Exploration of the minimum visual disability criteria for Para nordic and Para alpine skiing using simulated vision impairments.

The International Paralympic Committee Classification Code requires sports to develop evidence-based, sports-specific classification systems. This project aimed to determine the minimum eligibility criteria for Para nordic and Para alpine skiing by simulating vision impairments and measuring the impact of the impairments on performance in twenty-two nordic (28.09 ± 9.68 years; 16 male) and eleven alpine (37.91 ± 18.9 years, 11 male) able-sighted skiers. Eight visual acuity (VA)/contrast sensitivity (CS) (Cambridge Simulation Glasses, University of Cambridge) and six visual field (VF) impairments (bespoke goggles; University of Waterloo) were simulated. VA, CS and VF were measured in each participant before they completed an on-snow session, skiing short competition-style courses with each of the 14 simulated impairments in a randomized order. Clear goggle (no impairment) trials were used as controls. Receiver Operating Characteristic (ROC) and decision tree analyses were conducted to determine the optimum VA, CS and VF cut-offs for classifying performance based on differences from baseline in real time. Moderate impairments in VA, CS and VF negatively affect skiing performance. The recommended cut-off criteria based on both analyses were VA ≥0.90 logMAR and ≤48% VF extent for nordic and VA of ≥0.60 logMAR and VF extent of ≤59.0% for alpine.

Classification of Alpine Skiing Styles Using GNSS and Inertial Measurement Units.

In alpine skiing, four commonly used turning styles are snowplow, snowplow-steering, drifting and carving. They differ significantly in speed, directional control and difficulty to execute. While they are visually distinguishable, data-driven classification is underexplored. The aim of this work is to classify alpine skiing styles based on a global navigation satellite system (GNSS) and inertial measurement units (IMU). Data of 2000 turns of 20 advanced or expert skiers were collected with two IMU sensors on the upper cuff of each ski boot and a mobile phone with GNSS. After feature extraction and feature selection, turn style classification was applied separately for parallel (drifted or carved) and non-parallel (snowplow or snowplow-steering) turns. The most important features for style classification were identified via recursive feature elimination. Three different classification methods were then tested and compared: Decision trees, random forests and gradient boosted decision trees. Classification accuracies were lowest for the decision tree and similar for the random forests and gradient boosted classification trees, which both achieved accuracies of more than 93% in the parallel classification task and 88% in the non-parallel case. While the accuracy might be improved by considering slope and weather conditions, these first results suggest that IMU data can classify alpine skiing styles reasonably well.

Skiing and Snowboarding Injuries in Snow Parks: A Study Based on Self-Reported Practitioners' Statements.

INTRODUCTION: Snow parks (SPs) are an essential part of what draws individuals to winter resorts. When compared to traditional skiing and snowboarding, SPs heighten the risk and severity of injuries, as well as the rate of hospitalization. The aim of this study is to contribute to the knowledge on accidents in SPs based on the self-reported statements of practitioners. METHODS: A questionnaire measured self-reported accident frequency and type, the nature of injuries sustained, the duration of the discomfort caused, and contributing factors such as terrain features. Demographic and sport-related data, such as ability and frequency of participation, were also collected. The questionnaires were administered in several SPs in the French Alps. RESULTS: Teenagers and experienced freestylers are most frequently injured. The nature and location of injuries vary depending on the level of practice and type of feature. Few injured participants contact emergency services. CONCLUSIONS: The rate of injuries in SPs exceed that reported in prior research. Because expert and young participants expose themselves to particularly serious bodily impacts in SP, they must pay special attention to prevention.

