Ski-geometric parameters do not differ between ACL injury mechanisms in recreational alpine skiing

Purpose It is not known so far if ski-equipment-related factors differ between the ACL injury mechanisms, potentially influencing the circumstances and causes of falling, finally resulting in ACL injury. More specifically focusing on the injury mechanisms will provide a deeper understanding of injury causation. The aim of the study was to evaluate whether ACL injury mechanisms in recreational alpine skiing differ with regard to ski-geometric parameters, self-reported circumstances and causes of accident and injury severity. Methods Among a cohort of 392 ACL-injured (57.9% females) skiers, age, sex, height, weight, skill level, risk-taking behavior, circumstances and causes of accident, and ACL injury severity were collected by questionnaire. Additionally, patients had to recall their type of fall (ACL injury mechanism) by classifying forward and backward falls with and without body rotation. Ski length, side cut radius and widths of the tip, waist and tail were directly notated from the ski. Results The forward fall with body rotation was the most common reported ACL injury mechanism (63%). A riskier behavior was associated with forward falls without body rotation. Ski-geometric parameters did not significantly influence the type of ACL injury mechanism. Regarding accident characteristics, catching an edge of the ski was more frequent (p < 0.001) the cause for forward falls (75% and 67%) when compared to the backward falls (46 and 15%) and executing a turn was the most frequent action in all falls (39–68%). A complete rupture of the ACL (66–70%) was more commonly reported than a partial tear (30–34%) among all four non-contact ACL injury mechanisms (n.s.). Conclusion In contrast to risk-taking behavior and accident characteristics, ski-geometric parameters and injury severity do not significantly differ between ACL injury mechanisms in recreational skiing. Thus, an individual skiing style seems to have more impact on ACL injury mechanisms than ski equipment. Future studies should evaluate potential effects of ski geometry on the incidence of ACL injury. Level of evidence III.

CHRONOLOGICAL AGE OF ALPINE SKI MEDAL WINNERS IN THE 2015-2018 OLYMPIC CYCLE

Personal motivation, as well as engagement in alpine skiing, brought the authors to inspect the differences in average chronological age of alpine skiers, and to present the results to the professional public, in order to improve planning and programming of the training process. The paper analyzed the average chronological age of medal winning professional alpine skiers in the World Cups in the 2015-2018 Olympic cycle. The following alpine disciplines were analyzed: Slalom (SL), Giant Slalom (GS), Super-G (SG), Downhill (DH) and Alpine Combination (AC). The obtained results indicate that there was a significant difference in the average chronological age between male and female competitors. The results of the present study show that there were differences in GS, SG, DH, and AC, where male skiers are on average older than female skiers. Conversely, there was no significant difference between male and female skiers in SL. The results of this study could aid coaches and experts in future years of individual management of sports careers of male and female skiers.

Validity of the AdMos, Advanced Sport Instruments, GNSS Sensor for Use in Alpine Skiing

The AdMos receiver from Advanced Sport Instruments is a global navigation satellite system (GNSS) frequently used in alpine ski racing, with users from national and professional teams. Therefore, a validation was conducted for use of the AdMos in alpine skiing, using data from both recreational and competitive skiers. Athletes skied a total of 60 km in different measurement and skiing conditions, while carrying both an AdMos and a differential GNSS, which was used as the gold standard. From the GNSS position data, speed, acceleration, turn radius, trajectory incline and impulse were calculated as instantaneous and turn average measures for both GNSS systems and errors between the systems were calculated. The median and interquartile range (IQR) for the instantaneous errors were below 3.5 (3.5) m for horizontal plane position and below 7.0 (4.3) m for the 3D position. The median and IQR for instantaneous errors and turn average errors, respectively, were below 0.04 (0.24)/0.04 (0.16) m/s for speed, below 0.23 (1.06)/0.35 (0.63) m/s2 for acceleration, below 0.47 (5.65)/0.73 (5.3) m for turn radius, and below 0.043 (1.96)/0.42 (1.42) degrees for trajectory incline. The median and IQR for turn average impulse were 0.025 (0.099) BWs. The position error changed gradually and randomly over time, with low noise levels causing smooth trajectories of similar shape but spatially shifted from the true trajectory that allowed the position–time derivation of the performance parameters, and detection of turns with 3% median and 5% IQR error. The accuracy assessment revealed that (1) the error levels were comparable to other consumer-grade standalone GNSS units designed for sport; (2) the trajectories closely resembled the true trajectories but with a random shift that changed over time and had a low noise level; (3) there was a very low instantaneous speed error that may allow the detection of many performance aspects of skiing and other sports; and (4) there were larger instantaneous errors for the remaining performance parameters, which decreased substantially when averaged over a turn.

