| 1. |
- Majerič, Matej, et al.
(författare)
-
Application of Experimental Measurements in a Wind Tunnel to the Development of a Model for Aerodynamic Drag on Elite Slalom and Giant Slalom Alpine Skiers
- 2022
-
Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 12:2
-
Tidskriftsartikel (refereegranskat)abstract
- Aerodynamic drag is a major cause of energy losses during alpine ski racing. Here we developed two models for monitoring the aerodynamic drag on elite alpine skiers in the technical disciplines. While 10 skiers assumed standard positions (high, middle, tuck) with exposure to different wind speeds (40, 60, and 80 km/h) in a wind tunnel, aerodynamic drag was assessed with a force plate, shoulder height with video-based kinematics, and cross-sectional area with interactive image segmentation. The two regression models developed had 3.9–7.7% coefficients of variation and 4.5–16.5% relative limits of agreement. The first was based on the product of the coefficient of aerodynamic drag and cross-sectional area (Cd·S) and the second on the coefficient of aerodynamic drag Cd and normalized cross-sectional area of the skier Sn, both expressed as a function of normalized shoulder height (hn). In addition, normative values for Cd (0.75 ± 0.09–1.17 ± 0.09), Sn (0.51 ± 0.03–0.99 ± 0.05), hn (0.48 ± 0.03–0.79 ± 0.02), and Cd·S (0.23 ± 0.03–0.66 ± 0.09 m2) were determined for the three different positions and wind speeds. Since the uncertainty in the determination of energy losses due to aerodynamic drag relative to total energy loss with these models is expected to be <2.5%, they provide a valuable tool for analysis of skiing performance.
|
|
| 2. |
|
|
| 3. |
- Andersson, Erik, et al.
(författare)
-
Analysis of sprint cross-country skiing using a differential global navigation satellite system
- 2010
-
Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 110:3, s. 585-595
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose was to examine skiing velocities, gear choice (G2-7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (Vmax) performed using G3 skating, (2) Vmax test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9-12.9 m s-1) and multiple transitions (21-34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = -0.72, P < 0.05), and DP Vmax (r = -0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO2max (r = -0.78, P < 0.05). Vmax in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.
|
|
| 4. |
- Bortolan, Lorenzo, et al.
(författare)
-
Development of Equipment for Ski Mountaineering, a New Olympic Event
- 2023
-
Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 13:9
-
Tidskriftsartikel (refereegranskat)abstract
- Ski mountaineering, a new Olympic winter sport involving both climbing and descending snowy slopes, requires considerable physical and technical abilities, as well as highly specialized equipment. Herein, we briefly describe this equipment and its influence on performance and consider potential future advances. Skis, boots, and bindings must be light enough to facilitate climbing uphill (in which as much as 85% of the total racing time is spent) and, at the same time, provide stability and safety in often-challenging descents. A skier must be able to easily and rapidly attach and remove the adhesive skins under the skis that provide grip while skiing uphill. Poles and their baskets must be designed optimally to transfer propulsive force and help maintain balance. Despite the popularity of ski mountaineering, research on this sport is scarce, and we indicate a number of areas wherein improvements in equipment could potentially advance both performance and safety. Such advances must be based on a better understanding of the biomechanics of ski mountaineering, which could be obtained with novel sensor technology and can be best achieved via more extensive collaboration between researchers, skiers and their coaches, and manufacturers of ski mountaineering equipment.
|
|
| 5. |
- Bortolan, Lorenzo, et al.
(författare)
-
Ski Mountaineering : Perspectives on a Novel Sport to Be Introduced at the 2026 Winter Olympic Games
- 2021
-
Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Ski mountaineering is a rapidly growing winter sport that involves alternately climbing and descending slopes and various racing formats that differ in length and total vertical gain, as well as their distribution of downhill and uphill sections. In recent years, both participation in and media coverage of this sport have increased dramatically, contributing, at least in part, to its inclusion in the 2026 Winter Olympics in Milano-Cortina. Here, our aim has been to briefly describe the major characteristics of ski mountaineering, its physiological and biomechanical demands, equipment, and training/testing, as well as to provide some future perspectives. Despite its popularity, research on this discipline is scarce, but some general characteristics are already emerging. Pronounced aerobic capacity is an important requirement for success, as demonstrated by positive correlations between racing time and maximal oxygen uptake and oxygen uptake at the second ventilatory threshold. Moreover, due to the considerable mechanical work against gravity on demanding uphill terrain, the combined weight of the athlete and equipment is inversely correlated with performance, prompting the development of both lighter and better equipment in recent decades. In ski mountaineering, velocity uphill is achieved primarily by more frequent (rather than longer) strides due primarily to high resistive forces. The use of wearable technologies, designed specifically for analysis in the field (including at elevated altitudes and cold temperatures) and more extensive collaboration between researchers, industrial actors, and coaches/athletes, could further improve the development of this sport.
|
|
| 6. |
|
|
| 7. |
- Bucher Sandbakk, Silvana, et al.
(författare)
-
Downhill turn techniques and associated physical characteristics in cross-country skiers
- 2014
-
Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Blackwell Munksgaard. - 0905-7188 .- 1600-0838. ; 24:4, s. 708-716
-
Tidskriftsartikel (refereegranskat)abstract
- Three dominant techniques are used for downhill turning in cross-country skiing. In this study, kinematic, kinetic, and temporal characteristics of these techniques are described and related to skier strength and power. Twelve elite female cross-country skiers performed six consecutive turns of standardized geometry while being monitored by a Global Navigation Satellite System. Overall time was used as an indicator of performance. Skiing and turning parameters were determined from skier trajectories; the proportional use of each technique was determined from video analysis. Leg strength and power were determined by isometric squats and countermovement jumps on a force plate. Snow plowing, parallel skidding, and step turning were utilized for all turns. Faster skiers employed less snow plowing and more step turning, more rapid deceleration and earlier initiation of step turning at higher speed (r = 0.80–0.93; all P < 0.01). Better performance was significantly correlated to higher mean speed and shorter trajectory (r = 0.99/0.65; both P < 0.05) and to countermovement jump characteristics of peak force, time to peak force, and rate of force development (r = -0.71/0.78/-0.83; all P < 0.05). In conclusion, faster skiers used step turning to a greater extent and exhibited higher maximal leg power, which enabled them to combine high speeds with shorter trajectories during turns.
|
|
| 8. |
|
|
| 9. |
- Drobnič, Miha, et al.