Cambios hormonales en soldados aclimatados durante una marcha en gran altitud con esquí de montaña / Hormonal changes in acclimatized soldiers during a march at a high altitude with mountain skis

Background: The aim of the present study is to identify the physiological impact of acute exposure to high altitudes on special acclimatized troops of the Chilean Army. Twenty-nine soldiers carried out a nocturnal winter march on mountain skis at an initial altitude of 2,800 m and up to 3,640 m. Two separate blood measurements were taken. The first one was taken the day before the march (Pre-sample) and the second one just after returning to the base camp (Post-sample). All subjects had been acclimatized prior to the study. For hypothesis comparison purposes, the normality of the distribution was tested using the Shapiro-Wilk test. To determine if there were significant differences between the Pre and Post tests, a paired-samples Student t-test was applied for the variables with a normal distribution, and the Wilcoxon test was applied for the variables without a normal distribution. In all cases, a level of significance of 95% (p<0.05) was taken into consideration. Results: Exposure of acclimatized troops to altitudes of 2,800 m to 3,640 m has an impact on the endocrine parameters and on the reduction of cortisol (p<0.01), total testosterone (p<0.0001), free testosterone (p<0.0001) and the free testosterone-cortisol ratio (p<0.01). Likewise, an increase in total leukocytes (p<0.0001), neutrophils (p<0.0001), monocytes (p<0.0001) and basophils (p<0.001), as well as a decrease of eosinophils (p<0.0001) and lymphocytes (p<0.01), was observed. No hematological changes were detected. Conclusions: Endocrine changes were observed during high-altitude winter marches on mountain skis carried out by accli-matized Special Operation Troops, resulting in decreased cortisol and free and total testosterone levels. A stress condition due to the high altitudes also affected the anabolic/catabolic environment, which manifested as a significant decrease in the free testosterone/cortisol ratio. No hematological changes were identified. Marked changes were observed in some white cell series

Introducción: El objetivo del presente estudio es identificar el impacto fisiológico (con especial atención a los parámetros endocrinos y hematológicos) de la exposición aguda a gran altitud (GA) en tropas especiales aclimatadas del Ejército de Chile. Veintinueve soldados llevaron a cabo una marcha nocturna con esquí de montaña invernal a una GA de 2.800 m. hasta 3.640 m. Se tomaron dos muestras de sangre. La primera muestra fue tomada el día antes de la marcha (Pretest) y la segunda muestra justo después al regresar al campamento base Post test (a los 2.800 m). Todos los sujetos se encontraban aclimatados antes del estudio. Para cada análisis se testeo la normalidad de las distribuciones empleando el test de Shapiro-Wilk. Se calculó el promedio y la desviación estándar para cada medición. Para determinar si existían diferencias significativas entre el pre y post test se aplicó la prueba de t-Student pareada para las variables con distribución normal y el test de Wilcoxon para las variables que no tenían distribución normal. En todos los casos se consideró un nivel de confianza de 95% (valor p < 0,05). Resultados: La exposición de las tropas aclimatadas a GA tiene un impacto en los parámetros endocrinos y en la reducción de cortisol (p <0,01), testosterona total (p <0,0001), testosterona libre (p <0,0001) y el ratio testosterona libre-cortisol (p <0.01). Asimismo, se observaron un aumento de leucocitos (p <0,0001), neutrófilos (p <0,0001), monocitos (p <0,0001) y basófilos (p <0,001), así como una decrease de eosinófilos (p <0,0001) y linfocitos (p < 0.01). No se observaron cambios en la serie roja. Conclusiones: La marcha invernal nocturna con esquí de montaña en GA para tropas de operaciones especiales aclimatadas presento cambios endocrinos con disminución del cortisol, testosterona libre y total. Una condición de estrés por la marcha en GA también afectó al ambiente anabólico/catabólico, lo que se ve reflejado en una disminución significativa en el cociente testosterona libre/cortisol. No se observaron cambios hematológicos. Se observaron cambios significativos en algunas células de la serie blanca

Risk of Death and Major Injury from Natural Winter Hazards in Helicopter and Snowcat Skiing in Canada.

