| 1. |
- Stöggl, R., et al.
(författare)
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Motor abilities and anthropometrics in youth cross-country skiing
- 2015
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 25:1, s. E70-E81
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Tidskriftsartikel (refereegranskat)abstract
- The purposes were to validate whether general motor abilities and anthropometrics are determinants of youth cross-country (XC) skiing performance; evaluate gender-specific differences; and to establish noninvasive diagnostics. Fifty-one youth XC skiers (34 boys; 13.8 +/- 0.6 years and 17 girls; 13.4 +/- 0.9 years) performed motor skill and laboratory tests, and anthropometric data were collected and correlated with XC skiing performance. Anthropometrics and maturity status were related to boys but not to girls XC skiing performance. Push-ups and 20-m sprint were correlated to XC skiing performance in both boys and girls. XC skiing performance of boys was predominantly influenced by upper body and trunk strength capacities (medicine ball throw, push-ups, and pull-ups) and jumping power (standing long and triple jump), whereas XC skiing of girls was mainly influenced by aerobic capacities (3000-m run). Laboratory measures did not reveal greater correlations to XC skiing performance compared with simple test concepts of speed, strength, and endurance. Maturity was a major confounding variable in boys but not girls. Use of noninvasive simple test concepts for determination of upper body strength, speed, and endurance represent practicable support for ski clubs, schools, or skiing federations in the guidance and evaluation of young talent, being aware of the effect of maturity especially in boys.
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| 2. |
- Andersson, Erik, 1984-
(författare)
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PHYSIOLOGICAL AND BIOMECHANICAL FACTORS DETERMINING CROSS-COUNTRY SKIING PERFORMANCE
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cross-country (c.c.) skiing is a complex sport discipline from both physiological and biomechanical perspectives, with varying course topographies that require different proportions of the involved sub-techniques to be utilised. A relatively new event in c.c. skiing is the sprint race, involving four separate heats, each lasting 2-4 min, with diverse demands from distance races associated with longer durations. Therefore, the overall aim of the current thesis has been to examine the biomechanical and physiological factors associated with sprint c.c. skiing performance through novel measurements conducted both in the field (Studies I-III) and the laboratory (Studies IV and V).In Study I sprint skiing velocities and sub-techniques were analysed with a differential global navigation satellite system in combination with video recording. In Studies II and III the effects of an increasing velocity (moderate, high and maximal) on the biomechanics of uphill classical skiing with the diagonal stride (DS) (Study II) and herringbone (HB) (Study III) sub-techniques were examined.In Study I the skiers completed the 1,425 m (2 x 712 m) sprint time trial (STT) in 207 s, at an average velocity of 24.8 km/h, with multiple technique transitions (range: 21-34) between skiing techniques (i.e., the different gears [G2-7]). A pacing strategy involving a fast start followed by a gradual slowing down (i.e., positive pacing) was employed as indicated by the 2.9% faster first than second lap. The slower second lap was primarily related to a slower (12.9%) uphill velocity with a shift from G3 towards a greater use of G2. The maximal oxygen uptake ( O2max) was related to the ability to maintain uphill skiing velocity and the fastest skiers used G3 to a greater extent than G2. In addition, maximal speed over short distances (50 and 20 m) with the G3 and double poling (DP) sub-techniques exerted an important impact on STT performance.Study II demonstrated that during uphill skiing (7.5°) with DS, skiers increased cycle rate and cycle length from moderate to high velocity, while cycle rate increased and cycle length decreased at maximal velocity. Absolute poling, gliding and kick times became gradually shorter with an elevated velocity. The rate of pole and leg force development increased with elevated velocity and the development of leg force in the normal direction was substantially faster during skiing on snow than previous findings for roller skiing, although the peak force was similar in both cases. The fastest skiers applied greater peak leg forces over shorter durations.Study III revealed that when employing the HB technique on a steep uphill slope (15°), the skiers positioned their skis laterally (“V” between 