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MUSCLE INTERACTIONS INFLUENCE THE
MUSCULAR FORCES
Julien Stelletta, Raphaël Dumas, Yoann Lafon
To cite this version:
Julien Stelletta, Raphaël Dumas, Yoann Lafon. MUSCLE INTERACTIONS INFLUENCE THE MUSCULAR FORCES. 22nd Congress of the European Society of Biomechanics, Jul 2016, Lyon, France. �hal-01609529�
22nd Congress of the European Society of Biomechanics, July 10 - 13, 2016, Lyon, France
MUSCLE INTERACTIONS INFLUENCE THE MUSCULAR FORCES
Julien Stelletta (1), Raphaël Dumas (1), Yoann Lafon (1)
1. Université de Lyon, Université Claude Bernard Lyon 1, IFSTTAR, Lyon, France
Introduction
The development of solid deformable contractile muscle models is an ongoing research in biomechanics. Conversely to multibody musculoskeletal models with 1D forces along the muscle lines of action, such models can compute the 3D forces in the muscle volume. Specifically, the transverse force transmitted between the muscles can be considered. A recent in vitro animal study revealed that the axial force (i.e., obtained by electro-stimulation) is dependent on the transverse force applied during the contraction [1].
The present study aims at evaluating this effect on the human thigh musculature. This in silico study compares the forces obtained in the different muscles for a given set of activations with and without introducing contact between the muscle surfaces.
Methods
A 3D finite element model of the thigh was developed from the visible human geometry [2]. The pelvis, femur, patella and tibia bones were modelled with non-deformable tetrahedral shells. The thigh muscles (see Figure 1) were modelled using hexahedral elements with a Mooney-Rivlin hyper-elastic material. For the active part of muscles, a network of contractile beams driven by a thermo-mechanical elastic material [3] was embedded in the hexahedral elements. The set of activation levels, further transformed into temperatures [3], was determined using a multibody musculoskeletal model [4] to represent the dynamics of the thigh at loading response (i.e., 14% of gait cycle).
A first simulation was run without introducing contact between the muscles. The hip and knee joints angles were applied to the bones and all the temperature/activation levels were simultaneously applied to the muscles. A second simulation was similarly run with sliding contacts between the muscle surfaces. The muscle forces, computed as the integration of normal strains in the muscle cross sections, were compared.
Results
Figure 1 represents the muscle cross sections after contraction obtained with and without introducing contact. In the latter case, severe interpenetrations were found between A_mag and S_memb, Sart and V_med, BF_short and BF_long. Table 1 gives the main muscles forces that were modified by introducing the contact. Note that the activation levels of BF_long, S_tend, A_brev, Pect, A_mag, A_long and Grac were set to 0 as determined by the multibody musculoskeletal model [4].
Figure 1: Cross sections of the thigh muscles for simulations without (left) and with (right) contact: gluteus maximus, medius, minimus (G_max, G_med, G_min); adductor longus, brevis, magnus (A_long, A_brev, A_mag); pectineus (Pect); gracilis (Grac); sartorius (Sart); semimembranosus (S_memb); semitendinus (S_tend); biceps femoris long head, short head (BF_long, BF_short); rectus femoris (RF); vastus medialis, intermedialis, lateralis (V_med, V_int, V_lat).
Muscle Force without
contact (N) Force with contact (N)
G_min 446 532
Sart 29 31
S_memb 63 38
RF 105 112
V_int 125 138
Table 1: Muscle forces modified by muscle interactions
Discussion
This in silico study replicated the principle of an in vitro animal study [1]. Accordingly, a set of activations was imposed and the muscles forces were altered by additional transverse forces (i.e., the contact forces between muscles). In the in vitro animal study, transversal loading resulted in a decrease of the maximal isometric force of 13%. In the present study the muscle forces corresponding to one gait event were modified (up to 40% for the S_memb), being either increased or decreased depending on the muscle position.
These results confirmed the importance of considering 3D forces and interactions between the muscles in musculoskeletal modelling. Thus, the inclusion of connective tissue and fascias shall be the next step of development for solid deformable muscle models.
References
1. Sieber et al, J Biomech, 47:1822-1828, 2014. 2. Ackerman, J Biocommun, 18: 14, 1991.
3. Stelletta et al., Comput Methods Biomech Biomed Eng, 16:164-166, 2013.
