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Does nature still matter in sport? In the balancing between natural and scientific training, Swedish upper-secondary ski schools have played an important role. This paper deals with specific landscape features for testing at three Swedish ski schools: Hallstatestet in Sollefteå, Hovfjällsracet in Torsby, and Stoltjonastestet in Järpen. The following questions will be addressed: How do the coaches at each school use local tests to analyze performance? How is the importance of local tests articulated, and what roles do history and nature play in this process? The paper concludes that the use of local landscapes to articulate elite performance connects ideas of measurability and scientization to the lingering tradition of natural training. Local landscapes thereby become a mediator between scientific and experiential knowledge about sport performance and point out how local sport heritage can be used for addressing environmental issues in sport. [ABSTRACT FROM AUTHOR]

Purpose: In sprint biathlon, a J-shaped pacing pattern is commonly used. We investigated whether biathletes with a fast-start pacing pattern increase time-trial skiing and shooting performance by pacing more evenly. Methods: Thirty-eight highly trained biathletes (∼21 y, 27 men) performed an individual 7.5 (3 × 2.5 km for women) or 10-km (3 × 3.3 km for men) time trial on roller skis with a self-selected pacing strategy (day 1). Prone (after lap 1) and standing shooting (after lap 2) stages were performed using paper targets. Based on their pacing strategy in the first time trial (ratio between the initial ∼800-m segment pace on lap 1 and average ∼800-m segment pace on laps 1–3), participants were divided into an intervention group with the fastest starting pace (INT, n = 20) or a control group with a more conservative starting pace (CON, n = 18). On day 2, INT was instructed to reduce their starting pace, while CON was instructed to maintain their day 1 strategy. Results: INT increased their overall time-trial performance more than CON from day 1 to day 2 (mean ± 95% CI; 1.5% ± 0.7% vs 0.0% ± 0.9%, P =.02). From day 1 to day 2, INT reduced their starting pace (5.0% ± 1.5%, P <.01), with reduced ratings of perceived exertion during lap 1 (P <.05). For CON, no change was found for starting pace (−0.8% ± 1.2%) or ratings of perceived exertion between days. No differences were found for shooting performance for either group. Conclusion: Highly trained biathletes with a pronounced fast-start pattern improve skiing performance without any change in shooting performance by pacing more evenly. [ABSTRACT FROM AUTHOR]

Purpose: To investigate differences in time to exhaustion (TTE), O2 uptake ( V ˙ O 2 ), and accumulated O2 deficit ( O 2 def ) between competitive and recreational cross-country (XC) skiers during an intermittent-interval protocol standardized for maximal aerobic power (MAP). Methods: Twelve competitive (maximal V ˙ O 2 [ V ˙ O 2 max ] = 76.5 ± 3.8 mL · kg − 1 · min − 1 ) and 10 recreational ( V ˙ O 2 max = 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 ˙ O 2 , and accumulated O 2 def 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. Results: 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 ˙ O 2 max. 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 O 2 def (P =.001) than the recreational skiers during work phases. Conclusions: Competitive XC skiers have longer TTE and accumulate more O 2 def 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: To identify differences in heart rate (HR) and concentration of blood lactate ([La]) relationships between laboratory- and field-based skate-roller-skiing tests. Methods: Fourteen world-class biathletes (8 women, 6 men) completed a laboratory- and field-based roller-skiing test using the skate technique. The laboratory-based test comprised 5 to 7 submaximal steps at a fixed incline and speed on a roller-skiing treadmill. The field-based test comprised 5 steps on a course where the final hill was designed to mimic the conditions of the laboratory test. HR and [La] were measured for each step. The HR associated with 2 mmol·L−1 (HR@2 mmol) and 4 mmol·L−1 (HR@4 mmol) of [La] was calculated using an interpolation method. A 1-way analysis of variance and Bland–Altman analyses with 95% limits of agreement (LoA) were used to determine if test type influenced HR@2 mmol or HR@4 mmol. A second-order polynomial was fitted to group-level data to highlight the HR–[La] relationships for laboratory- and field-based tests. Results: HR@2 mmol was lower for field tests than for laboratory tests (mean bias: 1.9%HRmax; 95% LoA: −4.5 to +8.3%HRmax; P <.001). HR@4 mmol was also lower for field tests compared to laboratory tests (mean bias: 2.4%HRmax; 95% LoA: −1.2 to +6.0%HRmax; P <.001). On the group level, the lactate threshold occurred at a lower HR during roller skiing in the field compared to the laboratory. Conclusions: The findings from this study confirm that for a given HR, [La] was greater in field- compared with laboratory-based conditions. These results might have implications for how coaches define training-intensity "zones" during skate roller skiing based on laboratory tests. [ABSTRACT FROM AUTHOR]

Purpose: Endurance elite athletes are expected to present a cardiac remodelling, characterized by eccentric hypertrophy (EH), may be associated with higher sportive performances. However, not all can present a cardiac remodelling. The study aimed to identify endurance athletes without cardiac remodelling characterizing their physiologic and clinical features. Methods: We studied 309 endurance athletes (cycling, rowing, canoeing, triathlon, athletics, long-distance swimming, cross-country skiing, mid-long distance track, pentathlon, biathlon, long-distance skating and Nordic-combined) examined during period of training, by clinical evaluation, ECG, echocardiogram and exercise-stress test. Sport career achievements (Olympic\World championship medals or national\world records) were recorded. Results: EH was found in most of athletes, (n = 126, 67% of males; n = 85, 68.5% of females). A significant proportion,, exhibited normal geometry (NG) (n = 59, 31.3% in males; n = 39, 31.4% in females). At stress test, significant differences between EH and NG athletes were found in peak power (317.1 ± 71.2W in NG vs. 342.2 ± 60.6W in EH, p = 0.014 in males and 225.1 ± 38.7W in NG vs. 247.1 ± 37W in EH, p = 0.003 in females), rest heart rate (66.1 ± 13 in NG vs. 58.6 ± 11.6 in EH, p = 0.001 in males and 68 ± 13.2 in NG vs. 59.2 ± 11.2 in EH, p = 0.001 in females) with similar ventricular extrasystoles (p = 0.363 in males and p = 0.492 in females). However, no significant differences in athletic achievements were registered. Conclusion: Our study demonstrates a relatively high prevalence of NG in endurance athletes, in addition to the expected EH. Athletes with NG perform worse in exercise-stress test and exhibit some less advantageous functional heart characteristics. However, the type of heart geometry is not associated with negative clinical findings. [ABSTRACT FROM AUTHOR]

Ski-orienteering, which combines cross-country skiing with orienteering, dates back to the late 1800s, with the first World Championships in 1975. While researchers have explored the physiological and biomechanical determinants of success in cross-country skiing and orienteering separately in detail, scientific knowledge concerning ski-orienteering remains limited. Based on the information that is presently available together with interviews with elite ski-orienteers, we explore here for the first time the historical development, physiological, biomechanical, and psychological demands, certain training strategies, and future prospects and challenges associated with this sport, including its potential to become an Olympic event. A demanding endurance sport (with racing times of 12–120 min), ski-orienteering requires both considerable aerobic and anaerobic capacity, as well as well-trained upper and lower body muscles. In addition, ski-orienteering demands advanced skiing technique on various types of terrain, with frequent changes between sub-techniques, on both wide and narrow tracks and with numerous turns on downhill terrain. Moreover, success in this sport requires accurate and rapid orienteering—the ability to navigate a complex network of ski tracks with numerous intersections/crossings in a manner designed to pass the multiple control points in the order indicated on the map as rapidly as possible, i.e., advanced spatial cognition and highly developed navigational skills. Thus, ski-orienteering requires training designed to improve both relevant physiological characteristics and orienteering skills, which should become the focus of future interdisciplinary research on this complex sport. [ABSTRACT FROM AUTHOR]

