Ski Boots Research Articles

Effects of slight ski boot weight variations on ski mountaineering energy cost and mechanical work at race intensity

PurposeUphill ski mountaineering performance appears to be related to metabolic cost of locomotion and skiers’ weight. The present study aimed to evaluate the effects of slight variations in equipment weight on metabolic and mechanical work (MW) of ski mountaineering, at race pace.MethodsThirteen male ski mountaineers were asked to ski on a treadmill at 25% slope and 80% of their maximal aerobic speed. They completed four 5-min bouts with additional weights of 0 kg (control), 0.2 kg, 0.4 kg, and 0.6 kg added to each ski boot in a blind mode and random order. Ski mountaineering energy cost (EC) was determined by gas exchange measurements, while MW was determined from the changes in the mechanical energy of body centre of mass (COM), body segments and equipment.ResultsEC and total MW were significantly (all p < 0.001) and largely (η2 = 0.712 and η2 = 0.704, respectively) increased for every 0.2 kg of mass added, by around 2% and 1%, respectively. The increase in the MW was related to a significant increase in the work needed to lift the weight against gravity and to the increased work done to move the segments of the lower body with respect to COM.ConclusionThe present investigation shows that even small increments in racing gear weight are associated with an increase in ski mountaineering EC, possibly leading to a consequent decreased performance on uphill terrains.

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

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

Evaluating wrapping alpine ski boots during on-snow carving.

Alpine ski boots enable rapid and precise force transfer between skier and ski while carving. These boots are made of rigid plastic and fit tightly commonly through four buckles. Such a fit can improve speed and control but also pain and discomfort. In athletic footwear, alterations to the upper designed to wrap the foot improve performance during rapid changes of direction and during trail running. The purpose of this study was to systematically evaluate the performance and fit of two different ski boot shell closure mechanisms: a BOA closure and a Buckle closure. This was a two-part study with 22 subjects performing on-mountain skiing and 10 of those subjects completing an in-laboratory pressure evaluation. Subjects skied in both boots three times each while data from inertial measurement units (IMUs) and plantar pressures were collected along with subjective data. In lab, static dorsal and plantar pressures were collected while the subjects flexed into the boots. The BOA boots improved subjective and objective ski performance; qualitative carving scores were greater, likely through increasing the amount of normal force applied to the ski while turning. There were no differences in edge angles between the boots, as computed from IMUs. The BOA boot also reduced static peak plantar pressures in the rearfoot along with reducing overall static pressure on the dorsum as compared with the Buckle boot. This is the first study to systematically evaluate differences in ski boot closures. The improvements in carving performance in the BOA boot are supported by distinct differences in pressure distribution within each boot, which we speculate contributed to improved performance by reducing discomfort or pain while still facilitating effective force transfer.

A wrapping fit of ski boots improves performance and fit in skiers

A wrapping fit of ski boots improves performance and fit in skiers

Torsion and bending loads on a ski-touring boot shell during uphill and downhill skiing

Ski touring is an established winter activity that has experienced a recent increase in popularity. Differently to alpine skiing, skier gains altitude without lifts, thus equipment weight must be minimized. Nevertheless, structural properties of the equipment, such as ski boots, must be adequate to withstand skiing loads. Several studies provided data on flexural stiffness of alpine ski boots in bench and field tests. The present study focused on the torsional properties of ski-touring boots. Indeed, touring bindings design implies a higher torque transmission to the front piece which induces a torsional load throughout the shell. To conduct the study, we prepared a ski-touring boot with strain gage bridges, and we performed bench tests to determine the stiffness of the boot and the bridge sensitivity. We also positioned and calibrated strain gage bridges to measure bending load in the shell and axial load in the ski/walk lever placed between shell and cuff of the boot. Then, we conducted a field test measuring the loads during a ski-touring trip including ascent and descent. Bench tests evidenced linearity of the torsion sensor, and a variation of stiffness depending on dummy leg absence/presence and boot buckle setting. Field tests showed torque ranges of 17 Nm in climbing and of 27 Nm in skiing. Bending moment range on the boot shell was of 150 and 228 Nm, respectively. Maximum force on the ski/walk mechanism reached 570 N. Results could be useful to test ski-touring boot performances and to optimize their design.

