| 1. |
- Björklund, Glenn, 1972-, et al.
(författare)
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The effect of speed and gradient on running economy and oxygen uptake during downhill running
- 2019
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Konferensbidrag (refereegranskat)abstract
- Downhill running poses challenges were the gradient is of importance for energy cost and oxygen uptake. While demonstrated that downhill running at a slight gradient is most efficient, the energy cost increases with a steeper gradient (1). However, the additional effect of running speed has not been studied for downhill running. Therefore, the aim of the study was to analyse the combined effect of gradient and speed in downhill running on oxygen cost and running economy. METHODS:Runners (n=6) were recruited for the study and performed 1) VO2max and running economy (J·kg-1·m-1) tests and 2) an experimental running protocol at two speeds,12 km·h-1 and 80% of the speed at VO2max (V80) and three gradients (0, -5° and -10°). V80 was higher than 12 km·h-1 for all participants. All testing was performed on a large treadmill 3x5 m (Rodby, Sweden) that were controlled for speed and gradient. The experimental protocol was performed continuously with 5 min at each workload in a randomized order, 30 min in total. VO2 was measured throughout the experimental protocol using a mixing chamber (Moxus Metabolic Cart, USA). RESULTS:VO2 expressed as ml·kg-1·min-1 increased because of speed (F1,5=27.8, p=0.003) and decreased with gradient (F1,5=87.6, p<0.001). Between -5° and -10°, VO2 decreased less during V80 compared to 12 km·h-1 shown by an interaction (F2,10=7.9, p=0.009). However, speed did not influence running economy (F1,5=0.9, p=0.38) while gradient increased running economy (F1,5=90.1, p<0.001). A non-significant interaction effect suggests a shift in running economy between -5° and -10° depending on speed (F2,10=3.5, p=0.07). The running economy at V80 was higher compared to 12 km·h-1 at -5° but reversed at -10°. While a relation between running economy at V80 -10°, V80 -5° and 12 km·h-1 -10° (rs>0.88, p<0.019) was found, no relations between running economy on level terrain and steep downhill running (-10°) were recognised. CONCLUSION:While we found no effect on running economy from speed alone, we did see a shift in the running economy for different speeds at an increased downhill gradient. This indicates that a high speed (V80) is more efficient at moderate downhill gradients, while a lower speed (12 km·h-1) is more efficient in steeper downhill gradients. While previous research demonstrate that gradient is of great influence to running economy, the findings of this study suggest that speed also affects the running economy in downhill running.
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| 2. |
- Bäckström, Mikael, et al.
(författare)
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A New Wind Tunnel Facility Dedicated to Sports Technology Research and Development
- 2016
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Ingår i: Procedia Engineering. - : Elsevier. ; , s. 62-67
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 3. |
- Bäckström, Mikael, et al.
(författare)
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Sports Technology Education at Mid Sweden University
- 2013
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Ingår i: 6TH ASIA-PACIFIC CONGRESS ON SPORTS TECHNOLOGY (APCST). - : Elsevier. ; , s. 214-219
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 4. |
- Danvind, Jonas
(författare)
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Analysis of drying wood based on nondestructive measurements and numerical tools
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Improved understanding of moisture and mechanical behaviour is a general objective for wood drying research. The main objective of this doctoral thesis was to develop nondestructive experimental methods suitable for collecting valuable response data related to the moisture behaviour and mechanical behaviour of drying wood and to refine this information into modelling parameters. A method for simultaneous noncontact measurement of two-dimensional surface deformations and interior densities was developed. This was done using Digital Speckle Photography (DSP) and X-ray Computed Tomography (CT). Displacements and densities were used for calculation of strain and of moisture content. Experimental tests of the measurement method were done on cross sections of Scots pine. The following accuracy was stated for different properties: A typical calculated displacement error of approximately 10 micrometre was found. Strains derived from the displacements had a maximal error of 1.11 mstrain. Moisture content measuring accuracy was estimated to +-1.8% moisture content at a significance level of 0.05 in a measuring volume with the approximate size 2 x 2 x 1.5 mm3. A similar noncontact technique based only on X-ray CT scanning was developed. Displacements were then estimated from boundary movements of an object in CT images. The estimated standard deviation of the measured moisture content error for this method was 0.04% moisture content. The mean error was unknown. Two different approaches to determining moisture diffusion coefficients from the studied data were presented. The first was based on minimizing the difference between measured and computed values through an optimization scheme. This approach required an initial assumption of the functional form of the diffusion coefficient. The second approach calculated diffusion and mass transfer coefficients through direct finite difference calculations on measured moisture content data. Results on Norway spruce showed interesting local variations of the diffusion coefficient, especially near the evaporation surface. Comparisons between measured and FEM simulated data showed good results. An example showed that a multivariate method of analysis could be an effective and easy-to-use tool for untangling relationships between variables and for generating information from data. Finally, it could be stated that the methods presented will be of use to improve the understanding of the behaviour of drying wood, with the focus on moisture and mechanical properties.
