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Publications (10 of 24) Show all publications
Hansen, E., Nordén, H. & Lund Ohlsson, M. (2019). Adolescents with intellectual disability (ID) and their perceptions of activity and sports. In: 12th European Public Health Congress, Marseille, France, 20-23 november 2019: Building bridges for solidarity and public health. Paper presented at 12th European Public Health Congress Marseille, France, 20-23 november 2019.
Open this publication in new window or tab >>Adolescents with intellectual disability (ID) and their perceptions of activity and sports
2019 (English)In: 12th European Public Health Congress, Marseille, France, 20-23 november 2019: Building bridges for solidarity and public health, 2019Conference paper, Oral presentation with published abstract (Refereed)
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-38722 (URN)
Conference
12th European Public Health Congress Marseille, France, 20-23 november 2019
Available from: 2020-03-26 Created: 2020-03-26 Last updated: 2020-03-26
Hansen, E., Nordén, H. & Lund Ohlsson, M. (2019). Adolescents with intellectual disability (ID) and their perceptions of activity and sports. In: LICE-2019: . Paper presented at London International Conference on Education (LICE-2019), London, Storbritannien, 9-11 november 2019.
Open this publication in new window or tab >>Adolescents with intellectual disability (ID) and their perceptions of activity and sports
2019 (English)In: LICE-2019, 2019Conference paper, Oral presentation with published abstract (Refereed)
Identifiers
urn:nbn:se:miun:diva-38723 (URN)
Conference
London International Conference on Education (LICE-2019), London, Storbritannien, 9-11 november 2019
Note

Elisabeth Hansen, additionnaly to giving an oral presentation, were Chair for Session 20 titled "Inclusive Education"

Available from: 2020-03-26 Created: 2020-03-26 Last updated: 2020-03-26Bibliographically approved
Lund Ohlsson, M., Danvind, J. & Holmberg, L. J. (2019). Estimation of muscle work in cross-country sit-skiing. In: : . Paper presented at VISTA 2019, Healthy and fit for optimal performance, 4-7 september, 2019, Amsterdam, The Netherlands.
Open this publication in new window or tab >>Estimation of muscle work in cross-country sit-skiing
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Introduction: In Nordic skiing all sitting athletes compete in the same event competition. The sitting positions differ between athletes. Most of the athletes sit knee-seated, or with their thighs tilted downward (KL) and free to move their trunk. Some athletes do not have the possibility to sit in that position and therefore adjust their sitting position. For example, athletes with reduced muscle control in hips and lower trunk sit with their knees higher than their hips (KH) to increase stability.

Purpose: The purpose of this study was to examine how sitting position KL and KH affects the muscular power.

Methods: One female able-bodied athlete performed one test session in each sitting position (KL and KH) comprising five times 3 minutes sub-maximal exercise and a maximal time-trial in a double-poling ergometer (ThoraxTrainer A/S, Denmark). During the tests 3D kinematics (Qualisys AB, Sweden), pole forces and power output were measured. From the measured data, participant and test specific musculo-skeletal inverse-dynamics simulation models were created using the AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark). From the simulations of submaximal exercise power output 37 W, 52 W and maximal time-trial the muscular metabolic power (mMP) was computed according to Holmberg (2013).

Results: The power output in maximal exercise was higher in KL (90.1 W) compared to KH (74.7 W). During both submaximal and maximal exercise, the total muscular metabolic power was larger in KL compared to KH (KL mean 861 W and KH mean 682 W). The muscular metabolic power also showed larger relative involvement of legs in KL (KL mean 18 % and KH mean 4 %) and larger relative involvement of arms and trunk in KH.

Conclusion: That sitting position KL compared to KH is related to higher performance for athletes without impairment in hips and trunk is known before (Gastaldi, 2012). However, the results from this study explains why performance is higher in KL, i.e. that larger muscular metabolic power are produced in the legs. This study also shows the size of the involvement of legs, which could be interesting for development of classification rules.

Keywords
Technique, Equipment, Muscular work, Inverse-dynamics simulations, Nordic skiing
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-38114 (URN)
Conference
VISTA 2019, Healthy and fit for optimal performance, 4-7 september, 2019, Amsterdam, The Netherlands
Note

Finansiär: Rolf och Gunilla Enströms stiftelse.

Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2019-12-19Bibliographically approved
Wedeking, D., Swarén, M., Danvind, J. & Lund Ohlsson, M. (2019). The influence of arm and ski pole during alpine skiing. In: : . Paper presented at VISTA 2019, Healthy and fit for optimal performance, Amsterdam, 4-7 september, 2019.
Open this publication in new window or tab >>The influence of arm and ski pole during alpine skiing
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

INTRODUCTION: Research investigating the correlation between impairment and key performance indicators in para-alpine skiing is needed for a future evidence based classification system (Tweedy and Vanlandewijck 2011). Only a little research in para-alpine skiing exists, especially in the standing classes LW5/7 and LW6/8 (impairment of one or two arms). The use of arms and poles affects performance in alpine skiing[OM1]  but how underlying biomechanical parameters as kinematics and kinetics are related to performance has to the authors knowledge not been studied before.

PURPOSE: The purpose of this study was to further the understanding of slalom skiing with two ski poles, one pole or without poles (c2, c1, c0) by investigating the biomechanical differences (kinematics and foot plantar pressure) for able-bodied athletes.

METHODS: Ten able-bodied right-handed junior skiers on national level were tested in three conditions - c0, c1, c2, while skiing a slalom course (28 gates, 62 m vertical drop). 3D kinematic data were collected at 200 Hz by 12 inertial motion units (Myomotion, Noraxon Inc, USA) placed on head, trunk, pelvis, arms and legs. Ski-time was measured with timing gates (XS Crystal Synchronization, Brower Timing Systems, USA) and kinetics were measured with pressure insoles (Pedar, Novel GmbH, Germany) placed inside each ski boot. Normal ground reaction force (nGRF) and relative force time integrals (relFTI) were calculated according to Melai et. Al (2011). Kinematics and plantar pressure were analysed over three right and left turns and averaged for each condition. Right turn and left turn were distinguished at the time point where the shank was standing vertical.

RESULTS: Time analysis showed that time increased with the use of less ski poles, mean difference between c1c2 of 1.27 ± 1.69 s (p=0.001) and between c0c1 of 0.73 ± 1.95 s (p=0.003[OM2] ). Kinematic analysis showed that different approaches were used to attack a slalom gate in condition c1 and c0, for example slalom-attack, giant slalom attack or opposite arm attack. Interquartile range and median of the body angles [OM3] differed between conditions, e.g. lower median (indicate less deviation from anatomical  basic position[OM4] ) in c0 and mostly lower than in c1 and c2. Furthermore, relFTI was related to the turning side (right or left turn) and showed largest asymmetry for condition c1.

CONCLUSION: Reduced balance due to missing ski pole/s lead to compensatory movements in the upper body and asymmetry in foot plantar pressure. This reduced the ability for a controlled turn. Whether or not only reduced balance or also the skiers low experience of skiing with reduced number of poles influenced the performance remains unclear.

REFERENCES

Melai, Tom, T. Herman IJzerman, Nicolaas C. Schaper, Ton L.H. de Lange, Paul J.B. Willems, Kenneth Meijer, Aloysius G. Lieverse, and Hans H.C.M. Savelberg. 2011. ‘Calculation of Plantar Pressure Time Integral, an Alternative Approach’. Gait & Posture 34 (3): 379–83. https://doi.org/10.1016/j.gaitpost.2011.06.005.

Tweedy, S. M., and Y. C. Vanlandewijck. 2011. ‘International Paralympic Committee Position Stand--Background and Scientific Principles of Classification in Paralympic Sport’. British Journal of Sports Medicine 45 (4): 259–69. https://doi.org/10.1136/bjsm.2009.065060.

Keywords
para-sports, alpine skiing, biomechanics, slalom
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-38116 (URN)
Conference
VISTA 2019, Healthy and fit for optimal performance, Amsterdam, 4-7 september, 2019
Note

Finansiär, Rolf och Gunilla Enströms stiftelse.

Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2019-12-18Bibliographically approved
Lund Ohlsson, M. (2018). Double Poling Incross-Country Skiing: Biomechanical and Physiological Analysis of Sitting and Standing Positions. (Doctoral dissertation). Sundsvall: Mid Sweden University
Open this publication in new window or tab >>Double Poling Incross-Country Skiing: Biomechanical and Physiological Analysis of Sitting and Standing Positions
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
Keywords
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:nbn:se:miun:diva-32733 (URN)978-91-88527-38-7 (ISBN)
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: 2018-03-23Bibliographically approved
Lund Ohlsson, M., Danvind, J. & Holmberg, L. J. (2018). Shoulder and Lower Back Joint Reaction Forces in Seated Double Poling. Journal of Applied Biomechanics, 34(5), 369-376
Open this publication in new window or tab >>Shoulder and Lower Back Joint Reaction Forces in Seated Double Poling
2018 (English)In: Journal of Applied Biomechanics, ISSN 1065-8483, E-ISSN 1543-2688, Vol. 34, no 5, p. 369-376Article in journal (Refereed) Published
Abstract [en]

