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Gløersen Ø, Viken Å, Lund-Hansen M, Losnegard T. The influence of race duration on oxygen demand, uptake and deficit in competitive cross-country skiers. Eur J Appl Physiol 2024:10.1007/s00421-024-05531-1. [PMID: 38918220 DOI: 10.1007/s00421-024-05531-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 06/11/2024] [Indexed: 06/27/2024]
Abstract
PURPOSE To measure oxygen demand, uptake, and deficits in competitive cross-country skiers during outdoor roller skiing at different competition durations, ranging from the endurance domain to the sprint domain. METHODS Ten competitive cross-country skiers (6 males; V ˙ O2max 78 ± 3 and 4 females; V ˙ O2max 62 ± 3 mL∙kg-1∙min-1) raced time trials consisting of 1, 2, and 4 laps in a 1.6 km racecourse in a randomized order with 35 min recovery in-between. Oxygen uptake was measured using a wearable metabolic system while oxygen demand was estimated from kinematic data (GPS and IMU) and an athlete-specific model of skiing economy. Skiing economy and V ˙ O2max was established on a separate test day using six submaximal constant-load trials at different speeds and inclines, and one maximal-effort trial on a roller-skiing treadmill. RESULTS Average oxygen demand was 112 ± 8%, 103 ± 7% and 98 ± 7% of V ˙ O2max during the 1 (3:37 ± 0:20 m:ss), 2 (7:36 ± 0:38 m:ss) and 4 (15:43 ± 1:26 m:ss) lap time trials, respectively, and appeared to follow an inverse relationship with time-trial duration. Average oxygen uptake was unaffected by race length (86 ± 5%, 86 ± 5%, and 86 ± 7% of V ˙ O2max, respectively). Accumulated oxygen deficit at the end of each time trial was 85 ± 13, 106 ± 32 and 158 ± 62 mL∙kg-1, while oxygen deficits per work bout was 23 ± 3, 18 ± 3 and 16 ± 3 mL∙kg-1 for the 1, 2, and 4-lap time trials, respectively. CONCLUSION Elite cross-country skiers adjust their pacing strategies from attaining relatively small oxygen deficits per work bout in the endurance domain, to larger deficits in the sprint domain. This indicates a shift in strategy from prioritizing stable work-economy and rate-of-recovery in the endurance domain, to maximizing power output in the sprint domain.
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Affiliation(s)
- Øyvind Gløersen
- Department of Health Research, SINTEF Digital, Postboks 124 Blindern, 0314, Oslo, Norway.
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway.
| | - Ånung Viken
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Magne Lund-Hansen
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
| | - Thomas Losnegard
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway
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2
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van Dijk MP, Hoozemans MJM, Berger MAM, Veeger HEJ. From theory to practice: Monitoring mechanical power output during wheelchair field and court sports using inertial measurement units. J Biomech 2024; 166:112052. [PMID: 38560959 DOI: 10.1016/j.jbiomech.2024.112052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 03/06/2024] [Accepted: 03/14/2024] [Indexed: 04/04/2024]
Abstract
An important performance determinant in wheelchair sports is the power exchanged between the athlete-wheelchair combination and the environment, in short, mechanical power. Inertial measurement units (IMUs) might be used to estimate the exchanged mechanical power during wheelchair sports practice. However, to validly apply IMUs for mechanical power assessment in wheelchair sports, a well-founded and unambiguous theoretical framework is required that follows the dynamics of manual wheelchair propulsion. Therefore, this research has two goals. First, to present a theoretical framework that supports the use of IMUs to estimate power output via power balance equations. Second, to demonstrate the use of the IMU-based power estimates during wheelchair propulsion based on experimental data. Mechanical power during straight-line wheelchair propulsion on a treadmill was estimated using a wheel mounted IMU and was subsequently compared to optical motion capture data serving as a reference. IMU-based power was calculated from rolling resistance (estimated from drag tests) and change in kinetic energy (estimated using wheelchair velocity and wheelchair acceleration). The results reveal no significant difference between reference power values and the proposed IMU-based power (1.8% mean difference, N.S.). As the estimated rolling resistance shows a 0.9-1.7% underestimation, over time, IMU-based power will be slightly underestimated as well. To conclude, the theoretical framework and the resulting IMU model seems to provide acceptable estimates of mechanical power during straight-line wheelchair propulsion in wheelchair (sports) practice, and it is an important first step towards feasible power estimations in all wheelchair sports situations.
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Affiliation(s)
- Marit P van Dijk
- Department of Biomechanical Engineering, Delft University of Technology, Delft, the Netherlands.
| | - Marco J M Hoozemans
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Monique A M Berger
- Centre of Expertise Health Innovation, The Hague University of Applied Sciences, The Hague, the Netherlands
| | - H E J Veeger
- Department of Biomechanical Engineering, Delft University of Technology, Delft, the Netherlands
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3
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de Vette VG, Veeger D(HEJ, van Dijk MP. Using Wearable Sensors to Estimate Mechanical Power Output in Cyclical Sports Other than Cycling-A Review. SENSORS (BASEL, SWITZERLAND) 2022; 23:50. [PMID: 36616649 PMCID: PMC9823913 DOI: 10.3390/s23010050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/03/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
More insight into in-field mechanical power in cyclical sports is useful for coaches, sport scientists, and athletes for various reasons. To estimate in-field mechanical power, the use of wearable sensors can be a convenient solution. However, as many model options and approaches for mechanical power estimation using wearable sensors exist, and the optimal combination differs between sports and depends on the intended aim, determining the best setup for a given sport can be challenging. This review aims to provide an overview and discussion of the present methods to estimate in-field mechanical power in different cyclical sports. Overall, in-field mechanical power estimation can be complex, such that methods are often simplified to improve feasibility. For example, for some sports, power meters exist that use the main propulsive force for mechanical power estimation. Another non-invasive method usable for in-field mechanical power estimation is the use of inertial measurement units (IMUs). These wearable sensors can either be used as stand-alone approach or in combination with force sensors. However, every method has consequences for interpretation of power values. Based on the findings of this review, recommendations for mechanical power measurement and interpretation in kayaking, rowing, wheelchair propulsion, speed skating, and cross-country skiing are done.
