| 791. |
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| 792. |
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| 793. |
- Swarén, Mikael, 1982-, et al.
(författare)
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Power and pacing calculations based on real-time locating data from a cross-country skiing sprint race
- 2019
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Ingår i: Sports Biomechanics. - : Routledge. - 1476-3141 .- 1752-6116. ; 18:2, s. 190-201
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Tidskriftsartikel (refereegranskat)abstract
- Pacing strategies in cross-country skiing have been investigated in several studies. However, none of the previous studies have been verified by collected skiing data giving the skiing velocities along a measured track. These can be used to calculate the propulsive power output. Collected real-time positioning data from a cross-country sprint skiing race were used to estimate the propulsive power by applying a power balance model. Analyses were made for the time-trial and the final for one female and one male skier. The average propulsive power over the whole race times were 311 and 296 W during the time trial and 400 and 386 W during the final, for the female and male skier, respectively. Compared to the average propulsive power over the whole race, the average active propulsive phases were calculated as 33 and 44% higher in the time trials and 36 and 37% higher in the finals for the female and male, respectively. The current study presents a novel approach to use real-time positioning data to estimate continuous propulsive power during cross-country sprint skiing, enabling in-depth analyses of power output and pacing strategies.
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| 794. |
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| 795. |
- Swarén, Mikael, 1980-, et al.
(författare)
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Repeated low impacts in alpine ski helmets
- 2013
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Ingår i: Sports Technology. - : Informa UK Limited. - 1934-6182 .- 1934-6190. ; 6:1, s. 43-52
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 796. |
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| 797. |
- Swarén, Mikael, et al.
(författare)
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Repetitive Low Impacts on Alpine Ski Helmets
- 2013
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Ingår i: Proceedings for the 6<sup>th</sup> International Congress on Science and Skiing. - 9783200034174 ; , s. 22-
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Konferensbidrag (refereegranskat)
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| 798. |
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| 799. |
- Swarén, Mikael, et al.
(författare)
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Usage and validation of a tracking system to monitor position and velocity during cross-country skiing
- 2016
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Ingår i: International Journal of Performance Analysis in Sport. - : Informa UK Limited. - 2474-8668 .- 1474-8185. ; 16:2, s. 769-785
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, we investigate here the possibility of using a real-time locating system (RTLS) to track cross-country skiers during a competition. For validation, three RTLS tags were attached to the antenna of a real-time kinematics global navigation satellite system (RTK GNSS) carried by a skier, skiing the course at three different intensities. In addition, RTLS data were collected from 70 racers during a FIS cross-country skiing sprint race. Spline interpolations were fitted to the RTLS data. In comparison to the RTK GNSS, the spline models for the three RTLS tags overestimated the mean skiing velocity by 5% and 2% at low and medium intensities, respectively, with no difference between the two systems during high intensity. The corresponding overestimations of the peak velocity at skiing intensities were 15%, 10% and 8%, respectively. A decimated sampling frequency for the RTLS data from 50 Hz to 0.5 Hz resulted in lower typical mean errors for the x-(0.53 m vs. 1.40 m), y-(0.31 m vs. 1.36 m) and z-axis (0.10 m vs. 0.20 m). The spline models based on 0.5 Hz and 1 Hz RTLS data overestimated the finishing times by on average of 0.5 s and 0.3 s, respectively. If a sufficient number of locators is utilized and the number of tags simultaneously recorded is limited, this RTLS can track cross-country skiers accurately. In conclusion, a low RTLS sampling frequency in combination with a spline model offer considerable potential for analyzing performance during cross-country sprint skiing.
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| 800. |
- Swarén, Mikael, et al.
(författare)
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Validation of test setup to evaluate glide performance in skis
- 2014
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Ingår i: Sports Technology. - : Routledge. - 1934-6182 .- 1934-6190. ; 7:1-2, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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