Racing Experiences of Recreational Distance Runners following Omnivorous, Vegetarian, and Vegan Diets (Part B)-Results from the NURMI Study (Step 2).

The potential running or endurance performance difference based on following different general types of diets, such as omnivorous, vegetarian, or vegan, remains questionable. Several underlying modifiable factors of long-distance running performance, especially runner training behaviors and experience, diminish the clarity of results when analyzing dietary subgroups. Based on the cross-sectional design (survey), the NURMI Study Step 2 aimed to investigate a plethora of training behaviors among recreational long-distance running athletes and the relationship of general diet types with best time race performance. The statistical analysis was based on Chi-squared and Wilcoxon tests. The final sample (n = 245) included fit recreational long-distance runners following an omnivorous diet (n = 109), a vegetarian diet (n = 45), or a vegan diet (n = 91). Significant differences were found between the dietary subgroups in body mass index (p = 0.001), sex (p = 0.004), marital status (p = 0.029), and running-related motivations for well-being (p < 0.05) but not in age (p = 0.054). No significant difference was found for best time half-marathon, marathon, and/or ultra-marathon race performance based on diet type (p > 0.05). Whether the vegan diet is associated with enhanced endurance performance remains unclear. Although, the present results are suggestive that 100% plant-based (vegan) nutrition is compatible with distance running performance at the least.

Training Behaviors and Periodization Outline of Omnivorous, Vegetarian, and Vegan Recreational Runners (Part A)-Results from the NURMI Study (Step 2).

Runners train for long-distance competitions based on underlying motivations, which may be similar to individual dietary motivations (e.g., well-being and performance). Fundamental training differences may arise in recreational runners following different diet types (omnivore, vegetarian, vegan) considering possible motive variations. Following a cross-sectional design, distance runners completed a survey (online), including a thorough assessment of training behaviors with generic training details and periodization specifics in three phases: 1. an intermediary and rebound stage, 2. a main preparatory stage, and 3. a main event stage (tapering or interim event level/s). Kruskal-Wallis and chi-squared tests were used in the statistical analysis. A total of 245 fit recreational runners following omnivore (n = 109), vegetarian (n = 45), and vegan diets (n = 91) were included. Significant differences in the initial running motivation were found across dietary subgroups (p = 0.033) as well as for current motivations (p = 0.038), with vegetarians being the least health motivated (27% and 9%, respectively). No differences in each of the specific periods were found between diet types across the outline (p > 0.05). The present evidence shows that there is a lack of fundamental training differences based on recreational runners following different generic types of diets. The results of the present investigation may be especially relevant for future studies on safety, sustainability, and performance-enhancing dietary practices among athletes.

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.

Are There Associations Between Submaximal and Maximal Aerobic Power and International Ski Federation World Cup Ranking in Elite Alpine Skiers?

PURPOSE: To analyze the predictive value of parameters of submaximal and maximal cardiopulmonary exercise performance on International Ski Federation (Fédération Internationale de Ski) World Cup ranking (FIS ranking) in elite Austrian Alpine skiers. METHODS: Over 7 World Cup seasons (2012-2018), exercise data (maximal oxygen uptake and maximum power output, lactate threshold 2, and ventilatory threshold 2, based on stepwise cycle spiroergometry) were analyzed to determine whether there was a correlation between world FIS ranking and exercise capacity of male and female elite Alpine skiers. RESULTS: The data of 39 male skiers (age: 27.67 [4.20] y, body mass index: 26.03 [1.25] kg/m2) and 36 female skiers (age: 25.49 [3.18] y, body mass index: 22.97 [1.71] kg/m2) were included in this study. The maximum oxygen uptake and maximum power output ranged from 4.37 to 4.42 W/kg and 53.41 to 54.85 mL/kg/min in men and from 4.17 to 4.30 W/kg and 45.96 to 49.16 mL/kg/min in women, respectively, over the 7 seasons; the yearly mean FIS ranking ranged from 17 to 24 in men and 9 to 18 in women. In a fixed-effects model used for the subsequent panel regression analysis, no statistically significant effect on FIS ranking was found for the exercise parameters of interest. CONCLUSIONS: Neither maximal aerobic tests nor maximum power output significantly predicted competitive performance, as indexed by the FIS ranking. This reinforces the assumption that no single parameter determines competition performance in this complex sport. Therefore, identifying the optimum amount of endurance training remains a major challenge for athletes and coaches, as does identifying and improving the factors that determine performance.

