Injuries and illnesses in a cohort of elite youth alpine ski racers and the influence of biological maturity and relative age: a two-season prospective study

High Incidence of Injuries Among Adolescent Elite Skiers-A 5-Year Cohort Study

Competitive skiing has gained increasing popularity among adolescent, yet it comes with injury risks. The aim was to determine injury incidence, type and time of injury, localization, and diagnosis, among adolescent competitive skiers (alpine, cross-country, ski-cross, mogul), and to compare between skiing discipline, sex, and high school year. All students (n = 190) enrolled in a ski high school from August 2013 to June 2018 were included. All injuries during the study period were prospectively registered by the physiotherapist at the high school. Demographic and injury data were registered. Absolute injury incidence (injuries/100 skiers) was calculated. In total, 166 (87%) skiers reported 502 injuries, which corresponds to an absolute injury incidence of 264.2 injuries/100 skiers during the 5-year follow-up. A higher injury incidence was shown in school year 1 compared with year 2-4 (131.3 vs. 79.5-98.4; p < 0.05). No differences in injury incidence were found between sex or skiing discipline. Females were more prone of having a gradual-onset injury compared with males (179.3 vs. 96.3; p < 0.001). Mogul skiers had higher incidence of acute injuries compared with the other disciplines (220.0 vs. 71.4-160.0; p < 0.001). The knee was the most common localization across all skiing disciplines, except for cross-country (lower leg). Low back pain was the predominant diagnosis, except in ski-cross (concussion). Skiers attending specialized ski high schools exhibited a significantly high injury incidence, with first-year students being the most susceptible to injuries, across all skiing disciplines and both sexes. While the knee was the most common injury location, concussion was remarkably frequent, particularly among ski-cross skiers.

Associations between growth, maturation and injury in youth athletes engaged in elite pathways: a scoping review

OBJECTIVE

To describe the evidence pertaining to associations between growth, maturation and injury in elite youth athletes.

DESIGN

Scoping review.

DATA SOURCES

Electronic databases (SPORTDiscus, Embase, PubMed, MEDLINE and Web of Science) searched on 30 May 2023.

ELIGIBILITY CRITERIA

Original studies published since 2000 using quantitative or qualitative designs investigating associations between growth, maturation and injury in elite youth athletes.

RESULTS

From an initial 518 titles, 36 full-text articles were evaluated, of which 30 were eligible for final inclusion. Most studies were quantitative and employed prospective designs. Significant heterogeneity was evident across samples and in the operationalisation and measurement of growth, maturation and injury. Injury incidence and burden generally increased with maturity status, although growth-related injuries peaked during the adolescent growth spurt. More rapid growth in stature and of the lower limbs was associated with greater injury incidence and burden. While maturity timing did not show a clear or consistent association with injury, it may contribute to risk and burden due to variations in maturity status.

CONCLUSION

Evidence suggests that the processes of growth and maturation contribute to injury risk and burden in elite youth athletes, although the nature of the association varies with injury type. More research investigating the main and interactive effects on growth and maturation on injury is warranted, especially in female athletes and across a greater diversity of sports.

Efficacy of multicomponent interventions on injury risk among ice and snow sports participants-a systematic review and meta-analysis

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.

Differences in Injury Profiles Between Female and Male Athletes Across the Participant Classification Framework: A Systematic Review and Meta-Analysis

BACKGROUND

Female sex is a significant determinant of anterior cruciate ligament (ACL) injury. It is not understood if sex is a key determinant of other sports-related injuries.

OBJECTIVE

The aim of this systematic review was to identify where differences in injury profiles are most apparent between the sexes in all sports across the six-tiered participant classification framework.

METHODS

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and the 'implementing PRISMA in Exercise, Rehabilitation, Sport medicine and SporTs science'(PERSiST) guidance. The databases PubMed, CINAHL, Web of Science, SPORTDiscus, Medline, Scopus, Cochrane Library and EBSCO were searched from database inception to 24 April 2023. Longitudinal, prospective and retrospective cohort studies and cross-sectional and descriptive epidemiology studies that used standard injury data collection were included. Studies were excluded if injuries were not medically diagnosed and if injuries were not reported and/or analysed by sex. Two reviewers independently extracted data and assessed study quality using the Downs and Black checklist.

RESULTS

Overall, 180 studies were included (8 tier-5, 40 tier-4, 98 tier-3, 30 tier-2, 5 tier-1 studies; one study included data in two tiers). Of those, 174 studies were of moderate quality and six studies were of limited quality. In sex-comparable sports, there was moderate evidence that female athletes had greater risk of knee injury (relative risk (RR) 2.7; 95% CI 1.4-5.5), foot/ankle injuries (RR 1.25; 95% CI 1.17-1.34), bone stress injury (RR 3.4; 95% CI 2.1-5.4) and concussion (RR 8.46; 95% CI 1.04-68.77) than male athletes. Male athletes were at increased risk of hip/groin injuries (RR 2.26; 95% CI 1.31-3.88) and hamstring injuries (RR 2.4; 95% CI 1.8-3.2) compared with females, particularly in dynamic sports. Male athletes were 1.8 (1.37-2.7) to 2.8 (2.45-3.24) times more likely to sustain acute fractures than female athletes, with the highest risk in competition.

DISCUSSION

Most studies in all cohorts were of moderate quality (mean/range of scores tier-5: 17 ± 2.2 [14-20], tier-4: 16.9 ± 1.9 [11-21], tier-3: 16.9 ± 1.5 [11-20], tier-2: 16.3 ± 2.2 [11-20], tier-1 studies: 15.6 ± 1.3 [14-17] out of 28 on the Downs and Black checklist), with only six studies of limited quality. Female athletes' propensity for bone stress injuries highlights opportunities to reinforce development of optimal bone health during adolescence and to outline the effects of energy availability. Earlier strength development and exposure to neuromuscular training programmes and modification of skill development in female athletes may be effective strategies for reducing lower limb injury risk. Key components of neuromuscular training programmes could be beneficial for reducing hip/groin and hamstring injury risk in male athletes. There may be a need for sex-specific prevention and return-to-sport protocols for sports-related concussion in female athletes.

CONCLUSIONS

Female sex was a key determinant of sports-related injuries beyond ACL injury including foot/ankle injury, bone stress injury and sports-related concussion. Male sex was a key determinant of hip/groin, hamstring injury and upper limb injury.

TRIAL REGISTRY

PROSPERO registration number: CRD42017058806 (last updated on 7th June 2023).

We know a lot about little and little about a lot: A contextualized scoping review on injury prevention in alpine ski racing

BACKGROUND

Our goal was to summarize and contextualize the available literature on alpine ski racing injury epidemiology, injury etiology, injury prevention measures, injury prevention context, and implementation issues.

