IMU Data-Driven and PCA-Based Approach to Establish Quantifiable and Practically Applicable Measures for V2 Technique Elements in Cross-Country Skiing.

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.

Gender Differences in Core Muscle Morphology of Elite Alpine Skiers: Insights from Ultrasonography.

This study investigates gender differences in core muscle morphology among elite alpine skiers using ultrasonography, highlighting significant disparities that could influence training and injury prevention strategies. METHODS: A cross-sectional design was employed, examining ultrasound imaging (USI) in 22 elite skiers (11 male, 11 female) to assess the thickness of the external oblique (EO), internal oblique (IO), transversus abdominis (TrAb), and rectus abdominis (RA) muscles. RESULTS: Significant differences were noted, with male skiers displaying greater muscle thickness, particularly in the right IO and RA and left IO, EO, TrAb, and RA. CONCLUSIONS: These findings suggest that male and female skiers may require different training approaches to optimize performance and reduce injury risks. This research contributes to a deeper understanding of the physical demands on elite skiers and underscores the need for gender-specific training regimens to enhance athletic outcomes and prevent injuries.

Epidemiology of injuries among snowboarding athletes in the talent transfer program: A prospective cohort study of 39,880 athlete-exposures.

BACKGROUND: Talent transfer (TT) program is an appropriate approach to address the talent gap evident in specific sports activities, while little is known about the injury characteristics of snowboarding athletes involved in the TT program. OBJECTIVE: To determine the epidemiology of injuries among snowboarders involved in the TT program. METHODS: A total of 244 athletes who were not previously engaged in winter sports were selected for training in snowboarding that lasted for 109 days. The injuries and at-risk exposures (A-Es) data were recorded by physicians. Injury rates (IRs), incidence rate ratios (IRRs), and injury proportion ratios (IPRs) were calculated and compared by sex and age groups. RESULTS: The overall and time loss (TL) IR were 32.4/1000 A-Es and 12.2/1000 A-Es respectively. The overall and non-time loss (NTL) IRR were higher for female athletes than for male athletes. Additionally, the overall IRR and TL-IRR for female athletes were higher in those athletes who aged ≤15 years old. Over 93% of TL injuries resulted in participation restriction time of ≤7 days (male athletes, 93.94%; female athletes, 94.10%). Trunk (28.43%), knee joints (21.33%), and hand/wrist (16.53%) were found as the common sites of injury in both female and male athletes. The most frequent type of injury was contusion (male athletes: 53.00%, female athletes: 59.10%) resulted from ground/apparatus contact (male athletes: 75.10%, female athletes: 75.20%). CONCLUSION: The risk injury among snowboarding athletes involved in the TT program during the first snow season training was found noticeable, especially for younger female athletes. The high incidence of ground/apparatus contact-related injuries suggested the necessity of specifically designed training programs and braces for snowboarding athletes involved in the TT program.

A critically prolonged avalanche burial with recorded cardiac electrical activity and complete recovery - a case report.

The probability of survival in avalanche accidents is time-dependent. Critically buried victims who undergo a long burial duration (over 60 min) face a possible mortality rate of over 80%. Understanding the physiological response during critical avalanche burial is crucial for improving rescue strategies and outcomes. We present the case of a 55-year-old male skier buried under an avalanche for 4 h and 51 min in the Italian Alps. Continuous heart rate monitoring revealed distinct phases of cardiac activity during burial. Despite severe hypothermia, the victim survived without extracorporeal rewarming. This case highlights the importance of continuous monitoring and appropriate on-site management in avalanche accidents. Factors such as the presence of an air pocket may positively influence survival. This case underscores the importance of comprehensive resuscitative measures and guidelines for managing avalanche victims with prolonged burial durations.

[Bioimpedance analysis of body composition and rest energy expenditure in highly trained cross-country skiers].