Nationality and sociocultural factors influence athlete development and sport outcomes: Perspectives from United States and Austrian youth alpine ski racing.

Geographical regions possess distinct sporting cultures that can influence athletic development from a young age. The United States (US) and Austria both produce elite alpine ski racers, yet have distinct sport structures (i.e., funding, skiing prominence). In this exploratory study, we investigated sport outcomes and psychological profiles in adolescent alpine ski racers attending skill development academies in the US (N= 169) and Austria (N= 209). Sport participation and psychological questionnaires (mental toughness, perfectionism, grit, coping, burnout) were administered to athletes. In Austria, athletes participated in fewer extracurricular sports, began competing and training younger, and accumulated less practice hours than athletes in the US. Athletes in the US reported greater burnout than athletes in Austria. Finally, in the US, women accumulated more practice hours and experienced more parental pressure than men, while men accumulated more practice hours in Austria. Austria's skiing-centric sport culture may encourage athletes to fully immerse into the sport, contributing to positive psychological outcomes. Reduced sport opportunities in the US beyond educational institutions may pressure athletes to practice more to ensure continued competitive skiing. Stressors for sport participation will be unique to gender in each country though, given their implicit gender stigmas for sport participation.

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 (ß = 0.348; p = 0.044; R²â€¯= 0.121) and training volume represents a risk factor for illnesses in the following week (ß = 0.397; p = 0.027; R²â€¯= 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.

Changes in Anthropometric and Fitness Characteristics Over a Decade of Young Elite Alpine Ski Racers.

PURPOSE: The aim of this study was to evaluate whether anthropometric and fitness characteristics have changed between former and current elite male and female Austrian young ski racers (U11-U15). METHODS: A battery of anthropometric, general, and skiing-specific fitness tests was conducted annually. In total, 1517 participants (846 males, 671 females) who were tested in 2005-2009 ("former athletes" n = 805) and 2015-2019 ("current athletes" n = 712) were included. Independent t tests and Cohen d were calculated to compare the two 5-y periods, separated by sex and age group. The level of significance was set at P < .05. RESULTS: No significant change in anthropometric characteristics was found over the decade. Current young ski racers performed significantly better in the maximal core flexion strength test in all age categories (ES = 0.88-1.50; P < .02). Core extension strength values were higher in current male U12 and female U12 and U13 athletes (ES = 0.54-0.71; P < .01) and better postural stability values in the lateral direction were found in the age categories U12 and U14 (ES = 0.36-0.68; P < .05), as well as in the forward/backward direction in the age categories U12-U14 (ES = 0.38-1.12; P < .03). Lower-leg extension strength values were apparent in the current U13-U15 age categories (ES = 0.36-1.03; P ≤ .001) and lower drop-jump reactive strength indices in the U13-U15 male athletes (ES = 0.49-0.80; P < .01). CONCLUSIONS: Current and former young ski racers differ significantly in some fitness parameters, which might lead to the assumption that some aspects (such as core strength) have gained more focus in athletic training during the last years compared with 15 y ago.

Correction: The path to international medals: A supervised machine learning approach to explore the impact of coach-led sport-specific and non-specific practice.

[This corrects the article DOI: 10.1371/journal.pone.0239378.].

Using Wearable Sensors and a Convolutional Neural Network for Catch Detection in American Football.

Highly efficient training is a must in professional sports. Presently, this means doing exercises in high number and quality with some sort of data logging. In American football many things are logged, but there is no wearable sensor that logs a catch or a drop. Therefore, the goal of this paper was to develop and verify a sensor that is able to do exactly that. In a first step a sensor platform was used to gather nine degrees of freedom motion and audio data of both hands in 759 attempts to catch a pass. After preprocessing, the gathered data was used to train a neural network to classify all attempts, resulting in a classification accuracy of 93%. Additionally, the significance of each sensor signal was analysed. It turned out that the network relies most on acceleration and magnetometer data, neglecting most of the audio and gyroscope data. Besides the results, the paper introduces a new type of dataset and the possibility of autonomous training in American football to the research community.

The path to international medals: A supervised machine learning approach to explore the impact of coach-led sport-specific and non-specific practice.

