Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study the roller skis’ rolling resistance has been measured using equipment on the ski-treadmill. The study investigates the influence of significant changes in rolling resistance on physiological variables. The results show that during submaximal exercise, heart rate, blood lactate, power and oxygen uptake are significantly changed by different rolling resistances, while there are no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests show that time to exhaustion is significantly changed by different rolling resistances and this occurred without significant changes in maximal oxygen uptake and heart rate, and the influence on maximal power and ratings of perceived exertion were insignificant or small.

Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes, the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study, the roller skis’ rolling resistance was measured on the ski-treadmill’s surface using a roller ski rolling resistance measurement system specially produced for this purpose. The study investigated the influence of significant changes in rolling resistance on physiological variables. The results showed that during submaximal exercise, power, oxygen uptake, heart rate and blood lactate were significantly changed by different rolling resistances, while there were no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed by different rolling resistances and this occurred without significant changes in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion were insignificant or small.

Modern treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical performance under laboratory conditions using classical and freestyle techniques on roller skis. The differences in performance between tests are quite small for elite athletes, and it is therefore of great importance to control the rolling resistance of the roller skis. Otherwise different physiological tests cannot be accurately compared.

This study shows that during a warm-up period of  30 minutes the coefficient of rolling resistance (µ_R) decreases to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively.

Simultaneous measurements of temperature and µ_R shows that stabilized rolling resistance corresponds to a certain running temperature for a given normal force on the roller ski.

Tests were also performed on the influence on µ_R of normal force, velocity and inclination. Normal forces produced significant influence on µ_{R ,} while different velocities and inclinations of the treadmill only resulted in small changes in µ_R.

This study focused on the work economy of cross-country skiers during treadmill roller skiing in the perspectives; skill, age and gender. The study was investigating the external power output from elevating the transported mass against gravity and overcoming the roller skis rolling resistance, and the internal power from measured oxygen uptake and energy consumption. The roller skis rolling resistance was measured with a fixture on the ski-treadmill and the results showed a significant correlation between normal force and rolling resistance. The results also showed that it was only the amateur skiers who significantly differed in work economy among the five studied groups.

The purpose of this study was to investigate the influence of classical style roller skis' grip (static friction coefficients, μ S) on cross-country skiers' oxygen consumption and leg forces during treadmill roller skiing, when using the diagonal stride and kick double poling techniques. The study used ratcheted wheel roller skis from the open market and a uniquely designed roller ski with an adjustable camber and grip function. The results showed significantly (P≤0.05) higher oxygen consumption (∼14%), heart rate (∼7%), and lower propulsive forces from the legs during submaximal exercise and a shorter time to exhaustion (∼30%) in incremental maximal tests when using roller skis with a μ S similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a similar, higher μ S. Thus, we concluded that oxygen consumption (skiing economy), propulsive leg forces, and performance time are highly changed for the worse when using roller skis with a lower μ S, such as for on-snow skiing with grip-waxed cross-country skis, in comparison to ratcheted wheel roller skis with several times higher μ S.

Roller skis are used by cross-country skiers, biathletes and ski-orienteers for their snow-free training and in roller ski competitions. Additionally, much of the current sports research into the physiology and biomechanics of crosscountry skiing is conducted indoors on treadmills using roller skis. For elite athletes, the differences in performance are quite small, thus emphasising the importance of knowing the roller skis' rolling resistance coefficient, especially in connection to research and roller ski competitions. The purpose of this study was to develop a roller ski rolling resistance measurement system (P-RRMS) that is portable and therefore useful in different contexts and locations. The P-RRMS was designed as a small treadmill, equipped with roller ski stabilizing lateral supports and a screwed bar for applying different vertical loads on the roller ski. The design uses only one force sensor, with possible measurements of three directions of force and torque around three axes. The weight of the P-RRMS is 100 kg and it is equipped with wheels to facilitate transportation.

