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Double Poling Incross-Country Skiing: Biomechanical and Physiological Analysis of Sitting and Standing Positions
Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.ORCID iD: 0000-0001-5317-2779
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Double poling (DP) is a sub-technique in cross-country skiing that has increased in interest over the last decades, e.g. athletes in cross-country skiing have increased their utilisation of double poling during competitions. In cross-country sit-skiing athletes with impairments in legs and/or trunk sit in a sledge and utilise DP to propel themselves. Technique (i.e. movement pattern) is one key factor determining performance but also a factor that may affect the risk of overuse injuries in sports.

Therefore, the overall aim of the thesis was to improve the understanding of the human movement technique in cross-country skiing DP, in both standing (paper I-II) and sitting positions (paper III-IV, Thesis A-B) using biomechanical and physiological measurements and inverse dynamics simulations. All studies were carried out on a double poling ergometer in laboratory. Three experimental studies were performed with able-bodied participants (papers I-II, IV-VI), one study with one participant with growth defect in the legs (paper III), and one study (Thesis B) with one participant with complete spinal cord injury at thoracic vertebra 4.

In paper I the first full-body simulation of DP was performed and results were comparable to results found in literature when the kinematics and external kinetics were similar. Paper II showed how increased leg utilisation increased performance (forward impulse) but reduced skiing efficiency (output work divided by metabolic muscle work). These results indicate that both high performance (power output) and efficiency may not be achieved in the same technique.

In sitting DP many different sitting positions are utilised. Athletes with full muscle control in hip and trunk mainly sit with their knees lower than their hips (KLnoS). Athletes with paralysis in lower trunk and legs need trunk stability from the sit-ski. Most often, this is achieved by adopting a knees higher than hips (KH) position together with a support for the lower back. However, this position might induce large flexion in the spine, which is hypothesised to affect injury risk in the shoulders and lower back. This thesis has enabled the knees low sitting position for athletes with paralysis in the lower trunk and legs by supporting the anterior trunk with the sledge (KL).

 

In sitting DP in athletes with full hip and trunk muscle control, high performance was achieved through proximal-distal sequencing from the hips through the trunk to the arms, and large muscle work in spine and legs (IV, V, Thesis A). In order of performance, KLnoS utilised muscles in the hips-spine-arms, compared with utilisation of spine-arms in KH, and mainly arms in KL. Higher amount of activated muscle mass resulted in lower relative anaerobic metabolism during submaximal exercise (IV).

The lower back joint reactions were higher for the sitting position with larger spinal flexion, KH compared to KL (VI). These results suggest that there is an increased risk of injury in the lower back for the sitting position KH. Athletes with paraplegia generally have a high risk of injuries in the shoulders. The results of this thesis showed higher shoulder joint reactions in the sitting position with larger shoulder-arm muscle work, in KL compared to KH.

For the case study with one participant with thoracic spinal cord injury (Thesis B) highest performance was achieved in the KH sitting position where spinal flexion occurred at the beginning of the poling phase. When comparing the fixed trunk positions KL and KHS, higher performance was achieved in KHS. It was speculated that the difference between KL and KHS was due to the impairment of the vasoconstriction in paralysed muscles. The effect of gravity on venous pooling is probably larger when the legs are lower down as in KL. This effect was not present for individuals without paralysis (III), where KL was more economical than KHS.

Parasport classification needs evidence of how impairment affects sporting performance (Tweedy et al., 2014, Tweedy and Vanlandewijck, 2011). Classification might benefit from simulations as performed in this thesis. The musculoskeletal simulations of seated DP in paper V and the KLnoS position presented in the thesis have showed the relative contribution of different muscle groups on performance. These results are novel and might contribute to improvement of the classification system.

Abstract [sv]

Stakning är en delteknik inom längdskidåkning som har ökat i intresse de senaste årtiondena, bland annat har eliten ökat andelen stakning markant. Längdskidåkning i sit-ski utövas av individer med funktionsnedsättning i benen och/eller bålen. I denna sport används stakning uteslutande för att ta sig framåt. Tekniken, eller rörelsemönstret, är en faktor för prestation inom dessa sporter. Tekniken kan också påverka risken för överbelastningsskador.

