duration. Exhaustive exercise affected the physiological response in a differentiated manner. HR and RER remained, respectively, higher and lower after fatigue, while [Formula: see text] (and thereby GE) were affected only during approximately the first 8min of post-exhaustion exercise. Exhaustive exercise has a minimal effect on choice of technique in classic cross-country skiing with free choice of sub-technique, even though physiological stress is increased.

The role of speed and incline in the spontaneous choice of technique in classical roller-skiing

Cross-country skiers change technique depending on terrain (incline) and effort (work rate; speed at a particular incline or resistance). The literature is not unequivocal about the influence of incline or speed on the choice of technique, i.e., which of these act as a ‘control parameter’. Identifying task related control parameters for spontaneous technique shifts assists elucidating which mechanisms are active for triggering technique transitions. The aim of this study was to investigate whether speed or incline acted as such control parameter for technique shifts during classic style roller skiing. In this study, we kept the exercise intensity constant while changing two potential control parameters (speed and incline). Thus, any effect of work rate was excluded.Eight male competitive cross-country skiers performed roller skiing on a treadmill while incline was altered from 3 to 11% and back to 3% each minute by 1% and speed changed accordingly to obtain a constant work rate. This protocol was performed at three submaximal work rates (170, 200, and 230W) to obtain various combinations of speed and incline.The athletes were free to choose their technique (double poling, double poling with kick and diagonal stride), which was identified using continuous phase analysis on the motion of the skis. Physiological response (heart rate, oxygen uptake) was recorded continuously.The incline seemed to affect choice of technique shift more than speed: the ANOVA for repeated measures on all work rates showed no significant effect of incline (p>0.2) and an effect for speed (p<0.001). No effect of protocol order (increasing versus decreasing incline) was found for transitions. The physiological response was lowest for conditions of steep incline-low speed and was affected by protocol order. Cycle rate was affected by incline only in the double poling technique.Possible mechanisms related to the triggering of technique transitions are discussed.

Physiological and performance effects of nitrate supplementation during roller-skiing in normoxia and normobaric hypoxia

The present study examined the effects of acute nitrate (NO3−) supplementation ingested in the form of concentrated beetroot juice on cross-country roller-ski performance in normoxia (N) and normobaric hypoxia (H). Eight competitive cross-country skiers (five males: age 22 ± 3 years, V·O2max 71.5 ± 4.7 mL kg−1·min−1; three females: age 21 ± 1 years, V·O2max 58.4 ± 2.5 mL kg−1·min−1) were supplemented with a single dose of NO3−-rich beetroot juice (BRJ, ∼13 mmol NO3−) or a NO3−-depleted placebo (PL, ∼0 mmol NO3−) and performed 2 x 6-min submaximal exercise bouts and a 1000-m time-trial (TT) on a treadmill in N (20.9% O2) or H (16.8% O2). The four experimental trials were presented in a randomised, counter-balanced order. Plasma NO3− and nitrite concentrations were significantly higher following BRJ compared to PL (both p < 0.001). However, respiratory variables, heart rate, blood lactate concentration, ratings of perceived exertion, and near-infrared spectroscopy-derived measures of muscle tissue oxygenation during submaximal exercise were not significantly different between BRJ and PL (all p > 0.05). Likewise, time to complete the TT was unaffected by supplementation in both N and H (p > 0.05). In conclusion, an acute dose of ∼13 mmol NO3− does not affect physiological or performance responses to submaximal or maximal treadmill roller-skiing in competitive cross-country skiers exercising in N and H.

INJURY INCIDENCE IN CROSS-COUNTRY SKIERS

BackgroundProspective, cross-country ski injury incidence data is scarce.ObjectiveTo describe injury type and incidence sustained by elite cross-country skiers in north-eastern America. We hypothesized that lower extremity injury incidence would be...

The Influence of Pole Length on Performance, O2 Cost, and Kinematics in Double Poling.

In the double-poling (DP) cross-country-skiing technique, propulsive forces are transferred solely through the poles. The aim of the current study was to investigate how pole length influences DP performance, O2 cost, and kinematics during treadmill roller skiing. Nine male competitive cross-country skiers (24 ± 3 y, 180 ± 5 cm, 72 ± 5 kg, VO2max running 76 ± 6 mL · kg-1 · min-1) completed 2 identical test protocols using self-selected (84% ± 1% of body height) and long poles (self-selected + 7.5 cm; 88% ± 1% of body height) in a counterbalanced fashion. Each test protocol included a 5-min warm-up (2.5 m/s; 2.5°) and three 5-min submaximal sessions (3.0, 3.5, and 4.0 m/s; 2.5°) for assessment of O2 cost, followed by a selfpaced 1000-m time trial (~3 min, >5.0 m/s; 2.5°). Temporal patterns and kinematics were assessed using accelerometers and 2D video. Long poles reduced 1000-m time (mean ± 90% confidence interval; -1.0% ± 0.7%, P = .054) and submaximal O2 cost (-2.7% ± 1.0%, P = .002) compared with self-selected poles. The center-of-mass (CoM) vertical range of displacement tended to be smaller for long than for self-selected poles (23.3 ± 3.0 vs 24.3 ± 3.0 cm, P = .07). Cycle and reposition time did not differ between pole lengths at any speeds tested, whereas poling time tended to be shorter for self-selected than for long poles at the lower speeds (≤3.5 m/s, P ≤ .10) but not at the higher speeds (≥4.0 m/s, P ≥ .23). DP 1000-m time, submaximal O2 cost, and CoM vertical range of displacement were reduced in competitive cross-country skiers using poles 7.5 cm longer than self-selected ones.