Skill-Specific Differences in Equipment-Related Risk Factors for ACL Injury in Male and Female Recreational Skiers.

In recreational alpine skiing, the anterior cruciate ligament (ACL) is affected in approximately 50% of serious knee injuries. There are established sex-based and skill-based differences in ACL injury risk, but the potential impact of equipment used (eg, skis, bindings, and boots) has not been evaluated. To evaluate individual and equipment-related risk factors for an ACL injury depending on sex and skill level. Case-control study; Level of evidence, 3. This was a retrospective questionnaire-based, case-control study of female and male skiers with and without ACL injuries during 6 winter seasons (from 2014-2015 to 2019-2020). Demographic data, skill level, equipment specifications, risk-taking behavior, and ownership of ski equipment were recorded. Ski geometry (ski length; sidecut radius; and widths of the tip, waist, and tail) was taken from each participant's ski. The standing heights of the front and back part of the ski binding were measured using a digital sliding caliper, and the standing height ratio was calculated. Abrasion of the ski boot sole was also measured at the toe and heel. Participants were divided by sex into less and more skilled skiers. A total of 1817 recreational skiers participated in this study, of whom 392 (21.6%) sustained an ACL injury. A greater standing height ratio and more abrasion at the toe of the boot sole were associated with increased ACL injury risk in both sexes, independent of the skill level. Riskier behavior increased the injury risk only in male skiers, independent of the skill level, and longer skis increased the injury risk only in less skilled female skiers. Older age, the use of rented/borrowed skis, and more abrasion at the heel of the boot sole were independent risk factors for ACL injury in the more skilled skiers of both sexes. Individual and equipment-related risk factors for an ACL injury partly differed according to skill level and sex. Consideration of the demonstrated equipment-related factors should be implemented in order to reduce ACL injuries in recreational skiers.

An Innovative Compact System to Measure Skiing Ground Reaction Forces and Flexural Angles of Alpine and Touring Ski Boots.

Skiing is a popular winter activity spanning various subdisciplines. Key hardware are ski boots, bindings, and skis, which are designed to withstand loads generated during skiing. Obtaining service forces and moments has always been challenging to researchers in the past. The goal of the present study is to develop and test a lightweight and compact measurement system to obtain the Ground Reaction Forces and the kinematics for ski touring and alpine ski. To do so, we adapted two six-axis load cells to fit into ski touring and alpine skis adding 20 mm height and 500 g weight to the original ski. To measure kinematics, we created custom angular sensors from rotary potentiometers. The system was tested indoors using a force platform and motion capture system before a first set of field tests in which the sensors were used to measure ski touring and alpine skis kinetics and kinematics. Validation trials showed maximum errors of 10% for kinetics and 5% for kinematics. Field tests showed data in agreement with previous findings on the topic. The results of this study show the possibility of using our system to study biomechanics and equipment performances for ski touring, alpine skiing, and possibly other disciplines.

Association of personal and equipment-related factors on ACL injury risk in alpine skiers with cautious or risk-taking behaviour: A case-control study.

In recreational alpine skiing ACL injury risk depends on the interaction of individual characteristics and behaviours as well as on equipment-related factors. to evaluate if and to what extent personal characteristics and equipment-related parameters are associated with ACL injury risk in cautious and risk-taking recreational alpine skiers. A retrospective questionnaire-based, case-control study of ACL-injured and uninjured in a cohort of cautious as well as risk-taking recreational skiers was conducted. Participants self-reported their demographics, skiing skill level, and risk-taking behaviour. Ski length, side-cut radius, widths of the tip, waist, and tail were recorded from each participant's skis. Standing heights at the front and rear components of the ski binding were measured with a digital sliding caliper, and a standing height ratio between the front and rear components was calculated. Ski boot sole abrasion at the toe and heel pieces was also measured with the digital sliding caliper. In total, 1068 recreational skiers (50.8% females) with a mean age of 37.8 ± 12.3 years participated, of whom 193 (22.0%) sustained an ACL injury, and 330 (30.9%) participants reported a risk-taking behaviour. Results of the multiple logistic regression analyses revealed that a higher age, a lower skill level, a higher standing height ratio, and greater ski boot sole abrasion at the toe as well as heel pieces were independently associated with an increased ACL injury risk in both the cautious and the risk-taking group. Among cautious skiers, a longer ski length was an additional significant risk factor for sustaining an ACL injury. In conclusion, the same personal and equipment related characteristics contribute to an increase in the ACL injury risk regardless of risk-taking behaviour, with the only difference that longer skis represent an additional risk factor in cautious skiers.