Denna avhandling har studerat stakning med det övergripande målet att utöka förståelsen för tekniken i både stående (artikel I-II) och sittande positioner (artikel III-VI samt resultat i avhandlingen A-B). Tekniken har studerats med hjälp av biomekaniska och fysiologiska mätningar i laboratorium samt muskuloskelettära simuleringar. Tre experimentella studier har genomförts med försökspersoner utan funktionsnedsättningar. Två studier har genomförts med försökspersoner med funktionsnedsättningar,  en studie med en försöksperson med tillväxtstörning (förkortade ben) och en studie med en försöksperson med en fullständig ryggmärgsskada vid bröstkota 4.

Artikel I-II visade att stående stakningsteknik med böjda knän ökar prestationen under ett 30 s maximalt test. Med mer böjda ben ökas det metabola muskulära arbetet (beräknat genom simuleringar) och verkningsgraden av det muskuloskelettära systemet minskar jämfört med stakning med raka ben. Denna studie visar exempel på att samma teknik inte uppnådde både högst prestation och effektivitet.

En person med förlamning i nedre delen av bålen och benen behöver stabilitet för bålen av sin sit-ski. Detta uppnås vanligtvis genom att placera knän högre än höfterna (KH). Dock kan denna position skapa en stor flexion i ryggraden, vilket är en risk för skador i ländrygg och axlar. För personer med full muskelfunktion i höft och bål är den vanligaste sittposition knäsittande (KLnoS). Denna avhandling har möjliggjort knäsittande sittposition för personer med förlamning i nedre delen av bålen och benen genom ett stöd framifrån för bröstkorgen i sit-skin (KL).

För sittande positioner för personer utan nedsatt muskelfunktion i höft och bål påvisas att högst prestation uppnås när störst andel muskelmassa arbetar och rörelseomfånget i höft och ryggrad är störst, knän lägre än höft och utan stöd för bålen från sit-skin (KLnoS) (A). När arbetande muskelmassa minskar, minskar också prestationen. Prestationen var lägre i sittposition med knän högre än höfterna (KH) och än lägre i sittposition knän lägre än höft och med ett stöd för bröstkorgen från sit-skin (KL) (IV,V). Med lägre andel aktiv muskelmassa så ökade det relativa anaeroba metabola arbetet, medan det absoluta aeroba metabola arbetet och gross-efficiency (GE) var liknande. Sitt-positionen KH visade på högre flexion av ryggraden, högre metabolt muskelarbete i bålen och högre ledreaktionskrafter i ländryggen, medan sittpositionen KL visade på högre metabolt muskelarbete i axlar och armar och högre ledreaktionskrafter i axlarna (VI). Högre reaktionskraft i ländryggen kan vara kopplat till högre risk för överbelastningskada.

För en försöksperson med förlamning från revbenen och nedåt, var också prestationen högre när bröstkorgens position ej var fix, högre i KH jämfört med KL och knän högre än höft och ett bröststöd (KHS) (B). Resultaten visar också att det inte bara är biomekaniken som påverkar prestationen. I sittpositionerna där bröstkorgens position var fix, KHS och KL, böjdes ryggen bakåt vid stakfasen start och prestationen var högre i KHS. Avhandlingen diskuterar att prestationen påverkas av att låg position av benen medför ökad effekt av gravitationen på blodflödet. Denna effekt blir stor eftersom förlamad muskulatur också har nedsatt funktion av venernas pumpförmåga att återföra blodet till hjärtat. För en person utan förlamningen i benen visade sig det omvända, sittpositionen KL vara mer ekonomisk än sittposition KHS (III).

Sammanfattningsvis, denna avhandling har visat på att flera faktorer för att välja teknik inom stående stakning och sittposition inom sittande längdskidåkning i sit-ski. Samma teknik är inte optimal för alla individer. För stående indikeras att både ökad prestation och verkningsgrad inte uppnås när benen arbetar mer. För sittande är det viktigt att använda sig av höften och bålens muskelarbete och inte sitta fast varken för mycket eller för lite i sit-skin. Avhandlingen visar exempel på att en person med förlamning i nedre bål och ben, har fördel av bålrörelse trots sin förlamning och att benens position påverkar prestationen.