25 to 30°) and planted their poles at a slight lateral angle (8 to 12°), with most of the propulsive force being exerted on the inside forefoot. Of the total propulsive force, 77% was generated by the legs. The cycle rate increased across all three velocities (from 1.20 to 1.60 Hz), while cycle length only increased from moderate to high velocity (from 2.0 to 2.3 m). Finally, the magnitude and rate of leg force generation are important determinants of both DS and HB skiing performance, although the rate is more important in connection with DS, since this sub-technique involves gliding.In Studies IV and V skiers performed pre-tests for determination of gross efficiency (GE), O2max, and Vmax on a treadmill. The main performance test involved four self-paced STTs on a treadmill over a 1,300-m simulated course including three flat (1°) DP sections interspersed with two uphill (7°) DS sections.The modified GE method for estimating anaerobic energy production during skiing on varying terrain employed in Study IV revealed that the relative aerobic and anaerobic energy contributions were 82% and 18%, respectively, during the 232 s of skiing, with an accumulated oxygen (O2) deficit of 45 mL/kg. The STT performance time was largely explained by the GE (53%), followed by O2 (30%) and O2 deficit (15%). Therefore, training strategies designed to reduce energetic cost and improve GE should be examined in greater detail.In Study V metabolic responses and pacing strategies during the four successive STTs were investigated. The first and the last trials were the fastest (both 228 s) and were associated with both a substantially larger and a more rapid anaerobic energy supply, while the average O2 during all four STTs was similar. The individual variation in STT performance was explained primarily (69%) by the variation in O2 deficit. Furthermore, positive pacing was employed throughout all the STTs, but the pacing strategy became more even after the first trial. In addition, considerably higher (~ 30%) metabolic rates were generated on the uphill than on the flat sections of the course, reflecting an irregular production of anaerobic energy. Altogether, a fast start appears important for STT performance and high work rates during uphill skiing may exert a more pronounced impact on skiing performance outdoors, due to the reduction in velocity fluctuations and thereby overall air-drag.
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| 3. |
- Björklund, Glenn, 1972-, et al.
(författare)
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Biomechanical Adaptations and Performance Indicators in Short Trail Running
- 2019
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Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Our aims were to measure anthropometric and oxygen uptake ((V)over dot O-2) variables in the laboratory, to measure kinetic and stride characteristics during a trail running time trial, and then analyse the data for correlations with trail running performance. Runners (13 men, 4 women: mean age: 29 +/- 5 years; stature: 179.5 +/- 0.8 cm; body mass: 69.1 +/- 7.4 kg) performed laboratory tests to determine (V)over dot O-2 (max), running economy (RE), and anthropometric characteristics. On a separate day they performed an outdoor trail running time trial (two 3.5 km laps, total climb: 486 m) while we collected kinetic and time data. Comparing lap 2 with lap 1 (19:40 +/- 1:57 min vs. 21:08 +/- 2:09 min, P < 0.001), runners lost most time on the uphill sections and least on technical downhills (-2.5 +/- 9.1 s). Inter-individual performance varied most for the downhills (CV > 25%) and least on flat terrain (CV < 10%). Overall stride cycle and ground contact time (GCT) were shorter in downhill than uphill sections (0.64 +/- 0.03 vs. 0.84 +/- 0.09 s; 0.26 +/- 0.03 vs. 0.46 +/- 0.90 s, both P < 0.001). Force impulse was greatest on uphill (248 +/- 46 vs. 175 +/- 24 Ns, P < 0.001) and related to GCT (r = 0.904, P < 0.001). Peak force was greater during downhill than during uphill running (1106 +/- 135 vs. 959 +/- 104 N, P < 0.01). Performance was related to absolute and relative (V)over dot O-2 (max) (P < 0.01), vertical uphill treadmill speed (P < 0.001) and fat percent (P < 0.01). Running uphill involved the greatest impulse per step due to longer GCT while downhill running generated the highest peak forces. (V)over dot O-2 (max), vertical running speed and fat percent are important predictors for trail running performance. Performance between runners varied the most on downhills throughout the course, while pacing resembled a reversed J pattern. Future studies should focus on longer competition distances to verify these findings and with application of measures of 3D kinematics.
