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- Born, Dennis, et al.
(författare)
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Near-Infrared Spectroscopy: More Accurate Than Heart Rate for Monitoring Intensity in Running in Hilly Terrain
- 2017
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Ingår i: International Journal of Sports Physiology and Performance. - : Human Kinetics. - 1555-0265 .- 1555-0273. ; 12:4, s. 440-447
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Tidskriftsartikel (refereegranskat)abstract
- Purpose:To 1) investigate the cardiorespiratory and metabolic response of trail running and 2) evaluate whether heart rate (HR) adequately reflects the exercise intensity or whether the tissue saturation index (TSI) could provide a more accurate measure when running in hilly terrain.Methods:Seventeen competitive runners (female: n=4, V’O2max: 55±6 mL·kg−1·min−1; male: n=13, V’O2max: 68±6 mL·kg−1·min−1) performed a time trial on an off-road trail course. The course was made up of two laps covering a total distance of 7 km and included six steep up- and downhill sections with an elevation gain of 486 m. All runners were equipped with a portable breath-by-breath gas analyzer, HR belt, global positioning system receiver and near-infrared spectroscopy (NIRS) device to measure the TSI.Results:During the trail run, the exercise intensity within the uphill and downhill sections was 94±2% and 91±3% of HRmax, 84±8% and 68±7% of V’O2max, respectively. The oxygen uptake (V’O2) increased within the uphill and decreased within the downhill sections (P< .01). While HR was unaffected by the altering slope conditions, the TSI was inversely correlated to the changes in V’O2 (r = - .70, P< .05).Conclusions:The HR was unaffected by the continuously changing exercise intensity, however, the TSI reflected the alternations in V’O2. Recently used exclusively for scientific purpose, this NIRS based variable may offer a more accurate alternative to HR to monitor running intensity in the future, especially for training and competition in hilly terrain.
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- Swarén, Mikael, 1980-, et al.
(författare)
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How do custom made insoles affect the pressure distribution under the feet in alpine skiing?
- 2016
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Konferensbidrag (refereegranskat)abstract
- Introduction Elite alpine skiers frequently adjust insoles, boots and skis to optimize skiing performance. There are numerous different constructions of custom made insoles. However, nobody has, to the authors’ knowledge, investigated the mechanisms behind a plausible performance increase. The purpose of the study was therefore to investigate the potential difference in pressure distribution under the feet when skiing with regular insoles compared to custom made insoles. Method A pre-study investigated differently constructed insoles and their possible effects on the pressure distribution under the feet. One test subject performed different squat and fly-wheel exercises with six differently constructed insoles. Kinetics and 3D-kinematics were collected to identify possible differences. One insole construction, with a flat bottom and a semi-soft upper layer, was thereafter chosen to be used for field tests. Nine professional skiers, including both race skiers and full time ski instructors, were recruited for the field tests. Each skier performed in a randomized order, three runs with a standard insole and three runs with a custom made insole. Plantar pressure under the feet was measured with the Pedar Mobile System at 100 Hz, for eight consecutive carving turns. The skiers were instructed to have the smallest possible time difference between all runs. The three runs for each situation were synchronized and the mean total, forefoot and midfoot pressure distributions were calculated. Results The pre-study results show that the pressure distribution between foot and insole and between insole and ski-boot depends on the insole construction. The mean time for all 54 runs was 26.62 ± 2.41 s and the mean individual time difference between the fastest and the slowest runs was 0.62 ± 0.33 s. All skiers showed large individual differences in percentage of “used” area under the feet, between the two types of insoles (5-80%). When skiing with the custom made insole, the total mean difference in percentage usage of the forefoot was -17 ± 19% and 8 ± 12% for the midfoot. Discussion The results show that the pressure distribution under the feet depends on the type of insole. However, the effect of a custom made insole is very individual. Hence, when performing studies of skiing kinetics and/or equipment, it is of vast importance that all subjects use similarly constructed custom made insoles. It can also be hypothesized that e.g., different canting angles of the ski-boot, affect the skier differently depending on the type of insole. Our suggestion is therefore to perform measurements to optimize the insoles before investigating and optimizing canting angles. The results also show that custom made insoles can assist the skier to utilize different areas of the foot. However, future studies are needed to investigate whether the decreased usage of the forefoot affects the overall aggressiveness of the setup and whether custom made insoles have a positive effect on skiing performance.