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Ni X, Liu J, Zhang S, Ke P. Numerical optimization of pacing strategy in cross-country skiing based on Gauss pseudo-spectral method. Sci Rep 2022; 12:20457. [PMID: 36443334 PMCID: PMC9705566 DOI: 10.1038/s41598-022-24859-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 11/22/2022] [Indexed: 11/29/2022] Open
Abstract
In cross-country skiing competitions, the choice of pacing strategy is of decisive significance to athletes' performance. A reasonable pacing strategy is essential for athletes to improve their performance. In this paper, the mathematical models of cross-country skiing simulation and pacing optimization are established, including motion model, athlete power output model, and optimization model. The actual competition data of a Chinese athlete in Guyangshu 1.5 km track was compared with the model simulation results. The whole process time error is less than 3%, which verifies the accuracy of the motion and power output model. Gauss pseudo-spectral method is applied to the optimization model. By changing the distribution of athletes' power output, the racing time is minimized under the condition that the total energy output remains unchanged. Compared with the pacing strategy before optimization, the optimized racing time was shortened by 12.6 s, which verifies the effectiveness of the optimization model. Optimized results show that in the first significant uphill section, a recommendation is to use a more conservative strategy, while in the latter half of uphill sections the power output should be increased.
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Affiliation(s)
- Xu Ni
- grid.64939.310000 0000 9999 1211School of Transportation Science and Engineering, Beihang University, Beijing, 100191 China
| | - Jiawei Liu
- grid.64939.310000 0000 9999 1211School of Transportation Science and Engineering, Beihang University, Beijing, 100191 China
| | - Shuguang Zhang
- grid.64939.310000 0000 9999 1211School of Transportation Science and Engineering, Beihang University, Beijing, 100191 China
| | - Peng Ke
- grid.64939.310000 0000 9999 1211School of Transportation Science and Engineering, Beihang University, Beijing, 100191 China
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5
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Staunton CA, Sloof L, Brandts M, Jonsson Kårström M, Laaksonen MS, Björklund G. The Effect of Rifle Carriage on the Physiological and Accelerometer Responses During Biathlon Skiing. Front Sports Act Living 2022; 4:813784. [PMID: 35399594 PMCID: PMC8990322 DOI: 10.3389/fspor.2022.813784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 03/02/2022] [Indexed: 11/13/2022] Open
Abstract
Purpose Investigate the effect of biathlon rifle carriage on physiological and accelerometer-derived responses during biathlon skiing. Methods Twenty-eight biathletes (11F, 17M) completed two XC skiing time-trials (~2,300 m), once with and once without the biathlon rifle, with concurrent measurements of HR, skiing speed and accelerations recorded from three triaxial accelerometers attached at the Upper-spine, Lower-spine and Pelvis. Exercise intensity was quantified from HR, skiing speed as well from accelerometry-derived PlayerLoad™ per minute (PL·min-1) and average net force (AvFNet). All metrics were analyzed during Uphill, Flat and Downhill sections of the course. Relationships between accelerometry-derived metrics and skiing speed were examined. Results Time-trials were faster for males compared with females (mean difference: 97 ± 73 s) and No-Rifle compared to With-Rifle (mean difference: 16 ± 9 s). HR was greatest during Downhill (183 ± 5 bpm), followed by Uphill (181 ± 5 bpm) and was lowest in the Flat sections (177 ± 6 bpm, p <0.05). For PL·min-1 and AvFNet there were 3-way Rifle x Gradient x Sensor-Position interactions. Typically, these metrics were greatest during Uphill and Flat sections and were lowest during Downhill sections. Rifle carriage had no impact on the AvFNet at the Lower-Spine or Pelvis. Significant positive linear relationships were identified between skiing speed and accelerometer-derived metrics during Uphill, Flat and Downhill skiing (r = 0.12-0.61, p < 0.05). Conclusions The accelerometry-derived approach used in this study provides the potential of a novel method of monitoring the external demands during skiing. In particular, AvFNet with sensors located close to the center of mass displayed greatest utility because it followed the expected response of external intensity where responses were greatest during uphill sections, followed by flats and lowest during downhills. In addition, there were significant positive relationships between AvFNet and skiing speed ranging from small to large. Accelerometry-derived measures could provide useful estimates of the external demands in XC skiing and biathlon.
