| 1. |
- Ainegren, Mats, 1963-, et al.
(författare)
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A portable roller ski rolling resistance measurement system
- 2013
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Ingår i: The Impact of Technology on Sport V. - : Elsevier. ; , s. 79-83
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Roller ski rolling resistance and its effects on elite athletes’ performance
- 2009
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Ingår i: Sports Engineering. - Paris : Springer. - 1369-7072 .- 1460-2687. - 9782287990564 - 9782287990557 ; 11:3, s. 143-157
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Ainegren, Mats, 1963-, et al.
(författare)
-
Roller ski rolling resistance and its effects on elite athletes’ performance
- 2008
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Ingår i: ENGINEERING OF SPORT 7, VOL 2. - 9782287094125 ; , s. 393-400
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 4. |
- Ainegren, Mats, 1963-, et al.
(författare)
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The multifunctional roller ski
- 2013
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Ingår i: Science and Nordic Skiing II. - : University of Salzburg, University of Jyväskylä. - 9789513951757 ; , s. 253-261
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Bokkapitel (refereegranskat)
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| 5. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Work economy of amateur and elite cross-country skiers during treadmill roller skiing
- 2009
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Ingår i: 4th Asia Pacific Congress on Sports Technology, APCST2009. - 9781921426384
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 6. |
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| 7. |
- Carlsson, Peter, 1950-, et al.
(författare)
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Numerical Simulation of Cross Country Skiing
- 2011
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Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1025-5842 .- 1476-8259. ; 14:8, s. 741-746
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Bäckstöm, Mikael, 1963-, et al.
(författare)
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Essential ski characteristics for cross-country skis performance
- 2008
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Ingår i: ENGINEERING OF SPORT 7, VOL 2. - Paris : Springer. - 9782287094132 ; , s. 543-549
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 9. |
- Carlsson, Peter, 1950-, et al.
(författare)
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Optimization of Drying Schedules Adapted for a Mixture of Bords with Distribution of Sapwood and Heartwood
- 2002
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Ingår i: Drying Technology. - 0737-3937 .- 1532-2300. ; 20:2, s. 403-418
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Kuzmin, Leonid, 1958-, et al.
(författare)
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Contact angels on the running surface of cross-country skis
- 2005
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Ingår i: The Impact of Technology on Sport. - Melbourne : Australasian Sports Technology Alliance Pty Ltd. - 0646450255 ; , s. 318-323
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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