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This study investigated carbohydrate ingestion of varied doses and frequencies during a simulated cross-country skiing time trial. Ten men and three women (age: 30 ± 7 years; [ABSTRACT FROM AUTHOR]

The present study examined the reliability of work and power measures during a 5 x 6-s cycle ergometer test of repeated-sprint ability. Nine, well-trained, female soccer players performed five, 5 x 6-s repeated-sprint tests on a front-access cycle ergometer on separate days. Sprints were separated by 24 s of active recovery. Absolute measures of total work done (W (tot)), total peak power (PP(tot)), work done during sprint 1 (W (1)) and peak power output during sprint 1 (PP(1)) were recorded. Decrement scores in work done (W (dec)) and peak power output (PP(dec)), and fatigue indices for work done (FI( W )) and peak power (FI( P )), were calculated. Significant improvements in all of the work and power measures were observed between trial 1 and subsequent trials (P < 0.05), but no significant differences were identified between trials 2, 3, 4 and 5. The same was true for increases in the decrement scores. The coefficient of variation (CV) was established to reflect within-subject reproducibility for each variable. The CV was significantly improved by the third trial for work done (W (tot) CV: trials 1-2 = 5.5%; trials 3-4 = 2.8%), peak power (PP(tot) CV: trials 1-2 = 5.1%; trials 3-4 = 2.7%) and performance decrement scores (P < 0.05). The standard error of measurement (SEM) and intraclass correlation coefficient (ICC) were also calculated for each variable and expressed within 95% confidence intervals. It was concluded that two familiarisation trials are optimal for collecting reliable data from a 5 x 6-s repeated-sprint cycling test. Furthermore, due to the large variation around performance decrement it was suggested that decrement scores ought to be interpreted with caution. [ABSTRACT FROM AUTHOR]

The International Olympic Committee's (IOC) consensus statement on 'methods for recording and reporting of epidemiological data on injury and illness in sport' recommended standardising methods to advance data collection and reporting consistency. However, additional aspects need to be considered when these methods are applied to specific sports settings. Therefore, we have developed a snow sports-specific extension of the IOC statement to promote the harmonisation of injury and illness registration methods among athletes of all levels and categories in the different disciplines governed by the International Ski and Snowboard Federation (FIS), which is also applicable to other related snow sports such as biathlon, ski mountaineering, and to some extent, para snow sports. The panel was selected with the aim of representing as many different areas of expertise/backgrounds, perspectives and diversity as possible, and all members were assigned to thematic subgroups based on their profiles. After panel formation, all members were provided with an initial draft of this extension, which was used as a basis for discussion of aspects specific to the discipline, application context, level and sex within their snow sports subgroup topic. The outcomes were then aligned with the IOC's existing consensus recommendations and incorporated into a preliminary manuscript draft. The final version of this snow sports-specific extension was developed and approved in two iterative rounds of manuscript revisions by all consensus panel members and a final meeting to clarify open discussion points. This snow sports-specific extension of the IOC statement is intended to guide researchers, international and national sports governing bodies, and other entities recording and reporting epidemiological data in snow sports to help standardise data from different sources for comparison and future research., Competing Interests: Competing interests: MM is a deputy editor, LE is an IPHP editor and BC and EV are associate editors at BJSM., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: This study used metabolic phenotyping to explore the responses of highly-trained cross-country skiers to a standardized exercise test, which was part of the athletes' routine testing, and determine whether metabolic phenotyping could discriminate specific physiological, performance, and illness characteristics., Methods: Twenty-three highly-trained cross-country skiers (10 women and 13 men) participated in this study. Capillary whole-blood samples were collected before (at rest) and 2.5 min after (post-exercise) a roller-ski treadmill test consisting of 5-6 × 4-min submaximal stages followed by a self-paced time trial (~ 3 min) and analyzed using mass spectrometry. Performance level was defined by International Ski Federation distance and sprint rankings. Illness data were collected prospectively for 33 weeks using the Oslo Sports Trauma Research Center Questionnaire on Health Problems. Orthogonal partial least squares-discriminant analyses (OPLS-DA) followed by enrichment analyses were used to identify metabolic phenotypes of athlete groups with specific physiological, performance, and illness characteristics., Results: Blood metabolite phenotypes were significantly different after the standardized exercise test compared to rest for metabolites involved in energy, purine, and nucleotide metabolism (all OPLS-DA p < 0.001). Acute changes in the metabolic phenotype from rest to post-exercise could discriminate athletes with: (1) higher vs. lower peak blood lactate concentrations; (2) superior vs. inferior performance levels in sprint skiing, and (3) ≥ 2 vs. ≤ 1 self-reported illness episodes in the 33-week study period (all p < 0.05). The most important metabolites contributing to the distinction of groups according to (1) post-exercise blood lactate concentrations, (2) sprint performance, and (3) illness frequency were: (1) inosine, hypoxanthine, and deoxycholic acid, (2) sorbitol, adenosine monophosphate, and 2-hydroxyleuroylcarnitine, and (3) glucose-6-phosphate, squalene, and deoxycholic acid, respectively., Conclusion: Metabolic phenotyping discriminated between athlete groups with higher vs. lower post-exercise blood lactate concentrations, superior vs. inferior sprint skiing performance, and more vs. less self-reported illnesses. While the biological relevance of the identified biomarkers requires validation in future research, metabolic phenotyping shows promise as a tool for routine monitoring of highly-trained endurance athletes., (© 2024. The Author(s).)

Background: In the last decade, a growing body of research has focused on the many aspects and challenges of combining parenthood with elite sport. Although the number of father-athletes is significantly higher than the number of mother-athletes, few studies to date have focused on male athletes' experiences in a parenting context., Aim: The aims of the present study were to explore how father-athlete challenges manifest among elite Nordic skiers in Norway, and to better understand how male athletes balance their priorities as they initiate, maintain, and/or discontinue their athletic career as a father-athlete., Methods: Qualitative data were collected through semi-structured interviews with 10 world-class male Nordic skiers in Norway (3 athletes without a child, 4 current father-athletes and 3 former father-athletes) and the content was analyzed using thematic analysis., Results: Four main stages were identified in the father-athlete transition: (a) Expecting incompatibility (b) Taking the step, (c), The first blow, and (d) Finding the optimal balance. Through these stages the informants expected/had experienced challenges such as performance decline, disturbed sleeping patterns, fear of sickness and role conflicts. To manage these challenges, the father-athletes had developed various strategies to balance their dual roles (e.g., adapting training and competition seasons). Among the benefits, the father-athletes mentioned that they had become more structured, time efficient and ruthless with their priorities, enhanced motivation to train and a better work-life balance., Conclusion: This study offers valuable insights into father-athlete challenges that can be used to support career longevity and work-life balance among male athletes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Bergström, Solli, Sandbakk, McGawley and Sæther.)