The body composition monitoring using bioimpedance analysis (BIA) is important in assessing the functional state of athletes in sports. Based on changes of body composition, it is possible to optimize the actual dietary intake, as well as successfully organize the training process. The purpose of this research was to conduct a comparative assessment of BIA parameters and rest energy expenditure (REE) in highly trained cross-country skiers and young non-athletes. Material and methods. The members of the national cross-country skiing team from the Komi Republic and Russian Federation (n=30; age - 22.3±2.7 years) were examined. Practically healthy medical students served as a control group for the present study (n=40; age - 20.2±2.4 years). The participants successively passed the following study steps: assessment of the body composition by BIA (ACCUNIQ BC380), REE determination by indirect non-fasting calorimetry and calculation technique. Results. The parameters of total body water, fat-free mass, lean tissue and body cell mass were higher in contrast to the fat mass percentage in the athletes (р<0.001). The calculated REE was lower than measured REE among all the participants. At the same time, the REE calculated by the Ketch-McArdle formula significantly differed between the groups, while no differences were found between the REE calculated by the Harris-Benedict prediction equation. The measured REE were significantly higher by 16% (p<0.001) i n athletes compared to those in the control group. Conclusion. The body composition of athletes was distinguished by a significantly higher amounts of total body water, fat-free mass, skeletal muscle, active cell mass, and lower percentage of fat mass compared to healthy untrained individuals. The results obtained among athletes coincided with the idea that the magnitude of REE is determined by the mass of metabolically active tissues and to a lesser extent depends on the fat mass. BIA results can be used to monitor athletes' body composition during the training process.

Development of a simple algorithm to detect big air jumps and jumps during skiing.

Jumping is an important task in skiing, snowboarding, ski jumping, figure skating, volleyball and many other sports. In these examples, jumping tasks are a performance criterion, and therefore detailed insight into them is important for athletes and coaches. Therefore, this paper aims to introduce a simple and easy-to-implement jump detection algorithm for skiing using acceleration data from inertial measurement units attached to ski boots. The algorithm uses the average of the absolute vertical accelerations of the two boots. We provide results for different parameter settings of the algorithm and two types of jumps: Big Air jumps and jumps during skiing. The latter are divided into small (time of flight < 500 ms) and medium (time of flight ≥ 500 ms) jumps. The algorithm detects 100% of Big Air, 94% of medium and 44% of small jumps. In addition, the settings with the highest detection rates also have the highest number of overdetected jumps. To resolve this conflict, a penalty-adjusted score that considers the number of overdetected jumps in the final performance analysis is proposed.

Physical fitness characteristics of elite freestyle skiing aerials athletes.

OBJECTIVE: To analyze the physical fitness characteristics of elite freestyle skiing aerials athletes, thereby enhancing the understanding of exercise physiologists, sports scientists, and coaches regarding the demands in this discipline. METHODS: After health screenings, 29 athletes from the Chinese National Freestyle Skiing Aerials Team were divided into elite and general groups, including males and females. Physical fitness indexes were determined through literature reviews, expert interviews, and the Delphi method, followed by physical fitness tests assessing body morphology, physiological function, and physical quality. Data normality was verified using the Shapiro-Wilk test. Differences between the two groups were then evaluated using independent sample t-tests or Mann-Whitney U tests, after which effect sizes were calculated to assess the magnitude of the differences. RESULTS: Significant body morphology differences were noted between elite and general groups in fat-free body weight, leg, and waist circumferences (P < 0.05). Male athletes in the elite group exhibited a significantly lower percentage of body fat (P < 0.05), whereas the reduction in body fat percentage among female elite athletes was not statistically significant. In terms of physiological function assessment, elite athletes demonstrated superior performance in both maximum anaerobic capacity and relative maximum anaerobic capacity compared to their counterparts in the general group (P < 0.05). Notably, the difference in maximum anaerobic capacity was highly significant among male athletes (P < 0.01), and the relative maximum anaerobic capacity among female athletes was also markedly significant (P < 0.01). Regarding physical quality indexes, elite athletes outperformed those in the general group in all aspects except for the quick v-up and 12-minute run tests (P < 0.05 or P<0.01). CONCLUSION: Elite athletes exhibit superior physical fitness characteristics compared to general athletes, attributable to differences in age, years of training, and their participation in ongoing specialized physical training within structured, cyclical programs. Specifically, elite athletes demonstrated higher fat-free body weight, larger waist and leg circumferences in terms of body morphology. Particularly, male athletes showed a trend towards lower body fat percentage. Physiologically, they exhibited stronger anaerobic metabolism capabilities. In terms of physical quality, elite athletes displayed superior limb strength, lower limb explosive power, and specialized core strength, along with better speed, agility, and overall coordination.

