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Roller skis' rolling resistance and grip characteristics: influences on physiological and performance measures in cross-country skiers
Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski with a μS similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a (similar) higher μS.The part of the thesis which focused on skiing economy and efficiency as a function of skill, age and gender, showed that the elite cross-country skiers had better skiing economy and higher gross efficiency (5-18 %) compared with the recreational skiers, and the senior elite had better economy and higher efficiency (4-5 %) than their junior counterparts, while no differences could be found between the genders.

Abstract [sv]

Syftet med denna avhandling var att undersöka fristils- och klassiska rullskidors rullmotståndskoefficienter (μR) och klassiska rullskidors statiska friktionskoefficienter (μS) samt effekter av olika μR och μS på längdskidåkares prestation vid rullskidåkning på rullande band. Syftet var även att undersöka s.k. åkekonomi och mekanisk verkningsgrad mellan motionärer och kvinnliga och manliga junior- och seniorlängdskidåkare på elitnivå.Experimenten visade att under en period av 30 minuters kontinuerligt rullande, på rullande band, så sjönk μR signifikant (p<0.05) till 60-65 % och 70-75 % av initiala värden, för fristils- respektive klassiska rullskidor. Undersökandet av olika normalkrafter, hastigheter och lutningars påverkan på μR resulterade i en signifikant, negativ korrelation för μR som funktion av normalkraft, medan olika hastigheter och lutningar endast medförde små förändringar av μR.Studien som undersökte fysiologiska effekter av olika μR visade, vid submaximala konstanta arbetsbelastningar, att yttre effekt, syreupptagning, hjärtfrekvens och blodlaktat förändrades signifikant vid ~50 % förändring av μR. Försökspersonernas frekvens och sträcka per frekvens samt skattning av upplevd ansträngning resulterade dock i mestadels icke signifikanta eller små förändringar. Protokollen med successivt ökande arbetsbelastning (maxtest) resulterade i signifikant förändrad tid till utmattning, vid ~50 % förändring av μR. Detta inträffade utan signifikant skillnad i maximal syreupptagning, hjärtfrekvens och blodlaktat, vilket även mestadels gällde för skattning av upplevd ansträngning.Experimenten som undersökte klassiska rullskidors μS visade att dessa erhöll värden som är fem till åtta gånger högre än vad som rapporterats från studier av μS på snö med fästvallade skidor.Den efterföljande studien som undersökte fysiologiska och biomekaniska influenser av olika μS visade, vid submaximala konstanta arbetsbelastningar, att åkekonomin försämrades (~14 % högre syreförbrukning), hjärtfrekvensen ökade, den framåtdrivande kraften från benen på rullskidorna minskade samt att det blev kortare tid till utmattning (~30 %), vid maxtest, när skidåkarna använde rullskidor med en μS i likhet med vad som rapporterats för skidåkning på snö. För arbetsförsöken med olika rullskidor av olika fabrikat med en högre, och likartad, μS förelåg ingen skillnad i de undersökta variablerna.Studien som undersökte åkekonomi och mekanisk verkningsgrad som funktion av prestationsnivå, ålder och kön, visade att elitskidåkarna hade bättre åkekonomi och verkningsgrad (5-18 %) i jämförelse med motionärerna, att seniorerna hade bättre åkekonomi och verkningsgrad (4-5 %) än juniorerna och att ingen skillnad kunde konstateras mellan könen.

Place, publisher, year, edition, pages
Östersund: Mid Sweden University , 2012.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 125
Keyword [en]
Adjustable grip, blood lactate, centre of pressure, cycle length, cycle rate, economy, efficiency, friction coefficient, heart rate, normal force, OBLA, oxygen uptake, power, ratcheted wheel, ratings of perceived exertion, roller skis, rolling resistance, tangential force, time to exhaustion
National Category
Sport and Fitness Sciences Physiology Mechanical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-16446ISBN: 978-91-87103-15-5 (print)OAI: oai:DiVA.org:miun-16446DiVA: diva2:533614
Supervisors
Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2012-08-01Bibliographically approved
List of papers
1. Rolling resistance for treadmill roller skiing
Open this publication in new window or tab >>Rolling resistance for treadmill roller skiing
2008 (English)In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 11, no 1, 23-29 p.Article in journal (Refereed) Published
Abstract [en]

Modern treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical performance under laboratory conditions using classical and freestyle techniques on roller skis. The differences in performance between tests are quite small for elite athletes, and it is therefore of great importance to control the rolling resistance of the roller skis. Otherwise different physiological tests cannot be accurately compared.