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Affiliation(s)
- Craig A Staunton
- Swedish Winter Sports Research Centre, Faculty of Human Sciences, Mid Sweden University, Östersund, Sweden
| | - Luciën Sloof
- Swedish Winter Sports Research Centre, Faculty of Human Sciences, Mid Sweden University, Östersund, Sweden
| | - Maxime Brandts
- Swedish Winter Sports Research Centre, Faculty of Human Sciences, Mid Sweden University, Östersund, Sweden.,Institute of Sports Science, Saarland University, Saarbrücken, Germany
| | - Malin Jonsson Kårström
- Swedish Winter Sports Research Centre, Faculty of Human Sciences, Mid Sweden University, Östersund, Sweden
| | - Marko S Laaksonen
- Swedish Winter Sports Research Centre, Faculty of Human Sciences, Mid Sweden University, Östersund, Sweden
| | - Glenn Björklund
- Swedish Winter Sports Research Centre, Faculty of Human Sciences, Mid Sweden University, Östersund, Sweden
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Almqvist A, Pellegrini B, Lintzén N, Emami N, Holmberg HC, Larsson R. A Scientific Perspective on Reducing Ski-Snow Friction to Improve Performance in Olympic Cross-Country Skiing, the Biathlon and Nordic Combined. Front Sports Act Living 2022; 4:844883. [PMID: 35392593 PMCID: PMC8980609 DOI: 10.3389/fspor.2022.844883] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 02/23/2022] [Indexed: 11/29/2022] Open
Abstract
Of the medals awarded at the 2022 Winter Olympics in Beijing, 24% were for events involving cross-country skiing, the biathlon and Nordic combined. Although much research has focused on physiological and biomechanical characteristics that determine success in these sports, considerably less is yet known about the resistive forces. Here, we specifically describe what is presently known about ski-snow friction, one of the major resistive forces. Today, elite ski races take place on natural and/or machine-made snow. Prior to each race, several pairs of skis with different grinding and waxing of the base are tested against one another with respect to key parameters, such as how rapidly and for how long the ski glides, which is dependent on ski-snow friction. This friction arises from a combination of factors, including compaction, plowing, adhesion, viscous drag, and water bridging, as well as contaminants and dirt on the surface of and within the snow. In this context the stiffness of the ski, shape of its camber, and material composition and topography of the base exert a major influence. An understanding of the interactions between these factors, in combination with information concerning the temperature and humidity of both the air and snow, as well as the nature of the snow, provides a basis for designing specific strategies to minimize ski-snow friction. In conclusion, although performance on “narrow skis” has improved considerably in recent decades, future insights into how best to reduce ski-snow friction offer great promise for even further advances.
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Affiliation(s)
- Andreas Almqvist
- Division of Machine Elements, Luleå University of Technology, Luleå, Sweden
- *Correspondence: Andreas Almqvist
| | - Barbara Pellegrini
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
- CeRiSM, Sport Mountain and Health Research Centre, University of Verona, Verona, Italy
| | - Nina Lintzén
- Division of Machine Elements, Luleå University of Technology, Luleå, Sweden
| | - Nazanin Emami
- Division of Machine Elements, Luleå University of Technology, Luleå, Sweden
| | - H-C Holmberg
- Division of Health, Medicine and Rehabilitation, Luleå University of Technology, Luleå, Sweden
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Roland Larsson
- Division of Machine Elements, Luleå University of Technology, Luleå, Sweden
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Staunton CA, Colyer SL, Karlsson Ø, Swarén M, Ihalainen S, McGawley K. Performance and Micro-Pacing Strategies in a Freestyle Cross-Country Skiing Distance Race. Front Sports Act Living 2022; 4:834474. [PMID: 35252860 PMCID: PMC8893266 DOI: 10.3389/fspor.2022.834474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 01/24/2022] [Indexed: 11/16/2022] Open
Abstract
This study examined the micro-pacing strategies during a distance freestyle cross-country (XC) skiing competition. Nine female and 10 male highly trained XC skiers wore a GNSS device during a FIS-sanctioned race. The course was ~4900 m; women completed two-laps; men completed three-laps. The course was divided into uphill (S1, S3, S5, S7), downhill (S2, S4, S6, S8), and flat (S9) sections for analyses. Statistical parametric mapping was used to determine the course positions (clusters) where total race time or section time was significantly associated with instantaneous skiing speed. Total race time was associated with instantaneous skiing speed during a cluster in S1 on lap 2 for both sexes (t ≥ 5.899, p ≤ 0.008). The two longest uphill sections (S1; S5) and the flat section (S9) contained clusters where section times were related to instantaneous skiing speed for both sexes (p < 0.05). The fastest woman gained 6.9 s on the slowest woman during a cluster in S1 on lap 1 and 7.3 s during a cluster in S9 on lap 1. The fastest man gained 51.7 s on the slowest man over all clusters in S5 over the 3 laps combined. Compared to skiers with longer total race times, skiers with shorter race times skied with faster instantaneous speeds in some clusters of the uphill sections, as well as on the flat section of the course. This study also identified different relative micro-pacing strategies for women and men during freestyle distance XC skiing races. Finally, statistical parametric mapping analyses can help to identify individual strengths and weaknesses for guiding training programs and optimise competition pacing strategies.