Cross-country skiers use roller skis for their snow-free training with the aim of imitating skiing on snow. Also, exercise laboratories evaluate the biomechanics and physiology of cross-country skiing using roller skis on a treadmill. The roller skis on the market that are constructed for use in the classical style are equipped with a front and a back wheel, one of which has a ratchet to enable it to grip the surface when diagonal striding and kick double poling (static friction). The aim of this study was to investigate static friction coefficients (μS) of ratcheted wheel roller skis, and compare the results to the μS reported from skiing on snow with grip-waxed cross-country skis. Also, a new type of roller ski with a camber and adjustable grip function was evaluated. The results showed that ratcheted wheel roller skis, on a treadmill rubber mat and on dry and wet asphalt surfaces, reached μS values that were five to eight times greater than the values reported from on-snow skiing with grip-waxed cross-country skis. For the roller skis with a camber and adjustable grip function, the μs could be varied from no grip at all up to the level of the tested ratcheted wheel roller skis.

Roller skis are used by cross-country skiers for snow-free training, with the aim of imitating skiing on snow. The roller skis on the market that are constructed for use in the classical style are equipped with a front and a back wheel, one of which has a ratchet to enable it to grip the surface when diagonal striding and kick double poling.

A new type of roller ski was constructed with a function which makes it necessary to use the same kick technique as that used on snow, i.e. the ski has a camber that must be pushed down to obtain grip. Its stiffness can be adjusted based on factors that influence grip, i.e. the skier’s bodyweight and technical skiing skills.

Thus, our aim was to make comparative measurements as regards grip between ratcheted roller skis and the roller ski with a camber and compare with previous published results for grip waxed skis during cross-country skiing on snow.  The measurements were carried out using specially developed equipment, with a bottom plate and an overlying rubber mat of the same type as used on many treadmills and a function for applying different loads and generating traction on the back of the roller ski.

The purpose of this study was to investigate and compare skiing economy and gross efficiency in cross-country skiers of different performance levels, ages and genders; male recreational skiers and elite senior and junior cross-country skiers of both genders. The skiers performed tests involving roller skiing on a treadmill using the gear 3 and diagonal stride techniques. The elite crosscountry skiers were found to have better skiing economy and higher gross efficiency (5-18%) compared with the recreational skiers (p < 0.05) and the senior elite had better economy and higher efficiency (4-5%) than their junior counterparts (p < 0.05), whereas no differences could be found between the genders. Also, large ranges in economy and gross efficiency were found in all groups. It was concluded that, in addition to v̇O2peak, skiing economy and gross efficiency have a great influence on the differences in performance times between recreational and junior and senior elite cross-country skiers, as well as between individual skiers within the different categories. Thus, we recommend crosscountry skiers at all performance levels to test not only v̇O2peak, but also skiing economy and efficiency.

It is desirable to test sportswear and sports equipment at exactly the same conditions experienced during use. Although outdoor tests are in many cases the most adequate, they are at the same time quite complex, demand special measurement technology and wearable equipment. Results of such tests are often hard to interpret due to large variations because of rapidly varying ambient conditions and individual specifics of human objects, among other factors, which are hard or impossible to control. One common alternative is provided through indoor tests made in a stable, controlled environment. Controlling such parameters as temperature, wind speed and direction, air humidity with indoor facilities intended to replicate ambient conditions, and designed to house large objects, is a complex undertaking. Furthermore, replicating seasonal conditions complicates matters even more. A significant amount of research and development related to the operation of sports and other related equipment at high speeds and windy conditions has been carried out in wind tunnels with different degrees of climatic realism. However, the majority of such facilities are designed and constructed for the automotive industry, the aerospace industry and for marine research. A new wind tunnel facility, opened in March 2015 at the Sports Tech Research Centre at Mid Sweden University, is currently among the very few facilities in the world designed under the direct control of sports technology specialists and dedicated primarily to research and development within sports, outdoor clothing and footwear as well as equipment development and testing. The main goal when constructing this dedicated facility has been to successfully replicate ambient conditions for training and equipment testing in environments with controlled wind speed, temperature (+4 to +35°C) and precipitation (from fine mist to heavy downfall). The wind tunnel facility houses the largest moving belt in Sweden (5 m long and 2.7 m wide) which can be adjusted for leveled, uphill and downhill motion. The moving belt is placed in a 10 m2 test section in which the wind speed can be adjusted to match belt speed or independently up to 55 km/h (without narrowing the test section). A fog and rain system, mounted in the test section, can generate rainy conditions varying from fine mist to heavy monsoon. It is also possible to open the facility in order to allow experiments to be performed in wide range of outdoor, ambient conditions. This paper presents the basic parameters of the new wind tunnel facility. As this facility is open for wider international cooperation, we also report the general directions of current research and the future work planned to be carried out at this facility.