MATERIALS AND METHODS

We searched four electronic databases using predetermined search terms. We included original studies that assessed injury, injury risk factors, and injury mechanisms, and assessed and reported the effect of an injury prevention measure in alpine ski racing. Two authors independently conducted title-abstract screening, and one performed the full-text review. For data synthesis and categorization, we used the Translating Research into the Injury Prevention Practice framework and a modified and adapted version of the Haddon matrix.

RESULTS

Of the 157 included studies, most corresponded to injury epidemiology and etiology, whereas few studies encompassed injury prevention measure development, implementation and evaluation. Preventive interventions targeting equipment, rules and regulations, course design and snow preparation were the most prevalent in the literature. Furthermore, various contextual factors in the current literature have been found, including gender, competition level, countries and federations, and time periods within a season.

CONCLUSIONS

We provided an in-depth and comprehensive overview of the current state-of-the-art in the alpine ski racing context. We know a lot about little and little about a lot across all the areas associated with injury prevention in such context. The limitations in the literature yield a road map for designing future injury prevention studies to address the key gaps identified. A more comprehensive context-driven approach throughout all stages of injury prevention would benefit the ultimate implementation of effective preventive strategies.

The Relative Age Effect at Different Age Periods in Soccer: A Meta-Analysis

In the selection of young athletes, earlier-born adolescents often leverage their temporary biological advantage over their later-born peers from the same cohort, giving rise to the phenomenon known as the Relative Age Effect (RAE). In this study, we delved into the complexities of the RAE in soccer by reviewing 563 independent research samples across 90 articles. Our analysis showed that age period and performance level are pivotal factors influencing the magnitude of the RAE. The adolescent age period emerged as a significant RAE determinant, showcasing the highest effect size magnitudes in our findings. Among athletes of different performance levels, adult European soccer players have been extensively studied, and they have exhibited the most pronounced RAE magnitudes. Intriguingly, our findings reveal another compelling trend: the frequency of players born early versus late in the eligible birth year escalated as player performance levels increased, particularly during adolescence. Coaches and players appear to capitalize unconsciously on this maturational advantage, though this strategy wanes post-adolescence. While there are currently no penalties for this team selection practice, our findings stress the need for coaches to comprehend the ramifications of selecting athletes with an age bias We offer insights into RAE complexities, highlight the synergy of age and performance in these transitory advantages, and advance arguments for more fairly selecting and developing youth athletes.

Prospective Study on Dynamic Postural Stability in Youth Competitive Alpine Skiers: Test-Retest Reliability and Reference Values as a Function of Sex, Age and Biological Maturation

This study aimed 1) to assess the test-retest reliability of dynamic postural stability index (DPSI) assessments using a ski-specific jump protocol that consists of single-leg landings on a three-dimensional force plate after forward-performed double-leg drop jumps from a box over a hurdle (DJSLLs), 2) to provide reference values for female and male youth competitive alpine skiers; 3) to explore their changes in DPSI over 3 years during adolescence; and 4) to investigate potential associations of DPSI with age and biological maturation. Using three-dimensional force plates, 16 healthy subjects were tested on the same day (test-retest reliability experiment; five test-retest assessments of right leg landings), and 76 youth skiers aged 13–15 years were tested 3 times within 2 years (main experiment; average of two trials per leg each time). The test-retest reliability experiment revealed an ICC(3,1) and 95% CI of 0.86 [0.74, 0.94] for absolute DPSI assessment. The within-subject SEM of absolute DPSI was 16.30 N [13.66 N, 20.65 N], and the standardized typical error was moderate (0.39 [0.33, 0.50]). Both absolute and relative DPSI values were comparable between male and female youth competitive alpine skiers. The mean absolute DPSI in year 1 (195.7 ± 40.9 N), year 2 (196.5 ± 38.9 N) and year 3 (211.5 ± 41.3 N) continuously increased (i.e., worsened) (p < 0.001). Mean relative, i.e. body weight force normalized, DPSI values significantly decreased, i.e., improved, from year 1 to 2 (0.42 ± 0.01 vs. 0.36 ± 0.004; p < 0.001) and year 1 to 3 (0.42 ± 0.01 vs. 0.36 ± 0.01; p < 0.001). Absolute DPSI correlated with age and biological maturation, while no such correlations were found for relative DPSI values. Our findings suggest that DPSI is a reliable and sensitive measure of dynamic postural control during DJSLLs and that relative DPSI improves annually in competitive youth skiers when accounting for body weight. Future work should consider biological maturation testing during the growth spurt, and normalizing to body weight force could be a possible solution.

The ISPA Int Injury Prevention Programme for Youth Competitive Alpine Skiers: A Controlled 12-Month Experimental Study in a Real-World Training Setting

Evidence-based injury prevention programmes for youth competitive alpine skiers are widely absent. The aims of this controlled 12-month experimental study were to introduce a novel injury prevention programme targeted to the injury patterns of youth skiers, called ISPA_Int, and to compare the differences in injury occurrence between an intervention group (IG) additionally performing the ISPA_Int programme and an independent, historical control group (CG) following their regular training routines. None of the skiers of the CG were part of the IG and vice versa. The study was directly conducted within the real-world youth development structures of skiers competing at the under 16 years (U16) level in Switzerland. Seventy-one skiers (aged 14.4 ± 0.3 years) assigned to the IG were compared to 58 age- and gender-matched controls. The IG was offered the ISPA_Int programme with the recommendation to perform it at least once per week. Skiers’ adherence to this recommendation was surveyed but not enforced. Injuries were recorded using the Oslo Sports Trauma Research Centre Questionnaire. Primary outcomes were the absolute injury rates (number of injuries/100 athletes per season) and epidemiological incidence proportion (number of injured athletes/100 athletes per season). The secondary outcome was the average 2-weekly prevalence of traumatic knee, knee overuse, and lower back overuse injuries. There were lower absolute rates of all traumatic injuries [rate/risk difference, RD: −57.1 (−98.1, −16.0); rate/risk ratio, RR: 0.665 (0.485, 0.884)] and overuse injuries [RD: −35.9 (−71.0, −0.7); RR: 0.699 (0.493, 0.989)] in the IG than in the CG. Likewise, the epidemiological incidence proportion for all overuse injuries was smaller in the IG [RD: −28.4 (−44.8, −12.0); RR: 0.598 (0.435, 0.822)], while the proportion of skiers suffering from traumatic injuries did not significantly differ between the groups. Notably, the IG particularity differed from the CG in the average 2-weekly prevalence of knee trauma, knee overuse, and lower back overuse complaints, three of the major injury-related hot spots in youth skiers. Based on these promising results, the ISPA_Int programme may have great potential to prevent injuries in youth competitive alpine skiers, and the underlying exercises should be considered complementary training content at the U16 level.