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Affiliation(s)
- Craig A. Staunton
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
- *Correspondence: Craig A. Staunton
| | | | - Øyvind Karlsson
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
| | - Mikael Swarén
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
- Swedish Unit for Metrology in Sports, School of Education, Health and Social Studies, Dalarna University, Falun, Sweden
| | - Simo Ihalainen
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
- Research Institute for Olympic Sports, Jyväskylä, Finland
| | - Kerry McGawley
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
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8
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Performance Effects of Video- and Sensor-Based Feedback for Implementing a Terrain-Specific Micropacing Strategy in Cross-Country Skiing. Int J Sports Physiol Perform 2022; 17:1672-1682. [DOI: 10.1123/ijspp.2022-0106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 07/09/2022] [Accepted: 08/09/2022] [Indexed: 11/09/2022]
Abstract
Purpose: To investigate the performance effects of video- and sensor-based feedback for implementing a terrain-specific micropacing strategy in cross-country (XC) skiing. Methods: Following a simulated 10-km skating time trial (Race1) on snow, 26 national-level male XC skiers were randomly allocated into an intervention (n = 14) or control group (n = 12), before repeating the race (Race2) 2 days later. Between races, intervention received video- and sensor-based feedback through a theoretical lecture and a practical training session aiming to implement a terrain-specific micropacing strategy focusing on active power production over designated hilltops to save time in the subsequent downhill. The control group only received their overall results and performed a training session with matched training load. Results: From Race1 to Race2, the intervention group increased the total variation of chest acceleration on all hilltops (P < .001) and reduced time compared with the control group in a specifically targeted downhill segment (mean group difference: −0.55 s; 95% confidence interval [CI], −0.9 to −0.19 s; P = .003), as well as in overall time spent in downhill (−14.4 s; 95% CI, −21.4 to −7.4 s; P < .001) and flat terrain (−6.5 s; 95% CI, −11.0 to −1.9 s; P = .006). No between-groups differences were found for either overall uphill terrain (−9.3 s; 95% CI, −31.2 to 13.2 s; P = .426) or total race time (−32.2 s; 95% CI, −100.2 to 35.9 s; P = .339). Conclusion: Targeted training combined with video- and sensor-based feedback led to a successful implementation of a terrain-specific micropacing strategy in XC skiing, which reduced the time spent in downhill and flat terrain for intervention compared with a control group. However, no change in overall performance was observed between the 2 groups of XC skiers.
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Heart Rate Does Not Accurately Predict Metabolic Intensity During Variable-Intensity Roller Skiing or Cycling. Int J Sports Physiol Perform 2022; 17:1664-1671. [DOI: 10.1123/ijspp.2022-0114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/26/2022] [Accepted: 08/01/2022] [Indexed: 11/09/2022]
Abstract
Purpose: To critically appraise the utility of heart rate (HR) and power output (PO) to predict metabolic rate (MR) and oxygen consumption () during variable-intensity roller skiing and cycling. Methods: National-level cyclists (n = 8) and cross-country skiers (n = 9) completed a preliminary session to determine , and a variable-intensity protocol with 3 high-intensity stages at 90% for 3 minutes interspersed with 3 moderate-intensity stages at 70% for 6 minutes. Cardiorespiratory measures were recorded throughout. Linear HR–MR, , PO–MR, and regressions were computed from the preliminary session, individually, for all athletes and used to predict MR and from both HR and PO, separately, during the variable-intensity protocol. Mean differences with 95% limits of agreement (LOA) between measured and predicted MR and were calculated. Results: MR and estimated from HR displayed a mean bias close to zero but wide LOA. HR overestimated MR and during moderate intensity but underestimated MR and during high intensity, for both roller skiing and cycling. MR and estimated from PO were more consistent across the experimental trial, displaying a mean bias farther from zero but with tighter LOA. Conclusions: This study has demonstrated that HR has limited utility to predict metabolic intensity during variable-intensity roller skiing and cycling because of wide LOA. On the other hand, metabolic intensity predicted from PO had tighter LOA, suggesting better consistency. PO might provide a better prediction of metabolic intensity compared with HR, particularly when longer-duration steps are performed during preliminary testing.
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10
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Seeberg TM, Kocbach J, Danielsen J, Noordhof DA, Skovereng K, Meyer F, Sandbakk Ø. Physiological and Biomechanical Responses to Cross-Country Skiing in Varying Terrain: Low- vs. High-Intensity. Front Physiol 2021; 12:741573. [PMID: 34707511 PMCID: PMC8543002 DOI: 10.3389/fphys.2021.741573] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 09/07/2021] [Indexed: 11/13/2022] Open
Abstract
The purposes of our study were to investigate the physiological and biomechanical responses to low-intensity (LI) and high-intensity (HI) roller ski skating on varying terrain and compare these responses between training intensities. Nine elite male skiers performed treadmill roller skiing consisting of two 21 min sessions (7 × 3 min laps) at LI and HI with the same set inclines and intensity-dependent speeds (LI/HI: distance: 5.8/7.5 km, average speed: 16.7/21.3 km/h). Physiological and biomechanical variables were measured continuously, and each movement cycle and sub-technique employed were detected and classified with a machine learning model. Both the LI and HI sessions induced large terrain-dependent fluctuations (relative to the maximal levels) in heart rate (HR, 17.7 vs. 12.2%-points), oxygen uptake (V.O2, 33.0 vs. 31.7%-points), and muscle oxygen saturation in the triceps brachii (23.9 vs. 33.4%-points) and vastus lateralis (12.6 vs. 24.3%-points). A sub-technique dependency in relative power contribution from poles and skis exhibited a time-dependent shift from Lap 1 to Lap 7 toward gradually more ski power (6.6 vs. 7.8%-points, both p < 0.01). The terrain-dependent fluctuations did not differ between LI and HI for V.O2 (p = 0.50), whereas HR fluctuated less (p < 0.01) and displayed a time-dependent increase from Lap 2 to Lap 7 (7.8%-points, p > 0.01) during HI. Oxygen saturation shifted 2.4% points more for legs than arms from LI to HI (p > 0.05) and regarding sub-technique, 14.7% points more G3 on behalf of G2 was employed on the steepest uphill during HI (p < 0.05). Within all sub-techniques, cycle length increased two to three times more than cycle rate from LI to HI in the same terrains, while the corresponding poling time decreased more than ski contact time (all p > 0.05). In sum, both LI and HI cross-country (XC) skiing on varying terrain induce large terrain-dependent physiological and biomechanical fluctuations, similar to the patterns found during XC skiing competitions. The primary differences between training intensities were the time-dependent increase in HR, reduced relative oxygen saturation in the legs compared to the arms, and greater use of G3 on steep uphill terrain during HI training, whereas sub-technique selection, cycle rate, and pole vs. ski power distribution were similar across intensities on flat and moderately uphill terrain.