This study shows that during a warm-up period of  30 minutes the coefficient of rolling resistance (µR) decreases to about 60-65% and 70-75% of its initial value for freestyle and classical roller skis respectively.

Simultaneous measurements of temperature and µR shows that stabilized rolling resistance corresponds to a certain running temperature for a given normal force on the roller ski.

Tests were also performed on the influence on µR of normal force, velocity and inclination. Normal forces produced significant influence on µR , while different velocities and inclinations of the treadmill only resulted in small changes in µR.

Place, publisher, year, edition, pages
Springer, 2008
Keyword
Incline, Normal force, Roller skis, Velocity, Warm up, Sport science, Sport technology, Idrottsvetenskap, Sportteknologi
National Category
Mechanical Engineering Physiology Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-6361 (URN)10.1007/s12283-008-0004-1 (DOI)4197 (Local ID)4197 (Archive number)4197 (OAI)
Projects
Sportstech
Available from: 2008-11-19 Created: 2008-11-19 Last updated: 2012-06-14Bibliographically approved
2. Roller ski rolling resistance and its effects on elite athletes’ performance
Open this publication in new window or tab >>Roller ski rolling resistance and its effects on elite athletes’ performance
2009 (English)In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 11, no 3, 143-157 p.Article in journal (Refereed) Published
Abstract [en]

Modern ski-treadmills allow cross-country skiers, biathletes and ski-orienteers to test their physical fitness in a laboratory environment whilst performing classical and freestyle (skating) techniques on roller skis. For elite athletes, the differences in performance between test occasions are quite small, thus emphasising the importance of knowing the roller skis’ rolling resistance in order to allow the correct comparison between the results of different test occasions. In this study, the roller skis’ rolling resistance was measured on the ski-treadmill’s surface using a roller ski rolling resistance measurement system specially produced for this purpose. The study investigated the influence of significant changes in rolling resistance on physiological variables. The results showed that during submaximal exercise, power, oxygen uptake, heart rate and blood lactate were significantly changed by different rolling resistances, while there were no significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed by different rolling resistances and this occurred without significant changes in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion were insignificant or small.

 

Place, publisher, year, edition, pages
Paris: Springer, 2009
Keyword
Rolling resistance, roller skis, power, oxygen uptake, Blood lactate - Heart rate - Oxygen uptake - Power - Rolling resistance - Time to exhaustion, Sports science, Sports Technology, Idrottsvetenskap, Sportteknologi
National Category
Mechanical Engineering Physiology Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-7924 (URN)10.1007/s12283-009-0016-5 (DOI)2-s2.0-67349230301 (Scopus ID)978-2-287-99056-4 (ISBN)978-2-287-99055-7 (ISBN)
Available from: 2009-01-05 Created: 2009-01-05 Last updated: 2016-09-26Bibliographically approved
3. Skiing economy and efficiency in recreational and elite cross-country skiers
Open this publication in new window or tab >>Skiing economy and efficiency in recreational and elite cross-country skiers
2013 (English)In: Journal of Strength and Conditioning Research, ISSN 1064-8011, E-ISSN 1533-4287, Vol. 27, no 5, 1239-1252 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this study was to investigate and compare skiing economy and gross efficiency in cross-country skiers of different performance levels, ages and genders; male recreational skiers and elite senior and junior cross-country skiers of both genders. The skiers performed tests involving roller skiing on a treadmill using the gear 3 and diagonal stride techniques. The elite crosscountry skiers were found to have better skiing economy and higher gross efficiency (5-18%) compared with the recreational skiers (p < 0.05) and the senior elite had better economy and higher efficiency (4-5%) than their junior counterparts (p < 0.05), whereas no differences could be found between the genders. Also, large ranges in economy and gross efficiency were found in all groups. It was concluded that, in addition to v̇O2peak, skiing economy and gross efficiency have a great influence on the differences in performance times between recreational and junior and senior elite cross-country skiers, as well as between individual skiers within the different categories. Thus, we recommend crosscountry skiers at all performance levels to test not only v̇O2peak, but also skiing economy and efficiency.