In cross-country skiing, ski poles play a crucial role in technique, propulsion, and overall performance. The kinematic parameters of ski poles can provide valuable information about the skier's technique, which is of great significance for coaches and athletes seeking to improve their skiing performance. In this work, a new smart ski pole is proposed, which combines the uniaxial load cell and the inertial measurement unit (IMU), aiming to provide comprehensive data measurement functions more easily and to play an auxiliary role in training. The ski pole can collect data directly related to skiing technical actions, such as the skier's pole force, pole angle, inertia data, etc., and the system's design, based on wireless transmission, makes the system more convenient to provide comprehensive data acquisition functions, in order to achieve a more simple and efficient use experience. In this experiment, the characteristic data obtained from the ski poles during the Double Poling of three skiers were extracted and the sample t-test was conducted. The results showed that the three skiers had significant differences in pole force, pole angle, and pole time. Spearman correlation analysis was used to analyze the sports data of the people with good performance, and the results showed that the pole force and speed (r = 0.71) and pole support angle (r = 0.76) were significantly correlated. In addition, this study adopted the commonly used inertial sensor data for action recognition, combined with the load cell data as the input of the ski technical action recognition algorithm, and the recognition accuracy of five kinds of cross-country skiing technical actions (Diagonal Stride (DS), Double Poling (DP), Kick Double Poling (KDP), Two-stroke Glide (G2) and Five-stroke Glide (G5)) reached 99.5%, and the accuracy was significantly improved compared with similar recognition systems. Therefore, the equipment is expected to be a valuable training tool for coaches and athletes, helping them to better understand and improve their ski maneuver technique. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the aerodynamic characteristics of Chinese Nordic combined athletes during the ski jump take-off process, comparing them with elite athletes from the 2009 Nordic World Ski Championships using computational fluid dynamics (CFD) methods. Methods: Using 3D model analysis and continuous relative phase analysis, CFD methods were utilized to assess the mechanical characteristics of athletes during the take-off phase. Results: The analysis revealed that Chinese athletes displayed a lower dominance of the knee joint during the take-off phase, leading to increased air drag. Conclusion: Reduced knee joint dominance and an excessive ankle angle at the initiation of the ski jump take-off contribute to higher air drag. The lean angle of the body and the ankle angle post-take-off significantly affect the resultant lift and drag forces. [ABSTRACT FROM AUTHOR]

Quantifying movement coordination in cross‐country (XC) skiing, specifically the technique with its elemental forms, is challenging. Particularly, this applies when trying to establish a bidirectional transfer between scientific theory and practical experts' knowledge as expressed, for example, in ski instruction curricula. The objective of this study was to translate 14 curricula‐informed distinct elements of the V2 ski‐skating technique (horizontal and vertical posture, lateral tilt, head position, upper body rotation, arm swing, shoulder abduction, elbow flexion, hand and leg distance, plantar flexion, ski set‐down, leg push‐off, and gliding phase) into plausible, valid and applicable measures to make the technique training process more quantifiable and scientifically grounded. Inertial measurement unit (IMU) data of 10 highly experienced XC skiers who demonstrated the technique elements by two extreme forms each (e.g., anterior versus posterior positioning for the horizontal posture) were recorded. Element‐specific principal component analyses (PCAs)—driven by the variance produced by the technique extremes—resulted in movement components that express quantifiable measures of the underlying technique elements. Ten measures were found to be sensitive in distinguishing between the inputted extreme variations using statistical parametric mapping (SPM), whereas for four elements the SPM did not detect differences (lateral tilt, plantar flexion, ski set‐down, and leg push‐off). Applicability of the established technique measures was determined based on quantifying individual techniques through them. The study introduces a novel approach to quantitatively assess V2 ski‐skating technique, which might help to enhance technique feedback and bridge the communication gap that often exists between practitioners and scientists. [ABSTRACT FROM AUTHOR]

The human spleen acts as a reservoir for red blood cells, which is mobilized into the systemic circulation during various conditions such as hypoxia and physical exertion. Cross-country (XC) skiers, renowned for their exceptional aerobic capacity, are regularly exposed to high-intensity exercise and local oxygen deficits. We investigated a putative dose-dependent relationship between splenic contraction and concomitant hemoglobin concentration ([Hb]) elevation across four exercise intensities in well-trained XC skiers. Fourteen male XC skiers voluntarily participated in a 2-day protocol, encompassing a serial apnea test and a V ˙ O2max test (day 1), followed by three submaximal exercise intensities on a roller skiing treadmill corresponding to 55, 70, and 85% of V ˙ O2max (day 2). Spleen volume was measured via ultrasonic imaging, and venous blood samples were used to determine [Hb] levels. Baseline spleen volume was similar (266(35) mL) for all conditions (NS). Notably, all conditions induced significant splenic contractions and transient [Hb] elevations. The V ˙ O2max test exhibited the most pronounced splenic contraction (35.8%, p < 0.001) and a [Hb] increase of 8.1%, while the 85% exercise intensity led to 27.1% contraction and the greatest [Hb] increase (8.3%, < 0.001) compared to baseline. The apnea test induced relatively smaller responses (splenic contraction: 20.4%, [Hb] = 3.3%, p < 0.001), akin to the response observed at the 70% exercise intensity (splenic contraction = 23%, [Hb] = 6.4%, p < 0,001) and 55% (splenic contraction = 20.0%, [Hb] = 4.8%, p < 0.001). This study shows a discernible dose-dependent relationship between splenic contraction and [Hb] increase with levels of exercise, effectively distinguishing between submaximal and maximal exercise intensity. [ABSTRACT FROM AUTHOR]

The aim of this study was to test and adapt a treadmill-developed method for determination of inner-cycle parameters and sub-technique in cross-country roller ski skating for a field application. The method is based on detecting initial and final ground contact of poles and skis during cyclic movements. Eleven athletes skied 4 laps of 2.5 km at low- and high-endurance intensities, using 2 types of skis with different rolling coefficients. Participants were equipped with inertial measurement units attached to their wrists and skis, and insoles with pressure sensors and poles with force measurements were used as reference systems. The method based on inertial measurement units was able to detect >97% of the temporal events detected with the reference system. The inner-cycle temporal parameters had a precision ranging from 49 to 59 milliseconds, corresponding to 3.9% to 13.7% of the corresponding inner-cycle duration. Overall, this study showed good reliability of using inertial measurement units on athletes' wrists and skis to determine temporal events, inner-cycle parameters, and the performed sub-techniques in cross-country roller ski skating in field conditions. [ABSTRACT FROM AUTHOR]