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Affiliation(s)
- Trine M Seeberg
- Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway.,Smart Sensor System, SINTEF DIGITAL, SINTEF AS, Oslo, Norway
| | - Jan Kocbach
- Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway
| | - Jørgen Danielsen
- Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway
| | - Dionne A Noordhof
- Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway
| | - Knut Skovereng
- Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway
| | - Frédéric Meyer
- Digital Signal Processing Group, Department of Informatics, University of Oslo, Oslo, Norway
| | - Øyvind Sandbakk
- Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway
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11
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Uddin MZ, Seeberg TM, Kocbach J, Liverud AE, Gonzalez V, Sandbakk Ø, Meyer F. Estimation of Mechanical Power Output Employing Deep Learning on Inertial Measurement Data in Roller Ski Skating. SENSORS 2021; 21:s21196500. [PMID: 34640819 PMCID: PMC8512452 DOI: 10.3390/s21196500] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/16/2021] [Accepted: 09/24/2021] [Indexed: 11/16/2022]
Abstract
The ability to optimize power generation in sports is imperative, both for understanding and balancing training load correctly, and for optimizing competition performance. In this paper, we aim to estimate mechanical power output by employing a time-sequential information-based deep Long Short-Term Memory (LSTM) neural network from multiple inertial measurement units (IMUs). Thirteen athletes conducted roller ski skating trials on a treadmill with varying incline and speed. The acceleration and gyroscope data collected with the IMUs were run through statistical feature processing, before being used by the deep learning model to estimate power output. The model was thereafter used for prediction of power from test data using two approaches. First, a user-dependent case was explored, reaching a power estimation within 3.5% error. Second, a user-independent case was developed, reaching an error of 11.6% for the power estimation. Finally, the LSTM model was compared to two other machine learning models and was found to be superior. In conclusion, the user-dependent model allows for precise estimation of roller skiing power output after training the model on data from each athlete. The user-independent model provides less accurate estimation; however, the accuracy may be sufficient for providing valuable information for recreational skiers.
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Affiliation(s)
- Md Zia Uddin
- SINTEF Digital, 0373 Oslo, Norway; (M.Z.U.); (T.M.S.); (A.E.L.); (V.G.)
| | - Trine M. Seeberg
- SINTEF Digital, 0373 Oslo, Norway; (M.Z.U.); (T.M.S.); (A.E.L.); (V.G.)
| | - Jan Kocbach
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, 7491 Trondheim, Norway; (J.K.); (Ø.S.)
| | - Anders E. Liverud
- SINTEF Digital, 0373 Oslo, Norway; (M.Z.U.); (T.M.S.); (A.E.L.); (V.G.)
| | - Victor Gonzalez
- SINTEF Digital, 0373 Oslo, Norway; (M.Z.U.); (T.M.S.); (A.E.L.); (V.G.)
| | - Øyvind Sandbakk
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, 7491 Trondheim, Norway; (J.K.); (Ø.S.)
| | - Frédéric Meyer
- Department of Informatics, University of Oslo, 0316 Oslo, Norway
- Correspondence:
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12
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Sollie O, Holmsen K, Steinbo C, Ommundsen Y, Losnegard T. Observational vs coaching feedback on non-dominant whole-body motor skill performance - application to technique training. Scand J Med Sci Sports 2021; 31:2103-2114. [PMID: 34351642 DOI: 10.1111/sms.14030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 07/29/2021] [Indexed: 11/29/2022]
Abstract
We studied the effect of peer- and self-observational feedback versus coaching feedback during technique training on performance in competitive adolescent cross-country skiers. Fifty-four skiers (14.3 ± 0.6 years) were divided into a control group and three intervention groups (dyad practice, video, or coaching feedback), which practiced in the asymmetrical uphill sub-technique G2 on one side (non-dominant side), but not the other (dominant side) for 6 × 30 min over a 5 weeks period, on roller skis outdoors. High-speed performance and skiing economy were assessed on a roller ski treadmill before and after the intervention, and a questionnaire was answered post-intervention. The video feedback (p = .025, d = .65) and coaching feedback (p = .007, d = .89) groups improved high-speed performance during the intervention and an ANCOVA showed a tendency for different change scores between interventions (F3,49 = 2.5, p = .068, η p 2 = .134), with a difference between the coaching feedback and dyad practice (p = .05). No change was seen in skiing economy in any group. Coaching feedback ranked higher on enjoyment compared with dyad practice (p < .001) and led to higher self-perception of improved technique compared with the control group (p = .038). Overall, feedback from a competent coach seems better than observation for improving performance in young athletes, although self-observation through video with attentional cues seems a promising tool for increasing individual feedback when coaching large groups.