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| 4. |
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| 5. |
- Björklund, Glenn, et al.
(författare)
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The effects of prior high intensity double poling on subsequent diagonal stride skiing characteristics
- 2015
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Ingår i: SpringerPlus. - : Springer Science and Business Media LLC. - 2193-1801. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the influence of prior high intensity double poling (DP) on physiological and biomechanical responses during subsequent diagonal stride (DIA). Methods: Eight well-trained male cross-country skiers (age 22 ± 3 yr; VO2max 69 ± 3 ml · kg−1 · min−1) roller-skied on a treadmill sequentially for 3 min at 90% DIA VO2max (DIA1), 3 min at 90% DP VO2peak and 3 min at 90% DIA VO2max (DIA2). Cardio-respiratory responses were monitored continuously and gases and metabolites in blood from the a. femoralis, v. femoralis and v. subclavia determined. Pole and plantar forces and EMG from 6 lower- and upper-body muscles were measured. Results: VO2 decreased from DIA1 to DP and increased again to DIA2 (both P < 0.05), with no difference between the DIA sessions. Blood lactate rose from DIA1 to DP to DIA2. O2 extraction was attenuated during DP (P < 0.05), but was the same during DIA1 and DIA2. EMGRMS for arm muscles during poling phase, as well as peak pole force and cycle rate were higher, while leg muscle activity was lower during DP than both sessions of DIA (all P < 0.05). The ratio of upper-/whole-body EMGRMS correlated negatively with O2 extraction in the arms during both sessions of DIA (P < 0.05). Conclusions: In well-trained skiers skiing at high-intensity DP prior to DIA did not influence VO2, muscle activation or forces in the latter. At race intensity DP does not influence the distribution of work between upper- and lower-body during a subsequent bout of DIA. O2 extraction is coupled to technical skills during skiing.
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| 6. |
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| 7. |
- 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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| 8. |
- Hebert-Losier, Kim, 1985-, et al.
(författare)
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Factors that Influence the Performance of Elite Sprint Cross-Country Skiers
- 2017
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Ingår i: Sports Medicine. - : Springer Science and Business Media LLC. - 0112-1642 .- 1179-2035. ; 47:2, s. 319-342
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sprint events in cross-country skiing are unique not only with respect to their length (0.8–1.8 km), but also in involving four high-intensity heats of ~3 min in duration, separated by a relatively short recovery period (15–60 min). Objective: Our aim was to systematically review the scientific literature to identify factors related to the performance of elite sprint cross-country skiers. Methods: Four electronic databases were searched using relevant medical subject headings and keywords, as were reference lists, relevant journals, and key authors in the field. Only original research articles addressing physiology, biomechanics, anthropometry, or neuromuscular characteristics and elite sprint cross-country skiers and performance outcomes were included. All articles meeting inclusion criteria were quality assessed. Data were extracted from each article using a standardized form and subsequently summarized. Results: Thirty-one articles met the criteria for inclusion, were reviewed, and scored an average of 66 ± 7 % (range 56–78 %) upon quality assessment. All articles except for two were quasi-experimental, and only one had a fully-experimental research design. In total, articles comprised 567 subjects (74 % male), with only nine articles explicitly reporting their skiers’ sprint International Skiing Federation points (weighted mean 116 ± 78). A similar number of articles addressed skating and classical techniques, with more than half of the investigations involving roller-skiing assessments under laboratory conditions. A range of physiological, biomechanical, anthropometric, and neuromuscular characteristics was reported to relate to sprint skiing performance. Both aerobic and anaerobic capacities are important qualities, with the anaerobic system suggested to contribute more to the performance during the first of repeated heats; and the aerobic system during subsequent heats. A capacity for high speed in all the following instances is important for the performance of sprint cross-country skiers: at the start of the race, at any given point when required (e.g., when being challenged by a competitor), and in the final section of