(författare)
-
The Validity of a Three-Dimensional Motion Capture System and the Garmin Running Dynamics Pod in Connection with an Assessment of Ground Contact Time While Running in Place
- 2023
-
Ingår i: Sensors. - : Multidisciplinary Digital Publishing Institute (MDPI). - 1424-8220. ; 23:16
-
Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional motion capture system (MoCap) and the Garmin Running Dynamics Pod can be utilised to monitor a variety of dynamic parameters during running. The present investigation was designed to examine the validity of these two systems for determining ground contact times while running in place by comparing the values obtained with those provided by the bilateral force plate (gold standard). Eleven subjects completed three 20-s runs in place at self-selected rates, starting slowly, continuing at an intermediate pace, and finishing rapidly. The ground contact times obtained with both systems differed significantly from the gold standard at all three rates, as well as for all the rates combined (p < 0.001 in all cases), with the smallest mean bias at the fastest step rate for both (11.5 ± 14.4 ms for MoCap and −81.5 ± 18.4 ms for Garmin). This algorithm was developed for the determination of ground contact times during normal running and was adapted here for the assessment of running in place by the MoCap, which could be one explanation for its lack of validity. In conclusion, the wearables developed for monitoring normal running cannot be assumed to be suitable for determining ground contact times while running in place.
|
|
| 10. |
- Fasel, Benedikt, et al.
(författare)
-
Trajectory matching by low-cost GNSS allows continuous time comparisons during cross country skiing
- 2018
-
Konferensbidrag (refereegranskat)abstract
- In most endurance sports, including cross-country (XC) skiing, the fastest athlete wins the race. Successful performance requires an optimal pacing strategy i.e., effective distribution of work and energy throughout a race (Abbiss & Laursen, 2008). For any given lap of a race, no more than a few split times are usually available, due to the complex logistics of setting up a timing system. However, optimal tracking of pacing (speed) during a race requires determination of more split times at regular and shorter intervals. For example, a high-end Global Navigation Satellite System (GNSS) can be used to easily obtain a high number of split times based on a comparison of positions (Andersson et al., 2010; Supej & Holmberg, 2011). Accordingly, the aim here was to determine whether comparison of position at onemeter intervals using a standard GNSS gives reliable split times during XC skiing.
|
|
| 11. |
- Gilgien, Matthias, et al.
(författare)
-
The Training of Olympic Alpine Ski Racers
- 2018
-
Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Alpine combined was the only alpine ski racing event at the first Winter Olympic Games in 1936, but since then, slalom, giant slalom, super-G, downhill, and team events have also become Olympic events. Substantial improvements in slope preparation, design of courses, equipment, and the skills of Olympic alpine skiers have all helped this sport attain its present significance. Improved snow preparation has resulted in harder surfaces and improved equipment allows a more direct interaction between the skier and snow. At the same time, courses have become more challenging, with technical disciplines requiring more pronounced patterns of loading - unloading, with greater ground reaction forces. Athletes have adapted their training to meet these new demands, but little is presently known about these adaptations. Here, we describe how Olympic athletes from four of the major alpine ski racing nations prepared for the Olympic Games in South Korea in 2018. This overview describes their typical exercise programs with respect to physical conditioning, ski training and periodization, based on interviews with the coaching staff. Alpine ski racing requires mastery of a broad spectrum of physical, technical, mental, and social skills. We describe how athletes and teams deal with the multifactorial nature of the training required. Special emphasis is placed on sport-specific aspects, such as the combination of stimuli that interfere with training, training with chronic injury, training at altitude and in cold regions, the efficiency and effectiveness of ski training and testing, logistic challenges and their effects on fatigue, including the stress of frequent traveling. Our overall goal was to present as complete a picture of the training undertaken by Olympic alpine skiers as possible and on the basis of these findings propose how training for alpine ski racing might be improved.
|
|
| 12. |
- Hébert-Losier, Kim, et al.
(författare)
-
Biomechanical Factors Influencing the Performance of Elite Alpine Ski Racers
- 2014
-
Ingår i: Sports Medicine. - : IADIS Press. - 0112-1642 .- 1179-2035. ; 44:4, s. 519-533
-
Forskningsöversikt (refereegranskat)abstract
- BackgroundAlpine ski racing is a popular international winter sport that is complex and challenging from physical, technical, and tactical perspectives. Despite the vast amount of scientific literature focusing on this sport, including topical reviews on physiology, ski-snow friction, and injuries, no review has yet addressed the biomechanics of elite alpine ski racers and which factors influence performance. In World Cup events, winning margins are often mere fractions of a second and biomechanics may well be a determining factor in podium place finishes.Objective The aim of this paper was to systematically review the scientific literature to identify the biomechanical factors that influence the performance of elite alpine ski racers, with an emphasis on slalom, giant slalom, super-G, and downhill events.Methods Four electronic databases were searched using relevant medical subject headings and key words, with an additional manual search of reference lists, relevant journals, and key authors in the field. Articles were included if they addressed human biomechanics, elite alpine skiing, and performance. Only original research articles published in peer-reviewed journals and in the English language were reviewed. Articles that focused on skiing disciplines other than the four of primary interest were excluded (e.g., mogul, ski-cross and freestyle skiing). The articles subsequently included for review were quality assessed using a modified version of a validated quality assessment checklist. Data on the study population, design, location, and findings relating biomechanics to performance in alpine ski racers were extracted from each article using a standard data extraction form.Results A total of 12 articles met the inclusion criteria, were reviewed, and scored an average of 69 ± 13 % (range 40–89 %) upon quality assessment. Five of the studies focused on giant slalom, four on slalom, and three on downhill disciplines, although these latter three articles were also relevant to super-G events. Investigations on speed skiing (i.e., downhill and super-G) primarily examined the effect of aerodynamic drag on performance, whereas the others examined turn characteristics, energetic principles, technical and tactical skills, and individual traits of high-performing skiers. The range of biomechanical factors reported to influence performance included energy dissipation and conservation, aerodynamic drag and frictional forces, ground reaction force, turn radius, and trajectory of the skis and/or centre of mass. The biomechanical differences between turn techniques, inter-dependency of turns, and abilities of individuals were also identified as influential factors in skiing performance. In the case of slalom and giant slalom events, performance could be enhanced by steering the skis in such a manner to reduce the ski-snow friction and thereby energy dissipated. This was accomplished by earlier initiation of turns, longer path length and trajectory, earlier and smoother application of ground reaction forces, and carving (rather than skidding). During speed skiing, minimizing the exposed frontal area and positioning the arms close to the body were shown to reduce the energy loss due to aerodynamic drag and thereby decrease run times. In actual races, a consistently good performance (i.e., fast time) on different sections of the course, terrains, and snow conditions was a characteristic feature of winners during technical events because these skiers could maximize gains from their individual strengths and minimize losses from their respective weaknesses.Limitations Most of the articles reviewed were limited to investigating a relatively small sample size, which is a usual limitation in research on elite athletes. Of further concern was the low number of females studied, representing less than 4 % of all the subjects examined in the articles reviewed. In addition, although overall run time is the ultimate measure of performance in alpine ski racing, several other measures of instantaneous performance were also employed to compare skiers, including the aerodynamic drag coefficient, velocity, section time, time lost per change in elevation, and mechanical energy behaviours, which makes cross-study inferences problematic. Moreover, most studies examined performance through a limited number of gates (i.e., 2–4 gates), presumably because the most commonly used measurement systems can only capture small volumes on a ski field with a reasonable accuracy for positional data. Whether the biomechanical measures defining high instantaneous performance can be maintained throughout an entire race course remains to be determined for both male and female skiers.Conclusions Effective alpine skiing performance involves the efficient use of potential energy, the ability to minimize ski-snow friction and aerodynamic drag, maintain high velocities, and choose the optimal trajectory. Individual tactics and techniques should also be considered in both training and competition. To achieve better run times, consistency in performance across numerous sections and varied terrains should be emphasized over excellence in individual sections and specific conditions.