The International Olympic Committee (IOC) recently published a framework on fairness, inclusion, and nondiscrimination on the basis of gender identity and sex variations. Although we appreciate the IOC's recognition of the role of sports science and medicine in policy development, we disagree with the assertion that the IOC framework is consistent with existing scientific and medical evidence and question its recommendations for implementation. Testosterone exposure during male development results in physical differences between male and female bodies; this process underpins male athletic advantage in muscle mass, strength and power, and endurance and aerobic capacity. The IOC's "no presumption of advantage" principle disregards this reality. Studies show that transgender women (male-born individuals who identify as women) with suppressed testosterone retain muscle mass, strength, and other physical advantages compared to females; male performance advantage cannot be eliminated with testosterone suppression. The IOC's concept of "meaningful competition" is flawed because fairness of category does not hinge on closely matched performances. The female category ensures fair competition for female athletes by excluding male advantages. Case-by-case testing for transgender women may lead to stigmatization and cannot be robustly managed in practice. We argue that eligibility criteria for female competition must consider male development rather than relying on current testosterone levels. Female athletes should be recognized as the key stakeholders in the consultation and decision-making processes. We urge the IOC to reevaluate the recommendations of their Framework to include a comprehensive understanding of the biological advantages of male development to ensure fairness and safety in female sports., (© 2024 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

Background: Elite sport is continuously evolving. World records keep falling and athletes from a longer list of countries are involved., Purpose: This commentary was designed to provide insights into present and future trends associated with world-class endurance training based on the perspectives, experience, and knowledge of an expert panel of 25 applied sport scientists., Results: The key drivers of development observed in the past 10-15 years were related to (1) more accessible scientific knowledge for coaches and athletes combined with (2) better integration of practical and scientific exchange across multidisciplinary perspectives within professionalized elite athlete support structures, as well as (3) utilization of new technological advances. Based on these perspectives, we discerned and exemplified the main trends in the practice of endurance sports into the following categories: better understanding of sport-specific demands; improved competition execution; larger, more specific, and more precise training loads; improved training quality; and a more professional and healthier lifestyle. The main areas expected to drive future improvements were associated with more extensive use of advanced technology for monitoring and prescribing training and recovery, more precise use of environmental and nutritional interventions, better understanding of athlete-equipment interactions, and greater emphasis on preventing injuries and illnesses., Conclusions: These expert insights can serve as a platform and inspiration to develop new hypotheses and ideas, encourage future collaboration between researchers and sport practitioners, and, perhaps most important, stimulate curiosity and further collaborative studies about the training, physiology, and performance of endurance athletes.

Purpose: To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models., Methods: Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16-36 y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol., Results: Valid projective models were identified for female biathletes' IBU points (R2 = .80/Q2 = .65) and female XC skiers' FIS distance (R2 = .81/Q2 = .74) and sprint (R2 = .81/Q2 = .70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2 mmol·L-1, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2 mmol·L-1 and peak aerobic power., Conclusions: This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes' progression and designing training plans.

Purpose: This study aimed to investigate how rifle carriage and skiing speed during biathlon roller skiing affect range of motion (ROM) in joint angles and equipment (skis and poles), the vertical distance between shoulders and treadmill (vert dist ), as well as possible sex differences associated with rifle carriage., Methods: Fourteen biathletes (6 women, 8 men) roller-skied on a treadmill at submaximal and simulated race speeds, with (WR) and without (NR) a rifle, using gears 3 and 2. Kinematical data for the whole body, poles, roller-skis, rifle, and treadmill were monitored using a 3D motion capture system. Movements determined as flexion/extension (x), abduction/adduction (y), and/or internal/external rotation (z) were analyzed for the hip, shoulder, thorax, knee, ankle, elbow, poles, and roller skis. ROM (the difference between maximal and minimal angles) in joints and equipment, and vert dist were analyzed over six skiing cycles during each condition (WR and NR) and speed., Results: The maximal vert dist was lower for WR compared with NR (gear 3: 1.53 ± 0.06 vs 1.54 ± 0.06 m; gear 2: 1.49 ± 0.06 vs 1.51 ± 0.06 m; both p < 0.001). ROM in the upper body was altered when roller skiing WR (movements decreased in thorax and shoulder (x) and increased in elbow (only gear 3) (x), thorax (only gear 2), and shoulder (y) and (z); all p < 0.05) and increased with speed, without differences between sexes (p > 0.05)., Conclusion: Since rifle carriage and speed appear to affect the kinematics of roller skiing, coaches, and biathletes are advised to perform skiing technique training under competition-like conditions (i.e., at race speeds while carrying the rifle)., (© 2022 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

The aim was to investigate whether rifle carriage affects gear distribution during on-snow skiing in highly-trained biathletes, and whether there were any associated sex differences. Twenty-eight biathletes (11 women, 17 men) skied a 2230-m lap at competition speed twice, one lap with the rifle (WR) and the other lap without the rifle (NR). The biathletes wore a portable 3D-motion analysis system while skiing, which enabled characterisation of distance and time in different gears. Skiing WR increased lap time compared to NR (412 (90) vs. 395 (91) s, p < 0.001). The biathletes used gear 2 to a greater extent WR compared to NR (distance: 413 ± 139 vs. 365 ± 142 m; time: 133 (95) vs. 113 (86) s; both p < 0.001) and gear 3 less (distance: 713 ± 166 vs. 769 ± 182 m, p < 0.001; time: 141 ± 33 vs. 149 ± 37 s, p = 0.008), with similar patterns for women and men. Differences between WR and NR in the use of gears 3 and 2 were more extensive for moderate compared to steeper uphill terrain. Rifle carriage increased the use of gear 2, which was negatively associated with performance. Therefore, preparing biathletes to be able to cover more distance in gear 3 WR, especially in moderate uphill terrain, may improve biathlon skiing performance.

