Tensile response of the muscle-tendon complex using discrete element model

Tear of the muscle-tendon complex (MTC) is one of the main causes of sport injuries (De Labareyre et al. 2005). However, the mechanisms leading to such injury are still unclear (Uchiyama et al. 2011). Before modeling the tear of the MTC, its behavior in tensile test will be first studied. The MTC is a multi-scale, non isotropic and non continuous structure that is composed of numerous fascicles gathered together in a conjunctive sheath (epimysium). Many MTC models use the Finite Element Method (FEM) (Bosboom et al. 2001) to simulate MTC’s behavior as a hyperviscoelastic material. The Discrete Element Method (DEM) used for modeling composite materials (Iliescu et al. 2010) could be adapted to fibrous materials as the MTC. Compared to FEM, the DEM could allow to capture the complex behavior of a material with a simple discretization scheme in terms of concept and implementation as well as to understand the influence of fibers’ orientation on the MTC behavior. The aim of this study was to obtain the force/displacement relationship during a numerical tensile test of a pennate muscle model with DEM

MODEL OF CALF MUSCLE TEAR DURING A SIMULATED ECCENT RlC CONT RACTlON. A FEASABILITY STUDY

Tearing of muscle-tendon complex is one of the main causes of sport injuries. The aim of this study was to combine passive stretching and contraction to model the conditions of such injury, using the discrete element method. The mechanical behavior of the muscle-tendon complex was in agreement with data from the literature and data from in vittu experiments by tensile tests on calf muscle-tendon unit. The localization of the rupture and the pattern of rupture show a delamination of muscle's fibers close to the myotendinous junction during an active stretching of the muscle-tendon complex

LOWER BODY KINEMATICS AND MUSCLE ACTIVITY DURING EXERCICES IN 3D MOTORIZED ROTATING PLATFORM. IN-VIVO STUDY AND MODEL

The purpose of this study was to characterize muscle solicitations implied by the movement of a motorized rotating platform (MRP). Subjects performed five classical exercises on a MRP as part of lower limbs rehabilitation programs. EMG signals were recorded to quantify level and duration of activation of seven lower limbs muscles. Subject-specific musculoskeletal models were built and animated from kinematic recordings to estimate muscle lengths evolution. Results show that unipodal stance exercise was more demanding compared to bipodal ones. The characterization of solicitations imposed by MRP exercises could be useful for physiotherapists in order to help them to better select and configure exercises regarding to subject specificities, pathology and rehabilitation evolution

Interactions between fascicles and tendinous tissues in gastrocnemius medialis and vastus lateralis during drop landing

Animal tendons have been shown to act as shock absorbers to protect muscle fascicles from exercise-induced damage during landing tasks. Meanwhile, the contribution of tendinous tissues to damping activities such as landing has been less explored in humans. The aim of this study was to analyze in vivo fascicle-tendon interactions during drop landing to better understand their role in energy dissipation. Ultrafast ultrasound images of the gastrocnemius medialis (GM) and vastus lateralis (VL), lower limb electromyographic activity, 2-D kinematics, and ground reaction forces were collected from twelve participants during single- and double-leg drop landings from various heights. For both muscles, length changes were higher in tendinous tissues than in fascicles, demonstrating their key role in protecting fascicles from rapid active lengthening. Increasing landing height increased lengthening and peak lengthening velocity of VL fascicle and GM architectural gear ratio, whereas GM fascicle displayed similar length and velocity patterns. Single-leg landing lengthens the tendinous tissues of GM and, to a greater degree, VL muscles, without affecting the fascicles. These findings demonstrate the adjustment in fascicle-tendon interactions to withstand mechanical demand through the tendon buffer action and fascicle rotation. The higher VL fascicle contribution to negative work as the drop height increases would suggest muscle-specific damping responses during drop landing. This can originate from the distal-to-proximal sequence of joint kinetics, from differences in muscle and tendon functions (one- and two-joint muscles), architectural and morphological properties (eg, tendon stiffness), as well as from the muscle activity of the GM and VL muscles.Enzo Hollville is funded by the Natural Grass company. We warmly thank Hugo Hauraix for his technical support

An Initial Passive Phase That Limits the Time to Recover and Emphasizes the Role of Proprioceptive Information