|
|
| 13. |
- Holmberg, Joakim, et al.
(författare)
-
Skiing efficiency versus performance in double-poling ergometry
- 2013
-
Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1025-5842 .- 1476-8259. ; 16:9, s. 987-992
-
Tidskriftsartikel (refereegranskat)abstract
- This study is on how leg utilisation may affect skiing efficiency andperformance in double-poling ergometry. Three experiments wereconducted, each with a different style of the double-poling technique:traditional with small knee range-of-motion and fixed heels (TRAD);modern with large knee range-of-motion and fixed heels (MOD1) and modernwith large knee range-of-motion and free heels (MOD2). For each style,motion data were extracted with automatic marker recognition ofreflective markers and applied to a 3D full-body musculoskeletalsimulation model. Skiing efficiency (skiing work divided by metabolicmuscle work) and performance (forward impulse) were computed from thesimulation output. Skiing efficiency was 4.5%, 4.1% and 4.1% for TRAD,MOD1 and MOD2, respectively. Performance was 111, 143 and 149Ns forTRAD, MOD1 and MOD2, respectively. Thus, higher lower body utilisationincreased the performance but decreased the skiing efficiency. Theseresults demonstrate the potential of musculoskeletal simulations forskiing efficiency estimations.
|
|
| 14. |
- Jonsson, Malin, et al.
(författare)
-
Biomechanical differences in double poling (DP) for world- and national-class female elite cross-country (XC) skiers during a 10-km classical race
- 2016
-
Ingår i: Proceedings ICSS in St. Christoph am Arlberg, Austria.
-
Konferensbidrag (refereegranskat)abstract
- Introduction The DP technique of classical XC-skiing involves both the upper and lower body (Holmberg et al.,2005) and has become more important the last years with skiers using exclusively DP during some competitions. Our purpose was to characterize biomechanical differences in DP by world- (WC) and national-class (NC) women skiers. Methods The participants were 40 elite female XC skiers (20 WC and 20 NC) who competed in the 10-km classical race at the Norwegian National Championships, 2016. On a flat measurement section (22 m long) 0.8 km from the start, the skiers employed DP only and were video-filmed (Panasonic GH4, 96 Hz). Three DP cycles were analyzed using the Kinovea software (France, v 8.25) for joint and pole angles at pole plant (PP) and pole off (PO), as well as cycle length (CL) and rate (CR), and poling (PT) and swing times (ST). Results The total racing time for the WC-group was 10.5% faster than for the NC-skiers, with no differences in CL, CR, PT or ST. The WC-group skied faster on the flat section (6.30±0.23 vs 6.04±0.25 m/s) and exhibited a smaller ankle-shoulder angle relative to horizontal at PP (73.0±1.8 vs 75.0±1.5°) and a smaller hip angle at PO (62.7±5.2 vs 69.1±6.4°) with no difference in minimal trunk angle with respect to horizontal (19.2±3.2 vs 21.7±4.8°). 27 of the skiers (15 WC and 12 NC) used active heel raise to create force. There was a difference between the groups for when the heel raise ended, with the NC-group stopping just before PP and the WC-group after. No difference between the groups were found for when the heel raise started . There was a negative correlation between DP velocity and total racing time (r = -0.48, p<0.05) and a positive correlation between total racing time and the ankle-shoulder angle relative to horizontal at PP (r = 0.54, p<0.01), the hip angle at PO (r = 0.51, p<0.01) and minimal trunk angle relative to horizontal during the cycles (r = 0.41, p<0.01). Discussion The WC-group had 4.1% higher DP velocity which correlated with total racing time. Moreover, the finding that faster skiers have a more forward lean of the body at PP and a better timing of the ending of the heel raise, indicates that they can bring more bodyweight on their poles at PP. The WC-group had a smaller hip angle at PO which is in line with the findings of Lindinger et al.(2009). This study shows the importance of a high relative velocity during DP sections of the track and highlights the benefit of a more forward body position at PP to create higher DP velocity in female XC skiers. References Holmberg, H.C., Lindinger, S., Stöggl, T., Eitzlmair, E. & Müller, E. (2005). Biomechanical analysis of double poling in elite cross-country skiers. Med Sci Sports Exerc, 37(5), 807-818 Lindinger, S., Stöggl, T., Müller, E. & Holmberg, H.C. (2009). Control of speed during the double poling technique performed by elite cross-country skiers. Med Sci Sports Exerc, 41(1), 210-220
|
|
| 15. |
- Kalliorinne, Kalle, 1995-, et al.