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| 5. |
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| 6. |
- Danvind, Jonas, et al.
(författare)
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Calibration of a constitutive model for diffusive moisture transport in wood using data from X-ray CT-scanning and digital speckle photography
- 2004
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Ingår i: 5th Conference on Timber drying for value-added prducts, COST action E15 "advances in drying of wood". ; , s. 210-218
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An unsteady-state diffusion model is applied for studying wood drying below the fibre saturation point. The moisture diffusion coefficient in Fick's law for Norway spruce under isothermal drying conditions is determined. Using X-ray CT-scanning and Digital Speckle Photography, the wood density and moisture content are obtained in the radial direction of the wood samples. An optimization scheme is used to minimize the difference between observed and computed moisture content in order to calibrate the values of a set of parameters describing the diffusion coefficient. In this study the values of the parameters for a parameterization of Arrhenius' type are determined. The general idea discussed, however, is not limited to a specific model, butcan be used for a wide class of parameter identification problems. The results show a good agreement between observed and computed moisture content and it is concluded that the numerical realization of the optimization scheme works well. Nevertheless, the value of the diffusion coefficient is somewhat higher than expected. This is likely the consequence of a permeable coating of the samples.
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| 7. |
- Danvind, Jonas, et al.
(författare)
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Local water vapor diffusion coefficient when drying Norway spruce sapwood
- 2006
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Ingår i: Journal of Wood Science. - : Springer Science and Business Media LLC. - 1435-0211 .- 1611-4663. ; 52:3, s. 195-201
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a one-dimensional and a two-dimensional approach to the evaluation of local diffusion coefficients for Norway spruce sapwood from measured moisture content (MC) values are presented. A studied wood sample was dried from the initial green condition to about 15% mean MC, but here only the diffusive part of the drying process between approximately 25% and 15% mean MC was treated. Measured local MC values were based on nondestructive X-ray computed tomography data. Finite element calculations were performed with two alternative diffusion coefficients to test the appropriateness of the diffusion coefficients that were evaluated from the measured MC values. The evaluated diffusion coefficients show interesting dependence on MC and distance from the evaporation surface. The advantage of using the methods presented is that the diffusion coefficient is calculated on a local level without having to define a function for the diffusion coefficient's dependency on other parameters
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| 8. |
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| 9. |
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| 10. |
- Danvind, Jonas
(författare)
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Methods for collecting and analysing simultaneous strain and moisture data during wood drying
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Improved understanding of moisture and mechanical behaviour is an international objective for wood drying research. The main objective of this licentiate thesis work was to develop an experimental method suitable for collecting valuable response data related to the moisture and mechanical behaviour of drying wood. Another objective was to provide an example on how multivariate methods can be used to analyse response data. A method for simultaneous non contact measuring of two dimensional surface deformations and interior densities have been developed. This was done using Digital Speckle Photography, DSP, and X-ray Computerised Tomography (CT). Displacements and densities were used for calculation of strains and moisture contents using a custom software developed in Matlab. Experimental tests of the measuring method were made on cross sections of Scots pine. The following accuracy was stated for different properties: - Displacements measured with DSP could be measured with a random error down to 0.01 pixels. A more typical calculated displacement error of approximately 10 micrometres, was found in paper I. - Strains derived from the displacements had a maximal error of 1.11 mstrain in an experimental test in paper II. - Accuracy in density measurements was expected to be less than +-6 kg/m3 for wet wood with moisture contents ranging from 6-100% and less than +-2 kg/m3 in dry wood, at a significance level of 0.05. This was estimated for a 2x2x1.5 mm3 measuring volume. - Moisture content measuring accuracy was estimated by simulations in paper II, which resulted in a measuring accuracy of +-1.8% moisture content at a significance level of 0.05 in a measuring volume with the approximate size of 2x2x1.5 mm3. A multivariate analysing method has been used to present an example on multivariate modelling of shrinkage behaviour in Radiata pine. The method was found to be an easy-to-use tool and useful for valid prediction of radial, tangential, longitudinal and volume shrinkage in the moisture range between 0% and 22% moisture content of the studied wood. The method also proved to be effective for untangling relationships between variables and generating information out of data. Finally, it can be stated that the developed measuring technique and the tested multivariate analysing method will be of use to improve the understanding of the behaviour of drying wood, focusing on moisture and mechanical properties.