In present paper we would like to share some experiences of building new education in Sports Technology at MidSweden University and the results of 10 years of successfully running it in Östersund. The Sports Technologyeducation at Mid Sweden University started at Campus Östersund in 2003 as a part of the curriculum of theEngineering Department. This specialization was initially at the three-year Bachelor level, and later it was extendedto an additional two-year Master level. Aiming at the quality of Sports Technology education, three keystones areunderlying its process, representing the solid knowledge base, capacity to be flexible in problem solving and the usean innovative approaches. The Department unites researches with a background in both natural sciences andengineering disciplines, having a wide experience of working with and within the industry, equally active in researchand teaching. The unique constellation of the profiles forming the Department include not only the SportsTech®group, being “the backbone”, but also the Ecology and Eco-technology, and Quality Technology groups bringing theexcellence and extra competence needed to assure the quality of the Sports Technology education. We were the firsthigher education institution in Sweden to give this kind of education program and now some other SwedishUniversities have followed us. Our success can be measured by a number of graduates taking good jobs in theindustry. We also enjoy a steady flow of new students coming from all parts of Sweden, and Sports Technologyeducation stays among the most desirable ones in the country.

Winner or trail hog? Much depends on the ski characteristics. The manufacturing of skis is a complicated process involving several materials and different process steps. This gives as a result that every ski obtains unique characteristics such as span curve and bending stiffness etc. For high performance skiers as the member of the Swedish ski team the importance of equal characteristics of each ski in a pair is vital. The process of matching skis to a pair is the process of finding two individual skis with the most similar characteristics. This is traditionally done by hand with simpler equipment. Our measurement system is developed for faster and more accurate ski characteristics assessment. The characteristics do impose the overall performance of the ski. It produces the span curve with very high accuracy and gives a good representation of the pressure distribution over the full length of the ski. The measured characteristics could, in our opinion, also be used in selecting skis for different weather and track conditions. The ski measurement system has been used by the Swedish cross-country team during the last 2,5 years which have resulted in a faster and more accurate matching of skis. In collaboration with the Swedish ski team have also an investigation concerning correlation between ski characteristics and weather and track conditions has been initiated with some preliminary results already obtained.

Cross-country skiing, biathlon and ski orienteering are competitive sports with practitioners who are mostly from countries in the northern hemisphere. The competition season is during the time when the ground is covered with snow, which roughly extends from mid-November to late March. During the rest time of the year, which is a long preparatory period of training for the skiers before the competition season, the skiers use roller skis for dryland training with the aim of imitating skiing on snow. Furthermore, over the last few decades, fairly specific indoor testing methods for cross-country skiers have become possible due to the development of treadmills that allow roller skiing using classical and freestyle techniques.

Concurrent optimization is performed with two optimization methods on a violin top. The optimization methods used are SA (Simulated Annealing) and MMA (Method of Moving Asymptotes). All calculations in this study are made in a distributed environment for arbitrary processing. The distributed environment is constructed using extended File Servers running on remote computers and clients on a local computer, which can transfer, start, terminate, and finally remove arbitrary Java RMI Servers from the remote computers. The required processing is performed with the RMI Servers.