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Affiliation(s)
- Ove Sollie
- Department of Physical Performance, Norwegian School of Sports Sciences, Oslo, Norway
| | - Kristian Holmsen
- Department of Physical Performance, Norwegian School of Sports Sciences, Oslo, Norway
| | - Christian Steinbo
- Department of Sport and Social Sciences, Norwegian School of Sports Sciences, Oslo, Norway
| | - Yngvar Ommundsen
- Department of Sport and Social Sciences, Norwegian School of Sports Sciences, Oslo, Norway
| | - Thomas Losnegard
- Department of Physical Performance, Norwegian School of Sports Sciences, Oslo, Norway
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13
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Classification of Cross-Country Ski Skating Sub-Technique Can Be Automated Using Carrier-Phase Differential GNSS Measurements of the Head's Position. SENSORS 2021; 21:s21082705. [PMID: 33921408 PMCID: PMC8069750 DOI: 10.3390/s21082705] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 12/02/2022]
Abstract
Position–time tracking of athletes during a race can provide useful information about tactics and performance. However, carrier-phase differential global navigation satellite system (dGNSS)-based tracking, which is accurate to about 5 cm, might also allow for the extraction of variables reflecting an athlete’s technique. Such variables include cycle length, cycle frequency, and choice of sub-technique. The aim of this study was to develop a dGNSS-based method for automated determination of sub-technique and cycle characteristics in cross-country ski skating. Sub-technique classification was achieved using a combination of hard decision rules and a neural network classifier (NNC) on position measurements from a head-mounted dGNSS antenna. The NNC was trained to classify the three main sub-techniques (G2–G4) using optical marker motion data of the head trajectory of six subjects during treadmill skiing. Hard decision rules, based on the head’s sideways and vertical movement, were used to identify phases of turning, tucked position and G5 (skating without poles). Cycle length and duration were derived from the components of the head velocity vector. The classifier’s performance was evaluated on two subjects during an in-field roller skiing test race by comparison with manual classification from video recordings. Classification accuracy was 92–97% for G2–G4, 32% for G5, 75% for turning, and 88% for tucked position. Cycle duration and cycle length had a root mean square (RMS) deviation of 2–3%, which was reduced to <1% when cycle duration and length were averaged over five cycles. In conclusion, accurate dGNSS measurements of the head’s trajectory during cross-country skiing contain sufficient information to classify the three main skating sub-techniques and characterize cycle length and duration.
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14
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Seeberg TM, Kocbach J, Danielsen J, Noordhof DA, Skovereng K, Haugnes P, Tjønnås J, Sandbakk Ø. Physiological and Biomechanical Determinants of Sprint Ability Following Variable Intensity Exercise When Roller Ski Skating. Front Physiol 2021; 12:638499. [PMID: 33841176 PMCID: PMC8027482 DOI: 10.3389/fphys.2021.638499] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 03/05/2021] [Indexed: 11/16/2022] Open
Abstract
The most common race format in cross-country (XC) skiing is the mass-start event, which is under-explored in the scientific literature. To explore factors important for XC skiing mass-starts, the main purpose of this study was to investigate physiological and biomechanical determinants of sprint ability following variable intensity exercise when roller ski skating. Thirteen elite male XC skiers performed a simulated mass-start competition while roller ski skating on a treadmill. The protocol consisted of an initial 21-min bout with a varying track profile, designed as a competition track with preset inclines and speeds, directly followed by an all-out sprint (AOS) with gradually increased speed to rank their performance. The initial part was projected to simulate the “stay-in-the-group” condition during a mass-start, while the AOS was designed to assess the residual physiological capacities required to perform well during the final part of a mass-start race. Cardiorespiratory variables, kinematics and pole forces were measured continuously, and the cycles were automatically detected and classified into skating sub-techniques through a machine learning model. Better performance ranking was associated with higher VO2Max (r = 0.68) and gross efficiency (r = 0.70) measured on separate days, as well as the ability to ski on a lower relative intensity [i.e., %HRMax (r = 0.87), %VO2Max (r = 0.89), and rating of perceived exertion (r = 0.73)] during the initial 21-min of the simulated mass-start (all p-values < 0.05). Accordingly, the ability to increase HR (r = 0.76) and VO2 (r = 0.72), beyond the corresponding values achieved during the initial 21-min, in the AOS correlated positively with performance (both p < 0.05). In addition, greater utilization of the G3 sub-technique in the steepest uphill (r = 0.69, p < 0.05), as well as a trend for longer cycle lengths (CLs) during the AOS (r = 0.52, p = 0.07), were associated with performance. In conclusion, VO2Max and gross efficiency were the most significant performance-determining variables of simulated mass-start performance, enabling lower relative intensity and less accumulation of fatigue before entering the final AOS. Subsequently, better performance ranking was associated with more utilization of the demanding G3 sub-technique in the steepest uphill, and physiological reserves allowing better-performing skiers to utilize a larger portion of their aerobic potential and achieve longer CLs and higher speed during the AOS.