INTRODUCTION: Guests and guides partaking in helicopter and snowcat skiing (collectively known as mechanized skiing) are exposed to numerous natural winter hazards that can result in injury or death, but detailed quantitative risk estimates are currently lacking. This lack represents a considerable barrier for evaluating existing risk management practices and implementing evidence-based improvements. METHODS: We collected historical incident and exposure information from mechanized skiing operations in Canada to perform a retrospective risk analysis. Our analysis dataset includes 713 incidents that resulted in injuries or fatalities among guests or guides during a total of 3,258,000 skier days from the 1970 to 2016 winter season. RESULTS: Overall risk of death from natural winter hazards in mechanized skiing was 18.6 fatalities per million skier days (1997-2016). Although the risk of death from avalanches decreased substantially over the entire study period, avalanches remain the largest contributor to the overall risk of death (77%), followed by tree wells and other non-avalanche-related snow immersions. The risk of death from avalanches in snowcat skiing is about half of that in helicopter skiing, but other snow immersion fatalities are more common. The risk of major injury to guests is primarily associated with other falls and collisions. The risk of major injury for guides is higher in snowcat skiing than in helicopter skiing. CONCLUSION: We recommend the design of an industry-wide incident and near-miss reporting system to support evidence-based improvements of safety practices.

Evaluation of Explosive Power Performance in Ski Jumpers and Nordic Combined Competitive Athletes: A 19-Year Study.

Between 1992 and 2010, a total of 334 males participated in this study that assessed the differences and relationships between anthropometric variables and lower limb muscle strength in young and adult ski jumpers (n = 207) and Nordic combined (NC, n = 127) athletes. All athletes completed a maximal vertical jump from an in-run position and a maximal relative isometric force (MRIF) of the knee extensor measurement in a laboratory setting. The body mass index (BMI) in young competitors was lower than in adult groups (NC: p < 0.001; ski jumping [SJ]: p < 0.001). Similarly, the MRIF in both limbs was lower for both disciplines in the groups of young competitors. The vertical jump height (VJH) was lower for young competitors than for adults (NC: p ≤ 0.05; SJ: p < 0.001). When comparing SJ and NC athletes, BMI was lower in SJ athletes. In addition, the adult SJ competitors exhibited greater values of bilateral MRIF (p ≤ 0.05) and VJH (p < 0.01). There was a strong positive correlation in MRIF between the left and right lower limbs (p < 0.001) for all groups of SJ and NC athletes; therefore, it was determined to be sufficient to measure the MRIF on a single limb. Application of the new training methods (e.g., less emphasis on maximum resistance exercises) resulted in improved explosive power in ski jumpers even at lower-body weights. These changes are in accordance with the change in ski jump techniques.

[Recreational or professional participants in Nordic skiing. Differences in injury patterns and severity of injuries]. / Breiten- und Vereinssport beim Nordischen Skisport. Unterschiede in Verletzungsmuster und Verletzungsschwere.

A total of 441 Nordic skiing injuries were observed and analysed for a period of two winter seasons. The data showed that athletes in squads (0.02/1000 days) or professional clubs (0.09/1000 days) have lower injury risks compared to those doing Nordic skiing in their leisure time (0.51/1000 days). Amongst recreational athletes, women (0.65/1000 days) sustain trauma more frequently than men (0.40/1000 days). In professional athletes, the upper limb is commonly injured, whereas there are fewer head and trunk injuries. Furthermore the injured in this group are younger and have less severe injuries. Recreational athletes more often injure their lower limb and 20 % have injuries to the head and trunk. Those injured in this group are older and have a higher percentage of overweight people, are not well trained and have more severe or complex injuries compared to professionals.

Are snowboarders more likely to damage their spines than skiers? Lessons learned from a study of spinal injuries from the Otago skifields in New Zealand.

AIMS: The aim of this study was to determine the incidence, nature, and circumstances of spinal injuries caused by skiing and snowboarding at the Otago skifields and treated at Dunedin Hospital during the period 1991 to 2002. METHODS: Patients were identified from the audit records of the Department of Orthopaedic Surgery at Dunedin Hospital. RESULTS: Twenty-five cases were included in the study, 18 snowboarders, and 7 skiers. Twenty-two cases had spinal fractures, with skiers having a higher proportion of burst fractures and multiple fractures. The most frequently fractured vertebrae were T12 and L1, and wedge fractures were the most common fracture type. Jump-related activities were the most common cause of injury in snowboarders, in contrast to skiers whose injuries were more commonly fall-related. CONCLUSIONS: Skier-related spinal injuries were rare and sporadic over the study period, whereas snowboarder-related spinal injuries were more frequent and more recent in occurrence.