Objective: Few 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 over a competitive season., Methods: Forty national team XC skiers participated in this prospective, observational study. Two groups were characterised according to performance level: senior (n=18, ~26 years old, 9 women) and development (n=22, ~21 years old, 9 women). The skiers reported all and substantial injuries and illnesses weekly for 17 consecutive weeks throughout the 2019/2020 competitive season using the Oslo Sports Trauma Research Center Questionnaire on Health Problems., Results: The average weekly prevalence of all and substantial health problems was 19% (95% CI: 16% to 22%) and 12% (95% CI: 9% to 15%), respectively, and was similar between senior and development level skiers (p>0.05). The injury prevalence was higher in senior versus development level skiers (12%, 95% CI: 9% to 15% vs 5%, 95% CI: 3% to 7%; p<0.001), while illnesses were less common (8%, 95% CI: 3% to 13% vs 13%, 95% CI: 9% to 17%, respectively; p=0.031). Illnesses accounted for 72% of all problems. The prevalence of all health problems was higher in female than in male skiers (23%, 95% CI: 19% to 27% vs 15%, 95% CI: 11% to 19%; p<0.003)., Conclusions: Health problems, especially illnesses, were relatively common, with approximately one in five skiers (19%) reporting at least one problem in any given week. Both performance level and sex influenced the prevalence of different types of health problems., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction: Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be recommended as an ergogenic aid. Moreover, there is no consensus on the safe administration of dietary nitrate as an ergogenic aid. This study aimed to address these research gaps., Methods: The modified Delphi technique was used to establish the views of 12 expert panel members on the use of dietary nitrate as an ergogenic aid. Over three iterative rounds (two via questionnaire and one via videoconferencing), the expert panel members voted on 222 statements relating to dietary nitrate as an ergogenic aid. Consensus was reached when > 80% of the panel provided the same answer (i.e. yes or no). Statements for which > 80% of the panel cast a vote of insufficient evidence were categorised as such and removed from further voting. These statements were subsequently used to identify directions for future research., Results: The 12 panel members contributed to voting in all three rounds. A total of 39 statements (17.6%) reached consensus across the three rounds (20 yes, 19 no). In round one, 21 statements reached consensus (11 yes, 10 no). In round two, seven further statements reached consensus (4 yes, 3 no). In round three, an additional 11 statements reached consensus (5 yes, 6 no). The panel agreed that there was insufficient evidence for 134 (60.4%) of the statements, and were unable to agree on the outcome of the remaining statements., Conclusions: This study provides information on the current expert consensus on dietary nitrate, which may be of value to athletes, coaches, practitioners and researchers. The effects of dietary nitrate appear to be diminished in individuals with a higher aerobic fitness (peak oxygen consumption [V̇O 2peak ] > 60 ml/kg/min), and therefore, aerobic fitness should be taken into account when considering use of dietary nitrate as an ergogenic aid. It is recommended that athletes looking to benefit from dietary nitrate supplementation should consume 8-16 mmol nitrate acutely or 4-16 mmol/day nitrate chronically (with the final dose ingested 2-4 h pre-exercise) to maximise ergogenic effects, taking into consideration that, from a safety perspective, athletes may be best advised to increase their intake of nitrate via vegetables and vegetable juices. Acute nitrate supplementation up to ~ 16 mmol is believed to be safe, although the safety of chronic nitrate supplementation requires further investigation. The expert panel agreed that there was insufficient evidence for most of the appraised statements, highlighting the need for future research in this area., (© 2022. The Author(s).)

Objective: To monitor the daily variations and time course of changes in selected variables during a 17-21-day altitude training camp at 1,800 m in a group of elite cross-country skiers (9 women, 12 men) and biathletes (7 women, 4 men)., Methods: Among other variables, resting peripheral oxygen saturation (SpO 2rest ), resting heart rate (HR rest ) and urine specific gravity (USG) were monitored daily at altitude, while illness symptoms were monitored weekly. Before and after the camp, body composition (i.e., lean and fat mass) and body mass were assessed in all athletes, while roller-skiing speed at a blood lactate concentration of 4 mmol·L -1 (Speed @4mmol ) was assessed in the biathletes only., Results: Neither SpO 2rest , HR rest nor USG changed systematically during the camp ( p > 0.05), although some daily time points differed from day one for the latter two variables ( p < 0.05). In addition, body composition and body mass were unchanged from before to after the camp ( p > 0.05). Eleven out of 15 illness episodes were reported within 4 days of the outbound or homebound flight. The five biathletes who remained free of illness increased their Speed @4mmol by ~ 4% from before to after the camp ( p = 0.031)., Conclusions: The present results show that measures typically recommended to monitor acclimatization and responses to altitude in athletes (e.g., SpO 2rest and HR rest ) did not change systematically over time. Further research is needed to explore the utility of these and other measures in elite endurance athletes at altitudes typical of competition environments., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Karlsson, Laaksonen and McGawley.)

Background: Beetroot juice (BJ) and caffeine (CAF) are considered as ergogenic aids among athletes to enhance performance, however, the ergogenic effects of BJ and CAF co-ingestion are unclear during team-sport-specific performance. This study aimed to investigate the acute effects of BJ and CAF co-ingestion on team-sport-specific performance, compared with placebo (PL), BJ, and CAF alone., Method: Sixteen semi-professional male soccer players (age: 19.8 ± 2.2 years, body mass: 69.2 ± 6.1 kg, height: 177.3 ± 6.0 cm) completed four experimental trials using a randomized, double-blind study design: BJ + CAF, CAF + PL, BJ + PL, and PL + PL. Countermovement jump with arm swing (CMJAS) performance and cognitive function by Stroop Word-Color test were evaluated before and after the Yo-Yo Intermittent Recovery Test level 1 (YYIR1). Also, rate of perceived exertion (RPE), heart rate, and gastrointestinal (GI) discomfort were measured during each session., Results: No significant differences were shown between test conditions for total distance covered in YYIR1 (BJ + CAF: 1858 ± 455 m, CAF + PL: 1798 ± 422 m, BJ + PL: 1845 ± 408 m, PL + PL 1740 ± 362 m; p = 0.55). Moreover, CMJAS performance, cognitive function, and RPE during the YYIR1 were not significantly different among conditions (p > 0.05). However, the average heart rate during the YYIR1 was higher in CAF + PL compared to PL + PL (by 6 ± 9 beats/min; p < 0.05), and GI distress was greater in BJ + CAF compared to PL + PL (by 2.4 ± 3.6 a.u.; p < 0.05)., Conclusion: These results suggest, neither acute co-ingestion of BJ + CAF nor BJ or CAF supplementation alone significantly affected team-sport-specific performance compared to the PL treatment., (© 2022. The Author(s).)

This study examined the micro-pacing strategies during a distance freestyle cross-country (XC) skiing competition. Nine female and 10 male highly trained XC skiers wore a GNSS device during a FIS-sanctioned race. The course was ~4900 m; women completed two-laps; men completed three-laps. The course was divided into uphill (S1, S3, S5, S7), downhill (S2, S4, S6, S8), and flat (S9) sections for analyses. Statistical parametric mapping was used to determine the course positions (clusters) where total race time or section time was significantly associated with instantaneous skiing speed. Total race time was associated with instantaneous skiing speed during a cluster in S1 on lap 2 for both sexes (t ≥ 5.899, p ≤ 0.008). The two longest uphill sections (S1; S5) and the flat section (S9) contained clusters where section times were related to instantaneous skiing speed for both sexes ( p < 0.05). The fastest woman gained 6.9 s on the slowest woman during a cluster in S1 on lap 1 and 7.3 s during a cluster in S9 on lap 1. The fastest man gained 51.7 s on the slowest man over all clusters in S5 over the 3 laps combined. Compared to skiers with longer total race times, skiers with shorter race times skied with faster instantaneous speeds in some clusters of the uphill sections, as well as on the flat section of the course. This study also identified different relative micro-pacing strategies for women and men during freestyle distance XC skiing races. Finally, statistical parametric mapping analyses can help to identify individual strengths and weaknesses for guiding training programs and optimise competition pacing strategies., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Staunton, Colyer, Karlsson, Swarén, Ihalainen and McGawley.)