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Affiliation(s)
- Trine M Seeberg
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway.,Smart Sensor Systems, SINTEF Digital, Oslo, Norway
| | - Jan Kocbach
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Jørgen Danielsen
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Dionne A Noordhof
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Knut Skovereng
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | - Pål Haugnes
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
| | | | - Øyvind Sandbakk
- Centre for Elite Sports Research, Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
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15
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Spörri J, Stöggl T, Aminian K. Editorial: Health and Performance Assessment in Winter Sports. Front Sports Act Living 2021; 3:628574. [PMID: 33768202 PMCID: PMC7985436 DOI: 10.3389/fspor.2021.628574] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 02/12/2021] [Indexed: 12/11/2022] Open
Affiliation(s)
- Jörg Spörri
- Sports Medical Research Group, Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.,University Centre for Prevention and Sports Medicine, Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Thomas Stöggl
- Department of Sport Science and Kinesiology, University of Salzburg, Hallein, Austria.,Red Bull Athlete Performance Centre, Thalgau, Austria
| | - Kamiar Aminian
- Laboratory of Movement Analysis and Measurement, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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16
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Sollie O, Gløersen Ø, Gilgien M, Losnegard T. Differences in pacing pattern and sub‐technique selection between young and adult competitive cross‐country skiers. Scand J Med Sci Sports 2020; 31:553-563. [DOI: 10.1111/sms.13887] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 09/21/2020] [Accepted: 11/05/2020] [Indexed: 11/29/2022]
Affiliation(s)
- Ove Sollie
- Department of Physical Performance Norwegian School of Sports Sciences Oslo Norway
| | - Øyvind Gløersen
- Department of Physical Performance Norwegian School of Sports Sciences Oslo Norway
| | - Matthias Gilgien
- Department of Physical Performance Norwegian School of Sports Sciences Oslo Norway
- St. Moritz Health and Innovation Foundation Samedan Switzerland
| | - Thomas Losnegard
- Department of Physical Performance Norwegian School of Sports Sciences Oslo Norway
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17
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Ihalainen S, Colyer S, Andersson E, McGawley K. Performance and Micro-Pacing Strategies in a Classic Cross-Country Skiing Sprint Race. Front Sports Act Living 2020; 2:77. [PMID: 33345068 PMCID: PMC7739622 DOI: 10.3389/fspor.2020.00077] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 05/26/2020] [Indexed: 11/13/2022] Open
Abstract
The purpose of the present study was to analyze micro-pacing strategies in cross-country skiing, and their relation to section and total race times. Eleven competitive female cross-country skiers were tracked during a classic sprint time-trial race using a global navigation satellite system (GNSS) unit. A coordinate mapping procedure was applied to the GNSS unit measurements to analyze the instantaneous velocities and split times. The track was divided into nine sections and individual section times were calculated. Statistical parametric mapping (SPM) was used to analyze the relationships between instantaneous velocity and section or total race time. SPM analyses revealed two uphill sections and one flat section where greater instantaneous velocities were related to faster total race times. The first major uphill section on the track demonstrated a more conservative micro-pacing strategy (SPM supra-threshold clusters along the entire uphill, p < 0.05-0.001) compared to the more aggressive strategy used in the last uphill section (clusters on the first half of the uphill, p < 0.05-0.001). Faster flat section times were associated with greater instantaneous velocities throughout the section (p < 0.001), while faster downhill section times were related to greater instantaneous velocities at the top of the downhill (p < 0.001), and in the downhill turns (p < 0.001). In conclusion, micro-pacing strategies were related to overall skiing performance and distinct track sections were identified where instantaneous velocities were related to section or total race times. In order to improve skiing performance, athletes could focus on more aggressive pacing early on in the "end spurt", during the transitions from uphill to flat sections, and during the transitions from flat or uphill to downhill sections.
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Affiliation(s)
- Simo Ihalainen
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden.,Research Institute for Olympic Sports, Jyväskylä, Finland
| | - Steffi Colyer
- Department for Health, University of Bath, Bath, United Kingdom
| | - Erik Andersson
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
| | - Kerry McGawley
- Swedish Winter Sports Research Centre, Department of Health Sciences, Mid Sweden University, Östersund, Sweden
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18
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Gløersen Ø, Gilgien M, Dysthe DK, Malthe-Sørenssen A, Losnegard T. Oxygen Demand, Uptake, and Deficits in Elite Cross-Country Skiers during a 15-km Race. Med Sci Sports Exerc 2020; 52:983-992. [PMID: 31738350 DOI: 10.1249/mss.0000000000002209] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE This study aimed to quantify the repeated oxygen deficits attained during intermittent endurance exercise by measuring oxygen consumption (V˙O2) and oxygen demand (V˙O2) throughout a simulated roller ski race. METHODS Eight male elite cross-country skiers (V˙O2peak, 77.4 ± 4.4 mL·kg⋅min) raced a 13.5-km roller ski time trial on a World Cup course. On two additional days, athletes completed (i) six submaximal loads (~5 min) and ~4-min maximal trial to establish athlete-specific estimates of skiing economy, V˙O2peak, and maximal ΣO2 (MAOD); and (ii) a simulation of the time trial on a roller skiing treadmill. During the simulation, external work rate (Pprop) and skiing speed (v) were adjusted to match the Pprop and v measured during the time trial, and pulmonary V˙O2 was measured breath by breath. V˙O2 and ΣO2 were calculated using an athlete-specific model for skiing economy throughout the treadmill simulation. RESULTS During the treadmill simulation, V˙O2 was on average 0.77 V˙O2peak, and active V˙O2 (i.e., excluding the time in simulated downhill) was on average 1.01 V˙O2peak. The athletes repeatedly attained substantial oxygen deficits in individual uphill sections of the treadmill simulation, but the deficits were typically small compared with their MAOD (average 14%, range ~0%-50%). However, the ΣO2 summed over all periods of active propulsion was on average 3.8 MAOD. CONCLUSION Athletes repeatedly attain substantial oxygen deficits in the uphill segments of a distance cross-country ski race. Furthermore, the total accumulated oxygen deficit of all these segments is several times higher than the athletes' MAOD. This suggests that the rapid recovery of the energy stores represented by the oxygen deficit is necessary during downhill sections, and that this might be an important determinant of distance skiing performance.