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- Swarén, Mikael, 1980-, et al.
(författare)
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Key performance indicators of ice hockey sprint performance
- 2018
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Ingår i: Journal of Sports Sciences. - : Routledge. - 0264-0414 .- 1466-447X. ; , s. 1-94
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Konferensbidrag (refereegranskat)abstract
- Ice hockey is a physical demanding sport with high intensity and repetitive start and stop movements. Hence, players need to have excellent physical condition and ice skating skills with good acceleration and sprint capacities. However, little biomechanical research has been conducted on elite ice hockey players to analyse applicable key performance indicators of skating acceleration and short sprint performance. The aim of the study was to collect plantar forces data of elite ice hockey players during short sprints in order to analyse and identify plausible performance indicators. With institutional ethics approval, twelve professional male ice hockey players, (Age 22.8 ± 5.2 years, height 185.6 ± 5.0 cm, weight 86.9 ± 6.2 kg) from the Swedish Hockey League participated in the study. Following an individual warm up, each player performed three maximal sprints (18.4 m) from a stationary position, with three minutes of rest between each sprint. Sprint time was collected with timing gates (Brower Timing system, USA). The best trial for each player was chosen for further analysis. Plantar forces were collected at 100 Hz with pressure insoles (Novel GmbH, Germany), placed in both skates (Buckeridge et al., 2015, PLOS ONE, 10, 5). Analyses were made for stride rate, symmetry left-right, contact time, force production and impulse. Only the step frequency, 3.35 ± 0.38 strides/s was correlated to skating performance (r = -0.6, P < 0.05). For the second to seventh step, the mean contact time was 0.26 ± 0.04 s, the mean force was 844 ± 152 N and the mean peak force was 1335 ± 224 N. The mean impulse was 230 ± 52 Ns and the group showed greater force production for the left leg compared to the right leg −2.07 ± 9.08 %. The present study is the first study to analyse plantar forces on professional ice hockey players. The significance of stride rate is in line with previous research (Renaud et al., 2017, Sports Engineering, 20, 255–266) whereas the plantar force production is higher, compared to findings by Buckeridge et al. (2015). This is likely explained by the use of higher skilled players in the present study. Still, plantar force production is not significant for performance which points to the importance of skating kinematics and/or shear forces. Hence, the combination of kinetics and 3D kinematics on ice is important to enhance the knowledge about skating performance of elite ice hockey players as well as developing a kinetic measurement system to measure shear forces in combination with plantar forces.
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| 8. |
- Swarén, Mikael, 1980-
(författare)
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Objective Analysis Methods in the Mechanics of Sports
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sports engineering can be considered as the bridge between the knowledge of sports science and the principles of engineering and has an important role not only in improving the athletic performance, but also in increasing the safety of the athletes. Testing and optimization of sports equipment and athletic performance are essential for supporting athletes in their quest to reach the podium. However, most of the equipment used by world-class athletes is chosen based only on subjective tests and the athletes’ feelings. Consequently, one of the aims of this thesis was to combine mechanics and mathematics to develop new objective test methods for sports equipment. Another objective was to investigate the possibility to accurately track and analyse cross-country skiing performance by using a real-time locating system. A long term aim is the contribution to increased knowledge about objective test and analysis methods in sports. The main methodological advancements are the modification of established test methods for sports equipment and the implementation of spline-interpolated measured positioning data to evaluate cross-country skiing performance. The first two papers show that it is possible to design objective yet sport specific test methods for different sports equipment. New test devices and methodologies are proposed for alpine ski helmets and cross-country ski poles. The third paper gives suggestions for improved test setups and theoretical simulations are introduced for glide tests of skis. It is shown, it the fourth paper, that data from a real-time locating system in combination with a spline model offers considerable potential for performance analysis in cross-country sprint skiing. In the last paper, for the first time, propulsive power during a cross-country sprint skiing race is estimated by applying a power balance model to spline-interpolated measured positioning data, enabling in-depth analyses of power output and pacing strategies in cross-country skiing. Even though it has not been a first priority aim in this work, the results from the first two papers have been used by manufacturers to design new helmets with increased safety properties and cross-country ski poles with increased force transfer properties. In summary, the results of this thesis demonstrate the feasibility of using mechanics and mathematics to increase the objectiveness and relevance when analysing sports equipment and athletic performance.