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 (P FIX , QF FIX , and SF FIX ) corresponding to ∼96% of each individual's previously determined maximal effort. The final bout was performed as a self-paced sprint time trial (F STT ). Test conditions differed by the time durations prescribed between the QF FIX , SF FIX , and F STT , which simulated real-world XC ski competition conditions using maximum (MAX-REC) or minimum (MIN-REC) recovery periods., Results: The F STT 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 F STT 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 F STT 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., Competing Interests: Competing interests The authors declare that they have no competing interests., (Copyright © 2021. Production and hosting by Elsevier B.V.)

Purpose: To provide a descriptive analysis of the warm-up (WU) strategies employed by cross-country skiers prior to distance and sprint competitions at a national championship and to compare the skiers' planned and executed WUs prior to the respective competitions., Methods: Twenty-one national- and international-level skiers (11 women and 10 men) submitted WU plans prior to the distance and sprint competitions, and after the competitions, reported any deviations from the plans. Skiers used personal monitors to record heart rate (HR) during WU, races, and cooldown. Quantitative statistical analyses were conducted on WU durations, durations in HR-derived intensity zones, and WU loads. Qualitative analyses were conducted on skiers' WU plans and their reasons for deviating from the plans., Results: Skiers' planned WUs were similar in content and planned time in HR-derived intensity zones for both the distance and sprint competitions. However, 45% of the women and 20% of the men reported that their WU was not carried out as planned, with reasons detailed as being due to incorrect intensities and running out of time. WU activities including skiing across variable terrain, muscle-potentiating exercises, and heat-maintenance strategies were missing from the skiers' planned routines., Conclusions: Skiers favored a long, traditional WU approach for both the sprint and distance events, performing less high-intensity and more moderate-intensity exercise during their WUs than planned. In addition, elements likely relevant to successful performance in cross-country skiing were missing from WU plans.

Purpose: To examine the influence of menstrual cycle (MC) and hormonal contraceptive (HC) cycle phases on physiological variables monitored during incremental treadmill testing in physically active women (eumenorrheic, EUM = 16 and monophasic HC-users, CHC = 12). Methods: Four running tests to exhaustion were performed at bleeding, mid follicular (mid FOL)/active 1, ovulation/active 2, and mid luteal (mid LUT)/inactive. HC and MC phases were confirmed from serum hormones. Heart rate (HR), blood lactate (Bla), and V ˙ O 2 were monitored, while aerobic (AerT) and anaerobic (AnaT) thresholds were determined. V ˙ O 2peak , maximal running speed (RUN peak ), and total running time (RUN total ) were recorded. Results: No significant changes were observed in V ˙ O 2 or Bla at AerT or AnaT across phases in either group. At maximal effort, absolute and relative V ˙ O 2peak , RUN peak , and RUN total remained stable across phases in both groups. No significant fluctuations in HR max were observed across phases, but HR at both AerT and AnaT tended to be lower in EUM than in CHC across phases. Conclusion: Hormonal fluctuations over the MC and HC do not systematically influence physiological variables monitored during incremental treadmill testing. Between group differences in HR at AerT and AnaT underline why HR-based training should be prescribed individually, while recording of MC or HC use when testing should be encouraged as phase may explain minor, but possibly meaningful, changes in, e.g., Bla concentrations or differences in HR response., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Taipale-Mikkonen, Raitanen, Hackney, Solli, Valtonen, Peltonen, McGawley, Kyröläinen and Ihalainen.)

Purpose: This study aimed to describe changes in laboratory-assessed anthropometric and physiological characteristics, training volumes, and competitive performance in national development-team cross-country skiers over a 25-month period, and to analyze whether changes in competitive performance could be predicted by changes in laboratory-assessed qualities and training volumes., Methods: Data collected over 25 months from 30 national development-team cross-country skiers (14 women, 16 men; age, 18-23 yr) were analyzed retrospectively using multivariate statistics. Anthropometric and physiological characteristics were assessed via dual-energy x-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Total training volumes and distributions of low- and high-intensity training were analyzed from online training diaries, and competitive performance was determined by International Ski Federation (FIS) distance and sprint points., Results: Whole- and upper-body lean mass increased in the full cohort of skiers (n = 30; both P < 0.05), whereas lower-body lean mass, whole-body fat mass, speed and oxygen uptake (V˙O2) at a blood lactate concentration (BLa) of 2 and 4 mmol·L-1, as well as time-trial completion time, power output, and peak V˙O2, improved in the women only (all P < 0.05). Valid predictive models were identified for female skiers' best FIS distance points (R2 = 0.81/Q2 = 0.51) and changes in FIS distance points (R2 = 0.83/Q2 = 0.54), with body mass, fat mass, lean mass, V˙O2peak, and speed at a BLa of 4 mmol·L-1 identified as consistently important variables for projection., Conclusions: The valid prediction of competitive performance was achieved for women only in distance events. This study suggests that improvements in body composition and aerobic capacity may be more beneficial for elite female development-level skiers than for their male counterparts. These results have implications for athlete selection and performance development., (Copyright © 2021 by the American College of Sports Medicine.)

Objectives: To observe changes in sleep from baseline and during an altitude training camp in elite endurance athletes., Design: Prospective, observational., Setting: Baseline monitoring at <500 m for 2 weeks and altitude monitoring at 1800 m for 17-22 days., Participants: Thirty-three senior national-team endurance athletes (mean age 25.8 ± S.D. 2.8 years, 16 women)., Measurements: Daily measurements of sleep (using a microwave Doppler radar at baseline and altitude), oxygen saturation (SpO 2 ), training load and subjective recovery (at altitude)., Results: At altitude vs. baseline, sleep duration (P = .036) and light sleep (P < .001) decreased, while deep sleep (P < .001) and respiration rate (P = .020) increased. During the first altitude week vs. baseline, deep sleep increased (P = .001). During the first vs. the second and third altitude weeks, time in bed (P = .005), sleep duration (P = .001), and light sleep (P < .001) decreased. Generally, increased SpO 2 was associated with increased deep sleep while increased training load was associated with increased respiration rate., Conclusion: This is the first study to document changes in sleep from near-sea-level baseline and during a training camp at 1800 m in elite endurance athletes. Ascending to altitude reduced total sleep time and light sleep, while deep sleep and respiration rate increased. SpO 2 and training load at altitude were associated with these responses. This research informs our understanding of the changes in sleep occurring in elite endurance athletes attending training camps at competition altitudes., Competing Interests: Declaration of conflict of interest The authors have declared no conflicts of interest., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Competitive female athletes perceive their hormonal cycles to affect their training, competition performance and overall well-being. Despite this, athletes rarely discuss hormonal-cycle-related issues with others. The aim of this study was to gain an in-depth understanding of the perceptions and experiences of endurance athletes and their coaches in relation to barriers to athlete-coach communication about female hormonal cycles. Thirteen Swedish national-/international-level female cross-country skiers (age 25.8 ± 3.6 y) and eight of their coaches (two women and six men; age 47.8 ± 7.5 y) completed an online survey relating to their educational background, prior knowledge about female hormonal cycles and a coach-athlete relationship questionnaire (CART-Q). They then participated in an online education session about female hormonal cycles and athletic performance before participating in semi-structured focus-group interviews. Thematic analyses revealed three main barriers to communication: knowledge, interpersonal, and structural. In addition, the results suggested that a good coach-athlete relationship may facilitate open communication about female hormonal cycles, while low levels of knowledge may hinder communication. To overcome the perceived barriers to communication, a model is proposed to improve knowledge, develop interpersonal relationships and strengthen structural systems through educational exchanges and forums for open discussion.