A comprehensive review of castor oil‐derived renewable and sustainable industrial products

AbstractCastor oil is one important raw material that could serve as a renewable feedstock for industries in the age of exhausting fossil fuels. The chemical composition of oil and the structure of hydroxyl fatty acid are responsible for its unique physicochemical properties. The oil has diverse applications from pharmaceuticals to polyamides, from the manufacturing of ski boots to durable frames, and from lubricants to laxatives. The present review gives an insight into the physicochemical properties of castor oil and its application. The oil is used for the production of a great variety of its derivatives. Out of many derivatives of castor oil, four are produced and utilized at a larger scale. The names of the four derivates are ricinoleic acid, sebacic acid, undecylenic acid, and γ‐decalactone. The review will aim toward an insight into the evolved techniques for the manufacturing of these derivatives of castor oil, the biotechnological route of production, and metabolic engineering approaches. Though the industrial significance of castor oil and its derivatives had been known for ages, methods for their production are continuously changing.

Fractures of tibial shaft and tibial head in winter sports

Injuries in alpine skiing often affect the lower extremities, in particular the knee joint and lower leg. In addition to conventional radiological diagnostics, CT and, in the case of fractures of the knee joint area, MRI also play an important role. In the case of tibial head fractures, especially if there has been adislocation mechanism, there is an increased risk of vascular and nerve injuries. Lower leg fractures are predestined for the development of acompartment syndrome. For these reasons, an exact survey of the vascular-nerve status and amonitoring of the soft tissues should be carried out. In the further therapy, whether conservative or surgical, the soft tissue situation must also be included in the planning. In the case of tibial head fractures in particular, the choice of the right approach is essential for agood result in surgical therapy. Angle-stable plate osteosynthesis and screw osteosynthesis play the most important role as osteosynthesis methods in the knee joint area. In the case of fractures in the shaft area, medullary nail osteosynthesis or angle-stable plate systems are primarily used. In the case of severely compromised soft tissue or unstable situations, it may be necessary to apply an external fixator first. The initiated therapy should enable functional follow-up treatment as early as possible. Good physical fitness, driving-specific training, but also good core stabilization have apreventative effect against injuries. In addition, the correct material coordination between ski boot, binding and ski is important for accident prevention.

Epidemiology of Lower Leg Fractures at a Colorado Ski Resort

Category: Trauma; Ankle; Sports Introduction/Purpose: Lower extremity fractures are relatively common among winter sports participants. The purpose of this study is to evaluate the demographics, injury mechanisms and environmental features among patients evaluated for lower leg fractures at a high-volume Colorado ski resort during five consecutive ski seasons. Methods: We conducted a retrospective descriptive analysis of patients with lower leg fractures at the Denver Health Winter Park Medical Center during the 2012/13 to 2016/17 ski seasons. We included all fractures below the knee (excluding tibial plateau and isolated fibular head fractures) sustained by skiing or snowboarding. Chart review was performed on the patient cohort, confirming diagnosis and evaluating factors associated with these fractures. Results: There were 346 lower leg, ankle, and/or foot fractures (5.4% of all clinic visits) during the study period. The average age was 33.1 years (range 4-74) with the majority being male (60.7%) and mainly as a result of skiing (84.7%). The majority of fractures were sustained among skiers and snowboarders who self-identified as beginner or intermediate skill level (64.8%), and on easy (green) or intermediate (blue) runs (64.9%). The most common fractures sustained were complete tibia-fibula fractures (30.9%) and lateral malleolus fractures (27.5%). More than half (57.0%) of complete tibia-fibula fractures were classified and boot top (mid- shaft just above the ski boot) fractures. The most common type of lateral malleolus fractures was Danis-Weber B (72.0%) with only 5.4% being Weber C fractures. Foot fractures were rare with only 12 total cases (3.5%). Conclusion: Skiers are much more likely to sustain lower leg fractures compared to snowboarders. Men were much more likely than women to sustain lower leg fractures. Most fractures occurred in mild or moderately difficult ski runs relative to advanced runs. Fractures appear to be more common with advancing age. Complete tibia-fibula fractures were the most common fractures sustained in all riders with lateral malleolus fractures being the second most common. Foot fractures are very rare in this population. Given the frequency of these injuries, additional education around prevention may be warranted.