Research investigating the nature and scope of developmental participation patterns leading to international senior-level success is mainly explorative up to date. One of the criticisms of earlier research was its typical multiple testing for many individual participation variables using bivariate, linear analyses. Here, we applied state-of-the-art supervised machine learning to investigate potential non-linear and multivariate effects of coach-led practice in the athlete's respective main sport and in other sports on the achievement of international medals. Participants were matched pairs (sport, sex, age) of adult international medallists and non-medallists (n = 166). Comparison of several non-ensemble and tree-based ensemble binary classification algorithms identified "eXtreme gradient boosting" as the best-performing algorithm for our classification problem. The model showed fair discrimination power between the international medallists and non-medallists. The results indicate that coach-led other-sports practice until age 14 years was the most important feature. Furthermore, both main-sport and other-sports practice were non-linearly related to international success. The amount of main-sport practice displayed a parabolic pattern while the amount of other-sports practice displayed a saturation pattern. The findings question excess involvement in specialised coach-led main-sport practice at an early age and call for childhood/adolescent engagement in coach-led practice in various sports. In data analyses, combining traditional statistics with advanced supervised machine learning may improve both testing of the robustness of findings and new discovery of patterns among multivariate relationships of variables, and thereby of new hypotheses.

[Injuries and influencing factors on accidents in paragliding]. / Verletzungen und das Unfallgeschehen beeinflussende Faktoren im Paragleitsport.

Approximately 100 000 pilots worldwide practice the sport of paragliding. Most studies performed to date have been conducted retrospectively, using data from hospitals or emergency rescue organisations and focusing on injury patterns. Reasons for accidents and possible influencing factors have hardly been investigated. Therefore, the aim of this study was to analyse paragliding accidents in the Alps and to identify possible influencing factors. The data were taken from the "Flash-News" magazine (issues no. 149-160) covering the years 2015 to 2017. Only accidents occurring in Austria, Germany, Switzerland and Italy were considered. All in all, 487 accidents met the inclusion criteria of using a conventional paraglider and were analysed in this study. 88.5 % of the pilots involved were male and the average age was 42.9 ±â€Š13.7 years. Most accidents happened in summer and during the afternoon hours. The majority of incidents happened during the flight phase, but the comparison of tandem and solo pilots showed that tandem pilots had significantly more accidents during the take-off phase, whereas solo pilots had more accidents during the landing phase. Mistakes by pilots were identified as the main reason for accidents, followed by accidents caused by wind. In 71 of 487 (14,6 %) accidents, the pilots were not injured. If they were injured during the accident, the lower limbs were injured most frequently (35.5 %). In 45 of 487 accidents, the pilots died during the accident (9,2 %). The fact that more flights were executed during the summer months, combined with the more demanding flight conditions in summer (wind, weather, thermal conditions) may have led to the increased number of incidents in the period from April to August. Mistakes by pilots were identified as the major causes of accidents; therefore, training to handle difficult situations and the equipment are suggested. In general, the documentation of paragliding accidents is insufficient and inconsistent. The implementation of a harmonised, transnational form to document paragliding accidents is recommended to get unified and comparable data.

Physical Fitness after Anterior Cruciate Ligament Reconstruction: Influence of Graft, Age, and Sex.

Functional tests are used to facilitate return-to-sports decisions after anterior cruciate ligament reconstruction (ACLR). This study presents comprehensive physical fitness test data acquired in highly active patients within the first year after ACLR, for comparison between different grafts, age groups, and sexes. The outcomes from a specific seven-item test battery and isokinetic strength test data were extracted from a patient database. Results were compared to normative data from age- and sex-matched controls and between subgroups of patients. A total of 245 patients (94 women, 23.8 ± 8.4 years, pre-injury Tegner 7.4 ± 1.6) were tested 185 ± 44 days after surgery. In 116 patients (47.3%), one or more test results were classified as "poor" or "very poor" after comparison with normative data, with failures being most frequent during single-leg squat jump and plyometric strength tests. Test failures were more prevalent in adults than in adolescents <19 years (61.4%-62.2% vs. 24.5%, p < 0.001) and in men (61.6% vs. 24.5%, p < 0.001), but no differences were found between grafts. Isokinetic knee extensor strength was lower by 24.1% on the injured side. Six months after ACLR, nearly 50% of highly active patients presented with strength and functional fitness deficits. These deficits are particularly prevalent in older patients and men.