Introduction: To date, no study has compared anaerobic capacity (AnC) estimates computed with the maximal accumulated oxygen deficit (MAOD) method and the gross energy cost (GEC) method applied to treadmill running exercise., Purpose: Four different models for estimating anaerobic energy supply during treadmill running exercise were compared., Methods: Fifteen endurance-trained recreational athletes performed, after a 10-min warm-up, five 4-min stages at ∼55-80% of peak oxygen uptake, and a 4-min time trial (TT). Two linear speed-metabolic rate (MR) regression models were used to estimate the instantaneous required MR during the TT (MR TT&#95;req ), either including (5+Y LIN ) or excluding (5-Y LIN ) a measured Y-intercept. Also, the average GEC (GEC AVG ) based on all five submaximal stages, or the GEC based on the last submaximal stage (GEC LAST ), were used as models to estimate the instantaneous MR TT&#95;req . The AnC was computed as the difference between the MR TT&#95;req and the aerobic MR integrated over time., Results: The GEC remained constant at ∼4.39 ± 0.29 J⋅kg -1 ⋅m -1 across the five submaximal stages and the TT was performed at a speed of 4.7 ± 0.4 m⋅s -1 . Compared with the 5-Y LIN , GEC AVG , and GEC LAST models, the 5+Y LIN model generated a MR TT&#95;req that was ∼3.9% lower, with corresponding anaerobic capacities from the four models of 0.72 ± 0.20, 0.74 ± 0.16, 0.74 ± 0.15, and 0.54 ± 0.14 kJ⋅kg -1 , respectively ( F 1.07,42 = 13.9, P = 0.002). The GEC values associated with the TT were 4.22 ± 0.27 and 4.37 ± 0.30 J⋅kg -1 ⋅m -1 for 5+Y LIN and 5-Y LIN , respectively (calculated from the regression equation), and 4.39 ± 0.28 and 4.38 ± 0.27 J⋅kg -1 ⋅m -1 for GEC AVG and GEC LAST , respectively ( F 1.08,42 = 14.6, P < 0.001). The absolute typical errors in AnC ranged between 0.03 and 0.16 kJ⋅kg -1 for the six pair-wise comparisons and the overall standard error of measurement (SEM) was 0.16 kJ⋅kg -1 ., Conclusion: These findings demonstrate a generally high disagreement in estimated anaerobic capacities between models and show that the inclusion of a measured Y-intercept in the linear regression (i.e., 5+Y LIN ) is likely to underestimate the MR TT&#95;req and the GEC associated with the TT, and hence the AnC during maximal 4-min treadmill running., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Andersson, Björklund and McGawley.)

Purpose: This study aimed to compare physiological factors and cycle characteristics during cross-country (XC) roller-skiing at matched inclines and speeds using the double-poling (DP) and diagonal-stride (DS) sub-techniques in junior female and male XC skiers., Methods: Twenty-three well-trained junior XC skiers (11 women, 12 men; age 18.2 ± 1.2 yr.) completed two treadmill roller-skiing tests in a randomized order using either DP or DS. The exercise protocols were identical and included a 5 min warm-up, 4 × 5 min submaximal stages, and an incremental test to exhaustion, all performed at a 5° incline., Results: No significant three-way interactions were observed between sex, submaximal exercise intensity, and sub-technique. For the pooled sample, higher values were observed for DP versus DS during submaximal exercise for the mean oxygen uptake kinetics response time (33%), energy cost (18%), heart rate (HR) (9%), blood lactate concentration (5.1 versus 2.1 mmol·L -1 ), rating of perceived exertion (12%), and cycle rate (25%), while cycle length was lower (19%) (all P < 0.001). During the time-to-exhaustion (TTE) test, peak oxygen uptake ([Formula: see text]O 2 peak), peak HR, and peak oxygen pulse were 8%, 2%, and 6% lower, respectively, for DP than DS, with a 29% shorter TTE during DP (pooled data, all P < 0.001)., Conclusion: In well-trained junior XC skiers, DP was found to exert a greater physiological load than DS during uphill XC roller-skiing at submaximal intensities. During the TTE test, both female and male athletes were able to ski for longer and reached markedly higher [Formula: see text]O 2 peak values when using DS compared to DP.

Splenic contraction, which leads to ejection of stored erythrocytes, is greater in athletes involved in regular freediving or high-altitude activities. As this response facilitates oxygen-carrying capacity, similar characteristics may be expected of elite endurance athletes. Therefore, our aims were to compare resting and apnea-induced splenic volume in endurance athletes and untrained individuals, and to assess the athletes' exercise-induced splenic volume. Twelve elite biathletes (7 women) and 12 controls (6 women) performed a maximal effort apnea in a seated position. In addition, the biathletes completed a maximal roller-skiing time trial. Splenic dimensions were measured by ultrasonic imaging for subsequent volume calculations, whereas Hb was analyzed from capillary blood samples and cardiorespiratory variables were monitored continuously. Baseline splenic volume was larger in the biathletes (214 ± 56 mL) compared with controls (157 ± 39 mL, P = 0.008) and apnea-induced splenic contraction was also greater in the biathletes (46 ± 20 mL vs. 30 ± 16 mL, P = 0.035). Hb increased immediately after apnea in the biathletes (4.5 ± 4.8%, P = 0.029) but not in the controls (-0.7 ± 3.1%, P = 0.999). Increases in exercise-induced splenic contraction ( P = 0.008) and Hb ( P = 0.001) were greater compared with the apnea-induced responses among the athletes. Baseline splenic volume tended to be correlated with V̇o 2max ( r  = 0.584, P = 0.059). We conclude that elite biathletes have greater splenic volume with a greater ability to contract and elevate Hb compared with untrained individuals. These characteristics may transiently enhance O 2 -carrying capacity and possibly increase O 2 uptake, thereby helping biathletes to cope with high intermittent O 2 demands and severe O 2 deficits that occur during biathlon training and competition. NEW & NOTEWORTHY This study demonstrates that elite biathletes have larger splenic volume, apnea-induced splenic contraction, and Hb elevation compared with untrained individuals, which is likely functional to cope with high O 2 demands and substantial O 2 deficits. We believe that enhanced splenic contraction may be of importance during competitions involving cross-country skiing, to regulate circulating Hb and enhance O 2 -carrying capacity, which may protect [Formula: see text] and increase O 2 uptake.