Deadbug Bridging Performance in 6- to 15-Year-Old Competitive Alpine Skiers-A Cross-Sectional Study

In competitive alpine skiing, a superior antirotation and rear-chain stabilization capacity is essential to constantly remain in dynamic equilibrium while skiing and to counteract the ski-specific adverse loading patterns of the back. As such, skiers' trunk stabilization performance during deadbug bridging (DBB) exercises has been shown to be associated with both skiing performance and overuse complaints of the lower back in skiers under 16 years of age (U16). However, to date, little is known about the corresponding stabilization abilities in younger skiers, i.e., 6- to 15-year-old skiers. As part of a biomechanical field experiment during a national off-snow fitness competition, a total of 101 youth competitive alpine skiers were tested with respect to their trunk stabilization performance during DDB exercise. The maximum contralateral displacement of the pelvic drop during leg lift (DBBdisplacement) was quantified using reflective markers and a motion capture system (Vicon, Oxford, UK). Potential age group and sex differences in DBBdisplacement were assessed using analysis of variance (ANOVA) at p < 0.05. Within each subgroup, the associations of DBBdisplacement with age, anthropometrics and maturity offset were analysed using Pearson's correlation (p < 0.05). Female skiers under 15 years of age (U15) showed better DBB performance than male U15 skiers, while there was no sex difference at the under 10-year (U10) level. In female U10 skiers, DBBdisplacement was moderately associated with body height, while in all other subgroups, no confounding associations with anthropometrics or biological maturation were found. Biomechanically quantifying DBB performance may be considered a feasible and nonconfounded screening test approach in young skiers older than 6 years. Body height may represent a confounding bias in exclusively the U10 female skier cohort and, therefore, should be considered when interpreting the test results. In summary, this study provided sport-specific normative reference data that may be of equal interest to both researchers and sport practitioners.

Effect of Skiing on Physical Performance, Pain, and Quality of Life Based on Gender

Context: Identifying gender-specific differentiation in each sport type is significant. In this way, sport- and gender-specific gains can be predicted. Therefore, this study aimed to examine the effects of skiing on physical performance, pain, quality of life, and gender-based differentiation. Design: Crossover trial. Methods: Sixty-eight volunteers, between 18 and 25 years of age, with no history of severe trauma in the spine and extremities, participated in our study. The skiers group consisted of licensed athletes (17 males and 17 females) who did active skiing for at least the past 2 years, the control group consisted of nonathletic and age-matched participants with no skiing experience (17 males and 17 females). Step test, vertical jump test, Flamingo balance test, hand-grip strength, and back-leg-chest strength measurements were performed to evaluate physical performance. Visual Analog Scale, McGill Pain Questionnaire, and Oswestry Low Back Pain Disability Questionnaire were used to evaluate pain experience. Quality of life was evaluated with Short Form-36 (SF-36). Results: Compared to the sedentary controls, VAS-activity and Oswestry Disability Index scores were lower; and aerobic performance, balance, hand-grip strength, back-leg-chest strength, and quality of life (SF-36-general health, SF-36-vitality, SF-36-mental health, and SF-total score) were higher in skiers. Skiing was found to be effective in eliminating gender-based differentiation of the variables of hand-grip strength, pain, and quality of life; however, back-leg-chest strength and anaerobic performance variables were found to be ineffective in eliminating gender differentiation. Conclusions: Skiing allows that the individual increases physical performance and quality of life. It can also minimize gender-based differentiation of certain variables, such as muscular force, pain, and quality of life.

Incidence of injuries in professional snow sports: A systematic review and meta-analysis

PURPOSE

The study aimed to conduct a comprehensive systematic review and meta-analysis of injury incidence in professional skiers and snowboarders.

METHODS

We systematically searched PubMed, Web of Science, and MEDLINE for studies on injury incidence published from inception to April 2020. Injury data were extracted, alongside information on injury location, severity, type, cause, and sport discipline. Incidence of injuries was presented per 1000 athlete-days, with 95% confidence intervals (95%CIs).

RESULTS

The search identified 462 articles, and 22 were included in our review. The overall incidence of injuries among professional skiers and snowboarders was 3.49 per 1000 athlete-days (95%CI: 2.97-4.01). Lower extremity had the highest injury incidence (1.54 per 1000 athlete-days, 95%CI: 1.24-1.84). Incidence rates of slight, mild, moderate, and severe injuries were 0.26, 0.31, 0.57, and 0.59 per 1000 athlete-days, respectively. Contusion had the highest incidence rate (1.82 per 1000 athlete-days, 95%CI: 1.01-2.63). The most common cause of injury was contact trauma (3.20 per 1000 athlete-days, 95%CI: 1.32-5.08). Freestyle skiing had the highest incidence rate (6.83 per 1000 athlete-days, 95%CI: 4.00-9.66), and Nordic skiing had the lowest rate (2.70 per 1000 athlete-days, 95%CI: 1.94-3.46).

CONCLUSION

Professional skiers and snowboarders have a substantial risk of sustaining injuries. Our findings can be used to inform the planning and provision of healthcare for elite participants in different snow sports.

A Cross-Sectional Observation on Maximal Eccentric Hamstring Strength in 7- to 15-Year-Old Competitive Alpine Skiers

Simple Summary

Competitive alpine skiing is a sport with frequent occurrence of severe knee injuries, and it is well known that the hamstring muscles play an important role in preventing these injuries. The aim of this study was to assess the maximal strength capacity for braking, the downward movement during Nordic Hamstring Exercises, the so called maximal eccentric hamstring strength, in 7- to 15-year-old skiers. Absolute strength values were greater in skiers under 15 years old (U15) skiers than in those under 10 years old (U10), as well as in U15 males compared to their female counterparts. There were no sex differences in U10 skiers. Absolute strength values were generally dependent on age and biological developmental stage, but this dependence was considerably attenuated when body weight was considered. This should be kept in mind when testing athletes around the growth spurt.

Abstract

Severe knee injuries are common in alpine skiing and the hamstring muscles are known to counteract the anterior tibial displacement that typically accompanies major injury mechanisms. This study aimed to assess the Maximal Eccentric Hamstring Strength (MEHS) of youth competitive alpine skiers during Nordic Hamstring Exercise (NHE) in terms of dependence of sex, age and biological maturation. A total of 246 7- to 15-year-old skiers were tested with respect to their MEHS using an NHE-based measurement device (Vald Performance, Newstead, Australia). Significantly greater absolute MEHS was observed in skiers of the under 15 years (U15) category compared to skiers under 10 years old (U10) (227.9 ± 61.1 N vs. 142.6 ± 28.9 N; p < 0.001), also when grouped by sex. Absolute MEHS was revealed to be lower in U15 females compared to males (213.5 ± 49.0 N vs. 241.9 ± 68.4 N; p = 0.001); in U10 skiers there was no sex difference. For all age groups and sexes, absolute MEHS values were significantly correlated with age and biological maturation (p < 0.001). However, when normalized to body weight such associations disappeared, which is why this is strongly recommended when testing around their growth spurt. Overall, this study established sport-specific normative reference data that may be of interest to researchers and sport practitioners alike.