Jump performance and movement quality in 7- to 15-year-old competitive alpine skiers: a cross-sectional study.

INTRODUCTION: Injury rates in competitive alpine skiing are high. With current methods, identifying people at risk is expensive and thus often not feasible at the youth level. The aims of this study were (1) to describe the jump performance and movement quality of youth competitive alpine skiers according to age and sex, (2) to compare the jump distance among skiers of different sexes and movement quality grades, and (3) to assess the inter-rater grading reliability of the qualitative visual movement quality classification of such jumps and the agreement between live and video-based post-exercise grading. MATERIALS AND METHODS: This cross-sectional study is based on an anonymized dataset of 301 7- to 15-year-old competitive alpine skiers. The skiers performed two-legged forward triple jumps, whereby the jump distance was measured, and grades were assigned by experienced raters from the frontal and sagittal perspectives depending on the execution quality of the jumps. Furthermore, jumps were filmed and ultimately rated post-exercise. Differences in jump distance between various groups were assessed by multivariate analyses of variance (MANOVAs). Reliability was determined using Kendall's coefficient of concordance. RESULTS: The jump distance was significantly greater in U16 skiers than in U11 skiers of both sexes and in skiers with good execution quality than in those with reduced or poor execution quality. Overall, jump distance in U16 skiers significantly differed between female (5.37 m with 95% CI [5.21, 5.53]) and male skiers (5.90 m with 95%CI [5.69, 6.10]). Slightly better inter-rater grading reliability was observed for video-based post-exercise (strong agreement) ratings than for live ratings (moderate agreement). CONCLUSION: In competitive alpine skiers aged 7 to 15 years, jump performance increases with age, and around puberty, sex differences start to manifest. Our results highlight the importance of evaluating both jump distance and movement quality in youth skiers. To improve test-retest reliability, however, a video-based post-exercise evaluation is recommended.

In youth competitive alpine skiers, jump performance and movement quality matter, and both should be trained and tested.A qualitative assessment of movement quality while jumping by experts is a highly scalable and cost-effective approach; however, to ensure sufficient test-retest reliability, the assessment criteria need to be standardised and an additional video-based post-exercise assessment is recommended.

SnowMotion: A Wearable Sensor-Based Mobile Platform for Alpine Skiing Technique Assistance.

Skiing technique and performance improvements are crucial for athletes and enthusiasts alike. This study presents SnowMotion, a digital human motion training assistance platform that addresses the key challenges of reliability, real-time analysis, usability, and cost in current motion monitoring techniques for skiing. SnowMotion utilizes wearable sensors fixed at five key positions on the skier's body to achieve high-precision kinematic data monitoring. The monitored data are processed and analyzed in real time through the SnowMotion app, generating a panoramic digital human image and reproducing the skiing motion. Validation tests demonstrated high motion capture accuracy (cc > 0.95) and reliability compared to the Vicon system, with a mean error of 5.033 and a root-mean-square error of less than 12.50 for typical skiing movements. SnowMotion provides new ideas for technical advancement and training innovation in alpine skiing, enabling coaches and athletes to analyze movement details, identify deficiencies, and develop targeted training plans. The system is expected to contribute to popularization, training, and competition in alpine skiing, injecting new vitality into this challenging sport.

Endurance Sporting Events.

Endurance sports encompass a broad range of events from marathons and triathlons to ultramarathons, long-distance cycling, skiing, and swimming. As these events have experienced a surge in popularity, we have a greater need to understand the associated medical risks. This article reviews the history of endurance races, reviews the most critical and common causes of cardiovascular, heat, electrolyte, and musculoskeletal injuries/illnesses, and discusses considerations for medical directors/personnel associated with such events.

Athletes' Perspectives of the Classification System in Para Alpine Skiing for Those With Visual Impairment.