Context: Warming up in very cold climates and maintaining an elevated body temperature prior to a race is challenging for snow-sport athletes., Purpose: To investigate the effects of active (ACT), passive (PAS), and a combination of ACT and PAS (COM) warm-ups on maximal physical performance in a subzero environment among snow-sport athletes., Methods: Ten junior alpine skiers completed 3 experimental trials in -7.2 (0.2)°C. The ACT involved 5 minutes of moderate cycling, 3 × 15-second accelerations, a 6-second sprint, 5 countermovement jumps (CMJs), and a 10-minute passive transition phase, while in PAS, participants wore a lower-body heated garment for 24 minutes. In COM, participants completed the active warm-up, then wore the heated garment during the transition phase. Two maximal CMJs and a 90-second maximal isokinetic cycling test followed the warm-up., Results: CMJ performance was likely (P = .150) and very likely (P = .013) greater in ACT and COM, respectively, versus PAS. Average power output during the cycling test was likely (P = .074) greater in ACT and COM versus PAS. Participants felt likely to almost certainly warmer (P < .01) and more comfortable (P = .161) during ACT and COM versus PAS. In addition, participants felt likely warmer (P = .136) and very likely more comfortable (P = .161) in COM versus ACT., Conclusions: COM resulted in significantly improved CMJ performance versus PAS while both ACT and COM led to likely improved 90-second cycling performance. Participants felt significantly warmer during ACT and COM versus PAS and likely warmer in COM versus ACT. Therefore, a combined warm-up is recommended for alpine skiers performing in subzero temperatures.

Purpose: To determine body composition, energy availability, training load, and menstrual status in young elite endurance running athletes (ATH) over 1 year, and in a secondary analysis, to investigate how these factors differ between nonrunning controls (CON), and amenorrheic (AME) and eumenorrheic (EUM) ATH. Correlations to injury, illness, and performance were also examined., Methods: Altogether 13 ATH and 8 CON completed the Low Energy Availability in Females Questionnaire. Anthropometric, energy intake, and peak oxygen uptake assessments were made at 4 time points throughout the year: at baseline post competition season, post general preparation, post specific preparation, and post competition season the following year. Logs of physical activity, menstrual cycle, illness, and injury were kept by all participants. Performance was defined using the highest International Association of Athletics Federations points prior to and after the study., Results: ATH had significantly lower body mass (P < .008), fat percentage (P < .001), and body mass index (P < .027) compared with CON, while energy availability did not differ between ATH and CON. The Low Energy Availability in Females Questionnaire score was higher in ATH than in CON (P < .028), and 8 ATH (vs zero CON) were AME. The AME had significantly more injury days (P < .041) and ran less (P < .046) than EUM, while total annual running distance was positively related to changes in performance in ATH (r < .62, P < .043, n < 11)., Conclusions: More than half of this group of runners was AME, and they were injured more and ran less than their EUM counterparts. Furthermore, only the EUM runners increased their performance over the course of the year.

Objective: This study aimed to describe the endurance training and incidence of illnesses reported by a group of well-trained cross-country (XC) skiers throughout their transition from junior to senior level., Methods: Changes in self-reported training and performance, from 31 well-trained XC skiers, were analyzed from the start of the season they turned 16 y until the end of the season they turned 22 y, using linear mixed-effects models. Differences in the incidence of self-reported illness episodes were analyzed using incidence rate ratios, and the relationships between self-reported illness and training volumes were analyzed using linear mixed-effects models in a sub-group of 23 of the skiers., Results: In total, 145 seasons of training data (including 85,846 h of endurance training) and 109 person-years of illness data (including 380 self-reported illness episodes) were analyzed. The athletes progressively increased their annual endurance training volume from age 16 to 22 y in a linear fashion, from ~ 470 to 730 h. Low- and high-intensity training volumes increased by 51.4 ± 2.4 h·y-1 (p < .001) and 4.9 ± 0.6 h·y-1 (p < .001), respectively. Sport-specific and non-specific training increased by 50.0 ± 2.2 h·y-1 (p < .001) and 4.6 ± 2.0 h·y-1 (p < .001), respectively. The athletes reported a median (range) of 3 (0-8) illness episodes and 17 (0-80) days of illness per year, and there was an inverse relationship between self-reported illness days and annual training volume (-0.046 ± 0.013 d·h-1; p < .001)., Conclusions: This group of well-trained XC skiers increased their endurance training volume in a linear fashion by ~ 55 h annually. This was primarily achieved through an increase in low-intensity and sport-specific training. Furthermore, higher training volumes were associated with a lower number of self-reported illness days., Competing Interests: The authors have declared that no competing interests exist.

Purpose: To evaluate the effects of wearing upper- and lower-body compression garments on cross-country skiing performance in elite winter biathletes., Methods: A total of 7 senior biathletes (4 men and 3 women) from the Swedish national team performed 2 exercise trials in a randomized and counterbalanced order, wearing either commercially available upper- and lower-body compression garments (COMP) or a standard winter-biathlon racing suit (CON). In each trial, the athletes roller-skied on a customized treadmill, completing a time trial simulating the skiing duration of a biathlon sprint race, followed by a time-to-exhaustion test designed to elicit exhaustion within ∼60 to 90 seconds. Heart rate, blood lactate concentration, rating of perceived exertion, thermal sensation, and thermal comfort were monitored throughout each trial, while muscle soreness was measured up to 48 hours after each trial., Results: Pressure exerted by the clothing was significantly higher at all anatomical sites for COMP compared with CON (P ≤ .002). Wearing COMP led to small positive effects on time-trial (d = 0.31) and time-to-exhaustion test (d = 0.31) performances compared with CON, but these differences were not statistically significant (P > .05). No significant differences were found for any physiological (heart rate or blood lactate concentration) or subjective (rating of perceived exertion, thermal sensation, thermal comfort, or muscle soreness) responses between COMP and CON (P > .05)., Conclusion: Wearing COMP during maximal cross-country skiing may have small but worthwhile beneficial effects on performance for some individuals. Due to individual variation, athletes are advised to test COMP prior to competition.