[Comparison of acute sports injury between recreational skiers and skiers]

OBJECTIVE

To compare and analyze the difference between the injuries of recreational skiers in public ski resorts and those of skiing athletes in official competitions, and to explore the suggestions of medical insurance for these two types of skiers.

METHODS

The injury data of recreational skiers in Chongli District, Zhangjiakou City, Hebei Province during 2018-2019 and 2019-2020 snow seasons, and the injury data of skiers in two official international skiing competitions during 2019-2020 snow season and domestic test events in Chongli District of 2021 Winter Olympic Games were analyzed retrospectively, and the similarities and differences were compared.

RESULTS

A total of 1 187 injuries occurred to recreational skiers in the two public ski resorts during the 2018-2019 snow season, with an injury rate of 0.3%.There were 1 277 injury sites in total, and the most frequent injury sites were head and neck (230 cases, 18.0%), followed by knee joint (204 cases, 16.0%) and lower extremity (131 cases, 10.3%). Thirty-one skiers were injured in the two official international skiing competitions in the 2019-2020 and 2020-2021 snow season, and in the domestic test competitions in the 2021 Winter Olympic Games, and the injury rates were 11.5%, 17.2% and 12.0%, respectively. There were 37 injury sites in total, among which 11 (29.7%) were in the head and neck, followed by 6 (16.2%) in the knee joint and 5 (13.6%) in the chest, rib and abdomen.

CONCLUSION

In order to better guarantee the safety of skiers and timely provide corresponding medical help, safety facilities and technical guidance should be added to the snow resort for leisure skiing, and medical stations should be set up in the snow resort. As the formal ski racing for skiing athletes during the game has 30 to 80 times higher injury ratesthan recreational skiers, and compared with the recreational skiing, head and neck injury rate is higher, and the damage is much heavier, more complete first aid facilities and experienced medical workers are, needed so the field should be equipped with the circuit inside the quantities, track fixed outside the clinic, surrounding referral hospitals set up trauma centers to provide athletes with more timely medical care.

Perceptions of experts on key injury risk factors in alpine ski racing as a function of stakeholder role and associated level of competition

Objectives

(1) To update experts' priorities of perceived key injury risk factors in alpine ski racing based on a framework and list derived 10 years ago, (2) to identify additionally emerging risk factors since then and (3) to compile a list with countermeasure suggestions.

Methods

A sample of 532 expert stakeholders (athletes, coaches, team medical staff, Ski Racing Suppliers (SRS) and International Ski Federation (FIS) representatives) from the World Cup (WC), European Cup (EC) and FIS-race level participated in a cross-sectional online survey. Experts were asked to name those risk factors with the highest believed impact on injury risk and rank them according to their current priority from a predefined list. In addition, experts were encouraged to name additional (not listed) risk factors and to suggest countermeasures.

Results

Regardless of stakeholder role and competition level, snow-related factors appeared to have the highest perceived priority. However, WC athletes' and coaches' perceptions were also related to equipment, while at the EC and FIS-race level fatigue and physical fitness-related factors were considered important. Athletes' perceptions were largely in agreement with SRS (ie, snow-related and equipment-related factors). At the same time, while coaches, team medical staff and FIS representatives additionally emphasised fatigue and physical fitness-related factors.

Conclusion

Experts' perceptions on key injury risk factors in alpine ski racing depend on the stakeholder role and differ between the competition levels. Thus, to develop effective prevention measures and to successfully implement them, all relevant stakeholders should be given a voice, and prevention efforts should be targeted to the specific level.

Safety and Impact on Training of the Influenza Vaccines in Elite Athletes Participating in the Rio 2016 Olympics

OBJECTIVE

The aim of the study was to evaluate the safety and tolerance of influenza vaccines for the northern and southern hemispheres in Polish elite athletes participating in the Rio 2016 Olympics.

DESIGN

Prospective, observational, cohort study.

SETTING

Institutional level.

PARTICIPANTS

Ninety-seven athletes vaccinated only with the northern hemisphere vaccine; 98 athletes received the southern hemisphere vaccine alone, whereas 39 athletes were vaccinated with both vaccines.

INTERVENTIONS

The athletes were vaccinated with a trivalent, inactivated influenza vaccine recommended for the northern hemisphere 2015/2016 and then with the vaccine recommended for the southern hemisphere 2016. Athletes kept a diary of adverse events and effects (if any) on training for 6 days after vaccination.

MAIN OUTCOME MEASURES

The percentage of general and local adverse events, number of lost or modified training sessions.

RESULTS

Significantly more local adverse events (pain and redness) were found in the group immunized with the vaccine for the northern hemisphere. There were no differences in the frequency of general adverse events and influence on training between groups. Of total 273 athletes who had 1911 training days during 6 days after vaccination, 6 athletes (2.2%) lost 13 training days (0.7%) and 16 athletes (5.9%) had to modify 34 (1.7%) training days within first 2 days after vaccination.

CONCLUSIONS

Athletes tolerated influenza immunization well. If they are going to travel to the other hemisphere during the influenza season, the use of the second influenza vaccine should be advised. Athletes should anticipate modification of trainings for 2 days after vaccination.

Injury risks among elite competitive alpine skiers are underestimated if not registered prospectively, over the entire season and regardless of whether requiring medical attention

PURPOSE

Prospective studies assessing the injuries occurring in elite competitive alpine skiers are lacking, and a full picture of all injuries, including those not requiring medical attention, is absent. Likewise, little is known about the sex-specific injury risks and patterns of elite skiers throughout an entire season (i.e. an off-season preparation period and a competition period). Accordingly, this study investigated the injuries of a national team cohort with respect to season period and sex.

METHODS

Over an entire season, all injuries occurring in 44 Swiss National Ski Team members (25 females and 19 males) were registered, regardless of whether they required medical attention. Skiers were prospectively monitored by the Oslo Sports Trauma Research Centre (OSTRC) questionnaire and by continuously updated team medical records. Finally, these data were used as a reference for supplemental interviews, in which the correctness and completeness of the prospective data were verified.