each heat. Although high skiing speed is suggested to rely primarily on high cycle rates, longer cycle lengths are commonly observed in faster skiers. In addition, faster skiers rely on different technical strategies when approaching peak speeds, employ more effective techniques, and use better coordinated movements to optimize generation of propulsive force from the resultant ski and pole forces. Strong uphill technique is critical to race performance since uphill segments are the most influential on race outcomes. A certain strength level is required, although more does not necessarily translate to superior sprint skiing performance, and sufficient strength-endurance capacities are also of importance to minimize the impact and accumulation of fatigue during repeated heats. Lastly, higher lean mass does appear to benefit sprint skiers’ performance, with no clear advantage conferred via body height and mass. Limitations: Generalization of findings from one study to the next is challenging considering the array of experimental tasks, variables defining performance, fundamental differences between skiing techniques, and evolution of sprint skiing competitions. Although laboratory-based measures can effectively assess on-snow skiing performance, conclusions drawn from roller-skiing investigations might not fully apply to on-snow skiing performance. A low number of subjects were females (only 17 %), warranting further studies to better understand this population. Lastly, more training studies involving high-level elite sprint skiers and investigations pertaining to the ability of skiers to maintain high-sprint speeds at the end of races are recommended to assist in understanding and improving high-level sprint skiing performance, and resilience to fatigue. Conclusions: Successful sprint cross-country skiing involves well-developed aerobic and anaerobic capacities, high speed abilities, effective biomechanical techniques, and the ability to develop high forces rapidly. A certain level of strength is required, particularly ski-specific strength, as well as the ability to withstand fatigue across the repeated heats of sprint races. Cross-country sprint skiing is demonstrably a demanding and complex sport, where high-performance skiers need to simultaneously address physiological, biomechanical, anthropometric, and neuromuscular aspects to ensure success.
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| 9. |
- Jonsson, Malin, et al.
(författare)
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Biomechanical differences in double poling between sexes and level of performance during a classical cross-country skiing competition
- 2019
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Ingår i: Journal of Sports Sciences. - : Informa UK Limited. - 0264-0414 .- 1466-447X. ; 37:14, s. 1582-1590
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Tidskriftsartikel (refereegranskat)abstract
- Biomechanical differences in double poling (DP) between sex and performance level were investigated in female and male cross-country skiers during a classical race (10/15 km). Skiers were divided into faster and slower on basis of race performance: females faster (n=20), females slower (n=20), males faster (n=20), and males slower (n=20). Based on video analysis while DP in a flat section of the track, joint and pole angles at pole plant (PP) and pole-off, cycle characteristics and the use and coordination pattern of heel-raise (raise of heels from the ground to have a higher body position at PP) were analysed. Faster females and males had 4.3% and 7.8% higher DP velocity than their slower counterparts (both P<0.001). Faster males had 6.5% longer cycles than slower males (P<0.001). Faster skiers stopped heel-raise later than slower skiers (females: 2.0±3.4% vs. −1.0±3.5%, P<0.05; males: 3.9±2.4% vs. 0.8±3.2% of cycle time in relation to PP, P<0.001). At PP, faster skiers and male skiers had a smaller pole angle and greater ankle to hip and ankle to shoulder angle with respect to vertical, resulting in a more distinct forward body lean. However, the majority of the differences are likely due to higher DP velocity.
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| 10. |
- Jonsson, Malin, et al.
(författare)
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Biomechanical differences in double poling (DP) for world- and national-class female elite cross-country (XC) skiers during a 10-km classical race
- 2016
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Ingår i: Proceedings ICSS in St. Christoph am Arlberg, Austria.
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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
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| 11. |
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| 12. |
- Pellegrini, Barbara, et al.