Skiing in biathlon is a high-intensity, intermittent endurance discipline. This study aimed to evaluate the relationships between laboratory-derived physiological variables and skiing performance during a field-based biathlon competition (BC) for female and male biathletes. Fourteen female (23 ± 3 year, V ˙ O 2max 56 ± 4 mL·kg -1 ·min -1 ) and 14 male (24 ± 4 year, V ˙ O 2max 66 ± 3 mL·kg -1 ·min -1 ) biathletes performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing for the assessment of oxygen uptake at a lactate threshold of 4 mmol·L -1 ( V ˙ O 2@4mmol ), gross efficiency (GE), aerobic (MR ae ) and anaerobic (MR an ) metabolic rates, peak oxygen consumption ( V ˙ O 2peak ), anaerobic capacity and TT performance. Field-based skiing performance was assessed during a BC. The TT and BC skiing performances were significantly correlated in both sexes ( r = 0.68-0.69, p < 0.01). V ˙ O 2peak (31/21%), anaerobic capacity (1/0%), and GE (35/32%) explained 67 and 52% of the variance in BC skiing performance for the females ( p < 0.01) and males ( p = 0.051), respectively. A second model showed that V ˙ O 2@4mmol (30/35%), anaerobic capacity (0/0%) and GE (37/13%) explained 67 and 48% of the variance in BC skiing performance for the females ( p < 0.01) and males ( p = 0.077), respectively. Results of this study suggest that a high V ˙ O 2@4mmol and GE, but not anaerobic capacity, are important for BC skiing performance, especially for females. In addition, a laboratory-based TT could be useful for regular laboratory testing of biathletes due to its relationship with field-based skiing performance in biathlon., (Copyright © 2020 Laaksonen, Andersson, Jonsson Kårström, Lindblom and McGawley.)

The purpose of the present study was to analyze micro-pacing strategies in cross-country skiing, and their relation to section and total race times. Eleven competitive female cross-country skiers were tracked during a classic sprint time-trial race using a global navigation satellite system (GNSS) unit. A coordinate mapping procedure was applied to the GNSS unit measurements to analyze the instantaneous velocities and split times. The track was divided into nine sections and individual section times were calculated. Statistical parametric mapping (SPM) was used to analyze the relationships between instantaneous velocity and section or total race time. SPM analyses revealed two uphill sections and one flat section where greater instantaneous velocities were related to faster total race times. The first major uphill section on the track demonstrated a more conservative micro-pacing strategy (SPM supra-threshold clusters along the entire uphill, p < 0.05-0.001) compared to the more aggressive strategy used in the last uphill section (clusters on the first half of the uphill, p < 0.05-0.001). Faster flat section times were associated with greater instantaneous velocities throughout the section ( p < 0.001), while faster downhill section times were related to greater instantaneous velocities at the top of the downhill ( p < 0.001), and in the downhill turns ( p < 0.001). In conclusion, micro-pacing strategies were related to overall skiing performance and distinct track sections were identified where instantaneous velocities were related to section or total race times. In order to improve skiing performance, athletes could focus on more aggressive pacing early on in the "end spurt", during the transitions from uphill to flat sections, and during the transitions from flat or uphill to downhill sections., (Copyright © 2020 Ihalainen, Colyer, Andersson and McGawley.)

Balance as a skill and task-specific capacity is considered an essential physical quality in curling, required for executing effective stone delivery. However, no testing protocols have been developed to test curling-specific balance in the delivery position. Thus, the primary aim of this study was to investigate the reliability, validity and usefulness of a newly-developed, curling-specific balance test (CSBT) which involved the delivery position. The secondary aim was to examine the differences between elite and sub-elite curlers for core strength and flexibility, which have previously been identified as important qualities in curling and determinants of balance. Twenty curling players (13 females aged 19 ± 3.1 years; 7 males aged 19.6 ± 2.3 years) from five Swedish super-league curling clubs were divided into two groups according to playing level: elite and sub-elite. Variables included body mass, body height, body mass index, age, playing experience, training frequency, plank test, sit and reach test, standing single-leg balance test (SLBT) and CSBT. The CSBT was executed on a multiaxial tilting balance plate while mimicking the curling delivery position (i.e., a deep lunge position with the front foot on the plate). The participants completed the CSBT on three separate occasions, with each test consisting of three, 20-s attempts. Both the relative and absolute reliability were good for the CSBT (ICC = 0.90; CV = 14.5%). The CSBT demonstrated good measurement usefulness, being sensitive to detect moderate changes that exceeded 0.5 times the test standard deviation. Construct validity of the CSBT was evidenced by the large discriminatory capacity to differentiate expertise level in curling players (t-test: 2.85, p < 0.01; large ES), irrespective of other physical capacities (e.g., flexibility and core strength). However, the elite and sub-elite players also differed in age, playing experience and training frequency. Content validity was confirmed by a weak correlation (r = 0.21; 95%CI: -0.26 to 0.60) between the CSBT and SLBT, which suggests that curling-specific and standing balance should be considered as independent and task-specific motor skills. In conclusion, the CSBT can be used as a reliable, valid and useful tool for the assessment of curling-specific balance performance. In addition, longer and more extensive involvement in curling training contributed to superior specific balance in elite curlers., (© Journal of Sports Science and Medicine.)

Purpose: This study aimed to investigate the physiological factors affected by rifle carriage during biathlon skiing performance, as well as the sex differences associated with rifle carriage. Methods: Seventeen national- and international-level biathletes (nine females and eight males; age 23.0 ± 3.3 years, V . O 2 max 59.4 ± 7.6 mL.kg -1 .min -1 ) performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing (gear 3, skating technique) on two occasions separated by at least 48 h. One condition involved carrying the rifle on the back (WR) and the other condition no rifle (NR) and the tests were randomized. Submaximal V . O 2 , skiing speed at 4 mmol.L -1 of blood lactate (speed @ 4 mmol ), gross efficiency (GE), aerobic (MR ae ), and anaerobic (MR an ) metabolic rates, and V . O 2 max were determined. Results: Submaximal V . O 2 (at all intensities) and GE (16.7 ± 0.9 vs. 16.5 ± 1.1%) were higher for WR compared to NR ( p < 0.05), while speed @ 4 mmol was lower (3.1 ± 0.4 vs. 3.3 ± 0.5 m.s -1 , p = 0.040). TT performance was improved (4.6 ± 0.4 vs. 4.3 ± 0.4 m.s -1 , p < 0.001) and MR an was higher (31.3 ± 8.0 vs. 27.5 ± 6.5 kJ.min -1 , p < 0.01) for NR compared to WR, with no difference in V . O 2 max or MR ae . For skiing WR, TT performance was correlated to speed @ 4 mmol ( r = 0.81, p < 0.001), MR an ( r = 0.65, p < 0.01), V . O 2 max ( r = 0.51, p < 0.05), and relative muscle ( r = 0.67, p < 0.01) and fat ( r = -0.67, p < 0.01) masses. Speed @ 4 mmol together with MR an explained more than 80% of the variation in TT performance (WR 84%, NR 81%). Despite a higher relative mass of the rifle in females compared with males (5.6 ± 0.4 vs. 5.0 ± 0.4% of body mass, p = 0.012), there were no sex differences associated with rifle carriage measured as absolute or relative differences. Conclusion: Rifle carriage in biathlon skiing led to significantly higher physiological demands during submaximal exercise and reduced performance during maximal treadmill roller-skiing compared to NR for both sexes. The most important variables for performance in biathlon treadmill skiing seem to be speed @ 4 mmol combined with MR an , both of which were lower for WR compared to NR. To improve skiing performance in biathlon, improving speed at 4 mmol.L -1 of blood lactate and anaerobic energy delivery while carrying the rifle are recommended., (Copyright © 2019 Jonsson Kårström, McGawley and Laaksonen.)