RESULTS

The risk of suffering at least one injury during an entire season was 75.0% with a 95% confidence interval (73.1%, 76.9%) for traumatic injuries, and 52.3% (50.0%, 54.5%) for overuse injuries. Traumatic injuries concerned the head, lower leg and knee, while overuse injuries affected the lumbar spine, knee and hip. During the competition period, skiers were more prone to traumatic injuries, while during the off-season preparation period, skiers' risk was higher for overuse injuries. Over an entire season, there were no sex differences. However, females were more vulnerable to traumatic injuries during the preparation period and overuse injuries during the competition period, while males had a higher risk for overuse injuries during the preparation period.

CONCLUSIONS

When prospectively registering injuries among elite competitive alpine skiers over an entire season, regardless of whether the injuries required medical attention, the injury risks were alarmingly high and substantially larger than those previously reported. Moreover, since injury risks and patterns are season period and sex dependent, it is strongly recommended that (1) injury registration focuses on both the off-season preparation period and the competition period and (2) prevention efforts are specifically tailored to the sex of the athletes.

LEVEL OF EVIDENCE

II.

Studying Force Patterns in an Alpine Ski Boot and Their Relation to Riding Styles and Falling Mechanisms

In skiing, performance and safety can depend on small details. Consequently, the measurement of forces within the ski boots, which represent the essential form-fitting and force transmitting interface during skiing, will lead to enhanced performance and more importantly safety. This study presents a methodology to measure force patterns (continuous data acquisition) under laboratory as well as realistic slope conditions. The force measurements will be analyzed to gain insights of the skiing style, skiing technique, specific falling mechanisms (i.e., boot induced anterior drawer, phantom foot, hyperextension of the knee joint, and valgus-external rotation). Furthermore, the locations of force sensors in a overlap designed ski boot are discussed in terms of practicability and applicability. These insights are of particular interest to derive release conditions for predictive binding systems and furthermore provide data to improve the style of skiing (e.g., turn release action or center of gravity behavior). For that purpose, a ski boot was instrumented with seven force (piezoresistive) sensors while the basic structure of the boot and the binding remained unchanged. Three sensors were placed on the insole to measure ground reaction forces as well as the contact forces between the skier's foot and the boot. The other four sensors were positioned at spoiler/shaft and toecap (front sole) regions of the ski boot. The locations of the force sensors within the ski-boot are defined with regard to the main body movement while skiing (body-related planes). In addition, a commercially available ski and body mount measuring system were utilized to correlate speed, inclination and body position with the force patterns occurring during skiing on the slope as well as simulating specific body positions on an inclined ramp under laboratory conditions. The measured force revealed that the toecap (upper) sensors provide insufficient even non-conclusive data to deduce significant patterns. However, the insole sensors (heel and front sole area) as well as the spoiler/shaft (back) sensors are more reliable and show characteristic patterns indicating forward or backward lean. These results will have an important impact to the development of predictiveelectro-mechanical bindings to prevent knee-related injuries, which, from a statistical point of view, concerns largely women and young athletes.

The Influence of Age and Maturation on Trajectories of Stretch-Shortening Cycle Capability in Male Youth Team Sports

PURPOSE

To examine the influence of growth and maturation in the trajectory of stretch-shortening cycle capability.

METHOD

Using a mixed-longitudinal design, absolute and relative leg stiffness and reactive strength index (RSI) were measured 3 times over a 3-year period in 44 youth team-sport players. Maturation was determined as maturity offset and included within the Bayesian inference analysis as a covariate alongside chronological age.

RESULTS

Irrespective of age and maturation, there was no change in absolute leg stiffness, however relative leg stiffness decreased over time. Maturation and age reduced this decline, but the decline remained significant (Bayesian factor [10] = 5097, model averaged R2 = .61). The RSI increased over time and more so in older more mature youth players (Bayesian factor [10] = 9.29e8, model averaged R2 = .657).

CONCLUSION

In youth players who are at/post peak height velocity, relative leg stiffness appears to decline, which could have an impact on both performance and injury risk. However, RSI increases during this period, and these data reinforce that leg stiffness and RSI reflect different components of stretch-shortening cycle capability. Practitioners should consider these differences when planning training to maximize stretch-shortening cycle capability during growth and maturation in athletes on the developmental performance pathway.

Training load characteristics and injury and illness risk identification in elite youth ski racing: A prospective study

PURPOSE

The study aimed to investigate the role of training load characteristics and injury and illness risk in youth ski racing.

METHODS

The training load characteristics as well as traumatic injuries, overuse injuries, and illnesses of 91 elite youth ski racers (age = 12.1 ± 1.3 years, mean ± SD) were prospectively recorded over a period of 1 season by using a sport-specific online database. Multiple linear regression analyses were performed to monitor the influence of training load on injuries and illnesses. Differences in mean training load characteristics between preseason, in-season, and post-season were calculated using multivariate analyses of variance.

RESULTS

Differences were discovered in the number of weekly training sessions (p = 0.005) between pre-season (4.97 ± 1.57) and post-season (3.24 ± 0.71), in the mean training volume (p = 0.022) between in-season (865.8 ± 197.8 min) and post-season (497.0 ± 225.5 min) and in the mean weekly training intensity (Index) (p = 0.012) between in-season (11.7 ± 1.8) and post-season (8.9 ± 1.7). A total of 185 medical problems were reported (41 traumatic injuries, 12 overuse injuries, and 132 illnesses). The weekly training volume and training intensity was not a significant risk factor for injuries (p > 0.05). Training intensity was found to be a significant risk factor for illnesses in the same week (β = 0.348; p = 0.044; R² = 0.121) and training volume represents a risk factor for illnesses in the following week (β = 0.397; p = 0.027; R² = 0.157).

CONCLUSION

A higher training intensity and volume were associated with increased illnesses, but not with a higher risk of injury. Monitoring training and ensuring appropriate progression of training load between weeks may decrease incidents of illness in-season.

Maximal Isometric or Eccentric Hamstring Strength-Which Test Modality Might Be More Suitable for Assessments in Youth Alpine Ski Racers?