This study explored the classification experiences and views of Para Alpine skiers with visual impairment. Data from 11  interviews were analyzed using reflexive thematic analysis to generate three themes: Suitability-The skiers questioned the suitability of the visual measurements, testing environment, and the information they received regarding classification; Exclusivity-Skiers felt certain aspects of the system remain exclusive due to the restrictions of sport classes and lack of the athlete voice; and (Dis)trust-Skiers felt distrust in those implementing the system and in other athletes due to intentional misrepresentation. Speculation surrounding this resulted in the skiers' feeling doubt in their own classification. While there is not a "one size fits all" approach to classification, understanding skiers' experiences can be a vital first step and will help to guide future research into the evolution of this sport's classification.

Fatal injury of a skier during school training - case report.

The authors present the case of a fatal accident of a 16-year-old skier who crashed into a tree during a downhill skiing lesson at school. Although the skier was wearing a protective helmet at the time of the accident and his condition did not appear to be too serious immediately after the accident, he later died in hospital as a result of a craniocerebral injury with cerebral contusion and intracranial haemorrhage. His life could not be saved even by immediate neurosurgery, during which fragments of the broken protective helmet were removed from his cranial cavity. By analysing the international literature, the authors identify head and brain injuries as the most common immediate cause of death in downhill skiing and provide insights into the possibilities of preventing these injuries by simple technical means on the part of ski area operators. These means are in particular protective covers for lift columns and protective nets placed in front of fixed, non-movable obstacles on the track.

Tumor-Like Distal Femoral Cortical Irregularities of the Knee in Adolescent Competitive Alpine Skiers: Longitudinal Assessment Over 48 Months.

BACKGROUND: Tumor-like distal femoral cortical irregularities (DFCIs) are a frequent incidental finding on knee magnetic resonance imaging (MRI) and are common in young competitive athletes. PURPOSE: To assess and compare the morphology and prevalence of DFCIs in competitive alpine skiers over 48 months during adolescence. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Adolescent competitive alpine skiers were prospectively recruited in 2018 and received bilateral 3-T MRI of the knee at baseline and after 48 months. All MRIs were evaluated for the presence and location of DFCIs, which were marked at 1 of 3 anatomic positions: (1) the femoral attachment of the medial head of the gastrocnemius muscle, (2) the lateral head of the gastrocnemius muscle, or (3) the attachment of the adductor magnus aponeurosis. The size of the DFCI was measured by 2 radiologists independently. The measurements were compared using the Wilcoxon signed-rank test, the interclass correlation coefficient (ICC), and Cohen Kappa. RESULTS: A total of 63 athletes (mean age at follow-up, 19.6 ± 1.2 years; n = 25 female) were included in the study. At baseline, DFCIs were detected in 84 out of 126 knees (67%). At the 48-month follow-up, DFCIs were found in 88 out of 126 knees (70%), with multiple DFCIs in 3 knees and no significant difference between male and female patients (n = 24 male, n = 19 female; P = .71). No significant increase was detected for the number (P = .21) and size of the DFCIs between the baseline and the 48-month follow-up (mean size: baseline, 3.7 ± 0.8 mm; 48-month follow-up: 3.6 ± 0.9 mm; P = .66). The interrater agreement for the mean size measurements of DFCIs was good to excellent (ICC 0.88). CONCLUSION: DFCIs remain a frequent finding on knee MRI in competitive alpine skiers after skeletal maturation and do not disappear during adolescence. The DFCI size was constant in athletes aged between 15 and 19 years. Moreover, DFCIs should not be mistaken for a pathologic finding.

Neurological outcome of cardiac arrest patients in mountain areas: An analysis of the Northern French Alps Emergency Network.