(författare)
-
A Novel Method for Quantifying Ski-Snow Friction Using an Rtk-Gnss Equipped Sled
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In most winter sports, the athletes interact with snow with their equipment. In some of these sport, e.g. in cross-country skiing, a large amount of energy is spent by the athlete to overcome the restive force of friction. Consequently, a reduction in friction can be the difference between winning and coming second in a race. Over the years, researchers have come up with many ways of measuring the friction between snow and sports equipment, such as different types of skis. However, only a few of these experimental setups can be used to test the glide of real-sized skis under natural conditions during both accelerating and deceleration motion. In the present work, a novel experimental setup consisting of a sled and a base station that uses GNSS receivers communicating internally by radio, thus making up an RTK-GNSS system which can measure the position of the sled with centimetre accuracy, was established. The sled is equipped with authentic cross-country skis and accelerated and decelerated on a track with natural height variation prepared with a conventional snow-track setter mounted on a snowcat. The recorded altitude and velocity data are used to quantify the coefficient of friction (COF), both for accelerating and decelerating motion, with a model based on the preservation of energy. The results show that the COF during acceleration was more than 28% higher than during deceleration, while the difference in the COF during deceleration on flat ground at loading conditions resembling the acceleration and deceleration phases was less than 5%. This is an important discovery, as when all types of skiing techniques are executed, the athlete is either accelerating or decelerating while moving forward along the track. The ability of the current experimental set-up to distinguish between them may thus have positive implications for further development.
|
|
| 16. |
- Karlöf, Lars, et al.
(författare)
-
Snow - the performance surface for alpine skiing
- 2013
-
Ingår i: Routledge Handbook of Ergonomics in Sport and Exercise. - Oxon and New York : Routledge. - 9781138657106 ; , s. 323-334
-
Bokkapitel (refereegranskat)abstract
- Alpine skiing is a popular winter sport. Athletes use their equipment on different courses that are covered with snow. From this perspective, better knowledge of snow conditions and the interaction between the skis and snow is fundamental, because performance and choices between different techniques are related to the interaction beteeen the athlete, the ski eqiuipment and the snow.
|
|
| 17. |
- Ogrin, J., et al.
(författare)
-
Asymmetries in Ground Reaction Forces During Turns by Elite Slalom Alpine Skiers Are Not Related to Asymmetries in Muscular Strength
- 2021
-
Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- The ground reaction forces (GRF) associated with competitive alpine skiing, which are relatively large, might be asymmetric during left and right turns due to asymmetries in the strength of the legs and torso and the present investigation was designed to evaluate this possibility. While skiing a symmetrical, 20-gate slalom course, the asymmetries of 9 elite alpine skiers were calculated on the basis of measurements provided by inertial motion units (IMU), a Global Navigation Satellite System and pressure insoles. In addition, specialized dynamometers were utilized to assess potential asymmetry in the strength of their legs and torso in the laboratory. In total, seven variables related to GRF were assessed on-snow and eight related to strength of the legs and torso in the laboratory. The asymmetries in these parameters between left and right turns on snow were expressed in terms of the symmetry (SI) and Jaccard indices (JI), while the asymmetries between the left and right sides of the body in the case of the laboratory measurements were expressed as the SIs. The three hypotheses to be tested were examined using multivariable regression models. Our findings resulted in rejection of all three hypotheses: The asymmetries in total GRF (H1), as well as in the GRF acting on the inside and outside legs (H2) and on the rear- and forefeet GRF (H3) during left and right turns were not associated with asymmetries in parameters related to muscular strength. Nevertheless, this group of elite slalom skiers exhibited significant asymmetry between their right and left legs with respect to MVC during ankle flexion (0.53 ± 0.06 versus 0.60 ± 0.07 Nm/kg, respectively) and hip extension (2.68 ± 0.39 versus 2.17 ± 0.26 Nm/kg), as well as with respect to the GRFs on the inside leg while skiing (66.8 ± 7.39 versus 76.0 ± 10.0 %BW). As indicated by the JI values, there were also large asymmetries related to GRF as measured by pressure insoles (range: 42.7–56.0%). In conclusion, inter-limb asymmetries in GRFs during elite alpine skiing are not related to corresponding asymmetries in muscular strength. Although our elite athletes exhibited relatively small inter-limb asymmetries in strength, their asymmetries in GRF on-snow were relatively large.
|
|
| 18. |
- Rovan, Klemen, et al.
(författare)
-
The steps needed to perform acceleration and turning at different approach speeds
- 2014
-
Ingår i: Kinesiologia Slovenica. - : University of Ljubljana. - 1318-2269 .- 2232-4062. ; 20:1, s. 38-50
-
Tidskriftsartikel (refereegranskat)abstract
- The aims of the study were to examine: how many and which steps are needed to initiate and complete accelerations and turnings at different angles at different approach speeds; and how an intended turning angle and approach speed influence the magnitude of the actual turning angle in each step. Eight soccer players participated in the study. They performed acceleration and turnings: 1) from a standstill; 2) while already jogging; and 3) while already running on an outdoor soccer field. The speeds and angles were calculated from the data obtained from the high-end Global Navigation Satellite System. The high correlation between the intended turning angle and actual turning angle indicated the major turning steps during a turn. The intended turning angle revealed a large effect on the magnitude of the turning angle during the side-step (r = 0.995, p < 0.01) and the following step (r = 0.950, p < 0.01) for acceleration and turning from a standstill, and during the first two steps following the side-step for starts made while already jogging (r= 0.919, p < 0.01; r = 0.952, p < 0.01) and running (r = 0.897, p < 0.01; r = 0.881, p < 0.01). Further, a major part of the turning began earlier at a lower approach speed, which allowed the turning to be more quickly completed. In conclusion, the effect of acceleration with turning on the turning angle could already be seen two steps before and up to two steps after the major turning steps during a turn.
|
|
| 19. |
- Stöggl, Thomas, et al.