Background: Physical fitness is an important component in the development of youth alpine ski racers. To write systematically planned and age-appropriate fitness programs athletes need to be physically tested at regular intervals at an early age. Although well-developed hamstring muscle strength is important for alpine ski racing performance and the prevention of serious knee injuries, it has not been well investigated, especially in youth athletes. Accordingly, the first aim of the present study was to assess the test-retest reliability of the maximum bilateral eccentric (MBEHS) and unilateral isometric (MUIHS) hamstring tests. The second aim of the present study was to assess whether the results of these two methods correlate and if it is possible to commit to one of the two methods to provide an economic test procedure. Methods: The first study included 26 (14 females/12 males) youth alpine ski racers aged between 12 and 13 years. All athletes performed two MBEHS and two MUIHS tests, 7 days apart. The intraclass correlation coefficient (ICC 3,1) and their 95% confidence intervals based on a consistency two-way mixed model were used to estimate the reliability of the two different test modalities. The second study included 61 (27 females/34 males) youth alpine ski racers aged between 10 and 13 years. All athletes performed one MBEHS and one MUIHS test. Bland-Altman plots and the 95% limits of agreement as well as correlations by Pearson (r) between the different test modalities were assessed. Results: In study 1 “poor” to “moderate” (MBEHS right leg 0.79 (0.58–0.90); left leg 0.83 (0.66–0.92); MUIHS right leg 0.78 (0.56–0.89); left leg 0.66 (0.37–0.83)) ICC values and 95% confident intervals were obtained. Standard error of measurement (SEM) between trails was between 18.3 and 25.1 N. Smallest detectable difference (SDD) was between 50.8 and 69.5 N. In study 2 mean differences between MBEHS and MUIHS was around 20 N with higher values for MBEHS. Significant moderate-to-strong correlations were found between the test modalities (r = 0.74–0.84, p <0.001). Conclusions: The MBEHS test has higher ICC values, lower CV values, higher SEM values and lower SDD values than the MUIHS test. All this suggests that the MBEHS test is more suitable than the MUIHS test to determine the maximum hamstring force in young alpine ski racers.

Self-Reported Physical Activity, Injury, and Illness in Canadian Adolescent Ski Racers

Youth ski racers spend a considerable amount of time on snow and this may detract from other activities known to influence fundamental movement skills and overall health related outcomes. Parents of racers (n = 52 F; n = 44 M; age range 9–14 years) registered in the Canadian club system completed a baseline medical questionnaire during preseason testing in 2017. We describe physical activity volume and sport participation outside of physical education classes over the previous 12 months and report on injuries, medication use and health care utilization. The mean number of activities participated was five (range 1–14) with cycling, hiking, and swimming as the preferred choice and a cumulative mean of just under 400 h of activity was reported (range F 27–1,015; M 62–869 h/year) in the past year. During the past 12 months 16% of the athletes reported being injured and injury severity impacted return to sport with range of reported days missed from 1 to 365 days. Thirteen non-concussive injuries were reported in alpine skiing and females (12%, 6/52) reported more lower limb injuries than males (7%, 3/44). More males were concussed over their lifetime, with alpine skiing accounting for 46% and mountain biking 15%. Most athletes (85%) did not take medication on a regular basis and those that did had a medical diagnosis. The frequency of respiratory conditions was 13% (12/96) with males reporting slightly more cases than females. No difference in emergency visits occurred (25%) between males and females in the past 12 months, however females reported more (n = 102) allied health care, sport medicine and x-rays appointments when compared to males (n = 65). In summary, a high volume of physical activity (an hour plus per day) over the previous 12 months was reported with racers participating in several activities outside of skiing, likely honing their fundamental movement skills. Close proximity to the mountains may have influenced their choices of activity outside of ski racing, and their injuries and a variety of health conditions were typical of their age group. Future research employing wearable technology to objectively quantify the volume and intensity of physical activity participation is recommended.

Relationship of Changes in Physical Fitness and Anthropometric Characteristics over One Season, Biological Maturity Status and Injury Risk in Elite Youth Ski Racers: A Prospective Study

Alpine ski racing is a sport with a high risk of injuries. In order to contribute to the longitudinal career development of young athletes, prevention measures should be elaborated. Therefore, the aim of the present study was to investigate prospectively the role of biological maturity status, and changes in anthropometric characteristics and physical fitness parameters over one season in elite youth ski racers younger than 15 years. Eighty-nine elite youth ski racers (39 females, 50 males), aged 10-14 years (mean age: 12.1 ± 1.3), were investigated. Anthropometric characteristics and physical fitness parameters were assessed prior and after the winter season; traumatic and overuse injuries were recorded over the 32 weeks. Binary logistic regression analyses (R² = 0.202-0.188) revealed that the biological maturity (Wald = 4.818; p = 0.028), and changes over the season in the jump agility test (Wald = 4.692; p = 0.03), in body height (Wald = 6.229; p = 0.013), and in leg length (Wald = 4.321; p = 0.038) represented significant injury risk factors. Athletes who could improve their jump agility performance more, had smaller changes in the anthropometric characteristics and who were closer to their peak height velocity were at a lower injury risk. In the context of injury prevention, regular neuromuscular training should be incorporated, and phases of rapid growth have to be considered.

How do the new Olympic sports compare with the traditional Olympic sports? Injury and illness at the 2018 Youth Olympic Summer Games in Buenos Aires, Argentina

OBJECTIVE

To describe injuries and illnesses across traditional and new sports among the participating athletes of the Buenos Aires 2018 Youth Olympic Summer Games (BA YOG) (6-18 October 2018).

METHODS

We recorded the daily number of athlete injuries and illnesses (1) through the reporting of all National Olympic Committee (NOC) medical teams and (2) in the polyclinic and medical venues manned by the BA YOG 2018 medical staff.

RESULTS

In total, 3.984 athletes from 206 NOCs were observed. NOCs and BA YOG 2018 medical staff reported 619 injuries and 334 illnesses, equalling 15.5 injuries and 8.4 illnesses per 100 athletes over the 13-day period. The eight new sports on the Youth Olympic programme (futsal, beach handball, karate, roller speed skating, kitesurfing, BMX freestyle, climbing and break dancing) fell in between the other sports with respect to injury and illness risk. Injury incidence was highest in rugby (43% of all rugby players), followed by boxing (33%) and badminton (24%), and lowest in swimming, archery, roller speed skating, equestrian, climbing and rowing (<5%). The highest incidences of illness were recorded in golf (20%), followed by triathlon (16%), beach volleyball and diving (both 14%). Of the illnesses, 50% affected the respiratory system and 15% the gastrointestinal system. Injury and illness incidences varied between continents with athletes representing Europe having significantly fewer injuries and illnesses compared with other continents, apart from a similar illness incidence to Asian athletes.

CONCLUSION

The overall injury incidence of 15.5 injuries per 100 athletes was higher, while the overall illness incidence of 8.4 illnesses per 100 athletes was similar to previous youth and Olympic Games. The new sports did not differ significantly compared with the other sports with respect to injury and illness risk.

