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Biomechanical analysis of the herringbone technique as employed by elite cross-country skiers
Mittuniversitetet, Fakulteten för humanvetenskap, Avdelningen för hälsovetenskap. (Swedish Winter Sports Research Centre)
Mittuniversitetet, Fakulteten för humanvetenskap, Avdelningen för hälsovetenskap. (Swedish Winter Sports Research Centre)ORCID-id: 0000-0002-6685-1540
CeRiSM Research Center for Sport, Mountain and Health University of Verona Rovereto Italy.
Department of Human Movement Science Norwegian University of Science and Technology Trondheim Norway.
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2014 (Engelska)Ingår i: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, nr 3, s. 542-552Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This investigation was designed to analyse the kinematics and kinetics of cross-country skiing at different velocities with the herringbone technique on a steep incline. Eleven elite male cross-country skiers performed this technique at maximal, high, and moderate velocities on a snow-covered 15° incline. They positioned their skis laterally (25 to 30°) with a slight inside tilt and planted their poles laterally (8 to 12°) with most leg thrust force exerted on the inside forefoot. Although 77% of the total propulsive force was generated by the legs, the ratio between propulsive and total force was approximately fourfold higher for the poles. The cycle rate increased with velocity (1.20 to 1.60 Hz), whereas the cycle length increased from moderate up to high velocity, but then remained the same at maximal velocity (2.0 to 2.3 m). In conclusion, with the herringbone technique, the skis were angled laterally without gliding, with the forces distributed mainly on the inside forefoot to enable grip for propulsion. The skiers utilized high cycle rates with major propulsion by the legs, highlighting the importance of high peak and rapid generation of leg forces.

Ort, förlag, år, upplaga, sidor
Wiley-Blackwell, 2014. Vol. 24, nr 3, s. 542-552
Nyckelord [en]
Cycle characteristics, Cycle length, Cycle rate, Joint angles, Kinetics, Leg force, Pole force, Snow
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
URN: urn:nbn:se:miun:diva-18147DOI: 10.1111/sms.12026ISI: 000335984500020Scopus ID: 2-s2.0-84900796950OAI: oai:DiVA.org:miun-18147DiVA, id: diva2:583839
Tillgänglig från: 2013-01-08 Skapad: 2013-01-08 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Ingår i avhandling
1. PHYSIOLOGICAL AND BIOMECHANICAL FACTORS DETERMINING CROSS-COUNTRY SKIING PERFORMANCE
Öppna denna publikation i ny flik eller fönster >>PHYSIOLOGICAL AND BIOMECHANICAL FACTORS DETERMINING CROSS-COUNTRY SKIING PERFORMANCE
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

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.

Ort, förlag, år, upplaga, sidor
Östersund: Mittuniversitets tryckeri Sundsvall, 2016. s. 74
Serie
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 248
Nyckelord
cycle characteristics, energy cost, energy yield, incline, joint angles, kinematics, kinetics, mechanics, Nordic skiing, oxygen deficit, oxygen demand, technique transitions, total metabolic rate.
Nationell ämneskategori
Medicin och hälsovetenskap
Identifikatorer
urn:nbn:se:miun:diva-27898 (URN)978-91-88025-69-2 (ISBN)
Disputation
2016-06-10, Q221, Mittuniversitetet, Östersund, 13:00 (Engelska)
Opponent
Handledare
Anmärkning

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 inskickat

At the time of the doctoral defence the following papers were unpublished: paper 5 submitted

Tillgänglig från: 2016-06-13 Skapad: 2016-06-12 Senast uppdaterad: 2016-06-13Bibliografiskt granskad

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