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| 11. |
- Danvind, Jonas
(författare)
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PLS prediction as a tool for modeling wood properties
- 2002
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 60:2, s. 130-140
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Tidskriftsartikel (refereegranskat)abstract
- During an earlier study, material responses of shrinkage and deformation during air-drying were measured on small wood specimens cut from the cross section of a Pinus radiata log. In this paper the analysis of the collected data and the modeling of studied responses were done using multivariate methods. A first model with all variables and all 104 observations was created. In this model there were observations that deviated from the rest and some of them were therefore excluded from further modeling. Also, weak variables and undesired variables were excluded from further modeling. After these exclusions, 77 observations of wood responses below fiber saturation point remained. The results showed good modeling of radial, tangential and volumetric shrinkage between 0-22% MC, with explained variance (R2) and predicted variance (Q2) at approximately 0.9, and moderate modeling of longitudinal shrinkage, R2 = 0.67 and Q2 = 0.65. It was also shown that longitudinal shrinkage has weak correlation to density-related variables in the studied wood. No model with good predictability of deformation was found. This study showed that PLS prediction modeling of shrinkage and deformation in studied wood samples was found to be an effective and easy-to-use tool for untangling relationships between variables and generating information from data.
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| 12. |
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| 13. |
- Elmer, Steven, et al.
(författare)
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Development of a novel eccentric arm cycle ergometer for training the upper body
- 2013
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Ingår i: Medicine & Science in Sports & Exercise. - : Lippincott Williams & Wilkins. - 0195-9131 .- 1530-0315. ; 45:1, s. 206-211
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Tidskriftsartikel (refereegranskat)abstract
- Several investigators have demonstrated that chronic eccentric leg cycling is an effective method for improving lower body neuromuscular function (e.g., quadriceps muscle size, strength, and mobility) in a variety of patient and athletic populations. To date, there are no reports of using eccentricarm cycling (ECarm) as an exercise modality, probably in large part because of the lack of commercially available ECarm ergometers. Purpose: Our purposes for conducting this study were to 1) describe the design and construction of an ECarm ergometer and 2) compare ECarm to traditional concentric arm cycling (CCarm). Methods: All of the parts of a Monark 891E cycle ergometer (Monark Exercise AB, Vansbro, Sweden) were removed, leaving the frame and flywheel. An electric motor (2.2 kW) was connected to the flywheel via a pulley and a belt. Motor speed and pedaling rate were controlled by a variable frequency drive. A power meter quantified power and pedaling rate, and provided feedback to the individual. Eight individuals performed 3-min ECarm and CCarm trials at 40, 80, and 120 W (60 rpm) while V̇O2 was measured. Results: The ECarm ergometer was simple to use, was adjustable, provided feedback on power output to the user, and allowed for a range of eccentric powers. V̇O2 during ECarm was substantially lower compared with CCarm (P < 0.001). At similar V̇O2 (0.97 ± 0.18 vs 0.91 ± 0.09 L•min, for ECarm and CCarm, respectively, P = 0.26), power absorbed during ECarm was approximately threefold greater than that produced during CCarm (118 ± 1 vs 40 ± 1 W, P < 0.001). Conclusion: This novel ECarm ergometer can be used to perform repetitive, high-force, multijoint, eccentric actions with the upper body at a low level of metabolic demand and may allow researchers and clinicians to use ECarm as a training and rehabilitation modality. © 2012 by the American College of Sports Medicine.
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| 14. |
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| 15. |
- Eriksson, John, 1973, et al.
(författare)
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A Mass-Transport Model for Drying Wood under Isothermal Conditions
- 2005
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Ingår i: 9th international IUFRO wood drying conference, Nanjing, China, August 21-26, 2005. ; 1:1, s. 51-56
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mass transport in wood during drying is often described in terms of different periods. Depending on the current moisture content (MC) and the structure of the wood, the driving forces behind the mass transport are essentially different. Above a certain level of MC, the fibres are partially saturated and the transport of liquid (free) water occurs mainly as a consequence of capillary action. On the other hand, below the fibre saturation point, bound water within the cell walls is conveyed by diffusion, and water vapour in the lumen moves under influence of pressures. In this contribution, a unified model is presented that takes into account the transport of the different water phases. Simulation of the drying of a Norway spruce sample from about 135% to 7% MC is carried out using the finite element method (FEM). The resulting mean MC is compared with experimental observations obtained from X-ray Computed Tomography showing reasonable agreement. Possible simplifications in the model are briefly discussed as well as some aspects of the numerical implementation.
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| 16. |
- Eriksson, John, 1973, et al.