Business Roundup

BUSINESS Business Roundup ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2022, 100 (3), p 13January 24, 2022Cite this:C&EN 100, 3, 13AbstractSabic has formed a collaboration with PKN Orlen for the development of chemical facilities in Poland. The effort could result in a new ethylene cracker in the country and the expansion of existing facilities. Arkema plans to increase global capacity for its Pebax elastomers, derived in part from castor oil, by 25% by expanding its facility in Serquigny, France. Applications for the elastomers include running shoes and ski boots. Biosynthetic Technologies has acquired the castor oil derivative specialist Innoleo. Both firms convert biobased oils into lubricants, coatings, and personal care ingredients. Perstorp has purchased the dimethylolpropionic acid (DMPA) business of Geo Specialty Chemicals. DMPA is an ingredient in water-based polyurethane coatings and adhesives. MycoWorks has closed a $125 million series C funding round led by the investment group Prime Movers Lab. The company says it will use the funds to build the first full-scale plant for its leather alternative Reishi,View: PDF | Full Text HTML

アルペンスキー選手のターン動作の定量評価及びスキーブーツの調整に関する検討

Research Center for Winter Sports Science of Kitami Institute of Technology was established in 2016. Curling and alpine skiing are researched at this center located in a snowy and heavy cold area. In research on alpine skiing, we are conducting experiments to adjust the ski boots and improve their skills of Japanese skiers. Previous experimental studies have shown that the large inclination angle and a fast inclination angular velocity during turns have a great influence on the improvement of downhill speed in alpine skiing (2) ~ (5). Furthermore, it has been found that attaching parts to the underside of the footbed inside the ski boot changes the inclination angle and inclination angular velocity. In this study, we used the ski simulator "SkyTech" at this center and "the real-time experimental data collection system" with a pressure sensor and the inclination angle measuring devices, and performed an experiment to adjustment of depression angle. And we calculated the parameters for evaluating the athletes’ turn movements from the obtained experimental data, and investigated the quantitative evaluation of alpine skiers’ skill of turning motion.

Incidence of anterior tibial spine fracture among skiers does not differ with age.

Injury to the anterior cruciate ligament (ACL) is common in alpine skiing in the form of either an intra-substance ACL tear or anterior tibial spine fracture (ATSF). Anterior tibial spine fractures are typically reported in children. However, several case reports describe these injuries in adults while skiing. The purpose of this study is to describe the sport specific incidence of ATSF in alpine skiing. The study was conducted over a 22-year period. Skiers who suffered an ATSF were identified and radiographs were reviewed to confirm the diagnosis. Additionally, control data from intra-substance ACL injury groups were collected. The incidence of these injuries in children, adolescents, and adults (grouped as ages 0-10, 11-16, and 17 + years old, respectively) was evaluated and the risk factors for ATSF versus ACL tear were determined. There were 1688 intra-substance ACL and 51 ATSF injuries. The incidence of intra-substance ACL injury was greater in adults (40.0 per 100,000 skier days) compared to the adolescent (15.4 per 100,000) and child (1.1 per 100,000) age groups. In contrast, the incidence of ATSF was similar in the adult (0.9 per 100,000), adolescent (1.9 per 100,000), and child (1.9 per 100,000) age groups. Loose ski boot fit was identified as a risk factor for ATSF. The incidence of ATSF in alpine skiers is similar among all age groups. However, the incidence of intra-substance ACL injuries is far greater in adult skiers compared to adolescents and children. Risk factors for ATSF relate to compliance between the foot/ankle and the ski boot. III.