(författare)
-
Impact of incline, sex and level of performance on kinematics during a distance race in classical cross-country skiing
- 2018
-
Ingår i: Journal of Sports Science and Medicine (JSSM). - 1303-2968. ; 17:1, s. 124-133
-
Tidskriftsartikel (refereegranskat)abstract
- Here, female and male elite cross-country (XC) skiers were compared on varying terrain during an official 10-km (women) and 15-km (men) Norwegian championship race. On the basis of race performance, 82 skiers were classified as fast (FS) (20 women, 20 men) or slower (SS) (21, 21) skiers. All were video recorded on flat (0°), intermediate (3.5°), uphill (7.1°) and steep uphill (11°) terrain during the race at a distance of 0.8, 1.2, 2.1 and 7.1 km from the start, respectively. All skiers employed exclusively double-poling (DP) on the flat section and, except for the male winner, exclusively diagonal stride (DIA) on the uphill sections. On the intermediate section, more men than women utilized DP and fewer DIA (p = 0.001), with no difference in kick double-poling (DPK). More FS than SS utilized DPK and fewer DIA (p = 0.001), with similar usage of DP. Males skied with faster and longer cycles but lower cycle rate compared with females (p < 0.001), with largest absolute sex differences on flat terrain (p < 0.001) and largest relative differences for cycle velocity and length on intermediate and uphill terrain. External power output rose with increasing incline, being higher for men and FS (p < 0.001). Cycle velocity on flat terrain was the best predictor of mean race velocity for the men, while cycle velocity on steep uphill was the best predictor for the women (both p < 0.001). In conclusion, incline, sex and level of performance influenced cycle characteristics and power output. Greatest absolute sex gap was on flat terrain, whereas the relative difference was greatest on intermediate and steep uphill terrain. We recommend usage of more DP and/or DPK, and less DIA and fewer transitions between techniques on intermediate terrain. Predictors of race performance are sex specific with greatest potential for enhancing performance on flat terrain for men and on steep uphill terrain for women.
|
|
| 20. |
- Supej, Matej, et al.
(författare)
-
A new time measurement method using a high end Global Navigation Satellite System to analyze alpine skiing
- 2011
-
Ingår i: Research Quarterly for Exercise and Sport. - New York : Springer. - 0270-1367 .- 2168-3824. ; 82:3, s. 400-411
-
Tidskriftsartikel (refereegranskat)abstract
- Time measurement with photocells is a frequently used method in quantifying performance. Although this method has a high accuracy, it also has some limitations when performing a detailed temporal analysis of repetitive multiple movement cycles in a complex technical sport, such as alpine skiing. Therefore, the aim of the present study was to develop a new method for time computation from surveyed trajectories using a real time kinematics global navigation satellite system (GNSS RTK) and to compare this with traditional photocell measurements. Two validation experiments were performed with 1) a trolley and 2) running over a 10-m distance. An application experiment was performed on eight alpine skiers on a slalom run, in which the GNSS RTK system was compared to photocell time recordings. The validation experiment demonstrated small mean time differences (<.0015 s) with no systematic bias, with a scatter of time differences that were velocity dependent and were diminishing at higher velocities. In the ski experiment, the multiple gate to gate and lag times demonstrated that the GNSS enabled a detailed performance analysis. The measurements using GNSS RTK showed a high validity and potential as a tool for more specific analysis of performance in alpine skiing.
|
|
| 21. |
- Supej, Matej, et al.
(författare)
-
Aerodynamic drag is not the major determinant of performance during giant slalom skiing at the elite level
- 2013
-
Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley-Blackwell. - 0905-7188 .- 1600-0838. ; 23:1, s. e38-e47
-
Tidskriftsartikel (refereegranskat)abstract
- This investigation was designed to (a) develop an individualized mechanical model for measuring aerodynamic drag (Fd) while ski racing through multiple gates, (b) estimate energy dissipation (Ed) caused by Fd and compare this to the total energy loss (Et), and (c) investigate the relative contribution of Ed/Et to performance during giant slalom skiing (GS). Nine elite skiers were monitored in different positions and with different wind velocities in a wind tunnel, as well as during GS and straight downhill skiing employing a Global Navigation Satellite System. On the basis of the wind tunnel measurements, a linear regression model of drag coefficient multiplied by cross-sectional area as a function of shoulder height was established for each skier (r > 0.94, all P < 0.001). Skiing velocity, Fd, Et, and Ed per GS turn were 15–21 m/s, 20–60 N, −11 to −5 kJ, and −2.3 to −0.5 kJ, respectively. Ed/Et ranged from ∼5% to 28% and the relationship between Et/vin and Ed was r = −0.12 (all NS). In conclusion, (a) Fd during alpine skiing was calculated by mechanical modeling, (b) Ed made a relatively small contribution to Et, and (c) higher relative Ed was correlated to better performance in elite GS skiers, suggesting that reducing ski–snow friction can improve this performance.
|
|
| 22. |
|
|
| 23. |
- Supej, Matej, et al.
(författare)
-
How gate setup and turn radii influence energy dissipation in slalom ski racing
- 2010
-
Ingår i: Journal of Applied Biomechanics. - : Human Kinetics. - 1065-8483 .- 1543-2688. ; 26:4, s. 454-464
-
Tidskriftsartikel (refereegranskat)abstract
- Despite carving skis being introduced into alpine ski racing years ago, and the general opinion that they make smoother turns, no studies have yet investigated this topic. The aims were to investigate whether gate setup and turn radii influence energy dissipation. 3D kinematical measurements were performed for WC slalom ski racing over two runs on the same slope with two different gate setups: 1) open gates (OG) and 2) open gate setup with a delayed gate (DG). The results show differences between the different gate setups regarding: 1) the absolute centre of gravity’s (CG) velocity, 2) absolute acceleration, 3) CG and arithmetic mean of the skis’ turn radii, 4) ground reaction forces and 5) energy dissipation during skiing (all p<.05). The latter was also correlated to the turn radii on both courses (OG: r=.364 and DG: r=.214, both p<.001). In summary, compared to plain open gates an additional delayed gate prolonged the turn radii; the turn radii are related to energy dissipation in slalom skiing.
|
|
| 24. |
- Supej, Matej, et al.
