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  • 1.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Ainegren, Mats
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Roller ski rolling resistance and its effects on elite athletes’ performance2009In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 11, no 3, p. 143-157Article in journal (Refereed)
    Abstract [en]

    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.

     

  • 2.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Ainegren, Mats
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Rolling resistance for treadmill roller skiing2008In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 11, no 1, p. 23-29Article in journal (Refereed)
    Abstract [en]

    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 (µR) decreases to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively.

    Simultaneous measurements of temperature and µR 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 µR of normal force, velocity and inclination. Normal forces produced significant influence on µR , while different velocities and inclinations of the treadmill only resulted in small changes in µR.

  • 3.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    An experimental study to compare the grip of classical style roller skis with on-snow skiing2013In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 16, no 2, p. 115-122Article in journal (Refereed)
    Abstract [en]

    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.

  • 4.
    Hofmann, K. B.
    et al.
    Otto Bock Healthcare Products GmbH, Vienna, Austria.
    Ohlsson, M. L.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Höök, M.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, J.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Kersting, U. G.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Aalborgs Universitet.
    The influence of sitting posture on mechanics and metabolic energy requirements during sit-skiing: a case report2016In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 19, no 3, p. 213-218Article in journal (Refereed)
    Abstract [en]

    Several different sitting postures are used in Paralympic cross-country sit-skiing. The aim of this study was to evaluate the impact of sitting posture on physiological and mechanical variables during steady-state double-poling sit-skiing, as well as to determine how seat design can be improved for athletes without sufficient trunk control. Employing a novel, custom-designed seat, three trunk positions were tested while performing double-poling with submaximal oxygen consumption on an ergometer. Cycle kinematics, pole forces, and oxygen consumption were monitored. The athlete performed best, with longer cycle length and less pronounced metabolic responses, when kneeling with the trunk resting on a frontal support. For this case, a forward leaning trunk with knees below the hip joint was interpreted as most optimal, as it showed lower oxygen consumption and related parameters of performance during cross-country sit-skiing. Further investigations should examine whether such improvement is dependent on the level of the athlete’s handicap, as well as whether it is also seen on snow.

  • 5.
    Jensby Nedergaard, Niels
    et al.
    Department of Health Science and Technology, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
    Heinen, Frederik
    Department of Health Science and Technology, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
    Sloth, Simon
    Department of Health Science and Technology, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
    Hébert-Losier, Kim
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Kersting, Uwe
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The effect of light reflections from the snow on kinematic data collected using stereo-photogrammetry with passive markers2014In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 17, no 2, p. 97-102Article in journal (Refereed)
    Abstract [en]

    This study aimed to compare kinematic data collected during ski-cross starts outdoors on snow in daylight (high albedo) to similar data collected indoors with infiltrating sunlight but without light reflections from the snow (low albedo) using a video-based motion capture system with the active filtering function enabled. A 12-camera 3D motion capture system (Qualisys AB, Sweden) was used to measure test objects and eight skiers performing a ski-cross start on a slope outdoors and on a wooden start ramp indoors. The average residuals and standard deviations of the length of the calibration wand calculated indoors and outdoors by the calibration software were compared using descriptive statistics. Static and moving fixed length measures and thigh length measures were compared using Bland-Altman plots. Calibration residuals were slightly increased outdoors (1.77 mm) compared to indoors (1.54 mm), while wand length varied by 3.63 and 1.51 mm, respectively. Fixed static lengths differed by -8.65 ± 4.94 mm (shorter indoors), whereas fixed moving lengths differed by 0.85 ± 1.05 mm (longer indoors). A randomly chosen marker pair on one segment (Thigh) showed a mean difference of 1.19 ± 22.05 mm (longer indoors). It is concluded that 3D motion capture outdoors on snow in daylight is feasible, provides kinematic data comparable to indoors, and could be used to research biomechanics in snow sports.

  • 6.
    Koptyug, Andrey
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics. SportsTech Research Centre, Mid Sweden University.
    Burkett, Brendan
    School of Health and Sport Sciences, University of Sunshine Coast, Australia.
    Editorial for the special issue technology for disability sport2016In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 19, no 3, p. 1p. 139-139Article in journal (Refereed)
    Abstract [en]

    Major sporting events, including the Olympic Games, areroutinely ‘‘brought to our homes’’ by modern mass media.The Paralympic Games follow the Olympic Games, and areanother major competition event. With each summer andwinter Paralympic games, such as the 2012 London and the2014 Sochi Paralympic games, the elite sporting achievementsmay be new to many of us. The athletic skill andpersistent determination drive Paralympic sports. A commonthread with the Paralympic athlete is the reliance onsome form of technology to compete on the world stage.Engineering and technology have become an essentialpart of modern-day sports. This partnership is necessary forcoach and athlete as they prepare for, and participate incompetitions. From the audience perspective, sports technologycan provide a new perspective and insight into thecompetition and its highlights. The quality of equipment,garments and footwear, and their interaction with athlete’sbody become an integrated part of the winning strategy inmodern sports.For the athlete with a disability, engineering and technologyhas always been an essential partnership. Withoutthe assistive devices, the disabled athlete is not able toprepare and participate in sport. Equipment design fordisabled athletes is often more complex and customizedthan for many other applications.The fundamental principles for the use of equipment inParalympic Sport are safety, fairness, universality andphysical prowess. While the safety criterion is relativelystraightforward, fulfilling other three can be challenging forthe designers and classifiers. It is often impossible to showif the performance of an athlete with a particular assistivedevice is determined by the athlete rather than by ‘‘theimpact of technology and equipment’’. By working togetherwith all parties the sports engineering community canprovide affordable safe and reliable assistive devices,technologies for training and rehabilitation, and animproved basis for objective classification.Research papers in this issue deal with a wide variety ofsubjects and are multidisciplinary. Four papers in thisspecial issue are related to the athlete and equipmentinteraction, which is important in all sports but needsspecial care and precision when working with of paraathletes.The remaining five papers are related to issuesimportant for the training and classification.We hope that these contributions will improve theintegration between athlete and equipment, will provide abetter basis for proper classification of the equipment andassistive devices, and, according to the International ParalympicCommittee vision, will ‘‘enable para-athletes toachieve sporting excellence and inspire and excite theworld’’.