In the present experiments, multiple balance perturbations were provided by unpredictable support-surface translations in various directions and velocities. The aim of this study was to distinguish the passive and the active phases during the pre-impact period of a fall. It was hypothesized that it should be feasible if one uses a specific quantitative kinematic analysis to evaluate the dispersion of the body segments trajectories across trials. Moreover, a multi-joint kinematical model was created for each subject, based on a new 3-D minimally invasive stereoradiographic X-ray images to assess subject-specific geometry and inertial parameters. The simulations allowed discriminating between the contributions of the passive (inertia-induced properties) and the active (neuromuscular response) components during falls. Our data show that there is limited time to adjust the way one fall from a standing position. We showed that the pre-impact period is truncated of 200 ms. During the initial part of a fall, the observed trajectory results from the interaction between the destabilizing external force and the body: inertial properties intrinsic to joints, ligaments and musculotendinous system have then a major contribution, as suggested for the regulation of static upright stance. This passive phase is later followed by an active phase, which consists of a corrective response to the postural perturbation. We believe that during a fall from standing height, it takes about 300 ms for postural responses to start correcting the body trajectory, while the impact is expected to occur around 700 ms. It has been argued that this time is sufficient to change the way one falls and that this makes it possible to apply safer ways of falling, for example by using martial arts fall techniques. Also, our results imply visual and vestibular information are not congruent with the beginning of the on-going fall. This consequence is to be noted as subjects prepare to the impact on the basis of sensory information, which would be uniquely mainly of proprioceptive origin at the fall onset. One limitation of the present analysis is that no EMG was included so far but these data are the subject of a future study

An Attempt of Early Detection of Poor Outcome after Whiplash

The main concern with whiplash is that a large proportion of whiplash patients experience disabling symptoms or whiplash-associated disorders (WAD) for months if not years following the accident. Therefore, identifying early prognostic factors of WAD development is important as WAD have widespread clinical and economic consequences. In order to tackle that question, our study was specifically aimed at combining several methods of investigation in the same WAD patients at the acute stage and 6 months later. Our longitudinal, open, prospective, multi-center study included 38 whiplash patients, and 13 healthy volunteers matched for age, gender, and socio-economic status with the whiplash group. Whiplash patients were evaluated 15–21 days after road accident, and 6 months later. At each appointment, patients underwent a neuropsychological evaluation, a full clinical neurological examination, neurophysiological and postural tests, oto-neurological tests, cervical spine cord magnetic resonance imaging (MRI) with tractography (DTI). At 6 months, whiplash patients were categorized into two subgroups based on the results of the Diagnostic and Statistical Manual of Mental Disorders as having either favorable or unfavorable progression [an unfavorable classification corresponding to the presence of post-concussion symptom (PCS)] and we searched retrospectively for early prognostic factors of WAD predicting the passage to chronicity. We found that patients displaying high level of catastrophizing at the acute stage and/or post-traumatic stress disorder associated with either abnormalities in head or trunk kinematics, abnormal test of the otolithic function and at the Equitest or a combination of these syndromes, turned to chronicity. This study suggests that low-grade whiplash patients should be submitted as early as possible after the trauma to neuropsychological and motor control tests in a specialized consultation. In addition, they should be evaluated by a neuro-otologist for a detailed examination of vestibular functions, which should include cervical vestibular evoked myogenic potential. Then, if diagnosed at risk of WAD, these patients should be subjected to an intensive preventive rehabilitation program, including vestibular rehabilitation if required.This study was funded by the French Fondation Sécurité Routièr

Biomecanique du segment tete-cou in vivo & aeronautique militaire. Approches neuromusculaire et morphologique

