Gymnastik- och idrottshögskolan, GIH

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  • 1.
    Holmberg, Joakim
    et al.
    Linköpings Universitet.
    Lund, Marie
    Mittuniversitetet, Institutionen för teknik och hållbar utveckling (-2013).
    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.

  • 2.
    Holmberg, Joakim
    et al.
    Linköpings Universitet.
    Lund, Marie
    Mittuniversitetet, Institutionen för teknik, fysik och matematik (-2008).
    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)
  • 3.
    Lund, Marie
    et al.
    Mittuniversitetet, Institutionen för teknik och hållbar utveckling (-2013).
    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)
  • 4.
    Lund, Marie
    et al.
    Mittuniversitetet, Institutionen för teknik och hållbar utveckling (-2013).
    Ståhl, Fredrik
    Mittuniversitetet, Institutionen för teknik och hållbar utveckling (-2013).
    Gulliksson, Mårten
    Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik (-2012).
    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.

  • 5.
    Lund Ohlsson, Marie
    Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik (-2012).
    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.

  • 6.
    Lund Ohlsson, Marie
    et al.
    Mittuniversitetet, Institutionen för teknik och hållbar utveckling (-2013).
    Gulliksson, Mårten
    Mittuniversitetet, Institutionen för naturvetenskap, teknik och matematik (-2012).
    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.

1 - 6 of 6
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