In the strive of understanding how different parameters affects the vibration properties and the characteristics of the sound emanating from a violin, i.e. what makes a good violin good, numerical methods as FEM (finite element method) and BEM (boundary element method) are used. Numerical models of whole violins and/or part of it is created and studied. Crucial for the results from these studies is the correctness of the input data for the numerical analysis. One important group of input data is the wooden material parameters for the part of the violin subjected to analysis. In this study a new method for determining these important material parameters for blanks for violin tops is proposed. In the proposed method a FEM-code is linked together with a stochastic optimization algorithm in order to, in an automatic fashion, determine the material parameters. The method requires the geometrical dimensions, the density, and measured normal modes for the blank and it consider the fact that the Young’s modulus in the axial direction varies with respect to the radial direction.

Wood for violin bows from the pernambuco tree shows large variations in density. For high quality bows, the higher densities are preferred. Since pernambuco is rare and expensive, it is of interest to investigate if it is possible to compensate for variations in density between blanks for bows; particularly in such a way that important qualities of high quality bows are maintained in bows made of wood with a lower density. In this study, numerical optimization is used to replicate some of the static and dynamic properties of a reference bow, using wood with 10% lower density. The structural calculations of the bow are made with a finite element program (ANSYS), which is coupled to an external optimization routine. The automatic optimization process is performed using the Method of Moving Asymptotes. Included are also some remarks on how homogenous scaling of the cross section of a bow of constant length affects some of the static and dynamic properties when used as compensation for density variations.

The wood material for violin bows from the pernambuco tree (Caesalpina echinata) has large individual variations in the density. For high quality bows, the higher densities are preferred, but since pernambuco is rather rare and expensive, it is of interest to investigate if it is possible to compensate for density variations in the wood material, at the same time as important qualities of the bow are unchanged. In this study, numerical optimization is used to recover the static and dynamic properties of a reference bow, on a bow with 10% lower density. The structural calculations of the bows are made with a umerical model in the finite element program ANSYS, which in its is coupled to an external, gradient based optimiztion routine. The automatic optimization process is performed with a routine called the Method of Moving Asymptotes (MMA).

Stochastic optimization with the simulated annealing method (SA) is performed on a violin top made of Norway spruce (Picea Abies). A numerical example is presented which shows that it is possible, through changes in thickness variables, to compensate for changes in vibration properties caused by a variation in the material parameters in the top. A material model is also presented for the blank which considers the influence of density variations in the annual rings, the cellular structure of wood and reinforcement from the wood rays.

A distributed optimization model for wood drying with several different boards simultaneously is presented. Optimization is performed with a gradient-based program. During optimization, convex subproblems are created and transformed to the dual problem and solved. Arbitrary outtakes and board dimensions are possible, as well as different material data and distribution of sapwood and heartwood. It is also possible to optimize drying schedules where drying of boards with variations in environmental conditions is simulated. A two-dimensional orthotropic drying model is used in the moisture transport and structural analysis, where the variation in radial and tangential directions are considered. The influence of temperature and moisture content on material data and mechanical properties is also taken into account. The drying schedules achieved are optimized to minimize drying time for a representative mixture of boards. A numerical example is presented where the drying schedule is optimized for two boards with different outtakes and distributions of sapwood and heartwood. Optimization is performed with two computers in a network. Drying starts from the fibre saturation point in these simulations.

A program for numerical simulation of a whole ski race, from start to finish, is developed in MATLAB. The track ismodelled by a set of cubical splines in two dimensions and can be used to simulate a track in a closed loop or with the startand finish at different locations. The forces considered in the simulations are gravitational force, normal force between snowand skis, drag force from the wind, frictional force between snow and ski and driving force from the skier. The differentialequations of motion are solved from start to finish with the Runge–Kutta method. Different wind situations during the racecan be modelled, as well as different glide conditions on different parts of the track. It is also possible to vary the availablepower during the race. The simulation program’s output is the total time of the race, together with the forces and speedduring different parts of the race and intermediate times at selected points. Some preliminary simulations are also presented.

This paper shows how very tradition-bound construction can be improved through the use of modern technology. In this case, a cross-country ski, the construction can be traced back to a ski found in a swamp in Vasterbotten in northern Sweden, a ski approximately 5000 years old. (4 refs.)

