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  • 1.
    Hofmann, K. B.
    et al.
    Otto Bock Healthcare Products GmbH, Vienna, Austria.
    Ohlsson, M. L.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Höök, M.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, J.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Kersting, U. G.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Aalborgs Universitet.
    The influence of sitting posture on mechanics and metabolic energy requirements during sit-skiing: a case report2016In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 19, no 3, p. 213-218Article in journal (Refereed)
    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.

  • 2.
    Holmberg, Joakim
    et al.
    Linköpings Universitet.
    Lund, Marie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    A Musculoskeletal Full‐body Simulation of Cross‐Country Skiing2008In: 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)
    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.

  • 3.
    Holmberg, Joakim
    et al.
    Linköpings Universitet.
    Lund, Marie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Using Double‐Poling Simulations to Study the Load Distribution between Teres Major and Latissimus Dorsi2007In: Science and Nordic Skiing, Oxford: Meyer & Meyer Sport, 2007, p. 81-89Conference paper (Refereed)
  • 4.
    Holmberg, Joakim
    et al.
    Linköpings universitet.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Biomekaniska simuleringar adderar insikt om längdskidåkning2010In: Svensk Idrottsforskning: Organ för Centrum för Idrottsforskning, ISSN 1103-4629, Vol. 19, no 1, p. 38-40Article in journal (Other (popular science, discussion, etc.))
  • 5.
    Holmberg, Joakim
    et al.
    Univ, Div Mech, Dept Management & Engn, Inst Technol, SE-58183 Linkoping, Sweden.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Supej, Matej
    Univ Ljubljana, Fac Sport, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Skiing efficiency versus performance in double-poling ergometry2013In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 16, no 9, p. 987-992Article in journal (Refereed)
    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.

  • 6.
    Holmberg, L. Joakim
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ohlsson, Marie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Musculoskeletal simulations: a complementary tool for classification of athletes with physical impairments2012In: Prosthetics and orthotics international, ISSN 0309-3646, E-ISSN 1746-1553, Vol. 36, no 3, p. 396-397Article in journal (Refereed)
  • 7.
    Lund, Marie
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Holmberg, Joakim
    Linköpings Universitet.
    Which are the Antagonists to the Pectoralis MajorMuscle in 4th Gear, Free‐style Technique, Cross‐Country Skiing?2008In: Science and Nordic Skiing, Oxford: Meyer & Meyer Sport, 2008, p. 110-118Conference paper (Refereed)
  • 8.
    Lund, Marie
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Ståhl, Fredrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Gulliksson, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Regularity Aspects in Inverse Musculoskeletal Biomechanics2008In: NUMERICAL ANALYSIS AND APPLIED MATHEMATICS / [ed] Simos, TE; Psihoyios, G; Tsitouras, C, American Institute of Physics (AIP), 2008, p. 368-371Conference paper (Refereed)
    Abstract [en]

    Inverse simulations of musculoskeletal models computes the internal forces such as muscle and joint reaction forces, which are hard to measure, using the more easily measured motion and external forces as input data. Because of the difficulties of measuring muscle forces and joint reactions, simulations are hard to validate. One way of reducing errors for the simulations is to ensure that the mathematical problem is well-posed. This paper presents a study of regularity aspects for an inverse simulation method, often called forward dynamics or dynamical optimization, that takes into account both measurement errors and muscle dynamics. Regularity is examined for a test problem around the optimum using the approximated quadratic problem. The results shows improved rank by including a regularization term in the objective that handles the mechanical over-determinancy. Using the 3-element Hill muscle model the chosen regularization term is the norm of the activation. To make the problem full-rank only the excitation bounds should be included in the constraints. However, this results in small negative values of the activation which indicates that muscles are pushing and not pulling, which is unrealistic but the error maybe small enough to be accepted for specific applications. These results are a start to ensure better results of inverse musculoskeletal simulations from a numerical point of view.

  • 9.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Double Poling Incross-Country Skiing: Biomechanical and Physiological Analysis of Sitting and Standing Positions2018Doctoral 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.