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| 9. |
- 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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| 10. |
- 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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| 11. |
- Swarén, Mikael, 1980-, et al.
(författare)
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Using 3D motion capture to analyse ice hockey shooting technique on ice
- 2019
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Ingår i: icSPORTS 2019 - Proceedings of the 7th International Conference on Sport Sciences Research and Technology Support. - : Scitepress. - 9789897583834 ; , s. 204-208
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Konferensbidrag (refereegranskat)abstract
- This study investigates the feasibility to use a passive marker motion capture system on ice to collect 3D kinematics of slap shots and one timers. Kinematic data were collected within a volume of 40×15×2 m by 20 motion capture cameras at 300 Hz, a resolution of 12 megapixels and a mean residual for all cameras of 3.4±2.5 mm, at a distance of 11.6 m. Puck velocity, blade velocity, ice contact time and distance to the puck were analysed for ten consecutive shots for each technique, for two professional ice hockey players. The total mean puck velocity was 38.0 ± 2.7 m/s vs. 36.4 ± 1.0 m/s. (p=0.053), for one timers and slap shots respectively. One player had higher puck velocity with one timers compared to slap shots 40.5 ± 1.0 m/s vs. 36.9 ± 1.0 m/s (p=0.001). Puck contact time was longer for slap shots than for one timers, 0.020 ± 0.002 s vs. 0.015 ± 0.002 s, (p<0.001). The motion capture system allowed continuous kinematic analyses of the puck and blade velocities, ice contact times and detailed stance information. The results demonstrate the possibilities to use motion capture systems to collect and analyse shooting kinematics on ice, in detail.
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| 13. |
- Swarén, Mikael, 1980-, et al.
(författare)
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Using telecasting to identify key performance indicators in alpine skiing and evaluate the inter-analyst reliability of alpine ski coaches
- 2016
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Konferensbidrag (refereegranskat)abstract
- ntroduction The most frequently used analysis method in alpine skiing is video footage. However, using video footage to identifying key performance indicators (KPIs) and other characteristics are difficult as each coach analyzes video footage in a subjective manner, which decreases the reliability of the analyses. Even though alpine skiing is a “closed sport”, without any external disturbing moments, each race is unique therefore never identical. It is thus difficult for coaches to know the validity and reliability of their analyses as the majority of the video footage of alpine skiers is captured during training, not racing. A large number of analyzed races with high reliability could therefore facilitate to identify KPIs in alpine skiing. The purpose of this study was to use the standardized typical error to explore the possibility to use telecasting to analyze performance and skiing characteristics in world cup slalom races. Method Standard telecasting footage (25 fps) from four different WC-races (eight runs) was used for analyzing turn times for eleven skiers (nine males and two females). The footage was analyzed at three separate situations, by two different alpine World Cup coaches and one video analyst. Turn time was defined as boot passage of the gate and all video analyses were made in DartFish ProSuite 6. Typical error (TE) was calculated by; TE=σ_diff/√(N_obs ) The standardized typical error (STE) was calculated by; TE= TE/√(((n_1-1)^2 σ_1^2+(n_2-1)^2 σ_2^2 ) /((n_1+n_2-2))-TE^2 ) The index described by Hopkins [1] was used for evaluating the influence of the STE. Results The mean turn time for the male skiers was 0.83 ± 0.18 s, with a coefficient of variation of 22%. The mean turn time for the two female skiers was 0.85 ± 0.19 s and the coefficient of variation was 22%. The TE between the different analyses was 0.03 s and the STE was 0.14. The results provide a detailed analysis of gate-to-gate times for each skier. Discussion The TE value of 0.03 s is most likely due to the 25 fps telecasting footage, where each frame is 0.04 s. The analysts must therefore choose one frame if the point of interest is between two frames. Hence, TE will presumably decrease with increase framerate. As the STE < 0.2, the disagreement between the different analysts can be considered as trivial [1, 2]. We here show how the STE can be used to identify inter-analyst reliability of alpine skiing video analyses. Furthermore, the presented method provides a robust, cheap and effective method to objectively analyze skiing performance and identifying plausible key performance indicators in alpine skiing. References 1. Hopkins, W., Reliability from consecutive pairs of trials (Excel spreadsheet). A new view of statistics, 2000. 2. Liu, H., et al., Inter-operator reliability of live football match statistics from OPTA Sportsdata. International Journal of Performance Analysis in Sport, 2013. 13(3): p. 803-821.