BACKGROUND: Mountainous areas pose a challenge for the out-of-hospital cardiac arrest (OHCA) chain of survival. Survival rates for OHCAs in mountainous areas may differ depending on the location. Increased survival has been observed compared to standard location when OHCA occurred on ski slopes. Limited data is available about OHCA in other mountainous areas. The objective was to compare the survival rates with a good neurological outcome of OHCAs occurring on ski slopes (On-S) and off the ski slopes (OffS) compared to other locations (OL). METHODS: Analysis of prospectively collected data from the cardiac arrest registry of the Northern French Alps Emergency Network (RENAU) from 2015 to 2021. The RENAU corresponding to an Emergency Medicine Network between all Emergency Medical Services and hospitals of 3 counties (Isère, Savoie, Haute-Savoie). The primary outcome was survival at 30 days with a Cerebral Performance Category scale (CPC) of 1 or 2 (1: Good Cerebral Performance, 2: Moderate Cerebral Disability). RESULTS: A total of 9589 OHCAs were included: 213 in the On-S group, 141 in the Off-S group, and 9235 in the OL group. Cardiac etiology was more common in On-S conditions (On-S: 68.9% vs OffS: 51.1% vs OL: 66.7%, p < 0.001), while Off-S cardiac arrests were more often due to traumatic circumstances (OffS: 39.7% vs On-S: 21.7% vs OL: 7.7%, p < 0.001). Automated external defibrillator (AED) use before rescuers' arrival was lower in the Off-S group than in the other two groups (On-S: 15.2% vs OL: 4.5% vs OffS: 3.7%; p < 0.002). The first AED shock was longer in the Off-S group (median time in minutes: OffS: 22.0 (9.5-35.5) vs On-S: 10.0 (3.0-19.5) vs OL: 16.0 (11.0-27.0), p = 0.03). In multivariate analysis, on-slope OHCA remained a positive factor for 30-day survival with a CPC score of 1 or 2 with a 1.96 adjusted odds ratio (95% confidence interval (CI), 1.02-3.75, p = 0.04), whereas off-slope OHCA had an 0.88 adjusted odds ratio (95% CI, 0.28-2.72, p = 0.82). CONCLUSIONS: OHCAs in ski-slopes conditions were associated with an improvement in neurological outcomes at 30 days, whereas off-slopes OHCAs were not. Ski-slopes rescue patrols are efficient in improving outcomes.

Performance and micro-pacing in sprint cross-country skiing: A comparison of individual time-trial and head-to-head race formats.

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.

[Medical emergency support for the snowboarding project during the Beijing Winter Olympics].

OBJECTIVE: To analyze and summarize the medical security situation of the snowmobile, sled, and steel frame snowmobile tracks at the National Sliding Centre, and to provide experience for future event hosting and medical security work for mass ice and snow sports. METHODS: Retrospective analysis of injuries and treatment of athletes participating in the International Training Week and World Cup for Ski, Sled, and Steel Frame Ski from October to November 2021(hereinafter referred to as "International Training Week"), as well as the Ski, Sled, and Steel Frame Ski events at the Beijing Winter Olympics in February 2022 (hereinafter referred to as the "Beijing Winter Olympics"). We referred to and drew on the "Medical Security Standards for Winter Snow Sports" to develop specific classification standards for analyzing injured areas, types of injuries, and accident locations. RESULTS: A total of 743 athletes participated in the International Training Week and the Beijing Winter Olympics. During the competition, there were 58 incidents of overturning, prying, and collision, of which 28 (28 athletes) were injured, accounting for 48.3% of the total accidents and 3.8% of the total number of athletes. Among them, there were 9 males (32.1%) and 19 females (67.9%), with an average age of (26.3 ± 4.7) years. Among the 28 injured athletes, 20 cases (71.4%) received on-site treatment for Class Ⅰ injuries, while 8 cases (28.6%) had more severe injuries, including Class Ⅱ injuries (7 cases) and Class Ⅲ injuries (1 case), which were referred to designated hospitals for further treatment. Among the 28 injured athletes, 3 cases (10.7%) experienced multiple injuries, including 2 cases of 2 injuries and 1 case of 3 injuries. The most common injuries were in the ankle and toes (10/32, 31.3%). Out of 28 injured athletes, one (3.6%) experienced two types of injuries simultaneously, with joint and/or ligament injuries being the most common (11/29, 37.9%). The most accident prone point on the track was the ninth curve (18/58, 31.0%). CONCLUSION: Through the analysis and summary of medical security work, it can provide better experience and reference for the future development of snowmobile, sled, and steel frame snowmobile sports in China, making the National Snowy and Ski Center truly a sustainable Olympic heritage.

Skiing economy and kinematic during a field double poling roller skiing among novice and experienced cross-country skiers.