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Affiliation(s)
| | | | | | | | - Thomas Losnegard
- Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, NORWAY
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19
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Trøen E, Rud B, Karlsson Ø, Carlsen CH, Gilgien M, Paulsen G, Tosterud OK, Losnegard T. Pole Length's Influence on Performance During Classic-Style Snow Skiing in Well-Trained Cross-Country Skiers. Int J Sports Physiol Perform 2020; 15:884-891. [PMID: 32244223 DOI: 10.1123/ijspp.2019-0310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 09/02/2019] [Accepted: 09/30/2019] [Indexed: 11/18/2022]
Abstract
PURPOSE To investigate how self-selected pole length (PL) of ∼84% (PL84%) compared with ∼90% (PL90%) of body height influenced performance during a 700-m time trial with undulating terrain on snow. METHODS Twenty-one cross-country skiers, 7 of whom were women, performed 4 trials at a maximal effort in a counterbalanced fashion with PL84% and PL90% separated by 20-minute breaks between trials. In trials I and II, only double poling was allowed, while in trials III and IV, skiers used self-selected classical subtechniques. Continuous speed, cyclic parameters, and heart rate were collected using microsensors in addition to a post-time-trial rating of perceived exertion (RPE). RESULTS The 700-m times with only double poling were significantly shorter with PL90% than PL84% (mean ± 95% confidence limits -1.6% ± 1.0%). Segment analyses showed higher speed with PL90% in uphill sections than with PL84% (3.7% ± 2.1%), with the greatest difference found for the female skiers (5.6% ± 2.9%). In contrast, on flat terrain at high skiing speeds, speed was reduced with PL90% compared with PL84% (-1.5% ± 1.4%); this was only significant for the male skiers. During free choice of classical subtechniques, PL did not influence performance in any segments, choice of subtechnique, or cycle rate during the trials. No differences in rating of perceived exertion or heart rate between PLs were found. CONCLUSIONS PL90% improved performance in uphills at low speeds when using double poling but hindered performance on flat terrain and at higher speeds compared with self-selected PLs. Choice of PL should, therefore, be based on racecourse topography, preferred subtechniques, and the skier's physiological and technical abilities.
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20
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The Interval-Based Physiological and Mechanical Demands of Cross-Country Ski Training. Int J Sports Physiol Perform 2019; 14:1371-1377. [PMID: 30958055 DOI: 10.1123/ijspp.2018-1007] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 03/10/2019] [Accepted: 03/18/2019] [Indexed: 11/18/2022]
Abstract
PURPOSE To investigate fluctuations in speed, work rate, and heart rate (HR) when cross-country ski skating across varying terrains at different endurance-training intensities. METHODS Seven male junior Norwegian skiers performed maximal-speed (Vmax) tests in both flat and uphill terrains. Thereafter, 5-km sessions at low (LIT), moderate (MIT), and high intensity (HIT) were performed based on their own perception of intensity while monitored by a global navigation satellite system with integrated barometry and accompanying HR monitor. RESULTS Speed, HR, and rating of perceived exertion gradually increased from LIT to MIT and HIT, both for the total course and in flat and uphill terrains (all P < .05). Uphill work rates (214 [24] W, 298 [27] W, and 350 [54] W for LIT, MIT, and HIT, respectively) and the corresponding percentage of maximal HR (79.2% [6.1]%, 88.3% [2.4]%, and 91.0% [1.7]%) were higher than in flat terrain (159 [16] W, 206 [19] W, and 233 [72] W vs 72.3% [6.3]%, 83.2% [2.3]%, and 87.4% [2.0]% for LIT, MIT, and HIT, respectively) (all P < .01). In general, ∼13% point lower utilization of maximal work rate was reached in uphill than in flat terrain at all intensities (all P < .01). CONCLUSIONS Cross-country ski training across varying terrains is clearly interval based in terms of speed, external work rate, and metabolic intensity for all endurance-training intensities. Although work rate and HR were highest in uphill terrain at all intensities, the utilization of maximal work rate was higher in flat terrain. This demonstrates the large potential for generating external work rate when uphill skiing and the corresponding downregulation of effort due to the metabolic limitations.
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21
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Losnegard T. Energy system contribution during competitive cross-country skiing. Eur J Appl Physiol 2019; 119:1675-1690. [PMID: 31076890 PMCID: PMC6647095 DOI: 10.1007/s00421-019-04158-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/03/2019] [Indexed: 10/28/2022]
Abstract
Energy system contribution during cross-country (XC) skiing races is dependent on several factors, including the race duration, track profile, and sub-techniques applied, and their subsequent effects on the use of the upper and lower body. This review provides a scientific synopsis of the interactions of energy system contributions from a physiological, technical, and tactical perspective. On average, the aerobic proportion of the total energy expended during XC skiing competitions is comparable to the values for other sports with similar racing times. However, during both sprint (≤ 1.8 km) and distance races (≥ 10 and 15 km, women and men, respectively) a high aerobic turnover interacts with subsequent periods of very high work rates at ~ 120 to 160% of VO2peak during the uphill sections of the race. The repeated intensity fluctuations are possible due to the nature of skiing, which involves intermittent downhills where skiers can recover. Thus, the combination of high and sustained aerobic energy turnover and repeated work rates above VO2peak, interspersed with short recovery periods, distinguishes XC skiing from most other endurance sports. The substantially increased average speed in races over recent decades, frequent competitions in mass starts and sprints, and the greater importance of short periods at high speeds in various sub-techniques, have demanded changes in the physiological, technical, and tactical abilities needed to achieve world-class level within the specific disciplines.
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Affiliation(s)
- Thomas Losnegard
- Department of Physical Performance, Norwegian School of Sport Sciences, Ullevål Stadion, Post box 4014, 0806, Oslo, Norway.
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