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.

Can Hyperoxic Preconditioning in Normobaric Hypoxia (3500 m) Improve All-Out Exercise Performance in Highly Skilled Skiers? A Randomized Crossover Study.

BACKGROUND: The altering effects of hypoxia on aerobic/anaerobic performance are well documented and form the basis of this study. Application of hyperoxic gases (inspiratory fraction of oxygen [FiO2] > 0.2095) prior to competition or training (hyperoxic preconditioning) can compensate for the negative influence of acute hypoxia. PURPOSE: To investigate whether oxygen supplementation immediately prior to exercise (FiO2 = 1.0) improves all-out exercise performance in normobaric hypoxia (3500 m) in highly skilled skiers. METHODS: In this single-blind, randomized, crossover study, 17 subjects performed a 60-second constant-load, all-out test in a normobaric hypoxic chamber. After a short period of adaptation to hypoxia (60 min), they received either pure oxygen or chamber air for 5 minutes prior to the all-out test (hyperoxic preconditioning vs nonhyperoxic preconditioning). Capillary blood was collected 3 times, and muscle oxygenation was assessed with near-infrared spectroscopy. RESULTS: Absolute and relative peak power (P = .073 vs P = .103) as well as mean power (P = .330 vs P = .569) did not significantly differ after the hyperoxic preconditioning phase. PaO2 increased from 51.3 (3) to 451.9 (89.0) mm Hg, and SaO2 increased from 88.2% (1.7%) to 100% (0.2%) and dropped to 83.8% (4.2%) after the all-out test. Deoxygenation (P = .700) and reoxygenation rates (P = .185) did not significantly differ for both preconditioned settings. CONCLUSIONS: Therefore, the authors conclude that hyperoxic preconditioning did not enhance 60-second all-out exercise performance in acute hypoxia (3500 m).

Effects of Visual and Auditory Perturbations on Ski-Specific Balance among Males and Females-A Randomized Crossover Trial.

Injuries in skiing show sex-specific differences, especially when visual perception is reduced. Reduced visual perception impairs balance, which plays an important role in avoiding skiing injuries. However, males and females might cope differently with reduced visual perception. Thus, the aim of this study was to evaluate sex-related effects of environmental perturbations (reduced visual perception and listening to music) on ski-specific balance. Using a crossover design, ski-specific balance was tested in 50 young adults (50% female) in four conditions: with and without listening to music and/or with and without reduced visual perception (ski goggles with occlusion foil). A four × two (condition by sex) mixed ANOVA revealed a significant condition by sex interaction, partial η² = 0.06. Females showed an increase in balance from the condition without music/with normal visual perception to the condition with music/with normal visual perception, while males showed a decrease. Balance was significantly higher in females compared to males, partial η² = 0.31. The findings suggest that balance is affected differently by environmental perturbations in females and males. However, the differences observed were not in line with our initial hypotheses, which might be because the model was too simplistic for how visual/auditory perturbations may affect balance.

The 2 Minute Loaded Repeated Jump Test: Longitudinal Anaerobic Testing in Elite Alpine Ski Racers.

This study investigated the 4-year development of anaerobic power and capacity in Austrian elite female alpine ski racers and examined the relationship between the 2-minute loaded repeated jump test (LRJT) results and ski racing performance (International Ski Federation (FIS) points). Ten Austrian elite female ski racers were tested prior to four racing seasons. The LRJT consisted of 48 loaded countermovement jumps (LCMJs) with barbell load equivalent to 20% bodyweight. Before the LRJT, maximal body mass normalized average power of a single LCMJ (PMAX) was determined. The mean jump power was calculated across all jumps in the test (P0-120). Anaerobic power (PMAX) in season 2 (32.3 ± 2.3 W·kg-1) significantly improved over season 1 (30.5 ± 2.3 W·kg-1) (p < 0.05) but there were no further differences between seasons, with season 3 at 33.5 ± 3.4 W·kg-1 and season 4 at 33.6 ± 3.0 W·kg-1. Anaerobic capacity (P0-120) increased up to season 3 by 9.2% (27.1 ± 2.8 to 29.6 ± 2.4 W·kg-1), but was significantly higher only when comparing season 4 to seasons 1 and 2 (p < 0.05). FIS points changed significantly (p < 0.05), from 18.1 ± 8.2 in season 1 to 8.4 ± 4.8 in season 4 (lower FIS points indicates better racing results). FIS points had a positive relationship with PMAX (r = -0.73, p < 0.05) and P0-120 (r = -0.64, p < 0.05) only in season 4. Improvements in FIS points from year to year did not correlate with seasonal increases in LRJT results. In conclusion, anaerobic power improved only after season 1, and anaerobic capacity changes were evident only in season 4. Ski racing performance (FIS points) correlated with LRJT test results in only season 4. The LRJT can monitor a ski racer's anaerobic power and capacity, but does not correlate with ski racing performance.