스키부츠 특허: 조절형 신축 레버

Purpose: The purpose of this study is to develop ski boots that make it easier to wear ski boots that have hardened at sub-zero temperatures.<BR> Method: The study was conducted based on a patent document on an invention registered with the Korean Intellectual Property Office (Patent: No. 10-2208653). The present invention is related to a lever that locks a buckle to tighten the instep and ankle of the ski boot so that the ski boot does not separate from the body when wearing the ski boot, or releases the buckle to take off the ski boot. The adjustable telescoping lever of the present invention has a structure in which the length is adjusted, and is designed to facilitate the function of easily tightening or loosening the ski boots through this.<BR> Results: The advantages of the ski boots with this adjustable elastic lever are as follows. First, skiers with weak strength, such as children, women, and the elderly, will be able to easily wear ski boots. Second, skiers will be able to reduce exercise fatigue and enhance exercise performance by accurately wearing ski boots. Third, skiers wear ski boots correctly, so the risk of injury may be reduced.<BR> Conclusion: As a result, the ski boots with this adjustable telescoping lever can contribute to reducing skiers’ fatigue, improving safety, and enhancing athletic performance.

Connected skiing: Validation of edge angle and radial force estimation as motion quality parameters during alpine skiing

ABSTRACT Recent studies have developed wearable sensor systems to detect, classify and evaluate performance during alpine skiing. In order to enrich skiing data to provide motion quality feedback, edge angle (EA) and radial force (Fr) are parameters of interest. However, the estimation of these parameters via calibration-free wearable technologies has not been validated. The purpose of this study was to develop and validate a wearable method to estimate EA and Fr. Participants completed simulated skiing trials on an indoor skiing carpet. Two IMU’s mounted to the ski boots estimated EA and Fr and compared to reference values measured with a 3D motion capture system. The performance of the wearable system was quantified by accuracy and precision. The overall accuracy and precision of the wearable system was 97.6 ± 12.4% and 15.5 ± 17.6% for EA, and 105.5 ± 5.7% and 29.8 ± 10.0%, respectively for Fr. The developed wearable system was accurate for the estimation of EA and Fr, but was highly variable with low precision for both metrics. Further research is needed to improve the precision of field-relevant skiing metrics during in-field studies using simple measurement setups that can easily be implemented by recreational and expert skiers alike. Highlights IMU’s mounted on the boots are sufficient tools for accurate estimation of edge angle and radial force during both long and short style turns on a skiing simulator. As the estimation of edge angle and radial force are dependent on other estimated parameters (i.e. turn switch), the precision of these metrics is relatively low. The results of the current study apply only to simulated alpine skiing on a treadmill, and further work is required to prove the accuracy and precision of this system on snow.

Facile Synthesis of Thermoplastic Polyamide Elastomers Based on Amorphous Polyetheramine with Damping Performance.

Novel thermoplastic polyamide elastomers (TPAEs) consisting of long-chain semicrystalline polyamide 1212 (PA1212) and amorphous polyetheramine were synthesized via one-pot melt polycondensation. The method provides accessible routes to prepare TPAEs with a high tolerance of compatibility between polyamide and polyether oligomers compared with the traditional two-step method. These TPAEs with 10 wt % to 76 wt % of soft content were obtained by reaction of dodecanedioic acid, 1,12-dodecanediamine, and poly(propylene glycol) (PPG) diamine. The structure–property relationships of TPAEs were systematically studied. The chemical structure and the morphologic analyses have revealed that microphase separation occurs in the amorphous region. The TPAEs that have long-chain PPG segments consist of a crystalline polyamide domain, amorphous polyamide-rich domain, and amorphous polyetheramine-rich domain, while the ones containing short-chain PPG segments comprise of a crystalline polyamide domain and miscible amorphous polyamide phase and amorphous polyetheramine phase due to the compatibility between short-chain polyetheramine and amorphous polyamide. These novel TPAEs show good damping performance at low temperature, especially the TPAEs that incorporated 76 wt % and 62 wt % of PPG diamine. The TPAEs exhibit high elastic properties and low residual strain at room temperature. They are lightweight with density between 1.01 and 1.03 g/cm3. The long-chain TPAEs have well-balanced properties of low density, high elastic return, and high shock-absorbing ability. This work provides a route to expand TPAEs to damping materials with special application for sports equipment used in extremely cold conditions such as ski boots.