Background: Ice and snow sports, which are inherently high risk due to their physically demanding nature, pose significant challenges in terms of participant safety. These activities increase the likelihood of injuries, largely due to reduced bodily agility and responsiveness in cold, often unpredictable winter environments. The critical need for effective injury prevention in these sports is emphasized by the considerable impact injuries have on the health of participants, alongside the economic and social costs associated with medical and rehabilitative care. In the context of ice and snow sports environments, applying the E principles of injury prevention to evaluate intervention measures can guide the implementation of future sports safety and other health promotion intervention measures in this field. When well executed, this approach can substantially reduce both the frequency and severity of injuries, thereby significantly enhancing the safety and long-term viability of these challenging sports. Objective: The objective of this study was to rigorously assess and statistically substantiate the efficacy of diverse injury prevention strategies in ice and snow sports, aiming to bolster future safety measures with solid empirical evidence. Design: Systematic review and meta-analysis. Methods: The overarching aim of this research was to meticulously aggregate and scrutinize a broad spectrum of scholarly literature, focusing on the quantifiable efficacy of diverse, multicomponent intervention strategies in mitigating the incidence of injuries within the realm of ice and snow sports. This endeavour entailed an exhaustive extraction of data from esteemed academic databases, encompassing publications up to September 30, 2023. In pursuit of methodological excellence and analytical rigor, the study employed advanced bias assessment methodologies, notably the AMSTAR 2 and GRADE approaches, alongside sophisticated random-effects statistical modelling. This comprehensive approach was designed to ensure the utmost validity, reliability, and scholarly integrity of the study's findings. Results: Fifteen papers, including 9 randomized controlled trials, 3 case‒control studies, and 3 cohort studies with 26,123 participants and 4,382 injuries, were analysed. The findings showed a significant reduction in injury rates through various interventions: overall injury prevention (RR = 0.50, 95% CI 0.42–0.63), educational training (RR = 0.50, 95% CI 0.34–0.73), educational videos (RR = 0.53, 95% CI 0.34–0.81), protective equipment (RR = 0.64, 95% CI 0.46–0.87), and policy changes (RR = 0.28, 95% CI 0.16–0.49). Subgroup analysis revealed potential heterogeneity in compliance (p = 0.347). Compared to controls, multicomponent interventions effectively reduced injury rates. Conclusion: This systematic review and meta-analysis demonstrated that multicomponent interventions significantly prevent injuries in ice and snow sports. By applying the E principles of injury prevention and constructing a framework for practical injury prevention research in ice and snow sports, we can gradually shift towards a systemic paradigm for a better understanding of the development and prevention of sports injuries. Moreover, sports injury prevention is a complex and dynamic process. Therefore, high-quality experiments in different scenarios are needed in future research to provide more reliable evidence, offer valuable and relevant prevention information for practitioners and participants, and help formulate more effective preventive measures in practice. [ABSTRACT FROM AUTHOR]

The objective of this study was to test the vectorelectrocardiographic T-wave characteristics for their associations with oxygen consumption (VO2) and physical performance during a maximal cardiopulmonary exercise test (CPET) in highly trained cross-country skiers. Male highly trained cross-country skiers (n = 30) performed the maximal CPET on the bicycle ergospirometric "Oxycon Pro" system with simultaneous oxygen consumption (VO2) and electrocardiogram recording. The measurements were done at rest; the stage preceding anaerobic threshold (preAnT); peak load; and recovery. The anaerobic threshold was estimated by respiratory exchange ratio. Physical performance was estimated by maximal oxygen consumption (VO2max/kg). VECG characteristics were calculated using Kors transformation procedure. During the test, the magnitudes of T-vector, Tx and Ty components decreased until preAnT, then stayed relatively stable until peak load, and reversed during recovery. In univariate linear regression analysis, T-vector amplitude and Tx, Ty and Tz magnitudes were associated with VO2/kg during the test (p < 0.010). The baseline T-vector characteristics were not associated with physical performance. At the preAnT stage, Tx and T-vector amplitude were associated with VO2max/kg (RC 12.70, 95% CI 0.68–24.73, p = 0.039 and RC 10.64, 95% CI 1.62–19.67, p = 0.023, respectively). [ABSTRACT FROM AUTHOR]

Purpose: TRIMP and sRPE are both representative indicators of training load(TL), and the correlation between two has been widely demonstrated across various sports. The aim of this study was to investigate the reliability of sRPE-TRIMP correlation across different intensities/duration of training in cross-country skiing, and whether sRPE can serve as an validity supplement to TRIMP data in cases of lost heart rate data. Method: 10 athletes were used as the experimental objects. The intensity, duration and RPE of 273 different types of training sessions were collected, and statistical methods were used for data analysis. Results: 1. There was a significant correlation between sRPE and TRIMP (r = 0.68, p < 0.05), but the correlation differs among the LIT, MIT and HIT groups (r = 0.70, 0.46, r = 0.31, p < 0.05) 2. sRPE-TRIMP correlation among three different time duration in the LIT group (0-60 min, 60-120 min and 120-180 min), are all highly significant (r = 0.70, 0.67, 0.69, p < 0.05) and the LRsRPE-TRIMP of 3 duration have no significant differences (chow test, p > 0.05). 3. The difference in actual training duration between samples was the main reason for the difference in the application effect of sRPE, because the actual training duration ratio of LIT was 89.7 ± 16.4%; MIT, 98.5 ± 6.2%; and HIT, 94.4 ± 13.5%. Conclusion: 1. The linear relationship between sRPE and TRIMP (LRsRPETRIMP) is more significant in LIT compared to that in MIT and HIT. 2. Variations in the duration of LIT sessions do not affect the consistency of the relationship between sRPE and TRIMP. 3. Discrepancies between actual and planned training durations directly impact the significance of the LRsRPE-TRIMP. [ABSTRACT FROM AUTHOR]

Of the medals awarded during the Winter Olympics Games, most are awarded for sports involving cross-country (XC) skiing. The Double Poling (DP) technique, which is one of the sub-techniques used most frequently in XC skiing, has not yet been studied using simulations of the ski–snow contact mechanics. This work introduces a novel method for analysing how changes in the distribution of pressure on the sole of the foot (Plantar Pressure Distribution or PPD) during the DP motion affect the contact between the ski and the snow. The PPD recorded as the athlete performed DP, along with an Artificial Neural Network trained to predict the geometry of the ski (ski-camber profile), were used as input data for a solver based on the boundary element method, which models the interaction between the ski and the snow. This solver provides insights into how the area of contact and the distribution of pressure on the ski-snow interface change over time. The results reveal that variations in PPD, the type of ski, and the stiffness of the snow all have a significant impact on the contact between the ski and the snow. This information can be used to improve the Double Poling technique and make better choices of skis for specific snow conditions, ultimately leading to improved performance. [ABSTRACT FROM AUTHOR]