Klassificering inom parasport ska bedöma hur funktionsnedsättningen påverkar idrottsprestationen. Simuleringsmetoderna som använts i denna avhandling kan vara av intresse för utveckling av klassificeringssystem eftersom de har visat hur olika muskelgrupper påverkar prestationen.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2018. , p. 95
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 275
Keyword [en]
blood lactate concentration, cross-country sit-skiing, impairment, internal kinetics, inverse dynamics simulations, joint reaction forces, kinematics, metabolic rate, musculoskeletal modelling, musculoskeletal efficiency, nordic skiing, oxygen uptake, para-skiing, respiration, skiing efficiency.
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:miun:diva-32733ISBN: 978-91-88527-38-7 (print)OAI: oai:DiVA.org:miun-32733DiVA: diva2:1181248
Public defence
2018-03-02, Q221, Kunskapens väg 8, Östersund, 11:00 (English)
Opponent
Supervisors
Note

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 inskickat, delarbete 6 inskickat.

At the time of the doctoral defence the following papers were unpublished: paper 5 submitted, paper 6 submitted.

Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-02-08Bibliographically approved
List of papers
1. A Musculoskeletal Full‐body Simulation of Cross‐Country Skiing
Open this publication in new window or tab >>A Musculoskeletal Full‐body Simulation of Cross‐Country Skiing
2008 (English)In: Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, ISSN 1754-3371, Vol. 222, no P1, p. 11-22Article in journal (Refereed) Published
Abstract [en]

This paper presents a measurement-driven, musculoskeletal, full-body simulation model for biomechanical analysis of the double-poling (DP) technique in cross-country skiing. DP is a fast and powerful full-body movement; therefore, it is interesting to examine whether inverse dynamics using static optimization is working for a musculoskeletal full-body model with high accelerations, a large range of motion, and realistic loads. An experiment was carried out to measure motion and pole force of a skier on a double-poling ergometer. Using the measurement data, a simulation model was implemented in the AnyBody Modeling System (AnyBody Technology A/S, Denmark). Experimental results of motion and pole force from the DP ergometer, and also simulation results of relative muscle force profiles, are presented. These results agree with results found in literature when the kinematics and external kinetics are similar. Consequently, it should be possible to use computer simulations of this type for cross-country skiing simulations. With a simulation model, it is possible to perform optimization studies and to ask and answer ‘what if’ questions. Solutions to such problems are not easy to obtain by traditional testing alone.

Place, publisher, year, edition, pages
London: The Institution of Mechanical Engineers, 2008
Keyword
biomechanics, double poling, ergometer, inverse dynamics
National Category
Computational Mathematics
Identifiers
urn:nbn:se:miun:diva-9934 (URN)10.1243/17543371JSET10 (DOI)000207664600003 ()2-s2.0-84990348576 (Scopus ID)
Projects
Nationellt vintersportcentrum
Available from: 2009-09-29 Created: 2009-09-29 Last updated: 2018-02-08Bibliographically approved
2. Skiing efficiency versus performance in double-poling ergometry
Open this publication in new window or tab >>Skiing efficiency versus performance in double-poling ergometry
2013 (English)In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 16, no 9, p. 987-992Article in journal (Refereed) Published
Abstract [en]

This study is on how leg utilisation may affect skiing efficiency andperformance in double-poling ergometry. Three experiments wereconducted, each with a different style of the double-poling technique:traditional with small knee range-of-motion and fixed heels (TRAD);modern with large knee range-of-motion and fixed heels (MOD1) and modernwith large knee range-of-motion and free heels (MOD2). For each style,motion data were extracted with automatic marker recognition ofreflective markers and applied to a 3D full-body musculoskeletalsimulation model. Skiing efficiency (skiing work divided by metabolicmuscle work) and performance (forward impulse) were computed from thesimulation output. Skiing efficiency was 4.5%, 4.1% and 4.1% for TRAD,MOD1 and MOD2, respectively. Performance was 111, 143 and 149Ns forTRAD, MOD1 and MOD2, respectively. Thus, higher lower body utilisationincreased the performance but decreased the skiing efficiency. Theseresults demonstrate the potential of musculoskeletal simulations forskiing efficiency estimations.