This paper addresses the evaluation of clavicle fixation devices, by means of computational models. The aim was to develop

a method for comparison of stress distribution in various fixation devices, to determine whether the use of multibody

musculoskeletal input in such model is applicable and to report the approach. The focus was on realistic loading and the

motivation for the work is that the treatment can be enhanced by a better understanding of the loading of the clavicle and

fixation device. The method can be used to confirm the strength of customised plates, for optimisation of new plates and to

complement experimental studies. A finite element (FE) mesh of the clavicle geometry was created from computed

tomography data and imported into the FE solver where the model was subjected to muscle forces and other boundary

conditions from a multibody musculoskeletal model performing a typical activity of daily life. A reconstruction plate and

screws were also imported into the model. The combination models returned stresses and displacements of plausible

magnitudes in all included parts and the result, upon further development and validation, may serve as a design guideline for

improved clavicle fixation.

Phenomena of the ski and snow boards vibrations generated in gliding are known for years. In the cross country and jumping skis such vibrations are not very obvious but can play quite positive role reducing the effective gliding friction. The research into the nature of friction-induced vibrations and the factors influencing their frequencies and magnitudes is driven by the desire to control them for improving ski gliding performance. Significant amount of experimental data acquired in the field and laboratory studies is already available making it possible to formulate certain qualitative conclusions. But so far it did not bring comprehensive understanding of the phenomenon and specifically of the mechanisms controlling such vibrations. Modeling is one of the potent tools allowing to deeper understand experimentally studied phenomena and it can provide much stronger quantitative prediction capacity. Present paper discusses possible approaches to modeling of the phenomenon and first results of constructing simplified models. © 2014 The Authors.

Field and laboratory measurements show a presence of intense cross-country ski vibrations during free gliding. Thereare indications that such vibrations may and indeed do affect the average friction forces and thus should affect the skigliding. Our studies into the nature of these vibrations and the factors influencing their frequencies and magnitudesare driven by the desire to control them for improving ski gliding performance. The complexity of the correspondingresonance system, represented by constant interaction of the skier, the skis and the snow, and the mechanisms of thevibration excitation, most probably dominated by the stochastic forces caused by a stick-slip character of the friction,demand new approaches to the modelling and experiments. Present paper describes some results of the experimentallaboratory studies of such vibrations, and possible approaches to their modelling following the routes suggested inmodelling of the similar phenomena.

Present paper describes the results of experimental studies on the self-induced and forced vibrations of loaded cross country skis and presents the discussion on the possible mechanisms causing such vibrations and the ways they can influence the friction between the ski running surface and the snow. Studied vibrations of gliding skis are most probably caused by the frictional effects. Mechanisms involved are similar to the ones causing the brake disc squeal or the violin string excitation by the bow. Major factors responsible for the development of these vibrations such as micro roughness of the surfaces, nonlinearities in the material properties, thermo-elastic instabilities and instabilities due to decreasing friction with increasing sliding velocity are also common for the case of gliding skis. The results of this study indicate that the ski vibration pattern both in amplitude and in frequency could influence the ski gliding properties. Though it seems quite feasible that the control of the cross country ski vibrations can improve the gliding performance, further systematic studies are needed to confirm it and to formulate the consecutive strategies of cross country ski design improvement.

This paper considers the mechanically treated dry ski running surface. The difference in the shear wettability of ski running surfaces treated using different types of machining was studied by measuring the advanced and receding contact angles on two different ski base materials. The hypothesis regarding relationship between the shear wettability and the capillary drag of ski running surface have been presented. The study found, that ski running surfaces with a lower roughness (e.g. flattened by a steel drum or sliced) have a lower wettability factor and seem to be more effective in reducing capillary drag under homogenous wetting conditions.

The importance of high hydrophobicity for minimising snow-ski friction has been discussed in a number of scientific papers. The chemical modification of surface forces using fluoropolymeric coatings can result in water contact angles of up to 120°, but not more. To reach extreme values of the contact angle, a second factor has to be modified, namely surface structure. In this study a number of cross-country skis were treated with a modern method of stone grinding and with old-fashioned steel scraping. The surface roughness (3D) and the surface (solid-liquid) contact angle were then measured. After this, the skis were treated with a hot glide wax and new measurements were made. This study also examines the contact angles (solid-liquid) of the flowed surface of a sample of glide wax and the surface of a sample of solid press-sintered running base (UHMWPE). Unexpectedly low hydrophobicity was observed after stone grinding.