[Dangers in skiing]. / Gefahren beim Carvingskifahren.

The current study deals with the results of the examination of 685 patients, who were treated in the department of traumatology in the KKH Garmisch-Partenkirchen during the winter season 99/00 and 00/01. The study included 259 injured carvers (120 female, 139 male) with an average age of 33.9 years and 426 injured conventional skiers (212 female, 214 male) with an average age of 33.2 years. The aim of the investigation was to compare both ski groups concerning injuries, the pathomechanism and the skiing experience. The results of the investigation showed that the knee injuries of carvers were more severe than in the conventional skiers. The difference was significant (p < 0.05).

Radiographic abnormalities in the thoracolumbar spine of young elite skiers.

An increased frequency of radiologic abnormalities in the thoracolumbar spine has been reported among young athletes in various sports, but there are no data concerning ski sports. To evaluate the incidence of these abnormalities in young elite skiers, we compared 120 skiers younger than 17 years old (alpine skiers, ski jumpers, and Nordic cross-country skiers) with a random sample of 39 control subjects of the same age who had no history of high-performance sports participation. Standardized anteroposterior and lateral radiographs of the entire lumbar spine, the lower thoracic spine, and the upper part of the sacrum were obtained from each athlete and each control subject. Radiographs were evaluated by two independent observers for the presence and size of anterior and posterior endplate lesions and Schmorl's nodes. The elite alpine skiers and ski jumpers demonstrated a significantly higher rate of anterior endplate lesions than did the control subjects. This finding might be attributable to excessive loading and repetitive trauma of the immature spine under high velocity, especially in the forward bent posture.

Evaluation of skiing injuries by Injury Severity Score.

The goal of this study was to evaluate the Injury Severity Score (ISS) in an alpine area. Hafjell Alpine Centre was the 1994 Winter Olympic Alpine arena in Lillehammer. A total of 2,044,484 lift transportations and 183 injuries were registered in the two winter seasons 1991 and 1992. The injury rate was 1.8 injuries per 1000 skier days. The mean ISS was 3.6 per injury for this particular alpine area. Thirty-six per cent of the injured were women and 35.5% were between 15 and 19 years of age. There was no difference in mean ISS between male and female skiers, but mean ISS was higher in adolescents than in the other age groups. Injuries to the knee represented the single most frequently injured body region, but injuries to the abdomen had the highest mean ISS. Alpine skiers suffered more severe injuries than telemark and snowboard skiers. Severe injuries (ISS > 16) were recorded when unexpected objects, such as a grooming machine, a net, a root, etc., appeared on the slope. The Abbreviated Injury Scale (AIS) and ISS give us additional information about the condition of the slopes, and their use as a tool in preventing skiing injuries is recommended.

Occurrence and trends in ski injuries in Norway.

OBJECTIVES: To provide an overview of ski injuries in Norway and to describe the changes between 1990 and 1996. METHODS: All ski injuries (7966) treated at four hospitals providing health care to a defined population of about 11% of the Norwegian population were registered prospectively from 1990 to 1996. For this study, 6462 injuries sustained in cross country skiing, downhill skiing, telemark skiing, and snowboarding were selected for further analysis. RESULTS: The relative distribution of ski injuries by type of skiing changed significantly from 1990 to 1996 (p<0.001). Injuries from snowboarding showed the highest relative increase, and those sustained during downhill skiing showed a decline. The proportion of fractures in all types of skiing increased during the study period (p=0.001). The proportion of injuries to knee/lower leg decreased and the proportion to the forearm/wrist/hand increased during the study period (p=0.03). The mean age of the injured skiers differed significantly among the different types of skiing activity (p<0.001): cross country skiers were the oldest followed by telemark skiers, downhill skiers, and snowboarders. CONCLUSIONS: Ski injury surveillance results in early detection of changes in temporal injury trends, allowing timely adjustment of injury prevention strategies. Injuries from snowboarding are on the increase in Norway, warranting more effective injury prevention measures.