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| 14. |
- Swarén, Mikael, 1980-, et al.
(författare)
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Using telecasting to identify turn times in alpine skiing
- 2016
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Konferensbidrag (refereegranskat)abstract
- Alpine skiing can be considered as a “closed sport” where each athlete is alone in the course without any external disturbing moments. However, each alpine race is unique therefore never identical. In addition, the condition of the course is constantly changing as each skier makes new tracks in the snow. Identifying key performance indicators (KPI) and other characteristics are therefore difficult. The most frequently used analysis method in alpine skiing is video footage. However, it is not always possible for coaches to cover a complete course as they can be several kilometers long as e.g. downhill skiing. The purpose of this study was thus to explore the possibility to use telecasting to analyze performance and skiing characteristics in world cup slalom races to identify possible KPI.
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| 15. |
- Wedeking, Daniela, et al.
(författare)
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The influence of arm and ski pole during alpine skiing
- 2019
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Konferensbidrag (refereegranskat)abstract
- INTRODUCTION: Research investigating the correlation between impairment and key performance indicators in para-alpine skiing is needed for a future evidence based classification system (Tweedy and Vanlandewijck 2011). Only a little research in para-alpine skiing exists, especially in the standing classes LW5/7 and LW6/8 (impairment of one or two arms). The use of arms and poles affects performance in alpine skiing[OM1] but how underlying biomechanical parameters as kinematics and kinetics are related to performance has to the authors knowledge not been studied before.PURPOSE: The purpose of this study was to further the understanding of slalom skiing with two ski poles, one pole or without poles (c2, c1, c0) by investigating the biomechanical differences (kinematics and foot plantar pressure) for able-bodied athletes.METHODS: Ten able-bodied right-handed junior skiers on national level were tested in three conditions - c0, c1, c2, while skiing a slalom course (28 gates, 62 m vertical drop). 3D kinematic data were collected at 200 Hz by 12 inertial motion units (Myomotion, Noraxon Inc, USA) placed on head, trunk, pelvis, arms and legs. Ski-time was measured with timing gates (XS Crystal Synchronization, Brower Timing Systems, USA) and kinetics were measured with pressure insoles (Pedar, Novel GmbH, Germany) placed inside each ski boot. Normal ground reaction force (nGRF) and relative force time integrals (relFTI) were calculated according to Melai et. Al (2011). Kinematics and plantar pressure were analysed over three right and left turns and averaged for each condition. Right turn and left turn were distinguished at the time point where the shank was standing vertical.RESULTS: Time analysis showed that time increased with the use of less ski poles, mean difference between c1c2 of 1.27 ± 1.69 s (p=0.001) and between c0c1 of 0.73 ± 1.95 s (p=0.003[OM2] ). Kinematic analysis showed that different approaches were used to attack a slalom gate in condition c1 and c0, for example slalom-attack, giant slalom attack or opposite arm attack. Interquartile range and median of the body angles [OM3] differed between conditions, e.g. lower median (indicate less deviation from anatomical basic position[OM4] ) in c0 and mostly lower than in c1 and c2. Furthermore, relFTI was related to the turning side (right or left turn) and showed largest asymmetry for condition c1.CONCLUSION: Reduced balance due to missing ski pole/s lead to compensatory movements in the upper body and asymmetry in foot plantar pressure. This reduced the ability for a controlled turn. Whether or not only reduced balance or also the skiers low experience of skiing with reduced number of poles influenced the performance remains unclear.REFERENCESMelai, Tom, T. Herman IJzerman, Nicolaas C. Schaper, Ton L.H. de Lange, Paul J.B. Willems, Kenneth Meijer, Aloysius G. Lieverse, and Hans H.C.M. Savelberg. 2011. ‘Calculation of Plantar Pressure Time Integral, an Alternative Approach’. Gait & Posture 34 (3): 379–83. https://doi.org/10.1016/j.gaitpost.2011.06.005.Tweedy, S. M., and Y. C. Vanlandewijck. 2011. ‘International Paralympic Committee Position Stand--Background and Scientific Principles of Classification in Paralympic Sport’. British Journal of Sports Medicine 45 (4): 259–69. https://doi.org/10.1136/bjsm.2009.065060.
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