Keyword
OBLA, oxygen uptake, power, roller skis, VO2
National Category
Sport and Fitness Sciences Physiology
Identifiers
urn:nbn:se:miun:diva-16442 (URN)10.1519/JSC.0b013e31824f206c (DOI)000318479500010 ()22344058 (PubMedID)2-s2.0-84878040331 (Scopus ID)
Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2017-12-07Bibliographically approved
4. An experimental study to compare the grip of classical style roller skis with on-snow skiing
Open this publication in new window or tab >>An experimental study to compare the grip of classical style roller skis with on-snow skiing
2013 (English)In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 16, no 2, 115-122 p.Article in journal (Refereed) Published
Abstract [en]

Cross-country skiers use roller skis for their snow-free training with the aim of imitating skiing on snow. Also, exercise laboratories evaluate the biomechanics and physiology of cross-country skiing using roller skis on a treadmill. The roller skis on the market that are constructed for use in the classical style are equipped with a front and a back wheel, one of which has a ratchet to enable it to grip the surface when diagonal striding and kick double poling (static friction). The aim of this study was to investigate static friction coefficients (μS) of ratcheted wheel roller skis, and compare the results to the μS reported from skiing on snow with grip-waxed cross-country skis. Also, a new type of roller ski with a camber and adjustable grip function was evaluated. The results showed that ratcheted wheel roller skis, on a treadmill rubber mat and on dry and wet asphalt surfaces, reached μS values that were five to eight times greater than the values reported from on-snow skiing with grip-waxed cross-country skis. For the roller skis with a camber and adjustable grip function, the μs could be varied from no grip at all up to the level of the tested ratcheted wheel roller skis.

Keyword
Asphalt, adjustable grip, camber, ratcheted wheel, static friction coefficient, treadmill rubber mat
National Category
Sport and Fitness Sciences Physiology Mechanical Engineering
Identifiers
urn:nbn:se:miun:diva-16443 (URN)10.1007/s12283-012-0108-5 (DOI)2-s2.0-84878107284 (Scopus ID)
Note

Published online 6 january 2013.

Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2017-12-07Bibliographically approved
5. The influence of grip on oxygen consumption and leg forces when using classical style roller skis
Open this publication in new window or tab >>The influence of grip on oxygen consumption and leg forces when using classical style roller skis
2014 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 24, no 2, 301-310 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this study was to investigate the influence of classical style roller skis' grip (static friction coefficients, μ S) on cross-country skiers' oxygen consumption and leg forces during treadmill roller skiing, when using the diagonal stride and kick double poling techniques. The study used ratcheted wheel roller skis from the open market and a uniquely designed roller ski with an adjustable camber and grip function. The results showed significantly (P≤0.05) higher oxygen consumption (∼14%), heart rate (∼7%), and lower propulsive forces from the legs during submaximal exercise and a shorter time to exhaustion (∼30%) in incremental maximal tests when using roller skis with a μ S similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a similar, higher μ S. Thus, we concluded that oxygen consumption (skiing economy), propulsive leg forces, and performance time are highly changed for the worse when using roller skis with a lower μ S, such as for on-snow skiing with grip-waxed cross-country skis, in comparison to ratcheted wheel roller skis with several times higher μ S.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014
Keyword
adjustable grip, center of pressure, normal and tangential forces, ratcheted wheel, skiing economy, static friction
National Category
Sport and Fitness Sciences Mechanical Engineering Physiology
Identifiers
urn:nbn:se:miun:diva-16445 (URN)10.1111/sms.12006 (DOI)000332982700011 ()2-s2.0-84896404410 (Scopus ID)
Note

Published online 28 sep 2012

Available from: 2012-06-14 Created: 2012-06-14 Last updated: 2017-12-07Bibliographically approved

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