Gender-Specific Risk Factors of Physical Activity-Related Injuries among Middle School Students in Southern China

This cross-sectional study was carried out to explore the potential risk factors of physical activity-related injuries (PARI) among middle-school students of different genders. Selected by the random cluster sampling method, students aged from 12 to 16 years old in grades 7-8 from six middle schools in Shantou, southern China, were recruited for this investigation in November 2017. Information about socio-demographics, physical activity (PA) exposure time, individual exercise behaviors, risk-taking behaviors, and PARI experiences in the past 12 months was collected. A multivariate logistic regression model was used to explore the risk factors of PARI. A total of 1270 students completed valid questionnaires, with an overall injury incidence of 33.6% (boys: 42.0%; girls: 25.0%), an injury risk of 0.68 injuries/student/year, and an injury rate of 1.43 injuries per 1000 PA exposure hours. For boys, living in a school dormitory, participating in sports teams, exercising on a wet floor, rebellious behavior, and having longer PA exposure time were the risk factors of PARI. For girls, those who were sports team members, whose parents were divorced or separated, and those with longer PA exposure time were more vulnerable to suffer from PARI. In conclusion, PARI was a health problem among middle school students in southern China. Boys and girls differed in PARI occurrence and were affected by different risk factors, which provides a basis for targeted gender-specific intervention programs to reduce the occurrence of PARI among middle-school students.

Beighton scoring of joint laxity and injury incidence in Middle Eastern male youth athletes: a cohort study

Objectives

To examine the association between generalised joint laxity (GJL) and injury rates in Middle Eastern male youth athletes.

Design

Prospective observational study consisting of GJL screen and injury audit (season 2009/2010).

Setting

Aspire Sports Academy Doha, Qatar.

Participants

A total of 226 adolescent male athletes (mean age: 14.2 years; SD: 1.7; range: 10–18) involved in 15 sporting activities were grouped into contact and non-contact sports. All available athletes were included in this study.

Outcome measures

A seasonal injury audit, athletes’ anthropometric characteristics, for example, weight, height and body mass index and screen for GJL to determine Beighton Score (BS).

Results

The 226 athletes sustained 596 injuries and 75% reported at least one injury over a seasonal injury audit. Players in contact sports were injured more often than players in non-contact sports (more frequent injuries than injury-free time in contact sports; 127 days (95% CI 93 to 160) vs 176 days in non-contact sports (95% CI 118 to 234) (p<0.001). Survival analysis showed that gradient BS was not associated with injury HR=1.004 (95% CI 0.95 to 1.06) in the overall cohort. However, BS was associated with a greater injury risk in contact sports (HR: 1.29; 95% CI 1.05 to 1.59; p=0.015).

Conclusion

Greater GJL, defined by gradient BS, plus involvement in contact sports together influence injury risk in youth athletes. Preseason documentation of GJL scoring should be considered specifically for contact sports as injury pre-emptive measure.

Sports injuries aligned to predicted mature height in highly trained Middle-Eastern youth athletes: a cohort study

OBJECTIVES

To investigate the association of maturity status with injury incidence in Middle-Eastern youth athletes.

DESIGN

Prospective cohort study.

SETTING

Four consecutive seasons (2010-2014), Aspire Academy, Qatar.

PARTICIPANTS

Male athletes (age range: 11-18 years) representing four disciplines enrolled and grouped into two categories: individual sports and racquet sports.

OUTCOME MEASURES

Injury data collected over four seasons. Athletes' anthropometric characteristics assessed to calculate age at peak height velocity. Predicted mature heights (PMHs) collected and categorised into four quartiles. Athletes had wrist and hand radiographs for assessment of skeletal age (SA). Early and late maturers with an SA of >1 year older or younger than their chronological age (CA).

RESULTS

For the sample (n=67) across all groups, 43 (64%) athletes had one or more injuries: total of 212 injuries, 4.9 injuries per athlete across study. Survival analysis of maturity status using SA found early maturing athletes had two-fold greater injury risk compared with late maturers (HR 2.04, 95% CI 1.15 to 3.61, p=0.015). PMH associated with injury risk (HR 1.05, 95% CI 1.01 to 1.08, p=0.006).Athletes in fourth quartile (≥184 cm) had up to two-fold injury risk (HR 2.41, 95% CI 1.42 to 4.08, p=0.001). Racquet and individual sports involved similar injury risk (HR 1.14, 95% CI 0.86 to 1.52, p=0.37).

CONCLUSION

SA early maturity and PMH gradient were significant predictors of injury in youths.

Maximal Eccentric Hamstrings Strength in Competitive Alpine Skiers: Cross-Sectional Observations From Youth to Elite Level

Competitive alpine skiers are subject to substantial risks of injury, especially concerning the anterior cruciate ligament (ACL). During “landing back weighted” episodes, hamstrings may partially counteract the anterior shear force acting on the tibia by eccentrically resisting the boot-induced drawer of the tibia relative to the femur. The aim of the present study was to provide novel descriptive data and sport-specific reference values on maximal eccentric hamstrings strength (MEHS) in competitive alpine skiers from youth to elite level, and to explore potential relationships with sex, age and biological maturation. 170 competitive alpine skiers were investigated: 139 youth athletes (51 females, 88 males; age: 13.8 ± 0.59 years) and 31 elite athletes (19 females, 12 males; age: 21.7 ± 2.8 years). MEHS was assessed by the (Vald Performance, Newstead, Australia). U15 female skiers presented lower MEHS compared to female elite skiers for both limbs (R = 210 ± 44 N vs. 340 ± 48 N, respectively, p < 0.001, and L = 207 ± 46 N vs. 303 ± 35 N, respectively, p < 0.001). Similarly, lower MEHS was observed in U15 male skiers compared to male elite skiers for both limbs (R = 259 ± 51 N vs. 486 ± 62 N, respectively, p < 0.001, and L = 258 ± 57 N vs. 427 ± 54 N, respectively, p < 0.001). Correlations between MEHS and chronological age were modestly significant only for the U15 group (r = 0.37 and p < 0.001). When the correlations for the U15 group were performed between MHES and maturity offset (obtained from the calculation of biological age, i.e., age at peak height velocity), statistical significance was reached by all the correlations run for 3 variables (Males < 0: r = 0.59, p < 0.0001; Males > 0: r = 0.70, p < 0.0001; and Females > 0: r = 0.46, p < 0.0001, start of maturity offset = 0). This cross-sectional description of MEHS in alpine skiers from youth to elite level highlights the importance of biological maturation for MEHS values in youth athletes and presents novel data that may offer insights into new approaches for injury prevention.

Alpine Ski Racing Injuries

CONTEXT

This article reviews the epidemiology of alpine ski racing-related injuries, risk factors, mechanisms of injury, and injury prevention strategies.

EVIDENCE ACQUISITION

Pertinent literature from peer-reviewed publications from 1976 through 2018.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

The rate of injury in alpine ski racing is high. In general, knee injuries are the most common, with anterior cruciate ligament (ACL) disruptions being the most significant in terms of time loss from sport. Three specific mechanisms of ACL injury in alpine ski racers have recently been described (slip-catch, dynamic snowplow, and landing back-weighted). In contrast to other sports, female ski racers are not clearly at greater risk for ACL injury, especially at the highest level of competition. A high percentage of ski racers are able to return to their previous level of competition after ACL injury. Risk factors for injury and methods of injury prevention have been proposed; however, the rate of injury, particularly ACL injuries, has not decreased significantly.