A variable pacing profile is common in different endurance events. In these races, several factors, such as changes in elevation or race dynamics, lead participants to perform numerous surges in intensity. These surges are so frequent that certain events, such as cross-country (XC) skiing, mountain biking (MTB), triathlon, and road cycling, have been termed "intermittent endurance events". The characteristics of these surges vary depending on the sport: MTB and triathlon require athletes to perform numerous short (<10 s) bouts; XC skiing require periods of short- and moderate-(30 s to 2 min) duration efforts, while road cycling is comprised of a mix of short-, moderate-, and long-duration (>2 min) bouts. These bouts occur at intensities above the maximal metabolic steady state (MMSS), with many efforts performed at intensities above the athletes' maximal aerobic power or speed (MAP/MAS) (i.e., supramaximal intensities). Given the factors that influence the requirement to perform surges in these events, athletes must be prepared to always engage in a race with a highly stochastic pace. The aim of this review is to characterize the variable pacing profile seen in endurance events and to discuss how the performance of multiple maximal and supramaximal surges in intensity can affect how athletes fatigue during a race and influence training strategies that can lead to success in these races. [ABSTRACT FROM AUTHOR]

Exercise slows or helps reverse the shrinkage of key cognitive brain regions such as the hippocampus, which is important for information processing, learning, reasoning and planning. For this reason, it is thought that regular exercise of individuals, especially during adolescence, which is considered one of the most important processes of development, can increase their performance in areas where cognitive activities are at the forefront. Cross-country skiing, one of the leading branches of winter sports, has a much more complex structure, unlike the branches that are widely preferred today (football, basketball, volleyball, etc.) and is a branch where many motor skills are exhibited at the same time For this reason, the effect of cross-country skiing, which is defined as more complex and difficult in terms of biomotor than other branches, on cognitive activities is a matter of curiosity. Therefore, the aim of the research is; to examine the cognitive effects of cross-country skiing exercise. The study involved 54 (26 male, 28 female) adolescents who had no prior experience in any licensed sports. The average age of the participants was determined as 12.61 ± 1.32. The participants were divided in experimental and control groups. Reaction performances were determined using the ÇAĞIN Hand and Foot Reaction Tests, selective attention performances were evaluated using the Flanker Test and academic achievement was determined using the e-Okul system. Two-way ANOVA revealed significant group × time interactions for hand and foot simple, selective, discriminative reaction time, selective attention and academic achievement (p < 0.05) due to improved values at post-test for the experimental group but not for the control groups. No significant group × time interactions were observed for correct reaction rate for all reaction parameters (p > 0.05). The study concludes that the cross-country skiing exercise, which was applied to adolescents for eight weeks, had a positive impact on the parameters of reaction, selective attention and academic achievement. Therefore, parents are suggested to encourage their children to exercise and engage in sports practices like cross-country skiing to improve cognitive and academic performance during adolescence. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate non-specific and ski-specific performance development in male (M) and female (F) peri-pubertal cross-country skiers and to evaluate their relationship with cross-country skiing (XCS) performance and biological maturation within each age category and sex. Methods: Twenty-one and 19 athletes under 14 and 16 years old, respectively (U14 and U16), were tested for biological maturation; non-specific speed, agility, strength, endurance, and balance; ski-specific speed, agility, and endurance. XCS index was considered as average percentage time-gap from the winner in four official races. Sex and age-category effects were verified and a model predicting XCS index was extrapolated for each group. Results: Performance capacities raised across age categories (p < 0.05) except for non-specific speed, agility, balance, and relative arm strength (p > 0.05). F showed advanced biological maturation and greater balance than M (p < 0.05), while M showed higher performance capacities (p < 0.05). XCS index was not related to biological maturation within each group (p > 0.05); its variance was explained by non-specific speed and ski-specific upper-body endurance in M-U14 (p = 0.014), lower-limb strength and ski-specific agility in M-U16 and F-U14 (both p = 0.001), ski-specific upper-body endurance in F-U16 (p = 0.002). Conclusion: Ski-specific performance capacities still develop during peri-puberty, with peri-pubertal M overperforming with respect to F of comparable performance level. XCS index was not influenced by biological maturation withing each age category, but it was rather explained by specific parameters that commonly undergo the "adolescent spurts", accordingly to the average biological maturation level of M and F athletes of each age category. [ABSTRACT FROM AUTHOR]

Purpose: In order to better understand the imaging of severe trauma in sport, this study describes the imaging modalities utilized to image athletes who experienced severe traumatic injuries at the Beijing Winter Olympic Games 2022, the distribution of these modalities in relation to the sporting facilities, and the types of injuries imaged in each sport. Methods: This is a retrospective analysis with descriptive tables and figures, performed on a single population (athletes of the Beijing Winter Olympic Games 2022). Results: Of the 2871 athletes in the Beijing Winter Olympic Games, there were 40 athletes with severe injuries who underwent medical imaging. MRI was used more often than Radiography or CT. Athletes at venues without MRI on site had to be transferred to adjacent hospitals for care. Alpine and Freestyle skiing athletes experienced the majority of severe traumatic injuries at this Olympic Games, and the majority of injuries were to the lower limb. Conclusions: Access to medical imaging for severely injured athletes is a critical consideration in the organization of any sporting event. MRI in particular is highly utilized in this population. [ABSTRACT FROM AUTHOR]

Novel sensor solutions for sleep monitoring at home could alleviate bottlenecks in sleep medical care as well as enable selective or continuous observation over long periods of time and contribute to new insights in sleep medicine and beyond. Since especially in the latter case the sensor data differ strongly in signal, number and extent of sensors from the classical polysomnography (PSG) sensor technology, an automatic evaluation is essential for the application. However, the training of an automatic algorithm is complicated by the fact that the development phase of the new sensor technology, extensive comparative measurements with standardized reference systems, is often not possible and therefore only small datasets are available. In order to circumvent high system-specific training data requirements, we employ pre-training on large datasets with finetuning on small datasets of new sensor technology to enable automatic sleep phase detection for small test series. By pre-training on publicly available PSG datasets and finetuning on 12 nights recorded with new sensor technology based on a pre-gelled electrode grid to capture electroencephalography (EEG), electrooculography (EOG) and electromyography (EMG), an F 1 score across all sleep phases of 0.81 is achieved (wake 0.84, N1 0.62, N2 0.81, N3 0.87, REM 0.88), using only EEG and EOG. The analysis additionally considers the spatial distribution of the channels and an approach to approximate classical electrode positions based on specific linear combinations of the new sensor grid channels. [ABSTRACT FROM AUTHOR]

The old adage has two people out hiking who run into a bear. One starts running while the other asks 'why are you running? You can't outrun a bear'. To which the other responds, 'I don't have to outrun the bear. I only have to outrun you'. Hiking/trekking is not typically a competitive endeavor characterized by contests but, like many endeavors/pursuits/activities, competition can be injected into it; thereby sportifying it. Swimming is a sport (under certain conditions). At the same time, it is also a recreational activity and a form of physical exercise; likewise angling/fishing, climbing, cross-country skiing, mountain biking, kayaking, rowing, surfing, et al. The categorization of many activities under the umbrella of sport has it uses to understand the wider concept of what is sport, but the purpose of why one engages in 'physical activities taking place in a natural environment' can sometimes be more important than whether some activities might or might not qualify to be classified under the rubric of sports at all. Indicators exist to show whether participants are actually engaged toward—driven in a way, even—to further their skills in their focused activity (if it is a focused activity at all!––i.e. a 'serious leisure' pursuit or just a recreational hobby). From this perspective (of looking at sport-like and sporting activities in other than Olympic-style forms) this paper explores the differentiations between sport (including nature sport) contests, nature challenge activities (NCAs) and outdoor recreation from the standpoint of the most relevant factors that distinguish them: rules, skill development, purpose for engaging in them. This paper also makes the case that differentiating participants in the above activities by purpose (as either nature challenge recreationalists or nature sport devotees) has utility; to better help research into people's engagement in physical activities in natural environments. [ABSTRACT FROM AUTHOR]