Overuse injuries in the shoulders and lower back are hypothesized to be common in cross-country sit-skiing. Athletes with reduced trunk muscle control mainly sit with the knees higher than the hips (KH). To reduce spinal flexion, a position with the knees below the hips (KL) was enabled for these athletes using a frontal trunk support. The aim of the study was to compare the shoulder joint (glenohumeral joint) and L4-L5 joint reactions of the KL and KH sitting positions. Five able-bodied female athletes performed submaximal and maximal exercise tests in the sitting positions KL and KH on a ski ergometer. Measured pole forces and 3-dimensional kinematics served as input for inverse-dynamics simulations to compute the muscle forces and joint reactions in the shoulder and L4-L5 joint. This was the first musculoskeletal simulation study of seated double poling. The results showed that the KH position was favorable for higher performance and decreased values of the shoulder joint reactions for female able-bodied athletes with full trunk control. The KL position was favorable for lower L4-L5 joint reactions and might therefore reduce the risk of lower back injuries. These results indicate that it is hard to optimize both performance and safety in the same sit-ski.

Keywords
musculoskeletal modeling, inverse-dynamic simulations, muscular metabolic power, cross-country sit-skiing
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-32813 (URN)10.1123/jab.2017-0281 (DOI)000448161700004 ()29651902 (PubMedID)2-s2.0-85055597043 (Scopus ID)
Note

Forskningsfinansiärer

Stiftelsen Promobilia

Rolf & Gunilla Enströms stiftelse

Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-12-07Bibliographically approved
Lund Ohlsson, M., Danvind, J. & Holmberg, L. J. (2017). LUMBAR SPINE REACTION FORCES IN SEATED PARA-SPORT: CROSS-COUNTRY SIT-SKIING. In: Brisbane 2017: Abstract book. Paper presented at XXVI Congress of the International Society of Biomechanics, Brisbane, Australia, 23-27 July 2017..
Open this publication in new window or tab >>LUMBAR SPINE REACTION FORCES IN SEATED PARA-SPORT: CROSS-COUNTRY SIT-SKIING
2017 (English)In: Brisbane 2017: Abstract book, 2017Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

INTRODUCTION

For wheel-chair users shoulder injuries [1] and lower back injuries [2] are common. Lower back kyphosis of the spine, increases the anterior shear force in the lower back [3] and increases the risk of shoulder injuries [4].

 

Cross-country sit-skiing (CCSS) is an endurance sport where the athlete is seated in a sledge mounted on a pair of skis and propel themselves by poling with a pair of sticks. This sport creates more equal loading on the muscles around the shoulder than wheel-chair rolling [5] which is positive in an injury perspective for the gleno-humeral joint [1].

 

Athletes in CCSS with reduced trunk muscle control often sits in a sledge with their knees higher than their hips (KH) and a backrest. This position is hypothesized to be associated with spinal kyphosis and hence an increased risk of injuries. Therefore we have created a new sitting position with knees lower than hips (KL) with the trunk restrained on a frontal support.

 

The aim of this study was to compute the L4/L5 joint reactions and compare the results between the positions KH and KL.

METHODS

Five female abled-bodied cross-country skiing athletes (62.6 ± 8.1kg, 1.67 ± 0.05m)  performed one exercise test session in each sitting position; The sessions included a sub-maximal incremental test, including 4-6 exercise levels of 3 min (exercise intensity nr 4, 37W, reflected race-pace) and a maximal time-trial (MAX) of 3 min on a commercial skiing ergometer (ThoraxTrainer A/S, Denmark).

 

Full-body kinematics (Qualisys AB, Sweden) and pole forces (Biovision, Germany) were measured in 200 Hz. These data served as input to inverse dynamic simulations in The AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark). For each participant and sitting position, simulations were made for exercise intensity 37W and MAX over four poling cycles using a 5th order polynomial muscle recruitment criteria. Compression forces and anterior shear forces between L4 and L5 were computed and normalized to each participant’s standing joint reactions. Data were compared pair-wise between the two sitting positions.

 

Statistical significance (p ≤ 0.05) were marked with asterisk (*). Tendency of difference (0.05 ≤ p < 0.10) were marked (ǂ).

 

RESULTS AND DISCUSSION

Performance was higher in position KH (KL: 0.77±0.08 W/kg, KH: 1.00±0.14 W/kg, p < 0.01). No difference were observed in cycle length or cycle time. Kinematics results showed that KL had less spine flexion and range of motion in flexion. KH showed higher mean pole force in 37W and tendency of higher peak pole force in MAX.