  • 7.
    Kuzmin, Leonid
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Dirt absorption on the ski running surface - quantification and influence on the gliding ability2006In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 9, no 3, p. 137-146Article in journal (Refereed)
    Abstract [en]

    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.

  • 8.
    Sundström, David
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    On a bioenergetic four compartment model for human exercise2016In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 19, no 4, p. 251-263Article in journal (Refereed)
    Abstract [en]

    Bioenergetic models for exercise performance simulations and pacing strategy optimizations currently lag behind empirical knowledge in human bioenergetics. Therefore, the objective of this study was the construction of a four compartment bioenergetic model that incorporates separate oxidative phosphorylation of lipids and carbohydrates and describes the regulation of these energy substrates’ utilization. Furthermore, the aim was also to model efficiency and the impact of muscle fatigue and the force-velocity relationship on the maximal attainable rate of energy expenditure. The model was formulated with five systems of differential equations that regulated the fluid levels in three of the compartments, while the lipid compartment energy was kept constant. Regulations had to be imposed on the system of compartments to achieve the desired carbohydrate dependent functionality and efficiency of the model. Equilibrium equations were modeled for the alactic compound composition and a constraint was modeled for the maximal energy expenditure rate, dependent on the intramuscular inorganic phosphate. A separate force-velocity relationship was modeled to constrain power output at low speeds and efficiency was modeled with a linear but off-set relationship between power output and rate of energy expenditure. The relative aerobic contribution to total energy expenditure showed good congruence with empirical results, while time to exhaustion was overestimated due to the constraint on maximal rate of energy expenditure. Therefore, further experimental studies are necessary for complete validation of the model.

  • 9.
    Sundström, David
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Comparing bioenergetic models for the optimisation of pacing strategy in road cycling2014In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 17, no 4, p. 207-215Article in journal (Refereed)
    Abstract [en]

    Road cycling performance is dependent on race tactics and pacing strategy. To optimise the pacing strategy for any race performed with no drafting, a numerical model was introduced, one that solves equations of motion while minimising the finishing time by varying the power output along the course. The power output was constrained by two different hydraulic models: the simpler critical power model for intermittent exercise (CPIE) and the more sophisticated Margaria–Morton model (M–M). These were compared with a constant power strategy (CPS). The simulation of the three different models was carried out on a fictional 75 kg cyclist, riding a 2,000 m course. This resulted in finishing times of 162.4, 155.8 and 159.3 s and speed variances of 0.58, 0.26 and 0.29 % for the CPS, CPIE and M–M simulations, respectively. Furthermore, the average power output was 469.7, 469.7 and 469.1 W for the CPS, CPIE and M–M simulations, respectively. The M–M model takes more physiological phenomena into consideration compared to the CPIE model and, therefore, contributes to an optimised pacing strategy that is more realistic. Therefore, the M–M model might be more suitable for future studies on optimal pacing strategy, despite the relatively slower finishing time.

  • 10.
    Ørtenblad, Niels
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. University of Southern Denmark, Denmark.
    Jensen, Kurt
    University of Southern Denmark, Denmark.
    Gross efficiency predicts a 6-min double-poling ergometer performance in recreational cross-country skiers2017In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 20, no 4, p. 329-333Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to investigate which physiological parameters would most accurately predict a 6-min, all-out, double-poling (DP) performance in recreational cross-country skiers. Twelve male recreational cross-country skiers performed tests consisting of three series lasting 10 s, one lasting 60 s, plus a 6-min, all-out, DP performance test to estimate mean and peak power output. On a separate day, gross mechanical efficiency (GE) was estimated from a 10-min, submaximal, DP test and maximal oxygen consumption (VO2 max) was estimated from an incremental treadmill running test. Power was measured after each stroke from the acceleration and deceleration of the flywheel that induced the friction on the ergometer. The power was shown to the skier on a small computer placed on the ergometer. A multivariable correlation analysis showed that GE most strongly predicted 6-min DP performance (r = 0.79) and interestingly, neither DP VO2 max, nor treadmill-running VO2 max, correlated with 6-min DP performance. In conclusion, GE correlated most strongly with 6-min DP performance and GE at the ski ergometer was estimated to be 6.4 ± 1.1%. It is suggested that recreational cross-country skiers focus on skiing technique to improve gross mechanical efficiency during intense DP.

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