The article explores the realm of sport from an aesthetic point of view. Making a sustained physical effort regularly may have a positive impact on our psycho-somatic being and can sustain our health and well-being. But what exactly is this aesthetic component in sport and is it possible that this aesthetic component prevails over other components when it comes to individual sport? Moreover, is this aesthetic component complex in its nature or can it be reduced to some unique underlying principle? These are the main philosophical questions that this article strives to answer by exploring the aesthetic experience proper to sport. Abandoning the much-acclaimed perspective of the spectator (which consists of seeing sport as a spectacle or drama to be enjoyed and judged from a distance) entails that the aesthetic in sport has to be studied from the perspective of an active and individual participator. Ultimately, the article makes the claim that sport is both a way of interacting with one's environment and a way of aesthetic self-fulfilment which allows the individual to lead a meaningful life rich in aesthetic experiences and events. [ABSTRACT FROM AUTHOR]

Background: Troponin I and T are biomarkers to diagnose myocardial infarction and damage. Studies indicate that strenuous physical activity can cause transient increases in these troponin levels, typically considered physiological. However, current data show differences in the exercise-induced increase in troponin I and T in elite athletes. Method: This prospective clinical study aimed to determine troponin I and T levels in 36 top cross-country skiers of the German national team (18 male, 18 female) after a standardized competition load over two days. All study participants underwent a comprehensive sports medical and cardiological evaluation, including ECG and echocardiography. A multivariable regression analysis was utilized to identify possible predictors of increased troponin I levels. Results: Only three male athletes (8.1%) showed an isolated increase in Troponin I (Ø 112.49 ng/L, cut off < 45.2 ng/L), while no increase in troponin T in the study population was detected. Conclusions: The analysis suggested several potential predictors for increased troponin I levels, such as height, weight, weekly training hours, and indications of an enlarged sports heart, though none achieved statistical significance. Knowing the different exercise-induced detectability of the various troponins in the clinical setting is essential. [ABSTRACT FROM AUTHOR]

Challenges facing mother-athletes (MAs) have aroused research and media attention in recent years, with an increasing number of sportswomen attempting to successfully combine pregnancy and motherhood with an elite athletic career. The aims of this study were to explore how MA-specific challenges manifest in elite cross-country skiing in Scandinavia and to better understand how female athletes balance their priorities as they initiate, maintain, and/or discontinue their role as a MA. Qualitative data were collected through semistructured interviews with 13 female cross-country skiers from Norway and Sweden. Thematic analyses revealed four MA-specific challenges facing the athletes: (a) Biological clock versus peak performance, (b) Maintaining fitness versus training safely, (c) Receiving support versus facing deselection, and (d) Balancing competing MA demands. Many of the athletes felt pressured into prioritizing either motherhood or athletic excellence, particularly in their early to mid-30s when the window of opportunity for building a family was considered limited. Further, maintaining fitness and training safely during pregnancy were perceived as a challenge, as was balancing the MA role after childbirth. In many cases, athletes felt uncertain about whether they would receive support from their team or federation. Moreover, there were expectations of incompatibility surrounding the MA role. More research and educational efforts to promote MA-specific knowledge, as well as developing structured processes and providing policies to support female athletes, are identified as vital future steps. These measures may prolong athletic careers and enhance well-being for elite female athletes. [ABSTRACT FROM AUTHOR]

Tatra National Park (TNP) is one of the most popular national parks in Poland. The purpose of this study was to examine changes in the number of tourists visiting the Park each year from 1993 with a special focus on the COVID-19 period. The main part of this study focused on tourist traffic data for the period from 1993 to 2023. Daily, monthly, and annual data were examined. The source of most of the data is park entry ticket sales. The largest number of tourists entering TNP in the period of 1993–2022 was recorded in 2021 at 4,788,788. Tourist traffic in TNP is concentrated on so-called long weekends in May and June. An examination of data from 2010, 2015, and 2021 shows that tourist volumes on the long weekend of 1–3 May be up to 40 times larger than those on other weekends in May. On the other hand, long weekends in June can attract eight times more tourists relative to the average other weekends in June. The number of tourists engaging in hiking, climbing, spelunking, and ski touring declined during the COVID-19 pandemic in 2020. However, the number of ski tourers in TNP in 2021 was about four times larger than the total between 2015–2022. Data on traffic patterns are key in designing, implementing, and measuring the efficiency of solutions for sustainable management for both the peak usage periods and future patterns in tourism. [ABSTRACT FROM AUTHOR]

A total of nineteen elite youth cross-country skiers (16 ± 2 years) were divided into three groups: a low-load group (LL, n = 6) performing 15–20 repetitions per exercise, a high-load group (HL, n = 9) executing 6–12 repetitions, and a control group (CON, n = 4) exclusively engaging in endurance training. Testing included 1RM in upper-body exercises, VO2max running tests, and double-poling (DP) ergometer exhaustion and sprint tests to determine peak oxygen uptake (VO2peak-DP) and peak power (PP). The results indicated that HL and LL showed significant increases in VO2peak-DP, both in absolute values (d = −1.2 and −1.2, p < 0.05) and when normalized to body mass (d = 0.93 and 1.3, p < 0.05). Although there were no group*time effects for VO2peak-DP, PP during DP tests to exhaustion increased in both HL (d = −1.6, p < 0.05) and LL (d = 1.4, p < 0.05) compared to CON. Standardized to body mass, only HL showed significant improvements in PP during the sprint test (d = 1.7, p < 0.05). During the sprint test, both absolute and body-mass-normalized peak power increased only in the high-load group (d = −1.0 and 0.93, p < 0.05). In conclusion, high-load resistance training resulted in the greatest improvements in strength, DP performance, and VO2peak-DP, indicating a dose–response relationship to the load magnitude of resistance training. [ABSTRACT FROM AUTHOR]

Purpose: To compare self-selected speeds and corresponding physiological responses and perceived training stress between 1 long session versus 2 shorter sessions of low-intensity training (LIT) in 1 day among cross-country skiers. Methods: Thirteen national-level skiers performed 2 different LIT types during classical roller-skiing matched for the same distance in a counterbalanced order. The training consisted of either 1 long (approximately 3 h) session (1LIT) or 2 shorter (approximately 1.5 h each) sessions (2LIT) with 7 hours of recovery in between. Speed, heart rate, rating of perceived exertion, and blood lactate concentrations were measured, and perceived training stress (1–10) was assessed after sessions. Results: 2LIT was performed at mean (SD) 1.9% (2.0%) higher speeds versus 1LIT (P ≤.01). Higher speeds were also found in the second versus first session of 2LIT and the second versus first part of 1LIT (1.9% [3.2%] and 3.2% [3.6%], respectively, both P ≤.01). There were no significant differences between LIT types in heart rate, although rating of perceived exertion increased in the second versus first part of 1LIT (0.9 [0.8] point, P ≤.01). Blood lactate concentration was reduced in the second versus first session/part of both LIT types (approximately 0.16 [0.20] mmol·L−1, P ≤.05). There were no differences in perceived training stress between LIT types 7 and 23 hours after training, although higher perceived muscular exertion (2.0 [1.1] points, P ≤.01) was found directly after 1LIT. Conclusions: Compared with a distance-matched long session, skiers perform 2LIT at slightly higher self-selected speeds with the same physiological responses elicited, although minor differences in perceived training stress were observed. [ABSTRACT FROM AUTHOR]