CONCLUSION

Alpine ski racing has a high injury rate. ACL injuries in particular remain problematic. Further study is needed to identify modifiable risk factors and implementation of injury prevention strategies.

Challenges of talent development in alpine ski racing: a narrative review

Alpine ski racing is one of the most popular sports in many countries; nevertheless, selection disadvantages and severe injuries result in high dropout rates. In this review we summarize existing knowledge about the specific challenges associated with selection bias and injuries, and their effects on talent development in ski racing. The relative age effect (RAE) appears in all age categories of national Austrian and international alpine ski racing. Relatively younger athletes seem to only have a chance for selection if they are early maturing. Talent selection processes should consider both the biological maturity status as well as the relative age; additionally, a competition system based on a rotating cut-off date might contribute to a reduction of RAE. Youth and adolescent ski racers report lower injury rates compared to World Cup athletes. The knee was the most affected body part in relation to traumatic injuries. The most frequently reported overuse injuries were knee pain (youth) and low back pain (adolescent level). Athlete-related modifiable risk factors were core strength, neuromuscular control, leg extension strength and limb asymmetries. Based on these findings, prevention measures should be expanded to contribute to long-term injury prevention. In future research more multi-disciplinary, longitudinal studies should be performed.

Limb symmetry index in competitive alpine ski racers: Reference values and injury risk identification according to age-related performance levels

PURPOSE

The aims of this study were to assess differences of limb symmetry index (LSI) in strength- and coordination-related tasks between high-level, competitive, noninjured ski racers of different age-related performance levels and to prospectively assess limb differences as a possible risk factor for traumatic and overuse injury in youth ski racers.

METHODS

The study (Study 1) included 285 high-level competitive ski racers (125 females, 160 males) of 3 age-related performance levels and based on the school system: 95 youth (10-14 years, secondary modern school), 107 adolescent (15-19 years, grammar school), and 83 elite athletes (20-34 years). To investigate the second aim (Study 2), 67 of the 95 youth athletes were included and any traumatic or overuse injuries were prospectively recorded over 2 seasons. All athletes performed 4 unilateral tests (strength related: one-leg counter movement jump (OL-CMJ) and one-leg isometric/isokinetic press strength test (OL-ILS); coordination related: one-leg stability test (OL-ST) and one-leg speedy jump test (OL-SJ)). The LSI was calculated by dividing the dominant leg by the nondominant leg and multiplying by 100. Kruskal-Wallis H tests and binary logistic regression analyses were conducted.

RESULTS

There were significant differences between the LSI of the 3 age-related performance-level groups only in the strength-related tests: the OL-CMJ (χ²(2, 285) = 9.09; p = 0.01) and the OL-ILS (χ²(2, 285) = 14.79; p < 0.01). The LSI for OL-ILS was found to be a significant risk factor for traumatic injury in youth ski racers (Wald = 7.08; p < 0.01). No significant risk factors were found for overuse injuries.

CONCLUSION

Younger athletes display slightly greater LSI values only in the strength-related tests. The cut-off value of limb differences of <10% for return to sport decisions seems to be appropriate for elite athletes, but for youth and adolescent athletes it has to be critically discussed. It seems to be necessary to define thresholds based on specific performance tasks (strength vs. coordination related) rather than on generalizations, and age-related performance levels must be considered. Limb differences in unilateral leg extension strength represent a significant injury risk factor in youth ski racers.

Sex Differences in Balance Among Alpine Ski Racers: Cross-Sectional Age Comparisons

Although balance is a key ability in the strength demands of alpine ski racing, affecting both performance and injury prevention, few studies have examined balance or related sex differences among still-maturing athletes. In this 10-year study, we investigated cross-sectional balance performances at different age periods of a representative sample of over 500 11–18-year-old elite skiers of both genders. Participants performed balance tests using the MFT S3-Check. Left–right and forward–backward movements were used to calculate sensory and symmetry balance scores, which were both incorporated into a stability score. Mann–Whitney U tests assessed gender-specific differences by age-group with a significance level set at p < .05. Results showed gender differences only on forward–backward measurements for 14–16-year-olds, with females showing better stability and sensory (but not symmetry) scores than males. Thus, gender interacted with age and maturation to influence balance ability in these participants. Additionally, these rare 10-year data support coaches in their training and talent development of maturing athletes by providing important sport-, age-, and gender-specific normative comparison data for individual trainees.

Long-Term Athletic Development in Youth Alpine Ski Racing: The Effect of Physical Fitness, Ski Racing Technique, Anthropometrics and Biological Maturity Status on Injuries

Alpine ski racing is known to be a sport with a high risk of injuries. Because most studies have focused mainly on top-level athletes and on traumatic injuries, limited research exists about injury risk factors among youth ski racers. The aim of this study was to determine the intrinsic risk factors (anthropometrics, biological maturity, physical fitness, racing technique) for injury among youth alpine ski racers. Study participants were 81 youth ski racers attending a ski boarding school (50 males, 31 females; 9–14 years). A prospective longitudinal cohort design was used to monitor sports-related risk factors over two seasons and traumatic (TI) and overuse injuries (OI). At the beginning of the study, anthropometric characteristics (body height, body weight, sitting height, body mass index); biological maturity [status age at peak height velocity (APHV)]; physical performance parameters related to jump coordination, maximal leg and core strength, explosive and reactive strength, balance and endurance; and ski racing technique were assessed. Z score transformations normalized the age groups. Multivariate binary logistic regression (dependent variable: injury yes/no) and multivariate linear regression analyses (dependent variable: injury severity in total days of absence from training) were calculated. T-tests and multivariate analyses of variance were used to reveal differences between injured and non-injured athletes and between injury severity groups. The level of significance was set to p < 0.05. Relatively low rates of injuries were reported for both traumatic (0.63 TI/athlete) and overuse injuries (0.21 OI/athlete). Athletes with higher body weight, body height, and sitting height; lower APHV values; better core flexion strength; smaller core flexion:extension strength ratio; shorter drop jump contact time; and higher drop jump reactive strength index were at a lower injury risk or more vulnerable for fewer days of absence from training. However, significant differences between injured and non-injured athletes were only observed with respect to the drop jump reactive strength index. Regular documentation of anthropometric characteristics, biological maturity and physical fitness parameters is crucial to help to prevent injury in youth ski racing. The present findings suggest that neuromuscular training should be incorporated into the training regimen of youth ski racers to prevent injuries.