Keyword
AnyBody Modeling System, AviMes AD, biomechanics, cross-country skiing, impulse, musculoskeletal simulation
National Category
Sport and Fitness Sciences Other Engineering and Technologies not elsewhere specified Applied Mechanics
Identifiers
urn:nbn:se:miun:diva-15585 (URN)10.1080/10255842.2011.648376 (DOI)000324612300008 ()2-s2.0-84887953209 (Scopus ID)
Projects
Swedish Winter Sports Research Centre
Available from: 2011-12-20 Created: 2011-12-20 Last updated: 2018-02-08Bibliographically approved
3. The influence of sitting posture on mechanics and metabolic energy requirements during sit-skiing: a case report
Open this publication in new window or tab >>The influence of sitting posture on mechanics and metabolic energy requirements during sit-skiing: a case report
Show others...
2016 (English)In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 19, no 3, p. 213-218Article in journal (Refereed) Published
Abstract [en]

Several different sitting postures are used in Paralympic cross-country sit-skiing. The aim of this study was to evaluate the impact of sitting posture on physiological and mechanical variables during steady-state double-poling sit-skiing, as well as to determine how seat design can be improved for athletes without sufficient trunk control. Employing a novel, custom-designed seat, three trunk positions were tested while performing double-poling with submaximal oxygen consumption on an ergometer. Cycle kinematics, pole forces, and oxygen consumption were monitored. The athlete performed best, with longer cycle length and less pronounced metabolic responses, when kneeling with the trunk resting on a frontal support. For this case, a forward leaning trunk with knees below the hip joint was interpreted as most optimal, as it showed lower oxygen consumption and related parameters of performance during cross-country sit-skiing. Further investigations should examine whether such improvement is dependent on the level of the athlete’s handicap, as well as whether it is also seen on snow.

Keyword
Biomechanics, Oxygen consumption, Poling force, Seat, Sit-ski
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-28014 (URN)10.1007/s12283-016-0209-7 (DOI)000387943300010 ()2-s2.0-84982712590 (Scopus ID)
Available from: 2016-06-20 Created: 2016-06-20 Last updated: 2018-02-08Bibliographically approved
4. Sitting position affects performance in cross-country sit-skiing
Open this publication in new window or tab >>Sitting position affects performance in cross-country sit-skiing
2017 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 6, p. 1095-1106Article in journal (Refereed) Published
Abstract [en]

Purpose: In cross-country sit-skiing (XCSS), athletes with reduced trunk control predominantly sit with the knees higher than the hips (KH); a position often associated with large spinal flexion. Therefore, to improve spinal curvature a new sledge with frontal trunk support, where knees are lower than hips (KL) was created. It was hypothesized that the KL position would improve respiratory function and enhance performance in seated double-poling compared to KH.

Methods: Ten female able-bodied cross-country skiers (age 25.5 ± 3.8 years, height 1.65 ± 0.05 m, mass 61.1 ± 6.8 kg) completed a 30 s all-out test (WIN), a submaximal incremental test including 3–7 3 min loads (SUB) and a maximal 3 min time trial (MAX) in both KL and KH positions. During SUB and MAX external power, pole forces, surface electromyography, and kinematics were measured. Metabolic rates were calculated from oxygen consumption and blood lactate concentrations.

Results: KL reduced spinal flexion and range of motion at the hip joint and indicated more muscle activation in the triceps. Performance (W kg−1) was impeded in both WIN (KH 1.40 ± 0.30 vs. KL 1.13 ± 0.33, p < 0.01) and MAX (KH 0.88 ± 0.19 vs. KL 0.67 ± 0.14, p < 0.01). KH resulted in higher gross efficiency (GE) and lower lactate concentration, anaerobic metabolic rate, and minute ventilation for equal power output.