Purpose: To compare sex differences in physiological determinants of skiing performance in elite adolescent, junior, and senior cross-country skiers matched for within-age-group performance level. Methods: Eight male and 12 female adolescent (15 [1] y), 8 male and 7 female junior (18 [1] y), and 7 male and 6 female senior (28 [5] y) skiers participated. Gross efficiency was calculated during submaximal uphill treadmill roller skiing (approximately 84% of peak oxygen uptake [ V ˙ O 2 peak ]) using the G2 ski-skating technique. Distance covered, V ˙ O 2 peak , and maximal accumulated oxygen deficit were established from a 3-minute time-trial. Fifteen-second maximal skiing power was calculated from an incremental treadmill speed test. Finally, upper- and lower-body maximal strength tests were conducted. Results: The 3-minute time-trial distance and maximal skiing power were, respectively, 23% and 15% (adolescent), 24% and 19% (junior), and 17% and 14% (senior) greater for men than women (all groups, P ≤.01, effect size [ES] = 2.43–4.18; very large). V ˙ O 2 peak relative to body mass was 17% (adolescent, P =.002, ES = 1.66, large), 21% (junior, P <.01, ES = 2.60, very large), and 19% (senior, P <.01, ES = 2.35, very large) greater for men than women. The within-age-group sex differences in gross efficiency, relative accumulated oxygen deficit, and strength were not significant, with the exception of greater lower-body strength in male than female juniors (P =.01, ES = 1.26, large). Conclusion: The within-age-group sex difference in skiing performance is of similar magnitude for adolescent, junior, and senior skiers. This difference can likely be attributed to the large to very large sex difference in V ˙ O 2 peak within all age-groups. [ABSTRACT FROM AUTHOR]

This study compared performance strategies and sub-technique selection in cross-country skate skiing sprint races, specifically individual time-trial (ITT) and head-to-head (H2H) formats. Fourteen male cross-country skiers from the Chinese national team participated in the FIS-sanctioned sprint race day. GNSS and heart rate sensors recorded positioning, skiing speeds, heart rate, sub-technique usage, and skiing kinematics. Statistical parametric mapping (SPM) was used to determine the course positions (clusters) where instantaneous skiing speed was significantly associated with section time. One-way analyses of variance were used to examine differences between the ITT and H2H. H2H race speeds were 2.4 ± 0.2% faster than the ITT race (p < 0.05).Variations in sub-technique and skiing kinematics were observed between race formats, indicating different strategies and tactics employed by athletes. SPM identified specific clusters (primarily uphill) where the fastest athlete gained significant time over the slowest. The greatest time gains were associated with higher G3 sub-technique usage and longer G3 cycle length on steep uphill terrain (9–13% gradients). Integrating SPM analyses and sub-technique assessments can help optimise performance and tactics in sprint races. This study enhances our understanding of cross-country skiing dynamics and performance variations among elite competitors. [ABSTRACT FROM AUTHOR]

Roller skiing is one primary form of training method as it is an off-snow equivalent to cross-country (XC) skiing during the dry land preseason training, but the results could only be applied to on-snow skiing with appropriate caution. The aim of this present study was to investigate the similarities and differences in roller skiing and on-snow skiing with the diagonal stride (DS) technique. Six youth (age: 14.3 ± 2.9 years) skiers participated in this study. Two high-definition video camcorders and FastMove 3D Motion 2.23.3.3101 were used to obtain the three-dimensional kinematic data. The cycle characteristics and joint angle ROM of the DS technique while skiing on different surfaces were similar. Almost all joint angle–time curves that were obtained from roller skiing showed a moderate-to-high degree of similarity to the angle–time curves obtained from on-snow skiing, except the hip adduction–abduction angle. The differences between roller skiing and on-snow skiing were mainly found in the body and calf anteversion angles, and the joint angles at critical instants. DS roller skiing can simulate DS on-snow skiing to a large extent in youth athletes. The hip movement, knee flexion, and calf anteversion at ski/roller ski touchdown and take-off, pole inclination at pole touchdown, body anteversion angle, and trunk anteversion angle at pole touchdown were the points that required caution when transferring preseason practice roller skiing to on-snow skiing. [ABSTRACT FROM AUTHOR]

Purpose: To investigate performance, physiological, and perceptual responses of an entire sprint cross-country skiing competition in the skating style. Methods: Eighteen national-level male junior skiers participated in a simulated competition comprising an individual time trial (TT), followed by three heats (quarterfinals [QF], semifinals [SF], and final [F]). Participants' heart rate (HR) was continuously monitored while perceived readiness (RED, 1–10), rating of perceived exertion (RPE, 6–20), and blood lactate [La-] were assessed at standardized time points. Results: The total duration and distance covered were 03:30 ± 00:06 h and 25.2 ± 2.9 km, respectively. The participants spent 02:19 ± 00:27 h > 60% of their maximal HR (HRmax) and 00:16 ± 00:04 h > 85% of HRmax. Average HR decreased from TT to F (89.3 ± 2.0% vs. 86.9 ± 3.0% of HRmax, P < 0.01). [La-] levels were highest before (4.6 ± 2.0 vs. 2.9 ± 1.2, 3.2 ± 2.0 and 2.5 ± 1.3 mmol·L−1, all P < 0.01) and after (10.8 ± 1.4 vs. 9.8 ± 1.6, 9.1 ± 1.8 and 8.7 ± 1.7 mmol·L−1, all P < 0.05) F compared to TT, QF, and SF, respectively. RED was lowest before F compared to TT, QF, and SF (6.6 ± 1.4 vs. 7.9 ± 1.1, 7.6 ± 1.1, and 7.4 ± 1.4, respectively, all P < 0.05) while RPE was highest after TT compared to QF, SF, and F (17.8 ± 0.9 vs. 15.1 ± 2.0, 16.5 ± 1.2 and 16.6 ± 1.8, respectively, all P < 0.01). The six best-performing skiers demonstrated higher RED before F (7.2 ± 0.9 vs. 5.3 ± 1.2, P < 0.05) and higher [La-] after F (11.2 ± 0.2 vs. 10.2 ± 0.3, mmol·L−1, P < 0.05) than lower-performing competitors. Conclusion: This study provides novel insights into physiological demands of an entire sprint cross-country skiing competition, which involves repeated 3-min high-intensity efforts interspersed with > 2 h (25 km) of low- to moderate-intensity exercise. [ABSTRACT FROM AUTHOR]