Risk Assessment of Alpine Skiing Events Based on Knowledge Graph: A Focus on Meteorological Conditions

The alpine skiing event is particularly vulnerable to changes in meteorological conditions as a winter sport held outdoors. The commonly used risk assessment methods cannot be inflexible and cannot be dynamically adjusted to combine multiple risk factors and actual conditions. A knowledge graph can organize data resources in the risk domain as structured knowledge systems. This paper combines a knowledge graph and risk assessment to effectively assess the risk status. First of all, we introduce the relevant literature review of sports event risk assessment, combining the characteristics of alpine skiing events. Then, we summarize the risk types of alpine skiing events and related risk knowledge. Secondly, a model is proposed to introduce an event risk assessment model based on the RippleNet framework combined with the characteristics of large-scale sports events. Moreover, the validity of the model is verified. The results show that the RippleNet-based event risk assessment model can be used to assess the risk of alpine skiing events. In order to effectively deal with the large-scale sports events that occur with a variety of risks, the smooth implementation of large-scale sports events provides a strong guarantee.

Removal of the Cervical Spine Collar from Alpine Extrication and Evacuation Skiing Rescue Spinal Motion Restriction Protocols: A Biomechanical Controlled Study in Real-Life Mountain Conditions with a High-Fidelity Mannequin

Background: Alpine skiing rescues are unique because of the mountainous environment and risks of cervical spine motion (CSM) induced during victims’ extrication (EX) and downhill evacuation (DE). Current pre-hospital guidelines recommend the application of full spinal immobilization using various orthotic devices such as cervical collars (CC) when mobilizing and transfer+ring a victim with a suspected spine injury. The biomechanical benefits of applying CC in terms of spinal motion restriction during simulated alpine rescue are undocumented. Methods: Observational design of CSM measurement on a high-fidelity simulation mannequin with a motion sensors-instrumented cervical spine during simulated alpine skiing EX and DE. A total of 32 EXs and 4 DEs on different slope conditions were performed by six experienced active ski patrollers at a Canadian ski resort. The primary outcome was the 3D excursion vector (PeakΔθ) of the mannequin’s head. The secondary objectives were the time to extrication completion (tEX) depending on CC use and to identify which EX event is more likely to induce CSM. Results: PeakΔθ recorded during flat terrain EX using CC was 11.71° +/- 3.61° compared to 16.00° +/- 7.93° using MILS, and 18.29° +/- 9.78° for CC versus 17.90° +/- 4.16° using MILS on a steep slope. PeakΔθ with CC or using MILS during EXs were equivalent according to a 10 degrees non-inferiority hypothesis testing. Time to extrication completion (tEX) was significantly higher using CC as opposed to MILS for both flat and steep terrain conditions (100.6s vs. 219.2s and 106.2s vs. 268.8s longer respectively, 95% confidence interval). During DEs, CSM with and without CC across all terrain conditions were negligible (<5°). Task analysis during EX showed that when CC is used, its installation induces the highest CSM. When EXs are done using MILS without CC, the logroll initiation is the manipulation inducing the highest risk of CSM. Conclusion: For experienced ski patrollers, the biomechanical benefits of motion restriction provided by CC over MILS during alpine skiing rescues were found to be at best marginal and CC use negatively affected rescue time. Systematic use of CC during alpine rescue should be reconsidered.

Bilateral Occipital Neuralgia in a Patient with Neurofibromatosis Type 1: A Case Report

Plexiform neurofibromas (PNFs) represent an uncommon variant (30%) of neurofibromatosis type 1 (NF-1), in which neurofibromas arise from multiple nerves as bulging and deforming masses involving connective tissue and skin folds. We report the case of a 17-year-old man with known NF-1 presenting with bilateral occipital neuralgia that began in his late adolescence. His chief complaint was radiating pain in the occiput induced by protective helmet wear when riding alpine skiing. Craniofacial magnetic resonance imaging (MRI) confirmed the presence of fusiform masses arising from the bilateral greater occipital nerves. Histopathological examination of the biopsy samples showed PNFs. After surgical treatment, the patient's symptoms completely improved. Unlike cutaneous neurofibromas, PNFs have different clinical characteristics and have the risk of malignant mutations. Correct diagnosis and adequate surgical treatment are necessary for PNFs.

Mechanics of side-slipping in alpine skiing. Braking and skidded traversing

A recently proposed simple approximate theory of snow machining is applied to modelling of several basic manoeuvres of alpine skiing: fall-line side-slipping, traversing, and hockey stop. The results agree with the skiing practice and explain the abnormally high friction reported in previous field studies. They also prepare foundation for future rigorous testing of the theory, which will determine its accuracy and limits of applicability.