Poling forces during roller skiing: effects of grade.

PURPOSE: A substantial proportion of the propulsive forces required for uphill skiing are generated from the upper body, but no study has systematically examined poling forces at different slopes. In the present experiment, poling forces and timing were examined during roller skiing on 2.1% and 5.1% uphills. METHODS: Nine highly skilled cross-country skiers roller skied at paced submaximal and at maximal speeds using the V1 skate (V1) and double pole (DP) techniques. Poling forces and timing were measured with piezoelectric transducers. RESULTS: Peak force (PF), average force (AF) and average force over the entire cycle (ACF) were significantly greater (P < 0.01) at the steeper grade with both techniques. Values for the ratio of V1 to DP did not differ between the two grades for PF, AF, and ACF but tended to increase with velocity for both techniques. With both V1 and DP, upper body recovery time was shorter (P < 0.01) at the steeper grade, and cycle rate was greater (P < 0.01) at the steeper grade. CONCLUSIONS: We conclude that 1) the relative demands on the upper body with V1 compared with DP were similar between the two grades, and 2) the responses to an elevation in grade of increased poling forces, shortened poling recovery times, and increased cycle rate are comparable to the responses to an increase in speed.

Poling forces during roller skiing: effects of technique and speed.

PURPOSE: Although it has been reported that the majority of propulsive forces are generated through the poles with ski skating, no study has systematically examined poling forces among different skating techniques. The objective of the present study was to examine poling forces and timing during roller skiing on a 2.1% uphill. METHODS: Nine highly skilled cross-country skiers roller skied at three paced speeds and maximal speed using the V1 skate (V1), V2-alternate (V2A), V2 skate (V2), and double pole (DP) techniques while poling forces and timing were measured with piezoelectric transducers. RESULTS: Peak force (PF) values with the skating techniques were significantly lower than with DP and ranged from 18.9 +/- 3.1% of body weight (BW) to 31.5 +/- 5.6% BW across the speeds of the study. Average force over the entire cycle (ACF) increased with speed with DP, V2A and V1 (P < 0.01) but not with V2. PF and ACF were higher (P < 0.01) with V2 than V1 and V2A. Poling time was longer (P < 0.01) with V2A compared with V1 and V2. CONCLUSIONS: The results of this study suggest that 1) the use of the upper body is greater with V2 than with other skating techniques while there is a relatively greater reliance on the lower body for generation of the additional propulsive forces required to increase velocity, and (2) poling forces do not appear to be as effectively applied with V2 as with V2A.

Completion rates and injuries in alpine races during the 1994 Olympic Winter Games.

The starting lists for the alpine disciplines during the 1994 Olympic Winter Games in Lillehammer totalled 555 racers, but only 354 of them (64%) completed the different races. The race completion rate was 43% in the slalom, 51% in the giant slalom, 75% in the super giant slalom and 91% in the downhill. In combined downhill/slalom the race completion rate was 60%, but 96% in the downhill and 68% in the slalom part of the combination, respectively. Only three injuries were recorded, all in females. Including the training competitions a total of 1541 runs through the different alpine courses was recorded during the games. This means an injury rate of 1.9 injuries per 1000 runs. For downhill the injury rate was only 1.1 per 1000 runs. If the injury rate is related to the number of skiers who did not finish the race because of falls or skiing errors, the rate was 21.1 injuries per 1000 falls (skiing errors) for all alpine races. In conclusion, the race completion rate was twice as high in downhill as in slalom, and the injury rate was low.

Snowboarding injuries. An overview.