(författare)
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A Mass Transport Model for Drying Wood under Isothermal Conditions
- 2007
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Ingår i: Drying Technology. - : Informa UK Limited. - 1532-2300 .- 0737-3937. ; 25:3, s. 433-439
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Tidskriftsartikel (refereegranskat)abstract
- Mass transport in wood during drying can have different mechanisms at different periods of drying. Depending on the current moisture content (MC) and the structure of the wood, the driving forces for the mass transport are essentially different. Above the fiber saturation point (FSP), the lumens are partially saturated and the transport of liquid (free) water occurs as a consequence of capillary action. On the other hand, below the FSP, bound water within the cell walls is conveyed by diffusion, and water vapor in the lumens moves under influence of pressures gradient. Based on these considerations, a unified model is presented that takes into account the transport of the different moisture phases. Simulation of the drying of a Norway spruce sample at 50°C from about 135 to 7% MC is carried out using the finite element method (FEM). Comparison between the simulated average MC and the experimental observations obtained from X-ray computed tomography (CT) shows reasonable agreement. Possible simplifications in the model are briefly discussed as well as some aspects of the numerical implementation. Finally, the influence of absolute permeability on the average MC is studied.
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| 17. |
- Eriksson, John, et al.
(författare)
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Numerical determination of diffusion coefficients in wood using data from CT-scanning
- 2006
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 38:2, s. 334-344
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Tidskriftsartikel (refereegranskat)abstract
- The radial moisture diffusion coefficient in Fick's law for a sample of Norway spruce (Picea abies) under isothermal drying conditions was determined in a parameterization of Arrhenius' equation type. Using X-ray CT-scanning, the wood density and moisture content distributions were obtained in the radial direction for the wood sample. An optimization scheme, based on finite element computation, was then applied to find the parameter values such that the difference between observed and computed moisture content was minimized. The combined numerical and experimental technique was developed to reduce known disadvantages of similar approaches, and a specific algorithm to determine diffusion coefficients was presented. A comparison of the calibrated diffusion coefficient with those given in the literature showed a good fit. The computed moisture content based on the obtained diffusion coefficient and the observed moisture content agreed well. Finally, the effect of measurement errors on the computed material parameter was found to be small
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| 22. |
- Holmberg, L. Joakim, 1971-, et al.
(författare)
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Can Simulations Assist in Classification Development?
- 2013
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Ingår i: Equipment and Technology in Paralympic Sports. - : International Paralympic Committee.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is a critical need for research that describes the extent to which impairments of varying type, severity and distribution impact performance in Paralympic sports. It is important with evidence-based judgment on how the impairments aect performance. In the following, we present a complementary evidence-based tool for classication.Let us start with an example. We recently presented a study (Holmberg et al., 2012)1 that utilized two full-body musculoskeletal simulation models of cross-country skiing (double-poling). The models were identical except that one carried no muscles in the right lower leg and foot; thus mimicking a lower leg prosthesis. It was hypothesized that a lower leg prosthesis would inuence muscular work throughout the whole body. Results showed that to generate the same motion and external work, an able-bodied skier only had to produce about 80% metabolic muscle work compared to a disabled skier (with a non-active right lower leg prosthesis).In reality there is always psychological factors present and it is probably not possible to nd two human beings (one fully functional and one impaired) with the same tness, size, strength and technique. Thus, it is hard to nd the unbiased eect of an impairment on performance in a speci c sport. The example above shows the strength of using simulations because a musculoskeletal model yields quantitative data on the unbiased eect of dierent functional impairments.In cross-country skiing, athletes with functional impairments are, in 'competition format' classification, assigned to dierent categories with weight factors. Athletes perform their race and the result list is presented as race time multiplied by weight factor. In the future, musculoskeletal simulations may assist in answering how a specic functional impairment aects performance and thereby improve the fairness in assigning weight factors for classication.
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| 23. |
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| 24. |
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| 25. |
- Larsson, Robert, et al.
(författare)
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Styrsystem för ändamålsstyrd torkning : förutsättningar och industriförsök
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Del A: Inledningsvis behandlas allmänna principer för adaptiv reglering av torkprocessen vad gäller solitt trä. De grundläggande meknaismerna som ligger bakom fukttransporten i trä vid artificiell torkning beskrivs även. På basis av denna fundamentala kunskap kan exempelvis parameterstyrning utvecklas för industriella satstorksystem. Ett antal principer för sådan styrning har implementerats i en laboratorietork. Del B: Ett antal industriförsök i full skala har genomförts för att undersöka hur en dynamisk återkoppling i styrsystemet kan ske. Exempelvis finns tydliga samband mellan vireksstapelns krympning och dess medelfuktkvot, vilket tillsammans med andra signaler från torkningen kan ge återkoppling i styrsystemet. En multivariat ansats kan vara en möjlig utveckling till ett styrsystem som även innefattar ett integrerat expertsystem för färgstyrning bl a.
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