(författare)
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Developments in the Biomechanics and Equipment of Olympic Cross-Country Skiers
- 2018
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 9:JUL
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Tidskriftsartikel (refereegranskat)abstract
- Here, our aim was to describe the major changes in cross-country (XC) skiing in recent decades, as well as potential future developments. XC skiing has been an Olympic event since the very first Winter Games in Chamonix, France, in 1924. Over the past decades, considerable developments in skiing techniques and improvements in equipment and track preparation have increased skiing speed. In contrast to the numerous investigations on the physiological determinants of successful performance, key biomechanical factors have been less explored. Today's XC skier must master a wide range of speeds, terrains, and race distances and formats (e.g., distance races with individual start, mass-start or pursuit; knock-out and team-sprint; relays), continuously adapting by alternating between various sub-techniques. Moreover, several of the new events in which skiers compete head-to-head favor technical and tactical flexibility and encourage high-speed techniques (including more rapid development of propulsive force and higher peak forces), as well as appropriate training. Moreover, the trends toward more extensive use of double poling and skiing without grip wax in classical races have given rise to regulations in connection with Olympic distances that appear to have preserved utilization of the traditional classical sub-techniques. In conclusion, although both XC equipment and biomechanics have developed significantly in recent decades, there is clearly room for further improvement. In this context as well, for analyzing performance and optimizing training, sensor technology has a potentially important role to play.
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| 13. |
- Poetzelsberger, B., et al.
(författare)
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Alpine Skiing With total knee ArthroPlasty (ASWAP) : symmetric loading during skiing
- 2015
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 25:S1, s. 60-66
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this pilot study was to determine the pressure distribution, symmetry of load between operated (OP) and non-operated (NOP) leg, and pain level during alpine skiing in participants with unilateral total knee arthroplasty (TKA). The responses of the dependent variables were analyzed following a 10-week guided skiing intervention of 2-3 days of skiing per week. Ground reaction force (GRF) was recorded bilaterally and was determined for 13 participants with TKA (65 +/- 4 years) at pre- and post-test. Additionally, pain perception was determined using a numeric rating scale in the OP leg at both test sessions and after each skiing day. No statistical differences were observed between OP and NOP legs for peak and average GRF as well as the asymmetry indices at pre-test. Pain perception was low and was not increased as a consequence of the skiing intervention. In conclusion, alpine skiing did not lead to increased or decreased loading of the OP leg compared with the NOP leg. Therefore, alpine skiing may be allowed for patients with skiing experience and a good clinical outcome.
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| 14. |
- Poetzelsberger, B., et al.
(författare)
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Alpine Skiing With total knee ArthroPlasty (ASWAP) : effects on strength and cardiorespiratory fitness
- 2015
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 25, s. 16-25
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of a 12-week recreational skiing intervention on lower limb muscle strength and cardiorespiratory fitness in participants with unilateral total knee arthroplasty (TKA). Twenty-seven older adults (70 +/- 5 years) were assigned to the intervention (n=13) or control group (n=14) after surgery (2.5 +/- 1 years). Leg muscle strength was measured using an IsoMed 2000 dynamometer and cardiorespiratory fitness was determined by cycle ergometry before and after the intervention as well as after an 8-week retention period. The skiing intervention led to increased muscle strength in the operated leg during unilateral single joint isometric extension (maximal force: 11%; P<0.05; rate of torque development: 24%; P<0.05) and during the unilateral multi-joint isokinetic single leg strength test (8%; P<0.05). This resulted in a decreased asymmetry index in the isokinetic test (13% to 5%; P<0.05). These adaptations remained unchanged toward the retention test. No effect was observed for cardiorespiratory fitness. The results demonstrate that muscle contraction forces required during recreational skiing in individuals with TKA seem adequate and effective to increase quadriceps and hamstrings muscle strength in the initially weaker operated leg and to reduce an augmented post-operative asymmetry index.
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| 15. |
- Poetzelsberger, B., et al.
(författare)
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Alpine Skiing With total knee ArthroPlasty (ASWAP) : effects on gait asymmetries
- 2015
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 25, s. 49-59
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to examine the effect of a 12-week recreational skiing intervention on functional gait performance in people with unilateral total knee arthroplasty (TKA). Twenty-three older adults (71 +/- 5 years) were assigned to the intervention (IG) or control group (CG). Test time and ground reaction forces (GRF) were recorded at pre- and post-intervention and in the retention phase during functional gait tests. Ground contact was recorded bilaterally and divided into the weight acceptance and push-off phases. In IG, a faster stair descent time (16%) was observed at post-test with no further change at the retention test. The asymmetry indices for all analyzed variables were decreased in stair descent and during weight acceptance in stair ascent and level walking without further changes between post- and retention test. The reduced asymmetries occurred mainly because of increased loading of the operated leg. Most variables were unchanged in CG. Similar to the force data, the asymmetry index for temporal stride characteristics was reduced in all stair descent variables. These results demonstrate that alpine skiing as a leisure-time activity has a beneficial effect on gait performance and leads to a more balanced load distribution between the legs during daily activities.