To assess the skiing economy (SE) and kinematics during double poling (DP) roller skiing between two groups of skiers in a field setting. Five experienced and five novice male skiers performed a SEDP test at 16 km∙h-1 on an outdoor athletics track. Gas exchange parameters were measured to determine SEDP. A two-dimensional video was filmed to measure the kinematics variables. Experienced skiers exhibited a 21% lower oxygen cost than novice skiers (p = 0.016) in DP, indicating a strong association between SEDP, cycle length and cycle rate (p < 0.001). Additionally, before the poling phase, experienced skiers manifested significantly greater maximum hip and knee extension angles than novice skiers (p < 0.001). During the poling phase, experienced skiers with a greater pole plant angle (p = 0.001), longer flexion time (p < 0.001) and higher flexion angular velocity in the elbow joint (p < 0.05) demonstrated better SEDP. There was an interaction effect of the one-repetition maximum bench press × group in SEDP (b = - 0.656, SE = 0.097, t = - 6.78, p = 0.001). Therefore, experienced skiers with better SEDP demonstrated more efficient cycles, potentially accomplished using dynamic full-body DP motion to ascertain effective propulsion. Combined upper body strength and ski-specific skill training may enhance SEDP in novice skiers.

Global reduction of snow cover in ski areas under climate change.

Ongoing climate change substantially alters snowfall patterns with severe but diverging consequences for global ski areas. A global assessment as well as the investigation of potential implications for mountain ecosystems is currently lacking. We quantify future trends in natural snow cover days under different climate change scenarios until 2100 in seven major global skiing regions and discuss implications for mountainous biodiversity by analysing how natural snow cover days relate to regional human population density. Within all major skiing regions, snow cover days are projected to decrease substantially under every assessed climate change scenario. Thirteen percent of all current ski areas are projected to completely lose natural annual snow cover and one fifth will experience a reduction of more than 50% by 2071-2100 relative to historic baselines. Future skiable areas will concentrate in less populated areas, towards continental regions and inner parts of the mountain ranges. As skiable areas will be located at greater distances to highly populated areas in the future, we expect an expansion of infrastructure and increasing intervening actions (i.e., artificial snowmaking, slope grooming) to prolong snow duration. Our results are concerning for both the recreational and economic value of skiing as well as for mountain biodiversity since vulnerable high-altitude species might be threatened by space reductions with ski area expansion.

Comparative Analysis of the Diagonal Stride Technique during Roller Skiing and On-Snow Skiing in Youth Cross-Country Skiers.

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.

Adverse effects of unilateral transfemoral amputation on para-alpine sit skiers and mitigation methods.

OBJECTIVES: This study aimed to evaluate the adverse effects of unilateral transfemoral amputation on neuromuscular and kinematic parameters in alpine sit skiers, and to determine if additional restraints on the human-bucket interface could help mitigate the effects. DESIGN: Cross-sectional, repeated measures study. METHODS: Simulated skiing tests were conducted indoors involving 10 skiers with unilateral transfemoral amputation and 10 able-bodied participants. A Paralympic silver medalist performed slalom skiing tests on snow. These tests were conducted with and without additional strapping on the residual limb. Surface electromyography of trunk muscles and athletic performance was measured, and the asymmetry index was calculated. RESULTS: Athletes were significantly dependent on muscle activation on the dominant side (asymmetry index = 7.8 %-28.3 %, p < 0.05). Worse athletic performance to the dominant side was found based on inclination angles of the indoor board (asymmetry index = -9.8 %, p = 0.014) and outdoor sit ski (-11.1 %, p = 0.006), and distance to the gate poles during skiing turns (18.6 %, p < 0.001). After using additional restraints, the above asymmetry index declined significantly (asymmetry index < 4.5 %, p < 0.05). Furthermore, athletic performance was significantly improved on both body sides by 11.1 %-30.7 % (p < 0.05). CONCLUSIONS: Unilateral transfemoral amputation caused the dependence on the trunk muscles of the dominant side and the corresponding unilateral poor performance in athletes. Adjusting restraints in the human-equipment interface by additional strapping could mitigate the asymmetry issues and improve athletic performance.