 

In standing, L4/L5 compression and anterior shear forces were 354 ± 45N and 32 ± 11N respectively. The normalized L4/L5 reaction forces (fig. 1) were larger in KH, especially during MAX intensity due to higher power. For equal power output, 37W, the mean anterior shear force was larger in KH and the mean compression force showed tendency of larger in KH (p=0.077).

 

Figure 1: Normalized joint reaction forces, compression and anterior shear forces, between vertebrae L4/L5 for the two sitting positions KH and KL with trunk restraint. Min – minimal force, Maximal force and Mean – mean force over the four poling cycles.

 

CONCLUSIONS

Based on inverse-dynamics musculo-skeletal simulations of 5 abled-bodied athletes, the sitting position KL with frontal restraint reduced the compression and shear force between the L4/L5 vertebrae but impeded performance. This study shows the difficulty of comparing performance and safety in the same piece of equipment.

 

ACKNOWLEDGEMENTS

The authors acknowledge the Rolf & Gunilla Enström foundation and the Promobilia foundation, Sweden, for financial support, and the Ableway AB (Sweden) for construction of the sledges.

 

REFERENCES

  1. Burnham RS, et al., Am J Sports Med, 21: 238-242, 1993.
  2. Thyberg M, et al., Disabil rehabil. 23:677-682, 2001.
  3. McGill SM, et al., Clin Biomech, 15: 777-780, 2000.
  4. Samuelsson KA, et al., J Rehabil Res Dev, 41: 65-74, 2004.
  5. Bjerkefors A, et al., Int J Sports Med, 34: 176-182, 2013.
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-32191 (URN)
Conference
XXVI Congress of the International Society of Biomechanics, Brisbane, Australia, 23-27 July 2017.
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2017-12-11Bibliographically approved
Lund Ohlsson, M. & Laaksonen, M. (2017). Sitting position affects performance in cross-country sit-skiing. European Journal of Applied Physiology, 117(6), 1095-1106
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.

Keywords
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
Lund Ohlsson, M., Laaksonen, M. S. & Holmberg, L. J. (2016). Evaulation of two sitting positions in Cross-Country Sit-Skiing. In: ICSS 2016 - International Congress on Science and Skiing, Arlberg, Austria, 10-15th December.: . Paper presented at ICSS 2016 - International Congress on Science and Skiing, Arlberg, Austria, 10-15th December..
Open this publication in new window or tab >>Evaulation of two sitting positions in Cross-Country Sit-Skiing
2016 (English)In: ICSS 2016 - International Congress on Science and Skiing, Arlberg, Austria, 10-15th December., 2016Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

INTRODUCTION

In cross-country sit-skiing (CCSS) athletes with reduced trunk control mainly sit with their knees higher than the hips (KH) to increase trunk stability. To improve the spine curvature by reducing kyphosis a new sitting position was created where the knees are lower than the hips by help of a forward trunk support (KL). The aim of this study was to evaluate the new KL position and compare it to KH in terms of physiological and biomechanical measurements as well as musculoskeletal simulations.

METHODS

Five abled-bodied female cross-country skiers (62.6±8.1kg, 1.67±0.05m) performed two sets of tests; one in each sitting position on a skiing ergometer (ThoraxTrainer A/S, Denmark). Each test comprised a 30s all-out test (AO), an incremental submaximal test (4 to 6 x 3 min, SUB1-SUB6) and a maximal time-trial test of 3 min (MAX). During SUB and MAX external power and kinematics were measured. Metabolic rates (MR) were calculated from oxygen consumption and lactate concentrations.

The AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark) were used to simulate full-body musculoskeletal models over 4 poling cycles of SUB2, SUB4 and MAX. From the simulations muscular metabolic rate (mMR) and musculo-skeletal efficiency (ME) were computed (Holmberg et al., 2013).

RESULTS & DISCUSSION

The performance (W/kg) was higher in KH (p < 0.01) in both AO (24%) and MAX (32%). KL had more flexed knee, more extended hip and less kyphosis in trunk, while KH had larger range of motion (ROM) in hip and larger flexion and ROM in spine at SUB4 and MAX. Gross efficiency (GE) was higher in KH than KL. The total MR and ratio of anaerobic MR to total MR were higher in KL at SUB3 and SUB4.

Simulations showed that 4 subjects had higher ME in KH for both SUB4 and MAX, though no statistical significance were observed. mMR were higher for KL at SUB2 and SUB4 but it was higher for KH at MAX. The ratio of mMR in body parts to total mMR showed higher ratio for KL in arm-shoulders (6.7-9.1%) and higher ratio for KH in trunk (3.7-4.6%) and hip-legs (3.0-4.6%).

