Influence of selected modeling and computational issues on muscle force estimates

Abstract

Knowledge of muscle forces and joint reaction forces during human movement can provide insight into the underlying control and tissue loading. Since direct measurement of the internal loads is generally not feasible, non-invasive methods based on musculoskeletal modeling and computer simulations have been extensively developed. By applying observed motion data to the musculoskeletal models, inverse dynamic analysis allow to determine the resultant joint torques, transformed then into estimates of individual muscle forces by means of different optimization procedures. Assessment of the joint reaction forces and other internal loads is further possible. Comparison of the muscle force estimates obtained for different modeling assumptions and parameters in the model can be valuable for the improvement of validity of the model-based estimations. The present study is another contribution to this field. Using a sagittal plane model of an upper limb with a weight carried in hand, and applying the data of recorded flexion and extension movement of the upper limb, the resultant muscular forces are predicted using different modeling assumptions and simulation tools. This study relates to different coordinates (joint and natural coordinates) used to built the mathematical model, muscle path modeling, muscle decomposition (change in number of the modeled muscles), and different optimization methods used to share the joint torques into individual muscles.

Muscle decomposition and recruitment criteria influence muscle force estimates

“…2.2, a similar model ( Fig. 1) as the one used in [1] was created in the AnyBody modeling system 4.1 (AnyBody Technology A/S, Aalborg, Denmark). This software uses non-conventional musculoskeletal inverse dynamics with static optimization, in which the muscle forces are solved directly from body motion and external forces [3].…”

“…Recently, Blajer et al [1] published an interesting article concerning the influence of selected modeling and computational issues on muscle force estimates. This topic is important for users of biomechanical simulations because it can serve as an aid in the development of "best practice".…”

“…This topic is important for users of biomechanical simulations because it can serve as an aid in the development of "best practice". Using a planar arm model (comprising 2 segments, 2 joints and 8 muscles) Blajer et al [1] estimated the muscle forces by inverse dynamics and static optimization. They compared results due to differences in coordinate systems, muscle paths, muscle decomposition and muscle recruitment optimization criteria.…”

“…This behavior has not been noted in our own simulation work. But we also note that Blajer et al [1] used a polynomial criteria while we normally use a minmax criteria, both described in [2].…”

Modeling of the condyle elements within a biomechanical knee model

“…However, the human body system is far more complex than the great majority of the multibody systems. Its components have a complex behavior due to deformations associated with the soft tissues such as the muscles, tendons, and ligaments, and due to complexity of the anatomical articulations relative to the standard mechanical joints [1][2][3][4].…”