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.

Did the Relative Age Effect Change Over a Decade in Elite Youth Ski Racing?

The relative age effect (RAE) represents an asymmetry in birth quarter distribution, favoring athletes born early in the selection year and discriminating against late born athletes. The RAE was proven to be present in all age categories of national and international levels of alpine ski racing. Due to the existence of the RAE in all categories, it can be assumed that a selection error takes place favoring early born and early maturing youth ski racers. However, whether selection strategies have changed during the last years due to the high amount of research done in this field, has not been investigated so far in this sport. Therefore, the aim of the present study was to assess whether the magnitude of the RAE in youth ski racers aged 10-14 years has changed during the last decade by comparing the periods 2005-2009 ("former" athletes) and 2015-2019 ("current" athletes). Pupils of a well-known skiing-specific secondary modern school as well as members of the provincial ski team, who all competed at national levels, were included in the study. Next to the birth months, anthropometric characteristics (body height, weight, body mass index) were assessed. Chi-square tests were used to compare differences between the observed and expected relative age quarter distributions across five age categories (U11-U15). Additionally, Kruskal-Wallis-H-Tests were performed to assess differences in anthropometric characteristics between athletes of the four relative age quarters. Mann-Whitney U-Tests were performed to assess possible differences in anthropometric characteristics between former and current ski racers. A highly significant RAE was present in both former [χ2 (3, 764) = 60.36; p < 0.001; ω = 0.31] and current youth ski racers [χ2 (3, 702) = 43.13; p < 0.001; ω = 0.29] with an over-representation of athletes of Q1 (30.3-34.2%) and a clear under-representation of athletes of Q4 (14.8-15.0%). Generally, results indicated no change in the magnitude of the RAE in youth alpine ski racing over the past 10-15 years, emphasizing the robust nature of this phenomenon. No significant differences were found in any of the anthropometric characteristics between athletes of the four relative age quarters in both former and current athletes, indicating that relatively younger athletes of the last relative age quarter seem to have to have advanced anthropometric characteristics for being selected. Changes in the talent selection process should be performed to reduce the impact of the RAE.

Fitness, knee function and competition performance in professional alpine skiers after ACL injury.

OBJECTIVES: To assess the fitness of elite alpine skiers during recovery from anterior cruciate ligament (ACL) reconstruction and changes in performance level after return to competition. DESIGN: Retrospective cohort study. METHODS: The database of a specialized sports clinic was screened for professional alpine skiers with a history of ACL rupture and reconstruction. Strength and further functional tests as well as questionnaire data reflecting the athletes' subjective perception of pain, function in activities of daily living and physical activity levels were extracted. The website of the International Ski Federation (FIS) was used to obtain FIS points reflecting the competition performance level prior to injury, after return to competition as well as one year later. RESULTS: Questionnaire data revealed the highest patient satisfaction. Measurements performed 161.5±24.2days after surgery showed persistent muscle strength and power deficits, which primarily affected the knee extensor muscles and were more pronounced following reconstruction using quadriceps as compared to hamstring tendon grafts. FIS points increased immediately after return to competition (364.3±142.5days post-reconstruction) but dropped below pre-injury levels within the first year. CONCLUSIONS: ACL injuries sustained by professional skiers entail muscle strength and power deficits that persist for more than five months after surgery. The rate of recovery of knee extensor muscle function may be slower following ACL reconstruction using quadriceps tendon grafts. On average, athletes returned to competition within one year after surgery and succeeded in surpassing their baseline performance level within the first year after return to competition.

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.