This cross-sectional study aimed to compare clinical oral conditions as well as the self-reported oral health status of biathletes and cross-country skiers (A) to age- and gender-matched non-athletic controls (C). Thirty-one A and 68 C were examined in 2020 regarding caries experience (DMF-T), partially erupted wisdom teeth, non-carious tooth wear (erosion), dental plaque biofilm, gingival inflammation, periodontal screening (PSI), salivary active matrix-metalloproteinase-8 (aMMP-8) test and screening for temporomandibular disorders (TMD). Questionnaires recorded periodontal symptoms, TMD symptoms and oral health behaviour. Group A had a lower prevalence of carious teeth and positive aMMP-8 tests, but more of them had severe gingivitis and signs of periodontitis. Both groups reported similar oral health behaviour. Only in group C, associations between aMMP-8 and periodontal findings as well as clinical findings and self-reported symptoms of TMD were identified. Group A showed a high prevalence of oral inflammation and seemed to be less aware of oral symptoms. Clinical examination seems to be necessary for periodontal/TMD screening of athletes. [ABSTRACT FROM AUTHOR]

Purpose: Maximal oxygen uptake (V̇O2max) increases during adolescence parallel to the increase in fat‐free mass (FFM). How much endurance training adds to this effect is still controversial. Our aim was to investigate if inclusion of high‐intensity training (HIT) during an 8‐week training period was superior to low‐intensity strength and coordination training in 12‐year‐old youth athletes concerning the effect on V̇O2max. Methods: Thirty‐five cross‐country skiers were randomized into a HIT group (ET) and a strength and coordination group (SC), while 29 less active peers served as controls for growth and maturation (C). Anthropometrics and V̇O2max were assessed before and after the training period, and level of physical activity and training were monitored with accelerometers, training logs and a questionnaire. Results: The number of weekly training sessions were higher for ET (4.6 ± 1.2) and SC (4.1 ± 1.0) compared with C (1.8 ± 2.0) (p < 0.01), with only ET conducting HIT sessions (1.9 ± 0.2 per week). C spent more time sedentary and less time in moderate and vigorous activity compared with ET (p < 0.05). All groups had a similar %‐change pre‐post in absolute V̇O2max (mL min−1) of 6% ± 6% for ET (p < 0.01), 5% ± 7 for SC (p = 0.14), and 5% ± 13% for C (p = 0.03), with no significant differences between groups. V̇O2max relative to FFM did not change significantly for any groups. Conclusion: The change in V̇O2max paralleled the change in FFM for all groups, questioning the effect of HIT on V̇O2max over an 8‐week period in youth athletes. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the relationship between respiratory functions and body compositions of elite athletes in alpine disciplines and cross-country skiing through their comparison. The study included 32 male athletes (age: 18.3±2 year, height: 172.1±6.05 cm, body weight: 65.73±10.79 kg, and body mass index (BMI): 22.91±2.80 kg/m2) within the scope of alpine disciplines and cross-country skiing. The heights of the athletes were measured with a stadiometer (Holtain, UK) with an accuracy of ±1mm. The weights of the athletes and BMI values were measured using a Tanita brand (BC, 418 Tanita, Japan) body composition analyzer with a precision of 100 grams. The respiratory function and respiratory muscle strength of the athletes were evaluated using a digital spirometer (Pony FX Cosmed, Italy). Pearson's correlation analysis was used to determine the relationships between respiratory functions and anthropometric structures of the groups. The results indicated that cross-country skiing athletes had higher averages in FVC, FEV1, FEV1/FVC, PEF, MIP, MVV, and MEP parameters compared to alpine discipline athletes, with only the MIP value being higher in alpine discipline athletes. The results revealed positive correlations between age and FVC (0.563), FEV1 (0.521), PEF (0.679), and MVV (0.511) in cross-country skiing athletes. Negative correlations were found between body weight and FEV1/FVC (r=0.578), FEV1/FVC (r=0.545), height and MVV (r=0.541), and body mass index and FEV1/FVC (r=0.541), FEV1/FVC (r=0.676) in cross-country skiing and alpine discipline athletes, respectively (p<0.05). The study revealed no significant relationship in other variables (p>0.05). In order to achieve maximum performance, it is very important to identify and keep under control the factors affecting respiratory functions. The current study demonstrated that the characteristics of the sport have an impact on physiological changes in the respiratory system and also affect body compositions and respiratory functions. [ABSTRACT FROM AUTHOR]

Sports participation and the risk of osteoarthritis (OA) have been a concern for decades. Few research efforts have been dedicated to clarify this issue for females, although they are considered at greater risk of developing OA than males. In contrast, several reviews have established an association between sports participation and OA for males. The aim of the systematic review was to assess the association between OA and participation in popular sports for females. PubMed, Embase, and Google Scholar were searched and yielded 578 articles. Nine eligible studies were included and covered ballet (age range: 19–54 years), running or tennis (age range: 40–65 years), Olympic sports (age range: not specified), volleyball (age range: 16.0 ± 0.8 to 46.8 ± 5.1 years), and cross-country skiing (age range: 15 to ≥60 years). For females, participating in sports at an elite level was associated with a higher risk of OA and an increased need for surgical treatment. At non-elite level, it was associated with a higher risk of OA, but it did not materialize to an increased risk for surgical treatment. Few studies compared females and males, and these studies suggested that sex did not affect the risk of developing OA from participating in sports. Nevertheless, to isolate the precise effect of sports participation on the development of OA remains difficult as injuries are common among athletes and are independently associated with an increased risk of OA. [ABSTRACT FROM AUTHOR]

As countries transition from external assistance while pursuing ambitious plans to achieve universal health coverage (UHC), there is increasing need to facilitate knowledge sharing and learning among them. Country-led and country-owned knowledge management is foundational to sustainable, more equitable external assistance for health and is a useful complement to more conventional capacity-building modalities provided under external assistance. In the context of external assistance, few initiatives use country-to-country sharing of practitioner experiences, and link learning to receiving guidance on how to adapt, apply and sustain policy changes. Dominant knowledge exchange processes are didactic, implicitly assuming static technical needs, and that practitioners in low- and middle-income countries require problem-specific, time-bound solutions. In reality, the technical challenges of achieving UHC and the group of policymakers involved continuously evolve. This paper aims to explore factors which are supportive of experience-based knowledge exchange between practitioners from diverse settings, drawing from the experience of the Joint Learning Network (JLN) for UHC—a global network of practitioners and policymakers sharing experiences about common challenges to develop and implement knowledge products supporting reforms for UHC—as an illustration of a peer-to-peer learning approach. This paper considers: (1) an analysis of JLN monitoring and evaluation data between 2020 and 2023 and (2) a qualitative inquiry to explore policymakers' engagement with the JLN using semi-structured interviews (n = 14) with stakeholders from 10 countries. The JLN's experience provides insights to factors that contribute to successful peer-to-peer learning approaches. JLN relies on engaging a network of practitioners with diverse experiences who organically identify and pursue a common learning agenda. Meaningful peer-to-peer learning requires dynamic, structured interactions, and alignment with windows of opportunity for implementation that enable rapid response to emerging and timely issues. Peer-to-peer learning can facilitate in-country knowledge sharing, learning and catalyse action at the institutional and health system levels. [ABSTRACT FROM AUTHOR]

Flow field measurements around cross-country skiers (xc skiers) are lacking in the literature to date. The aim was therefore to investigate the possibility of using particle tracking velocimetry for visualization and measurement of the flow field around xc skiers roller skiing on a treadmill in a wind tunnel. The airflow was seeded with neutrally buoyant helium-filled soap bubbles as tracer particles, following the flow without affecting it. As illumination, two different approaches were tested: first, a laser in the cameras’ line of sight (sagittal plane), then an LED unit directed vertically in a narrow slice, clearly limiting the depth of the measurement volume in the cameras’ line of sight. The flow field was studied at various speeds (3-7 m/s) around a single skier as well as around two skiers in line with the streaming airflow. It was found that the experimental approach has the potential to provide detailed insights, both qualitatively and quantitatively, into the flow field dynamics. The main challenges regarding setup, illumination, seeding, and cameras were identified, and possible improvements to streamline the experimental methodology were discussed.