Background: Whilst the ergogenic effects of carbohydrate intake during prolonged exercise are well-documented, few investigations have studied the effects of carbohydrate ingestion during cross-country skiing, a mode of exercise that presents unique metabolic demands on athletes due to the combined use of large upper- and lower-body muscle masses. Moreover, no previous studies have investigated exogenous carbohydrate oxidation rates during cross-country skiing. The current study investigated the effects of a 13 C-enriched 18% multiple-transportable carbohydrate solution (1:0.8 maltodextrin:fructose) with additional gelling polysaccharides (CHO-HG) on substrate utilization and gastrointestinal symptoms during prolonged cross-country skiing exercise in the cold, and subsequent double-poling time-trial performance in ~ 20 °C., Methods: Twelve elite cross-country ski athletes (6 females, 6 males) performed 120-min of submaximal roller-skiing (69.3 ± 2.9% of [Formula: see text]O 2 peak) in -5 °C while receiving either 2.2 g CHO-HG·min - 1 or a non-caloric placebo administered in a double-blind, randomized manner. Whole-body substrate utilization and exogenous carbohydrate oxidation was calculated for the last 60 min of the submaximal exercise. The maximal time-trial (2000 m for females, 2400 m for males) immediately followed the 120-min submaximal bout. Repeated-measures ANOVAs with univariate follow-ups were conducted, as well as independent and paired t-tests, and significance was set at P < 0.05. Data are presented as mean ± SD., Results: Exogenous carbohydrate oxidation contributed 27.6 ± 6.6% to the total energy yield with CHO-HG and the peak exogenous carbohydrate oxidation rate reached 1.33 ± 0.27 g·min - 1 . Compared to placebo, fat oxidation decreased by 9.5 ± 4.8% with CHO-HG, total carbohydrate oxidation increased by 9.5 ± 4.8% and endogenous carbohydrate utilization decreased by 18.1 ± 6.4% (all P < 0.05). No severe gastrointestinal symptoms were reported in either trial and euhydration was maintained in both trials. Time-trial performance (8.4 ± 0.4 min) was not improved following CHO-HG compared to placebo (- 0.8 ± 3.5 s; 95% confidence interval - 3.0 to 1.5 s; P = 0.46). No sex differences were identified in substrate utilization or relative performance., Conclusions: Ingestion of an 18% multiple-transportable carbohydrate solution with gelling polysaccharides was found to be well-tolerated during 120 min of submaximal whole-body exercise, but did not improve subsequent maximal double-poling performance.

This study investigated the energy, macronutrient, and fluid intakes, as well as hydration status (urine specific gravity), in elite cross-country skiers during a typical day of training (Day 1) and a sprint skiing competition the following day (Day 2). A total of 31 (18 males and 13 females) national team skiers recorded their food and fluid intakes and urine specific gravity was measured on Days 1 and 2. In addition, the females completed the Low Energy Availability in Females Questionnaire to assess their risk of long-term energy deficiency. Energy intake for males was 65 ± 9 kcal/kg on Day 1 versus 58 ± 9 kcal/kg on Day 2 ( p  = .002) and for females was 57 ± 10 on Day 1 versus 55 ± 5 kcal/kg on Day 2 ( p  = .445). Carbohydrate intake recommendations of 10-12 g·kg -1 ·day -1 were not met by 89% of males and 92% of females. All males and females had a protein intake above the recommended 1.2-2.0 g/kg on both days and a postexercise protein intake above the recommended 0.3 g/kg. Of the females, 31% were classified as being at risk of long-term energy deficiency. In the morning of Day 1, 50% of males and 46% of females were dehydrated; on Day 2, this was the case for 56% of males and 38% of females. In conclusion, these data suggest that elite cross-country skiers ingested more protein and less carbohydrate than recommended and one third of the females were considered at risk of long-term energy deficiency. Furthermore, many of the athletes were dehydrated prior to training and competition.

Purpose: This study aimed to compare performance and pacing strategies between elite male and female cross-country skiers during a sprint competition on snow using the skating technique. Methods: Twenty male and 14 female skiers completed an individual time-trial prolog (TT) and three head-to-head races (quarter, semi, and final) on the same 1,572-m course, which was divided into flat, uphill and downhill sections. Section-specific speeds, choice of sub-technique (i.e., gear), cycle characteristics, heart rate and post-race blood lactate concentration were monitored. Power output was estimated for the different sections during the TT, while metabolic demand was estimated for two uphill camera sections and the final 50-m flat camera section. Results: Average speed during the four races was ∼12.5% faster for males than females ( P < 0.001), while speeds on the flat, uphill and downhill sections were ∼11, 18, and 9% faster for the males than females (all P < 0.001 for terrain, sex, and interaction). Differences in uphill TT speed between the sexes were associated with different sub-technique preferences, with males using a higher gear more frequently than females ( P < 0.05). The estimated metabolic demand relative to maximal oxygen uptake ( V ˙ O 2max ) was similar for both sexes during the two uphill camera sections (∼129% of V ˙ O 2max ) and for the final 50-m flat section (∼153% of V ˙ O 2max ). Relative power output during the TT was 18% higher for males compared to females ( P < 0.001) and was highly variable along the course for both sexes (coefficient of variation [CV] between sections 4-9 was 53%), while the same variation in heart rate was low (CV was ∼3%). The head-to-head races were ∼2.4% faster than the TT for both sexes and most race winners (61%) were positioned first already after 30 m of the race. No sex differences were observed during any of the races for heart rate or blood lactate concentration. Conclusion: The average sex difference in sprint skiing performance was ∼12.5%, with varying differences for terrain-specific speeds. Moreover, females skied relatively slower uphill (at a lower gear) and thereby elicited more variation in their speed profiles compared to the males.