CONCLUSION

The physiological results were comparable to others (Lajunen, 2014 & Verellen et al, 2012) and the simulation results were novel by showing how the motion of the trunk contributes to the total metabolic rate. KH position showed higher performance and GE while the KL position indicated higher mMR for arm-shoulders, and had also higher anaerobic MR. Therefore the KH position is favorable for abled-bodied athletes because KL limits trunk motion.

REFERENCES

Holmberg, L. J. et al. (2013). Comput Methods Biomech Biomed Engin16(9), 987-992. Lajunen, K. (2014). Effect of sitting posture on sit-skiing economy. Bachelor’s thesis, University of Jyväskylä.Verellen, J. et al. (2012). Eur J Appl Physiol, 112(3), 983-989.

Keywords
Musculo-skeletal simulations, muscular efficiency, metabolic rate, gross efficiency
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-30372 (URN)
Conference
ICSS 2016 - International Congress on Science and Skiing, Arlberg, Austria, 10-15th December.
Available from: 2017-03-02 Created: 2017-03-02 Last updated: 2017-03-02Bibliographically approved
Lund Ohlsson, M., Höök, M. & Laaksonen, M. S. (2016). On the effect of sitting position, in simulated cross-country sit-skiing. In: : . Paper presented at 21st annual congress of the European college of sport science, 6-9 July, Vienna, Austria.
Open this publication in new window or tab >>On the effect of sitting position, in simulated cross-country sit-skiing
2016 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Introduction

In Cross-country sit-skiing (CCSS), athletes with severe reduced trunk control are mainly seated with the knees higher than the hip (KH; arm and trunk powered). However this posture is hypothesized to have high risk for lower back and shoulder injuries. Therefore, a new seat was created where the knees were lower than hip and the trunk frontal supported (KL), to improve spinal curvature. Thus, the aim of this study was to examine performance between these two different sitting positions.

Methods

10 female abled-bodied elite cross-country skiers (age 25.5 ± 3.8 years (mean ± standard deviation), height 1.65 ± 0.05 m and weight 61.1 ± 6.8 kg) were tested on a skiing ergometer (ThoraxTrainer, ThoraxTrainer A/S, Kokkedal, Denmark) in a 30 s all-out test (WIN), a submaximal incremental test with 3-6 levels of 3 min (SUB), and a maximal 3 min time-trial test (MAX). The SUB and MAX tests were monitored breath-by-breath with a stationary metabolimeter (Quark CPET, COSMED, Italy). Aerobic metabolism and gross efficiency were computed from oxygen uptake, and anaerobic metabolism were estimated from net blood lactate concentrations. Muscle oxygenation saturation (SmO2) in right vastus lateralis (VL) was monitored with NIRS methodology (Moxy Monitor, Fortiori Design LLC, Minnesota, USA).

Results

Higher performance (W·kg-1) was observed for KH both in WIN (KL: 1.13 ± 0.33, KH: 1.40 ± 0.30) and MAX (KL: 0.67 ± 0.14, KH: 0.88 ± 0.19) compared to KL (p < 0.01). No differences were observed in breathing rate, cycle rate, oxygen consumption or aerobic metabolic rate neither in SUB nor MAX. The KH position showed higher gross efficiency and lower anaerobic metabolic rate and minute ventilation. SmO2 was higher for KH compared to baseline bench (12.2 ± 7.2%) whereas no difference was observed between baseline and KL position (3.2 ± 5.5%). During SUB levels 1-4, higher SmO2 was observed for KH compared to KL when normalizing data with baseline bench (p < 0.05).

Discussion

This study showed that abled bodied athletes perform better and have higher efficiency in KH compared to KL. The position using larger part of the body (joint range of motion and amount of active muscle mass) have higher gross efficiency, lower lactate concentration and lower ventilation, also shown by Lajunen (2014). It was also concluded that SmO2 was higher in KH compared to KL, and thus there might be a smaller risk for injuries in the legs connected to circulation. This study of abled-bodied athletes have the potential to serve as a control for future studies of para-athletes. 

References

Lajunen K (2014). Effect of sitting posture on sit-skiing economy. Bachelor’s thesis, University of Jyväskylä.

National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:miun:diva-29450 (URN)
Conference
21st annual congress of the European college of sport science, 6-9 July, Vienna, Austria
Available from: 2016-12-07 Created: 2016-12-07 Last updated: 2016-12-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5317-2779

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