(författare)
-
Impact of the Steepness of the Slope on the Biomechanics of World Cup Slalom Skiers
- 2015
-
Ingår i: International Journal of Sports Physiology and Performance. - : Human Kinetics. - 1555-0265 .- 1555-0273. ; 10:3, s. 361-368
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: Numerous environmental factors can affect alpine-ski-racing performance, including the steepness of the slope. However, little research has focused on this factor. Accordingly, the authors' aim was to determine the impact of the steepness of the slope on the biomechanics of World Cup slalom ski racers. Methods: The authors collected 3-dimensional kinematic data during a World Cup race from 10 male slalom skiers throughout turns performed on a relatively flat (19.8 degrees) and steep (25.2 degrees) slope under otherwise similar course conditions. Results: Kinematic data revealed differences between the 2 slopes regarding the turn radii of the skis and center of gravity, velocity, acceleration, and differential specific mechanical energy (all P < .001). Ground-reaction forces (GRFs) also tended toward differences (P = .06). Examining the time-course behaviors of variables during turn cycles indicated that steeper slopes were associated with slower velocities but greater accelerations during turn initiation, narrower turns with peak GRFs concentrated at the midpoint of steering, more pronounced lateral angulations of the knees and hips at the start of steering that later became less pronounced, and overall slower turns that involved deceleration at completion. Consequently, distinct energy-dissipation-patterns were apparent on the 2 slope inclines, with greater pregate and lesser postgate dissipation on the steeper slope. The steepness of the slope also affected the relationships between mechanical skiing variables. Conclusions: The findings suggest that specific considerations during training and preparation would benefit the race performance of slalom skiers on courses involving sections of varying steepness.
|
|
| 25. |
- Supej, Matej, et al.
(författare)
-
Mechanical parameters as predictors of performance in alpine World Cup slalom racing
- 2011
-
Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 21:6, s. e72-e81
-
Tidskriftsartikel (refereegranskat)abstract
- The aims of the present study were to develop a method for classifying slalom skiing performance and to examine differences in mechanical parameters. Eighteen elite skiers were recorded with 3-D kinematical measurements and thereafter divided into a higher (HP) and lower performance (LP) group, using the ratio between the difference in mechanical energy divided by the mass of the skier and section entrance velocity (Δemech/vin). Moreover, the skiers’ velocity (v), acceleration (a), centre of mass turn radii (RCM) and skis’ turn radii (RAMS), ground reaction forces (GRF) and differential specific mechanical energy (diff(emech)) were calculated. v and diff(emech) were different between the performance groups (P < 0.001 and P < 0.05), while no inter-group differences in RCM, RAMS, a and GRF were observed. A relationship between RAMS and diff(emech) was demonstrated (r = 0.58; P < 0.001). The highest GRFs were related to the lowest diff(emech) and a was related to GRF (r = -0.60; P < 0.001). The Δemech/vin predicted performance over short course sections. The HP skiers skied with a higher v and a similar range of diff(emech). We suggest that shortest RAMS and the highest GRFs should be reduced in elite slalom in order to increase performance.
|
|
| 26. |
- Supej, Matej, et al.
(författare)
-
Methodological and Practical Considerations Associated With Assessment of Alpine Skiing Performance Using Global Navigation Satellite Systems
- 2020
-
Ingår i: Frontiers in Sports and Active Living. - : Frontiers Media SA. - 2624-9367. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- Reliable assessment of the performance of alpine skiers is essential. Previous studies have highlighted the potential of Global Navigation Satellite Systems (GNSS) for evaluating this performance. Accordingly, the present perspective summarizes published research concerning methodological and practical aspects of the assessment of alpine skiing performance by GNSS. Methodologically, in connection with trajectory analysis, a resolution of 1-10 cm, which can be achieved with the most advanced GNSS systems, has proven to provide acceptable accuracy. The antenna should be positioned to follow the trajectory of the skier's center-of-mass (CoM) as closely as possible and estimation of this trajectory can be further improved by applying advanced modeling and/or other computerized approaches. From a practical point of view, effective assessment requires consideration of numerous parameters related to performance, including gate-to-gate times, trajectory, speed, and energy dissipation. For an analysis that is both more comprehensive and more easily accessible to coaches/athletes, video filming should be synchronized with the GNSS data. In summary, recent advances in GNSS technology already allow, at least to some extent, precise biomechanical analysis of performance over an entire alpine skiing race course in real-time. Such feedback has both facilitated and improved the work of coaches. Thus, athletes and coaches are becoming more and more aware of the advantages of analyzing alpine skiing performance by GNSS in combination with advanced computer software, paving the way for the digital revolution in both the applied research on and practice of this sport.
|
|
| 27. |
- Supej, Matej, et al.
(författare)
-
Monitoring the Performance of Alpine Skiers with Inertial Motion Units : Practical and Methodological Considerations
- 2021
-
Ingår i: Journal of Science in Sport and Exercise. - : Springer Science and Business Media LLC. - 2096-6709 .- 2662-1371. ; 3:3, s. 249-256
-
Forskningsöversikt (refereegranskat)abstract
- Although reliable feedback is crucial to improving the performance of competitive alpine skiers, the coach's eye may not be sensitive enough to detect small, but highly significant “mistakes”. Monitoring of the performance of alpine ski racers by inertial motion units (IMU) has proven to be of value in this context and here we summarize practical and methodological aspects of this approach. Methodologically, the IMUs employed should combine high sampling frequencies with minimal signal drift. The sensors should be positioned to sense the movement of the bones in a given body segment while being protected as much as possible against impact with the ski gates. The data obtained, often synchronized with input from Global Satellite Navigation Systems (GNSS), are usually refined utilizing advanced biomechanical models and other computerized approaches. In practice, the combination of inertial sensors and GNSS allows accurate monitoring of skiing kinematics (technique) and the movement of the skier’s center-of-mass, also allowing analysis of both whole-body vibrations (WBV) and loss of mechanical energy. Presentation of the findings to coaches and athletes can be facilitated by synchronizing them with video recordings. Recent advances in IMU technology, including miniaturization, wireless communication, direct storage of data in the cloud, and processing with artificial intelligence may allow these sensors, in-combination with GNSS, to become real-time virtual alpine ski coaches, perhaps the next step in the development of this sport.
|
|
| 28. |
- Supej, Matej, et al.