Over the last 10 years, snowboarding has become established as a popular and legitimate alpine sport. However, at present, there are few epidemiological studies examining the spectrum of injuries associated with this new sport. Snowboarders are typically male (male: female ratio of 3:1) and in their early twenties. They have an injury rate of 4 to 6 per 1000 visits, which is comparable to that which occurs with skiing. However, in contrast to skiing, in which only 34% of those injured are beginners, the majority (60%) of snowboarders injured are beginners. This is a reflection of the participant profile of this developing sport. 57% of injuries occur in the lower limbs, and 30% in the upper limbs. The most common injuries are simple sprains (31 to 53%), particularly of the ankles (23 to 26%) and knees (12 to 23%), followed by fractures (24 to 27%) and contusions (12%). Compared with skiing injuries, snowboarders have 2.4 times as many fractures, particularly of the upper limbs (constituting 21 vs 35% of upper limb injuries), fewer knee injuries (23 vs 44% of lower limb injuries), but more ankle injuries (23 vs 6% of lower limb injuries). Snowboarding knee injuries are less severe than those associated with skiing. Fracture of the lateral process of the talus is an unusual and uncommon snowboarding injury that can be misdiagnosed as a severe ankle sprain. Ankle injuries are more common with soft shell boots, whereas knee injuries and distal tibia fractures are more common with hard shell boots.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of drafting on work intensity in classical cross-country skiing.

The purpose of this study was to compare the heart rate responses during cross-country skiing as a leading skier, as well as in a drafting situation, three meters behind the leader. Eight male and two female cross-country ski racers, paired for skiing ability, skied a 2 km course (two loops of 1 km) using the diagonal stride and double-poling techniques at a fixed speed (4.75 m.s-1 and 4.45 m.s-1 for males and females respectively) on two different occasions, once as a leading skier, the other as a drafter. A recovery period of 30 minutes was allowed between the two trials. Heart rates (HR) were registered every five seconds during all performances. Results revealed that HR were significantly lower (165 vs 172 beats.min-1) when skiing behind another skier as opposed to leading. Results also revealed that projected frontal areas appeared to influence the effects of drafting such that the HR differences between the leading and the drafting situations were larger for smaller skiers drafting behind larger skiers. These results showed that skiing behind another skier in a classical cross-country ski race would be very advantageous when the situation is encountered and could help racers using this energy saving strategy.

Aspects on muscle properties and use in competitive Alpine skiing.

This brief report describes the physiological demands in competitive Alpine skiing as well as the physiological profile of elite skiers. Maximal heart rate is typically attained by the end of either of the four Alpine ski disciplines. The giant slalom probably calls for the largest reliance upon aerobic energy metabolism and oxygen uptake may increase to 75%-100% of maximal aerobic power. Although high caliber skiers typically show increased maximal aerobic power, it is unlikely that this is an important factor determining success in skiing. Also, anaerobic energy provision accounts for more than half of the total energy yield. Accordingly, plasma and muscle lactate accumulation is substantial after a single race. Similarly, during skiing there is a high rate of glycogen utilization that eventually may result in depletion of muscle glycogen stores by the end of a day of intense skiing. Muscles of Alpine skiers do not possess a distinct fiber type composition and, if anything, skiers tend to show a preponderance of slow twitch fibers. This concords with the recruitment of both muscle fiber types during slalom or giant slalom. Elite skiers show increased knee extensor strength. This seems warranted because there is great reliance upon slow and forceful eccentric muscle actions when performing turns in the giant slalom or slalom.

Muscle activity in slalom and giant slalom skiing.

The purpose of this study was to document and compare the muscular activity patterns observed in seven competitive racers during slalom (SL) and giant slalom (GS) skiing using quantitative parameters of EMG and qualitative video recordings. Twelve muscles of the leg and trunk were monitored using surface electrodes and telemetry. EMG activity was related to phases of movement determined from the video. SL was partitioned into two phases (initiation and turning) and a third phase (completion) was distinguished for GS. The majority of muscles were active at a moderate to high level for the whole turn, with average amplitudes (AA) between 58% and 112% maximum voluntary contraction. Large peak amplitudes (PA) were attributed to the substantial components of centrifugal and gravitational force that the skier must resist in the latter part of the turn. The similarity in muscle activity between SL and GS was surprising. The only significant differences were increases of 11.8% in AA for the AT in SL and 8.8% in PA for the EO in GS. There was ample evidence of co-contraction, suggesting a quasistatic component to skiing.