Purpose: To investigate whether skiers with a fast-start pacing pattern increase time-trial performance by use of a more even pacing strategy. Methods: Thirty-four skiers (∼17 y, 16 male) performed an individual 7.5 (3 × 2.5) km free-technique race on snow with a self-selected pacing strategy (day 1). Based on the starting pace the first ∼2 minutes (lap-1 first 600-m segment pace·7.5 km pace−1), subjects were ranked into 2 groups: an intervention group with the fastest start pace (INT, n = 17) and a control group with a more conservative pace (CON, n = 17). On day 2, INT were instructed to reduce their start pace based on their average laps-1-to-3 segment pace from day 1, while CON were instructed to maintain their day 1 strategy. Results: INT increased their time-trial performance more than CON from day 1 to day 2 (effect size; ES = 0.87, P <.05). From day 1 to day 2, INT slowed their start pace (mean ± 95% confidence interval; 7.7% ± 2.0%, ES = 2.00), with lowered heart rate (HR) (83% ± 2% to 81% ± 2% of HRmax) and 1 to 10 ratings of perceived exertion (5 ± 1 to 4 ± 1), but finished with a faster overall 7.5-km time (−1.9% ± 0.9%, ES = 0.99) (all P <.05). For CON, no change was found for starting pace (−0.7% ± 2.0%, P =.47), overall 7.5-km time (−0.2% ± 1.4%, ES = 0.02, P =.81), ratings of perceived exertion, or HR between days. No differences were found for end-ratings of perceived exertion (9 ± 1) or average HR between day 1 and 2 for either group. Conclusion: Skiers with a pronounced fast-start pattern benefit by using a more even pacing strategy to optimize time-trial distance skiing performance. [ABSTRACT FROM AUTHOR]

In cross-country skiing, ski poles play a crucial role in technique, propulsion, and overall performance. The kinematic parameters of ski poles can provide valuable information about the skier’s technique, which is of great significance for coaches and athletes seeking to improve their skiing performance. In this work, a new smart ski pole is proposed, which combines the uniaxial load cell and the inertial measurement unit (IMU), aiming to provide comprehensive data measurement functions more easily and to play an auxiliary role in training. The ski pole can collect data directly related to skiing technical actions, such as the skier’s pole force, pole angle, inertia data, etc., and the system’s design, based on wireless transmission, makes the system more convenient to provide comprehensive data acquisition functions, in order to achieve a more simple and efficient use experience. In this experiment, the characteristic data obtained from the ski poles during the Double Poling of three skiers were extracted and the sample t-test was conducted. The results showed that the three skiers had significant differences in pole force, pole angle, and pole time. Spearman correlation analysis was used to analyze the sports data of the people with good performance, and the results showed that the pole force and speed (r = 0.71) and pole support angle (r = 0.76) were significantly correlated. In addition, this study adopted the commonly used inertial sensor data for action recognition, combined with the load cell data as the input of the ski technical action recognition algorithm, and the recognition accuracy of five kinds of cross-country skiing technical actions (Diagonal Stride (DS), Double Poling (DP), Kick Double Poling (KDP), Two-stroke Glide (G2) and Five-stroke Glide (G5)) reached 99.5%, and the accuracy was significantly improved compared with similar recognition systems. Therefore, the equipment is expected to be a valuable training tool for coaches and athletes, helping them to better understand and improve their ski maneuver technique.

Purpose: Accumulated time at a high percentage of peak oxygen consumption (VO2peak) is important for improving performance in endurance athletes. The present study compared the acute physiological and perceived effects of performing high-intensity intervals with roller ski double poling containing work intervals with (1) fast start followed by decreasing speed (DEC), (2) systematic variation in exercise intensity (VAR), and (3) constant speed (CON). Methods: Ten well-trained cross-country skiers (double-poling VO2peak 69.6 [3.5] mL·min−1·kg−1) performed speed- and duration-matched DEC, VAR, and CON on 3 separate days in a randomized order (5 × 5-min work intervals and 3-min recovery). Results: DEC and VAR led to longer time ≥90% VO2peak (P =.016 and P =.033, respectively) and higher mean %VO2peak (P =.036, and P =.009) compared with CON, with no differences between DEC and VAR (P =.930 and P =.759, respectively). VAR, DEC, and CON led to similar time ≥90% of peak heart rate (HRpeak), mean HR, mean breathing frequency, mean ventilation, and mean blood lactate concentration ([La−]). Furthermore, no differences between sessions were observed for perceptual responses, such as mean rate of perceived exertion, session rate of perceived exertion or pain score (all Ps >.147). Conclusions: In well-trained XC skiers, DEC and VAR led to longer time ≥90% of VO2peak compared with CON, without excessive perceptual effort, indicating that these intervals can be a good alternative for accumulating more time at a high percentage of VO2peak and at the same time mimicking the pronounced variation in exercise intensities experienced during XC-skiing competitions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: To quantify peak age and relative performance progression toward peak age in cross-country skiing according to event type, sex, and athlete performance level. Methods: International Ski Federation (FIS) points (performance expressed relative to the best athlete) of athletes born between 1981 and 1991, competing in junior world championships or finishing top 30 in world championships or Olympics, were downloaded from the FIS website. Individual performance trends were derived by fitting a quadratic curve to each athletes FIS point and age data. Results: Peak age was 26.2 (2.3) years in distance and 26.0 (1.7) years in sprint events. The sex difference in peak age in sprint events was ∼0.8 years (small, P =.001), while there was no significant sex difference in peak age in distance events (P =.668). Top performers displayed higher peak ages than other athletes in distance (mean difference, ±95% confidence limits = 1.6 y, ±0.6 y, moderate, P <.001) and sprint events (1.0, ±0.6 y, moderate, P <.001). FIS point improvement over the 5 years preceding peak age did not differ between event types (P =.325), while men improved more than women in both events (8.8, ±5.4%, small, P =.002 and 7.5, ±6.4%, small, P =.002). Performance level had a large effect on improvement in FIS points in both events (P <.001). Conclusion: This study provides novel insights on peak age and relative performance progression among world-class cross-country skiers and can assist practitioners, sport institutions, and federations with goal setting and evaluating strategies for achieving success. [ABSTRACT FROM AUTHOR]