Computational methods for the investigation of ski boots ergonomics

Ski boots are known to cause vasoconstriction in the wearer’s lower limbs and, thus, cause a “cold leg” phenomenon. To address this problem, this work provides a computational framework for analysing interactions between the ski boot and the lower limb. The geometry of the lower limb was derived from magnetic resonance imaging and computed tomography techniques and anthropometric data. The geometry of the ski boot shell was obtained by means of three-dimensional computer aided design models from a manufacturer. Concerning the ski boot liner, laser scanning techniques were implemented to capture the geometry of each layer. The mechanical models of the ski boot and the lower limb were identified and validated by means of coupled experimental investigations and computational analyses. The computational models were exploited to simulate the buckling process and to investigate interaction phenomena between the boot and the lower limb. Similarly, experimental activities were performed to further analyse the buckling phenomena. The obtained computational and experimental results were compared regarding both interaction pressure and displacements between the buckle and the corresponding buckle hooks. These comparisons provided reasonable agreement (mean value of discrepancy between the model and mean experimental results in the tibial region: 20%), underlining the model’s capability to correctly interpret results from experimental measurements. Results identified the critical areas of the leg, such as the tibial region, the calcaneal region of the foot and the anterior sole, which may suffer the most due to the hydrostatic pressure and compressive strain exerted on them. The results highlight that computational methods allow investigation of the interaction phenomena between the lower leg and ski boot, potentially providing an effective framework for a more comfortable and ergonomic design of ski boots.

Connected Skiing: Motion Quality Quantification in Alpine Skiing.

Recent developments in sensing technology have made wearable computing smaller and cheaper. While many wearable technologies aim to quantify motion, there are few which aim to qualify motion. (2) To develop a wearable system to quantify motion quality during alpine skiing, IMUs were affixed to the ski boots of nineteen expert alpine skiers while they completed a set protocol of skiing styles, included carving and drifting in long, medium, and short radii. The IMU data were processed according to the previously published skiing activity recognition chain algorithms for turn segmentation, enrichment, and turn style classification Principal component models were learned on the time series variables edge angle, symmetry, radial force, and speed to identify the sources of variability in a subset of reference skiers. The remaining data were scored by comparing the PC score distributions of variables to the reference dataset. (3) The algorithm was able to differentiate between an expert and beginner skier, but not between an expert and a ski instructor, or a ski instructor and a beginner. (4) The scoring algorithm is a novel concept to quantify motion quality but is limited by the accuracy and relevance of the input data.

Limitations of current alpine touring ski bindings

ObjectivesQuantify various parameters of safety and performance of modern alpine touring bindings in particular their release characteristics. DesignFor n = 16 alpine touring bindings from season 2018/19 and 2019/20, we performed multiple tests under standardized conditions using identical test soles built from one market relevant alpine touring boot. MethodsReferring to the standard of the International Organization for Standardization for alpine touring bindings ISO 13992 we measured both the impact tolerance as well as the influence of forward and backward lean on the bindings' twist release behavior. Further rigidity measurements were performed to determine the torsional and deflection stiffness of the ski–boot–binding system. Additionally, we determined the accordance of the bindings' indicator settings with the real release values. In order to test the consistency of the bindings' twist release behavior, the torque deviation over 25 releases was measured. ResultsThe bindings showed very different behavior. Nine out of the sixteen bindings exceeded the given limit for twist release in case of additional backward lean. Especially lightweight Tech/Pin bindings did not show sufficient rebound elasticity when being impacted laterally. Some bindings revealed imprecise indicator setting values. ConclusionA comparable level of reliable release characteristics, as it is true for alpine ski bindings, should not be expected from alpine touring equipment - especially with respect to release under combined loads. Low impact tolerance might also be a safety issue leading to inadvertent releases.