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  • 1.
    Ferdinands, R. E. D.
    et al.
    Exercise, Health and Performance Research Group, The University of Sydney, Sydney, Australia.
    Kersting, Uwe G.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
    Marshall, R. N.
    Eastern Institute of Technology, Hawke's Bay, New Zealand .
    A new taxonomic system for the sub-classification of cricket bowling actions2014In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 7, no 1-2, p. 26-38Article in journal (Refereed)
    Abstract [en]

    The mixed bowling action is associated with injuries in the lumbar spine and has been shown to have no performance benefits over other bowling actions. The purpose of this study was to assess the mixed bowling action with reference to a more comprehensive classification system to facilitate the development of more targeted bowling action remediation programs. A total of 70 fast bowlers were tested using a three-dimensional motion analysis system (240 Hz). Kinematic data of the shoulders and pelvis were analysed with respect to a modified set of angle threshold criteria to classify bowling actions. It was found that the mixed action bowlers (49% of the sample) could be sub-divided into seven distinct mixed action types. The most common of these types were the mixed front-on bowlers with respect to shoulder counter-rotation (19%) and the mixed front-on bowlers with respect to both pelvis-shoulder separation angle and shoulder counter-rotation (14%). It is envisaged that a more comprehensive classification of bowling actions may assist researchers in the future to define mixed action types with a tighter domain of variables that are more indicative of lumbar injury risk. © 2014 Taylor & Francis.

  • 2.
    Kersting, Uwe G
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ferdinands,, René E.D.
    Faculty of Health Sciences, University of Sydney, Sydney, Australia.
    Marshall, Robert N.
    Eastern Institute of Technology, Hawke's Bay, New Zealand.
    Kinematic and kinetic energy analysis of segmental sequencing in cricket fast bowling2013In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 6, no 1, p. 10-21Article in journal (Refereed)
    Abstract [en]

    Although there have been many studies to quantify the segmental sequencing in other sports, there has been little such research applied to cricket bowling. In this study, 34 fast bowlers (22.3 ± 3.7 years) of premier grade level and above were tested using 3D motion analysis, their balls speed ranging from 27.0 to 35.6 m s− 1. One-way repeated measures ANOVA was used to test for within-participant differences in segmental sequencing based on the timings of maximum segmental angular velocities and kinetic energies, the data showing that bowlers exhibited a general order of proximal-to-distal sequencing. Bivariate Pearson's product-movement correlation coefficients were calculated to assess the relationships between kinematic variables and ball release speed, yielding a set of variables for entry into a stepwise multiple regression model. The multiple regression model with the sequential timing variables of thoracic linear kinetic energy (KE), upper-arm circumduction velocity and forearm rotation KE, as well as the pelvic–shoulder separation acceleration accounted for 55% of the variability in ball speed (R 2 = 0.55, adjusted R 2 = 0.49, F(4, 29) = 8.86, p < 0.001). This study showed that both the magnitude and the timing of segmental activation are important to generate ball speed in fast bowling.

  • 3.
    Kuzmin, Leonid
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    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.
    The relationship between the type of machining of the ski running surface and its wettability and capillary drag2010In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 3, no 2, p. 121-130Article in journal (Refereed)
    Abstract [en]

    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.

  • 4.
    Lintzén, Nina
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Almqvist, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Span curve temperature dependence of classic style cross country skis2016In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190Article in journal (Refereed)
  • 5.
    Sturm, Dennis
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701).
    Yousaf, Khurram
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701).
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Halvorsen, Kjartan
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS) (Closed 20130701). Uppsala University, Uppsala, Sweden .
    Wireless kayak on-water ergometry - Part 1: Paddle blade force2013In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 6, no 1, p. 29-42Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to present a new wireless paddle force measurement system and to evaluate this measurement system. The system is redeveloped from a previous design and includes inertial motion sensors, which allows for the movement and inertia of the paddle to be taken into account. The system consists of two sensor nodes, designed for quick attachment to virtually any kayak paddle and an Android phone or tablet. Each sensor node measures the bending of the shaft in one plane. We derive the expressions necessary for computing the force on the paddle blade in two directions, ignoring the force in the direction of the shaft. Two different schemes for calibrating the system are presented. The accuracy and reliability of the system is evaluated in a laboratory setting using a material testing machine. An average error of 0.4% can be achieved for force measurements following directly after calibration. When the sensors are removed and reattached between calibration and measurements, average error between loading and measured force increased to 2.0% (linear model) and 1.8% (quadratic model). The limits of agreement depend on the position of the sensor nodes along the shaft and the feather angle if transverse sensitivity of the sensors is used to determine two-dimensional force on the paddle blade. On-water stroke force is presented, averaged over 10 strokes for each side with force levels >200 N to show the applicability of the study. The accuracy of the measurement is affected by the calibration method, placement of the paddle nodes and the shaft's properties.