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| 16. |
- Stöggl, Thomas, et al.
(författare)
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Effect of carrying a rifle on physiology and biomechanical responses in biathletes
- 2015
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 47:3, s. 617-624
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: This study aimed to assess the effect of carrying a rifle on the physiological and biomechanical responses of well-trained biathletes. Methods: Ten elite biathletes (five men and five women) performed ski skating with (R) or without a rifle (NR) on a treadmill using the V2 (5- incline) and V1 techniques (8-) at 8 and 6 kmIhj1, respectively, as well as at racing intensity (approximately 95% of peak oxygen uptake (VO2peak), 10.7 T 0.8 and 7.7 T 0.9 kmIhj1, respectively). VO2, ventilation (VE), HR, blood lactate concentration (BLa), and cycle characteristics as well as pole and leg kinetics were evaluated during these trials. Results: Metabolic data were all higher for R than for NR, as follows:VO2, +2.5%;VE, +8.1%; RER, +4.2%; all P G 0.001; HR, +1.7%; and BLa, +15.1%; both P G 0.05. Biomechanically, carrying a rifle reduced cycle time and length, poling and arm swing times, and leg ground contact time and increased cycle rate, the peak and impulse of leg force, average cycle force, and impulse of forefoot force (all P G 0.05). With the exception of elevated pole forces when V2 skating at racing velocity, there were no differences between the peak and impulse of pole force. The difference inVE between R and NR was greater for the women than that for men (P G 0.05), and the difference in BLa also tended to be larger for the women (P G 0.1). Conclusions: Carrying a rifle elevated physiological responses, accelerated cycle rate, and involved greater leg work, with no differences between the V1 and V2 techniques.
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| 17. |
- Stöggl, Thomas, 1977-, et al.
(författare)
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High intensity interval training leads to greater improvements in acute heart rate recovery and anaerobic power as high volume low intensity training
- 2017
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the current study was to explore if training regimes utilizing diverse training intensity distributions result in different responses on neuromuscular status, anaerobic capacity/power and acute heart rate recovery (HRR) in well-trained endurance athletes.Methods: Thirty-six male (n = 33) and female (n = 3) runners, cyclists, triathletes and cross-country skiers [peak oxygen uptake: (VO2peak): 61.9 ± 8.0 mL·kg−1·min−1] were randomly assigned to one of three groups (blocked high intensity interval training HIIT; polarized training POL; high volume low intensity oriented control group CG/HVLIT applying no HIIT). A maximal anaerobic running/cycling test (MART/MACT) was performed prior to and following a 9-week training period.Results: Only the HIIT group achieved improvements in peak power/velocity (+6.4%, P < 0.001) and peak lactate (P = 0.001) during the MART/MACT, while, unexpectedly, in none of the groups the performance at the established lactate concentrations (4, 6, 10 mmol·L−1) was changed (P > 0.05). Acute HRR was improved in HIIT (11.2%, P = 0.002) and POL (7.9%, P = 0.023) with no change in the HVLIT oriented control group.Conclusion: Only a training regime that includes a significant amount of HIIT improves the neuromuscular status, anaerobic power and the acute HRR in well-trained endurance athletes. A training regime that followed more a low and moderate intensity oriented model (CG/HVLIT) had no effect on any performance or HRR outcomes.
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| 18. |
- Stöggl, Thomas, et al.
(författare)
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Impact of incline, sex and level of performance on kinematics during a distance race in classical cross-country skiing
- 2018
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Ingår i: Journal of Sports Science and Medicine (JSSM). - 1303-2968. ; 17:1, s. 124-133
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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.
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| 19. |
- Stöggl, Thomas, et al.