  • 10.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    New methods for movement technique development in cross-country skiing using mathematical models and simulation2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Licentiate Thesis is devoted to the presentation and discussion of some new contributions in applied mathematics directed towards scientific computing in sports engineering. It considers inverse problems of biomechanical simulations with rigid body musculoskeletal systems especially in cross-country skiing. This is a contrast to the main research on cross-country skiing biomechanics, which is based mainly on experimental testing alone. The thesis consists of an introduction and five papers. The introduction motivates the context of the papers and puts them into a more general framework. Two papers (D and E) consider studies of real questions in cross-country skiing, which are modelled and simulated. The results give some interesting indications, concerning these challenging questions, which can be used as a basis for further research. However, the measurements are not accurate enough to give the final answers. Paper C is a simulation study which is more extensive than paper D and E, and is compared to electromyography measurements in the literature. Validation in biomechanical simulations is difficult and reducing mathematical errors is one way of reaching closer to more realistic results. Paper A examines well-posedness for forward dynamics with full muscle dynamics. Moreover, paper B is a technical report which describes the problem formulation and mathematical models and simulation from paper A in more detail. Our new modelling together with the simulations enable new possibilities. This is similar to simulations of applications in other engineering fields, and need in the same way be handled with care in order to achieve reliable results. The results in this thesis indicate that it can be very useful to use mathematical modelling and numerical simulations when describing cross-country skiing biomechanics. Hence, this thesis contributes to the possibility of beginning to use and develop such modelling and simulation techniques also in this context.

  • 11.
    Lund Ohlsson, Marie
    et al.
    Linköpings universitet.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, Joakim
    Linköpings universitet.
    Can Simulations Assist in Classification Development?2013In: Equipment and Technology in Paralympic Sports, International Paralympic Committee , 2013Conference paper (Refereed)
  • 12.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, L. Joakim
    Linköpings Universitet.
    Descriptive comparison of three technique analysis methods in the context of cross-country sit-skiing: energy expenditure and gross efficiency, descriptive biomechanics and musculoskeletal simulationsManuscript (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.

  • 13.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics. Swedish Parasport Federation.
    Holmberg, L. Joakim
    Linköping University.
    LUMBAR SPINE REACTION FORCES IN SEATED PARA-SPORT: CROSS-COUNTRY SIT-SKIING2017In: Brisbane 2017: Abstract book, 2017Conference paper (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.
  • 14.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, L. Joakim
    Linköpings Universitet.
    Shoulder and Lower Back Joint Reaction Forces in Seated Double Poling2018In: Journal of Applied Biomechanics, ISSN 1065-8483, E-ISSN 1543-2688, Vol. 34, no 5, p. 369-376Article in journal (Refereed)
    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.

  • 15.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Gulliksson, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Least Squares Approach to Inverse Problems in Musculoskeletal Biomechanics2009Report (Other academic)
    Abstract [en]

    Inverse simulations of musculoskeletal models computes the internal forces such as muscle and joint reaction forces, which are hard to measure, using the more easily measured motion and external forces as input data. Because of the difficulties of measuring muscle forces and joint reactions, simulations are hard to validate. One way of reducing errors for the simulations is to ensure that the mathematical problem is well-posed. This paper presents a study of regularity aspects for an inverse simulation method, often called forward dynamics or dynamical optimization, that takes into account both measurement errors and muscle dynamics. The simulation method is explained in detail. Regularity is examined for a test problem around the optimum using the approximated quadratic problem. The results shows improved rank by including a regularization term in the objective that handles the mechanical over-determinancy. Using the 3-element Hill muscle model the chosen regularization term is the norm of the activation. To make the problem full-rank only the excitation bounds should be included in the constraints. However, this results in small negative values of the activation which indicates that muscles are pushing and not pulling. Despite this unrealistic behavior the error maybe small enough to be accepted for specific applications. These results is a starting point start for achieving better results of inverse musculoskeletal simulations from a numerical point of view.

  • 16.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Höök, M.
    Laaksonen, Marko S.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    On the effect of sitting position, in simulated cross-country sit-skiing2016Conference paper (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.

  • 17.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Laaksonen, Marko
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Sitting position affects performance in cross-country sit-skiing2017In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 117, no 6, p. 1095-1106Article in journal (Refereed)
    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.

  • 18.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Laaksonen, Marko S.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Holmberg, L. Joakim
    Linköpings Universitet.
    Evaulation of two sitting positions in Cross-Country Sit-Skiing2016In: ICSS 2016 - International Congress on Science and Skiing, Arlberg, Austria, 10-15th December., 2016Conference paper (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.

  • 19.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Stöggl, T.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Asymmetry case study during skiing in the diagonal stride using a lower leg prosthesis2012Conference paper (Refereed)
  • 20.
    Skoglund, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Lower Leg Prosthesis for Cross-Country Skiing Classical Technique2013Conference paper (Refereed)
1 - 20 of 20
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