Conclusions: The new KL position can be recommended due to improved respiratory function but may impede performance. Generalization of results to XCSS athletes with reduced trunk muscle control may be limited, but these results can serve as a control for future studies of para-athletes.

Keyword
Biomechanics, Metabolic rate, Respiratory function, Oxygen uptake
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-30592 (URN)10.1007/s00421-017-3596-y (DOI)000401025200004 ()2-s2.0-85017125246 (Scopus ID)
Note

Forskningsfinansiärer

Stiftelsen Promobilia 

Rolf & Gunilla Enströms stiftelse

Erratum 

European Journal of Applied PhysiologyVolume 117, Issue 10, 1 October 2017, Pages 2123-2124  DOI: 10.1007/s00421-017-3694-x

Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2018-02-08Bibliographically approved
5. Descriptive comparison of three technique analysis methods in the context of cross-country sit-skiing: energy expenditure and gross efficiency, descriptive biomechanics and musculoskeletal simulations
Open this publication in new window or tab >>Descriptive comparison of three technique analysis methods in the context of cross-country sit-skiing: energy expenditure and gross efficiency, descriptive biomechanics and musculoskeletal simulations
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In parasports, technique analysis on how impairments and equipment affects athletic performance is important for classification. The purpose of this study was to compare three quantitative technique analysis methods: energy expenditure and gross efficiency, descriptive biomechanics, and musculoskeletal simulations for two cross-country sit-skiing sitting positions. These are: 1) knees higher than hips (KH) and 2) knees lower than hips with a frontal trunk support (KL).Five able-bodied cross-country skiers performed a sub-maximal incremental test and a 3 min maximal time-trial in each sitting position. During the tests, respiration, blood lactate concentrations, 3D full-body kinematics, pole forces and electromyography were measured.All three methods complement each other and by different parameters they all indicate superior technique in KH. Descriptive biomechanics showed differences in movement pattern, larger hip and spine flexion in KH. The method of energy expenditure and gross-efficiency capture both physiology and technique, showing lower anaerobic metabolism in KH. The musculoskeletal simulations showed how different muscle groups contributed to performance, showing higher contribution from spine and less in arms for KH. This study indicated why and how performance was enhanced in the human-equipment interaction, which is important for parasport classification and competition rules.

Keyword
seated double poling, kinematics, kinetics, inverse dynamics simulations, musculoskeletal modelling
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-32812 (URN)
Note

Forskningsfinansiärer

Stiftelsen Promobilia

Rolf & Gunilla Enströms stiftelse

Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-02-08Bibliographically approved
6. Shoulder and lower back joint reaction forces in seated parasport cross-country sit-skiing
Open this publication in new window or tab >>Shoulder and lower back joint reaction forces in seated parasport cross-country sit-skiing
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Prevalence of over-use injuries in shoulders and lower back are hypothesized to be common in cross-country sit-skiing. Athletes with reduced trunk muscle control mainly sits with their knees higher than their hips (KH). To reduce spinal flexion, a position with knees lower than their hips (KL) was enabled for these athletes by a frontal trunk support. The aim of the study was to compare the shoulder joint (glenohumeral joint) and L4-L5 joint reactions between the sitting positions KL and KH.Five able-bodied female athletes performed submaximal and maximal exercise tests in the sitting positions KL and KH on a skiing ergometer. During the tests, pole forces and 3-D kinematics were measured. The data served as input to inverse-dynamics simulations (AnyBody Modeling System, Anybody Technology A/S, Aalborg, Denmark) that computed the shoulder and L4-L5 joint reactions.The results showed that the KH position was favorable for higher performance and lower shoulder joint reactions for female able-bodied athletes with full trunk control. The KL position instead, was favorable for lower L4-L5 joint reactions and might therefore be associated to lower risk of lower back injuries. These results suggest that both performance and safety parameters cannot be optimized in the same sit-ski.

Keyword
musculoskeletal modeling, inverse-dynamic simulations, muscular metabolic power
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-32813 (URN)
Note

Forskningsfinansiärer

Stiftelsen Promobilia

Rolf & Gunilla Enströms stiftelse

Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-02-08Bibliographically approved

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