(författare)
-
Recent Kinematic and Kinetic Advances in Olympic Alpine Skiing : Pyeongchang and Beyond
- 2019
-
Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 10:FEB
-
Tidskriftsartikel (refereegranskat)abstract
- Alpine skiing has been an Olympic event since the first Winter Games in 1936. Nowadays, skiers compete in four main events: slalom, giant slalom, super-G and downhill. Here, we present an update on the biomechanics of alpine ski racers and their equipment. The technical and tactical ability of today's world-class skiers have adapted substantially to changes in equipment, snow conditions and courses. The wide variety of terrain, slopes, gate setups and snow conditions involved in alpine skiing requires skiers to continuously adapt, alternating between the carving and skidding turning techniques. The technical complexity places a premium on minimizing energy dissipation, employing strategies and ski equipment that minimize ski-snow friction and aerodynamic drag. Access to multiple split times along the racing course, in combination with analysis of the trajectory and speed provide information that can be utilized to enhance performance. Peak ground reaction forces, which can be as high as five times body weight, serve as a measure of the external load on the skier and equipment. Although the biomechanics of alpine skiing have significantly improved, several questions concerning optimization of skiers' performance remain to be investigated. Recent advances in sensor technology that allow kinematics and kinetics to be monitored can provide detailed information about the biomechanical factors related to success in competitions. Moreover, collection of data during training and actual competitions will enhance the quality of guidelines for training future Olympic champions. At the same time, the need to individualize training and skiing equipment for each unique skier will motivate innovative scientific research for years to come.
|
|
| 29. |
|
|
| 30. |
- Supej, Matej, et al.
(författare)
-
Special issue on “sports performance and health”
- 2021
-
Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 11:6
-
Tidskriftsartikel (refereegranskat)abstract
- Sports performance is primarily perceived to be associated with elite sport, where athletes strive for a place on the podium, with the most prestigious result probably being an Olympic gold medal [...]
|
|
| 31. |
- Supej, Matej, et al.
(författare)
-
The Contribution of Ski Poles to Aerodynamic Drag in Alpine Skiing
- 2023
-
Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 13:14
-
Tidskriftsartikel (refereegranskat)abstract
- The present study was designed to determine the contribution of the cross-sectional area of the ski poles (Sp) to the total aerodynamic drag during alpine skiing. At three different wind speeds in a wind tunnel, 10 skiers assumed typical alpine skiing postures (high, middle, and tuck), and their frontal aerodynamic drag was assessed with a force plate and their cross-sectional area, along with that of their ski poles, determined by interactive image segmentation. The data collected were utilized to examine intra-subject variation in Sp, the effects of Sp on the coefficient of aerodynamic drag (Cd), and the product of Cd and total cross-sectional area (Cd∙S. The major findings were as follows: (i) Sp ranged from 0.0067 (tuck position) to 0.0262 m2 (middle position), contributing 2.2–4.8% of the total cross-sectional area, respectively; (ii) Sp was dependent on wind speed in the high and middle positions; (iii) intra-subject variations ranged from 0.0018 m2 (27.6%) in the tuck position to 0.0072 m2 (30.5%) in the high position; (iv) Sp exerted a likely effect on Cd and Cd∙S. The extensive intra- and inter-skier variability in Sp can account for as much as ~5% of the total frontal cross-sectional area and future investigations on how elite skiers optimize their positioning of the poles in a manner that reduces aerodynamic drag are warranted.
|
|
| 32. |
- Supej, Matej, et al.
(författare)
-
The impact of start strategy on start performance in alpine skiing exists on flat, but not on steep inclines
- 2019
-
Ingår i: Journal of Sports Sciences. - : Informa UK Limited. - 0264-0414 .- 1466-447X. ; 37:6, s. 647-655
-
Tidskriftsartikel (refereegranskat)abstract
- Here, we explored the relationship between incline and start strategy during alpine skiing. Eight FIS skiers performed starts on a flat (3°) and steep (21°) incline employing five different strategies. Their times, trajectories and velocities were monitored with a GNSS system and video. A significant interaction was observed between slope incline and start strategy with respect to the skier’s exit velocity (p < 0.001, ƞ2 p = 0.716), but not for the start section time (p = 0.732, ƞ2 p = 0.037). On the almost flat incline, both section time (p = 0.022, ƞ2 p = 0.438) and exit velocity (p < 0.001, ƞ2 p = 0.786) were influenced significantly by start strategy, with four V2 skate-pushes being optimal. On the steep incline, neither section time nor exit velocity was affected significantly by start strategy, the fastest section time and exit velocity being attained with four and two V2 skate-pushes, respectively. In conclusion, these findings demonstrate that the start strategy exerts considerable impact on start performance on almost flat inclines, with strategies involving three or more V2 skate-pushes being optimal. In contrast, start performance on the steep incline was not influenced by strategy.
|
|
| 33. |
- Swarén, Mikael, et al.
(författare)
-
Usage and validation of a tracking system to monitor position and velocity during cross-country skiing
- 2016
-
Ingår i: International Journal of Performance Analysis in Sport. - : Informa UK Limited. - 2474-8668 .- 1474-8185. ; 16:2, s. 769-785
-
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.
|
|
| 34. |
- Verdel, Nina, et al.
(författare)
-
A Comparison of a Novel Stretchable Smart Patch for Measuring Runner’s Step Rates with Existing Measuring Technologies
- 2022
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 22:13
-
Tidskriftsartikel (refereegranskat)abstract
- A novel wearable smart patch can monitor various aspects of physical activity, including the dynamics of running, but like any new device developed for such applications, it must first be tested for validity. Here, we compare the step rate while running in place as measured by this smart patch to the corresponding values obtained utilizing ‘‘gold standard’’ MEMS accelerometers in combination with bilateral force plates equipped with HBM load cells, as well as the values provided by a three-dimensional motion capture system and the Garmin Dynamics Running Pod. The 15 healthy, physically active volunteers (age = 23 ± 3 years; body mass = 74 ± 17 kg, height = 176 ± 10 cm) completed three consecutive 20-s bouts of running in place, starting at low, followed by medium, and finally at high intensity, all self-chosen. Our major findings are that the rates of running in place provided by all four systems were valid, with the notable exception of the fast step rate as measured by the Garmin Running Pod. The lowest mean bias and LoA for these measurements at all rates were associated consistently with the smart patch.
|
|
| 35. |
- Verdel, Nina, et al.