We propose a thesis that minimizing dirt on the running surface of skis improves the surface glide. Waxing usually improves the gliding ability of skis in the short term. But how does waxing affect pollution absorption in the long term? In this study a number of skis with a transparent base and a white background were treated by steel scraping and with different glide waxes. The gliding ability of waxed and unwaxed skis, the sliding surface whiteness and the hydrophobicity were tested and documented. Tests were performed before and after the skis had been used for different distances. It was observed that all the waxed skis (regardless of the wax used) absorbed more dirt than unwaxed and as result all waxed skis lose their glide ability sooner then unwaxed (fresh scraped) skis on wet snow conditions.

Methods for analysing impurities in snow are used in glaciology and ecological studies. However, the relationship between the dirt accumulation on the ski running surface and the concentration of pollution in the snow is not straightforward, since the interaction between the top layer of snow in the ski track and the ski running surface is responsible for the dirt accumulation on the running surface. In this paper the dirt film accumulated on the gliding surface is studied. A number of XC skis with a transparent base and a white background were examined after undergoing different treatments. Measurements of the whiteness of the running surface of the skis were carried out and glide tests were performed. The measurements and tests were repeated after skiing various distances on a ski track under varying snow conditions. The following observations were made during the study: - The experimental setup could deliver a reliable value of the whiteness of the ski running surface. We achieved 0,3% standard deviation in a test on a control sample; - The correlation between the ski glide and the amount of dirt is obvious and significant.

In the cross country skiing community, hot wax treatment of the ski running surface (SRS) is used in order to influence the surface hardness of the skis in relation to the hardness of the snow crystals. This is discussed in a number of scientific papers and recommended in almost every ski waxing manual. The general idea is to decrease (soften) the surface hardness by the use of a soft glide wax treatment for wet snow conditions and to increase (harden) the hardness of the surface by a hard (synthetic) glide wax treatment for cold, dry snow conditions. The question is; does the hot glide wax treatment of the ski running surface influence the surface hardness? And if so, in what way?In our experiment, ski base specimens of UHMWPE (transparent and “graphite”) were treated with ski glide wax. Half of the specimens were treated with soft yellow glide wax, and half with hard green glide wax. After the wax treatment, the surface hardness (Shore D) was measured with a durometer. The study revealed that: both soft glide wax and hard glide wax treatment make the SRS softer; after a long immersion (12 hours) in the bath of melted glide wax, both the hardness of the specimens treated with soft glide wax and of those treated with hard glide wax decreased significant. Conclusion: The hot wax treatment of the SRS with available glide waxes cannot make the SRS harder than it was initially (unwaxed).

The UHMWPE (press-sintered) ski base and ski glide waxes are very similar substances. Hence, it should be possible to achieve a same or even better glide on a bare ski base. In this study we examined waxed and unwaxed skis before and after skiing for the purpose of gliding ability, dirt accumulation and wettability. We observed that the skis with unwaxed running surface did retain a same or higher comparative level of all three tested parameters. We can assume that it is a consequence of a soft wax dirt accumulation under warm conditions and of the excessively hot ski base treatment under cold and dry conditions.

In this paper the outdoor gear and clothing companieś experiences ofcustomerinvolvement in product development are investigated and discussed. The purpose is to examine howcustomersare involved in product development and whether the companies believe there is a need for greater involvement. The study focuses on threecustomergroups: users, retailers and professional users. Surveys were sent out to 33 Swedish and Norwegian companies within the Scandinavian Outdoor Group. The results of the study indicate that the companies think there is a need to involve the users more than today in the early phases of the product development process. Smaller companies seem to have a need for greater user involvement. Most of the participants also explained that they would increase theircustomerinvolvement if they had more time and greater financial resources. © 2011 Published by Elsevier Ltd.