(författare)
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Three-dimensional Force and Kinematic Interactions in V1 Skating at High Speeds
- 2015
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 47:6, s. 1232-1242
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To describe the detailed kinetics and kinematics associated with use of the V1 skating technique at high skiing speeds and to identify factors that predict performance. Methods: Fifteen elite male cross-country skiers performed an incremental roller-skiing speed test (V-peak) on a treadmill using the V1 skating technique. Pole and plantar forces and whole-body kinematics were monitored at four submaximal speeds. Results: The propulsive force of the "strong side'' pole was greater than that of the "weak side'' (P < 0.01), but no difference was observed for the legs. The poles generated approximately 44% of the total propulsion, being more effective than the legs in this respect (similar to 59% vs 11%, P < 0.001). Faster skiers exhibited more well-synchronized poling, exhibited more symmetric edging by and forces from the legs, and were more effective in transformation of resultant forces into propulsion. Cycle length was not correlated with either V-peak or the impulse of total propulsive forces. Conclusions: The present findings provide novel insights into the coordination, kinetics, and kinematics of the arm and leg motion by elite athletes while V1 skating at high speeds. The faster skiers exhibit more symmetric leg motion on the "strong'' and "weak'' sides, as well as more synchronized poling. With respect to methods, the pressure insoles and three-dimensional kinematics in combination with the leg push-off model described here can easily be applied to all skating techniques, aiding in the evaluation of skiing techniques and comparison of effectiveness.
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| 20. |
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| 21. |
- 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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| 22. |
- 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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| 23. |
- 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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| 24. |
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| 25. |
- Takeda, Masaki, et al.
(författare)
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Cross-country skiing analysis and ski technique detection by high-precision kinematic global navigation satellite system
- 2019
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 19:22
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 by the authors. Licensee MDPI, Basel, Switzerland. Cross-country skiing (XCS) embraces a broad variety of techniques applied like a gear system according to external conditions, slope topography, and skier-related factors. The continuous detection of applied skiing techniques and cycle characteristics by application of unobtrusive sensor technology can provide useful information to enhance the quality of training and competition. (1) Background: We evaluated the possibility of using a high-precision kinematic global navigation satellite system (GNSS) to detect cross-country skiing classical style technique. (2) Methods: A world-class male XC skier was analyzed during a classical style 5.3-km time trial recorded with a high-precision kinematic GNSS attached to the skier’s head. A video camera was mounted on the lumbar region of the skier to detect the type and number of cycles of each technique used during the entire time trial. Based on the GNSS trajectory, distinct patterns of head displacement (up-down head motion) for each classical technique (e.g., diagonal stride (DIA), double poling (DP), kick double poling (KDP), herringbone (HB), and downhill) were defined. The applied skiing technique, skiing duration, skiing distance, skiing speed, and cycle time within a technique and the number of cycles were visually analyzed using both the GNSS signal and the video data by independent persons. Distinct patterns for each technique were counted by two methods: Head displacement with course inclination and without course inclination (net up-down head motion). (3) Results: Within the time trial, 49.6% (6 min, 46 s) was DP, 18.7% (2 min, 33 s) DIA, 6.1% (50 s) KDP, 3.3% (27 s) HB, and 22.3% (3 min, 03 s) downhill with respect to total skiing time (13 min, 09 s). The %Match for both methods 1 and 2 (net head motion) was high: 99.2% and 102.4%, respectively, for DP; 101.7% and 95.9%, respectively, for DIA; 89.4% and 100.0%, respectively, for KDP; 86.0% and 96.5%, respectively, in HB; and 98.6% and 99.6%, respectively, in total. (4) Conclusions: Based on the results of our study, it is suggested that a high-precision kinematic GNSS can be applied for precise detection of the type of technique, and the number of cycles used, duration, skiing speed, skiing distance, and cycle time for each technique, during a classical style XCS race.
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| 26. |
- Welde, Boye, et al.
(författare)
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The pacing strategy and technique of male cross-country skiers with different levels of performance during a 15-km classical race
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:11
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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.
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