(författare)
-
Reliability and validity of running step rate derived from a novel wearable Smart Patch
- 2024
-
Ingår i: IEEE Sensors Journal. - : IEEE. - 1530-437X .- 1558-1748. ; 24:9, s. 14343-14351
-
Tidskriftsartikel (refereegranskat)abstract
- A novel, wearable, stretchable Smart Patch can monitor various aspects of physical activity, including the dynamics of running. However, like any new device developed for such applications, it must first be tested for validity and reliability. Here, we compare the step rate while running on a treadmill measured by this smart patch with the corresponding values obtained with the ”gold standard” OptoGait, as well as with other devices commonly used to assess running dynamics, i.e., the MEMS accelerometer and commercially available and widely used Garmin Running Dynamic Pod. The 14 healthy, physically active volunteers completed two identical sessions with a 5-minute rest between. Each session involved two one-minute runs at 11 km/h and 14 km/h separated by a one-min rest. The major finding was that the Smart Patch demonstrated fair to good test-retest reliability. The best test-retest reliability for the Running Pod was observed in connection with running at 11 km/h and both velocities combined (good and excellent, respectively) and for the OptoGait when running at 14 km/h (good). The best concurrent validity was achieved with the Smart Patch, as reflected in the highest Pearson correlation coefficient for this device when running at 11 or 14 km/h, as well as for both velocities combined. In conclusion, this study demonstrates that the novel wearable Smart Patch shows promising reliability and excellent concurrent validity in measuring step rate during treadmill running, making it a viable tool for both research and practical applications in sports and exercise science.
|
|
| 36. |
- Verdel, Nina, et al.
(författare)
-
Reliability and Validity of the CORE Sensor to Assess Core Body Temperature during Cycling Exercise
- 2021
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 21:17
-
Tidskriftsartikel (refereegranskat)abstract
- Monitoring core body temperature (Tc) during training and competitions, especially in a hot environment, can help enhance an athlete’s performance, as well as lower the risk for heat stroke. Accordingly, a noninvasive sensor that allows reliable monitoring of Tc would be highly beneficial in this context. One such novel non-invasive sensor was recently introduced onto the market (CORE, greenTEG, Rümlang, Switzerland), but, to our knowledge, a validation study of this device has not yet been reported. Therefore, the purpose of this study was to evaluate the validity and reliability of the CORE sensor. In Study I, 12 males were subjected to a low-to-moderate heat load by performing, on two separate occasions several days apart, two identical 60-min bouts of steady-state cycling in the laboratory at 19 °C and 30% relative humidity. In Study II, 13 males were subjected to moderate-to-high heat load by performing 90 min of cycling in the laboratory at 31 °C and 39% relative humidity. In both cases the core body temperatures indicated by the CORE sensor were compared to the corresponding values obtained using a rectal sensor (Trec). The first major finding was that the reliability of the CORE sensor is acceptable, since the mean bias between the two identical trials of exercise (0.02 °C) was not statistically significant. However, under both levels of heat load, the body temperature indicated by the CORE sensor did not agree well with Trec, with approximately 50% of all paired measurements differing by more than the predefined threshold for validity of ≤0.3 °C. In conclusion, the results obtained do not support the manufacturer’s claim that the CORE sensor provides a valid measure of core body temperature.
|
|
| 37. |
- Verdel, Nina, et al.
(författare)
-
Time Synchronization in Wireless IMU Sensors for Accurate Gait Analysis during Running
- 2023
-
Ingår i: 2023 IEEE International Workshop on Sport, Technology and Research (STAR). - : IEEE conference proceedings. - 9798350316056 ; , s. 126-129
-
Konferensbidrag (refereegranskat)abstract
- With the advancements in wearable technology, continuous monitoring of physiological and biomechanical parameters has become possible, providing valuable insights into health and fitness. This technology allows for remote patient monitoring, medical support, and even virtual coaching. One area of focus is gait analysis, which can help reduce the risk of running-related injuries. This study aims to develop a small, lightweight, and affordable wireless sensor device for collecting gait data. The device utilizes IMU sensors positioned on the pelvis and foot to measure stability and detect changes due to fatigue during running. Precise time synchronization between the sensors and an Android phone is crucial for accurate data analysis. The study employs Bluetooth LE technology for wireless transmission and proposes a synchronization method to align the data from the asynchronous sensors. The hardware and software components of the sensor device are described, along with the synchronization process. Additionally, a pilot study involving the use of the sensors during treadmill running was performed.
|
|
| 38. |
|
|
| 39. |
- Welde, Boye, et al.
(författare)
-
The pacing strategy and technique of male cross-country skiers with different levels of performance during a 15-km classical race
- 2017
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:11
-
Tidskriftsartikel (refereegranskat)abstract
- In this study the pacing strategy, cycle characteristics and choice of technique of elite male cross-country (XC) skiers during a three-lap, 15-km classical race with interval start were measured. During the Norwegian Championships in 2016, fast (n = 18, age: 26±4 yr; height: 182±4 cm; body mass: 78±3 kg (means±SD)) and slow skiers (n = 18, age: 22±2 yr; height: 183±5 cm; body mass: 78±6 kg) were video recorded on flat (0), intermediate (3.5) and uphill sections (7.1) of the first and final laps. All skiers adopted a positive pacing strategy, skiing more slowly (11.8%) with shorter cycles (11.7%) on the final than first lap (both p<0.001; pη2 = 0.93 and 0.87, respectively). The fast skiers were 7.0% faster overall (p<0.001, d = 4.20), and 6.1% (p<0.001, d = 3.32) and 7.0% (p<0.001, d = 3.68) faster on the first and final laps, respectively, compared to slower skiers. On all sections of both laps, the fast skiers exhibited 9.5% more rapid (pη2 = 0.74) and 8.9% (pη2 = 0.48) longer cycles (both p<0.001). On intermediate terrain, the fast skiers employed primarily double poling (DP, 38.9% on the first lap) and double poling with a kick (DPKICK, 50% on the final lap). In contrast, the slow skiers utilized for the most part DP alone (lap 1: 33.3%, lap 3: 38.9%) or in combination with other techniques (lap 1: 33.3%, lap 3: 38.9%) and decreased their usage of DPKICK from 27.8% on the first to 16.7% on the final lap. Skiing velocity on flat and intermediate terrain proved to be the best predictor of race performance (p<0.001). In conclusion, during a 15-km classical XC skiing race, velocity and cycle length decreased from the first to the final lap, most extensively on flat terrain and least uphill. Moreover, on the intermediate sections the fast and slow skiers chose to use different techniques.
|
|