  • 6.
    Swarén, Mikael
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Mechanics, Royal Institute of Technology, Stockholm, Sweden.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Eriksson, Anders
    Department of Mechanics, Royal Institute of Technology, Stockholm, Sweden.
    Repeated low impacts in alpine ski helmets2013In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 6, no 1, p. 43-52Article in journal (Refereed)
    Abstract [en]

    Alpine ski race helmets are subjected to multiple impacts during a race caused by the skiers hitting the gates on their way down the course. This study investigated the difference between expanded polystyrene (EPS) and expanded polypropylene (EPP) cores in alpine ski race helmets when subjected to repetitive violence, caused by alpine slalom gates. A special test rig was developed where a rotating slalom pole impacted the helmets with a velocity of 13.3 m·s− 1. All helmets (six EPS and six EPP) were attached to a headform, monitored with a triaxial accelerometer at the center of mass. Each helmet sustained 1000 impacts and acceleration data were collected around every 200 impacts. No significant differences were observed between the first hit and after 1000 hits for either the EPS or the EPP helmets. However, the total group mean acceleration and mean peak acceleration were 15% and 16% higher, respectively, for the EPS series compared with the EPP series. Also, all EPS helmets showed cracked cores after 1000 impacts compared with 1 cracked EPP core. Findings suggest that EPP cores might be more suitable for absorbing multiple low impacts caused by alpine gates and that repeated violence is a relevant parameter to consider when constructing alpine ski race helmets.

  • 7.
    Swarén, Mikael
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Mechanics, Royal Institute of Technology, Stockholm, Sweden .
    Karlöf, L.
    Swix Sport AS, Frysajv. 40, Oslo, Norway .
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Swedish Olympic Committee, Stockholm, Sweden.
    Eriksson, A
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Department of Mechanics, Royal Institute of Technology, Stockholm, Sweden .
    Validation of test setup to evaluate glide performance in skis2014In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 7, no 1-2, p. 89-97Article in journal (Refereed)
    Abstract [en]

    Although today's ski waxing chemicals and micro-machining techniques of the ski base are highly sophisticated, objective procedures for testing and verification of the results have not yet been developed and evaluation is based on comparison of subjective experience. The purpose of the present study was thus to compare different setups for testing the glide of cross-country skis. Two differently waxed ski pairs were tested for glide inside a ski tunnel. Inertial measurement units (IMUs) were attached to each ski; instantaneous velocities monitored by three different speed-traps; the velocities during the acceleration phase determined by Doppler radar. Kinetic, potential and total energy, giving the energy dissipation, were calculated for four representative trials during the acceleration phase. No reliable data were obtained from the IMUs due to high drift. The mean maximal velocity for the two ski pairs were 6.97, s = 0.09 and 6.70, s = 0.09 m·s − 1, respectively. Higher differences between the skis were identified during the retardation phase compared to the acceleration phase. The mean difference between the velocities determined by the speed-trap and Doppler radar was 0.6, s = 1%, demonstrating that the latter provides accurate data for evaluation of gliding characteristics and performance. However, theoretical confirmation of the friction coefficient, on the basis of data provided by Doppler radar and energy calculations requires exact measurements of the inclination and topography of the track in question. © 2015 Taylor & Francis.

  • 8.
    Swarén, Mikael
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. Mid Sweden University, Sweden.
    Karlöf, L.
    Holmberg, Hans-Christer
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. Mid Sweden University, Sweden.
    Validation of test setup to evaluate glide performance in skis2014In: Sports Technology, ISSN 1934-6182, E-ISSN 1934-6190, Vol. 7, no 1-2, p. 89-97Article in journal (Refereed)
    Abstract [en]

    Although today's ski waxing chemicals and micro-machining techniques of the ski base are highly sophisticated, objective procedures for testing and verification of the results have not yet been developed and evaluation is based on comparison of subjective experience. The purpose of the present study was thus to compare different setups for testing the glide of cross-country skis. Two differently waxed ski pairs were tested for glide inside a ski tunnel. Inertial measurement units (IMUs) were attached to each ski; instantaneous velocities monitored by three different speed-traps; the velocities during the acceleration phase determined by Doppler radar. Kinetic, potential and total energy, giving the energy dissipation, were calculated for four representative trials during the acceleration phase. No reliable data were obtained from the IMUs due to high drift. The mean maximal velocity for the two ski pairs were 6.97, s = 0.09 and 6.70, s = 0.09 m·s − 1, respectively. Higher differences between the skis were identified during the retardation phase compared to the acceleration phase. The mean difference between the velocities determined by the speed-trap and Doppler radar was 0.6, s = 1%, demonstrating that the latter provides accurate data for evaluation of gliding characteristics and performance. However, theoretical confirmation of the friction coefficient, on the basis of data provided by Doppler radar and energy calculations requires exact measurements of the inclination and topography of the track in question.

1 - 8 of 8
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  • en-US
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  • nn-NO
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  • Other locale
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  • asciidoc
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