The aims of this study were to 1) better understand the relative contribution of morphological (muscle CSA) and muscle activation (EMG) underlying the between-gender differences in neck torque ratios in healthy male and female non-pilots and also between neck pain and asymptomatic fighter pilots and 2) to examine the impact of helmet mounted display and gender on the neural activation patterns of neck muscles induced by simulated flight under acceleration with different head-neck configurations in non-pilots subjects and on the 3D kinematics of the head-neck segment of fighter pilots under normal gravity (lG). Non-pilot men displayed higher specific tension of neck flexors and neuromuscular efficiency compared with women, the latter exhibiting also higher levels of coactivation of antagonistic and stabilizer muscles. Neck pain pilots displayed lower specific tension of neck muscles during side-bending contractions likely related to neuromuscular and morphological differences of lateral neck muscle s such as the splenius capitis. The second part of the study revealed that muscles responses were different across gender; the women showing higher levels of muscle activity during sustained head-neck posture under Gz loading and particularly when helmet with mounted display was tested. In addition, 3D-kinematics analysis showed that neck pain pilots displayed lower coupled motions and lower joint position sense. Furthermore, during actual moderate flight, this type of helmet altered the strength of neck muscles even in asymptomatic pilot s. These findings underscore the potential higher risk of injury in women compared with men when helmet mounted display are used during flight and the need to improve the neck strength and CSA in women and/or weak pilots.Ce travail a pour objectifs 1) d'examiner la part des facteurs morphologiques (surface de section musculaire) et nerveux (électromyographie de surface) responsables des différences de rapport de force du segment tête-cou entre hommes et femmes ainsi qu'entre pilotes de chasse sains et cervicalgiques, et 2) de mieux cerner l'influence des propriétés inertielles du casque et du genre sur les patrons de recrutement musculaire lors de vols simulés de sujets non-pilotes et également chez des pilotes sains et cervicalgiques en analysant le comportement cinématique 3D à 1G. L'étude I montre que les muscles fléchisseurs présentent une force spécifique et une efficience neuromusculaire supérieures chez les hommes ainsi qu'une coactivation des muscles stabilisateurs et antagonistes plus élevés chez les femmes. L'étude II rapporte une force spécifique des muscles participant à l'inclinaison plus élevée chez les pilotes sains et associée à des différences d'efficience neuromusculaire et/ou de surface de section des muscles splenius capitis notamment. L'impact des caractéristiques inertielles du casque sur les patrons de recrutement lors du maintien de postures spécifiques sous accélérations est plus marqué chez les femmes notamment lors du port du casque équipé de jumelles de vision nocturne. L'analyse cinématique 3D à 1G montre que les pilotes cervicalgiques présentent une limitation de l'amplitude des mouvements couplés ainsi qu'une altération du sens de repositionnement. En condition de vol réel modéré, le port d'un casque intégrant un viseur semble altérer la capacité de production de force de pilotes de chasse asymptomatiques. Ces résultats soulignent la prépondérance des risques encourus par le personnel naviguant féminin et/ou masculin ayant un segment tête-cou faible, et la nécessité d'un renforcement les muscles cervicaux

Biomecanique du segment tete-cou in vivo et aéronautique militaire (approches neuromusculaire et morphologique)

Ce travail a pour objectifs 1) d examiner la part des facteurs morphologiques (surface de section musculaire) et nerveux (électromyographie de surface) responsables des différences de rapport de force du segment tête-cou entre hommes et femmes ainsi qu'entre pilotes de chasse sains et cervicalgiques, et 2) de mieux cerner l'influence des propriétés inertielles du casque et du genre sur les patrons de recrutement musculaire lors de vols simulés de sujets non-pilotes et également chez des pilotes sains et cervicalgiques en analysant le comportement cinématique 3D à 1G. L'étude I montre que les muscles fléchisseurs présentent une force spécifique et une efficience neuromusculaire supérieures chez les hommes ainsi qu'une coactivation des muscles stabilisateurs et antagonistes plus élevés chez les femmes. L'étude II rapporte une force spécifique des muscles participant à l inclinaison plus élevée chez les pilotes sains et associée à des différences d efficience neuromusculaire et/ou de surface de section des muscles splenius capitis notamment. L impact des caractéristiques inertielles du casque sur les patrons de recrutement lors du maintien de postures spécifiques sous accélérations est plus marqué chez les femmes notamment lors du port du casque équipé de jumelles de vision nocturne. L'analyse cinématique 3D à 1G montre que les pilotes cervicalgiques présentent une limitation de l'amplitude des mouvements couplés ainsi qu'une altération du sens de repositionnement. En condition de vol réel modéré, le port d un casque intégrant un viseur semble altérer la capacité de production de force de pilotes de chasse asymptomatiques. Ces résultats soulignent la prépondérance des risques encourus par le personnel naviguant féminin et/ou masculin ayant un segment tête-cou faible, et la nécessité d'un renforcement les muscles cervicaux.The aims of this study were to 1) better understand the relative contribution of morphological (muscle CSA) and muscle activation (EMG) underlying the between-gender differences in neck torque ratios in healthy male and female non-pilots and also between neck pain and asymptomatic fighter pilots and 2) to examine the impact of helmet mounted display and gender on the neural activation patterns of neck muscles induced by simulated flight under acceleration with different head-neck configurations in non-pilots subjects and on the 3D kinematics of the head-neck segment of fighter pilots under normal gravity (lG). Non-pilot men displayed higher specific tension of neck flexors and neuromuscular efficiency compared with women, the latter exhibiting also higher levels of coactivation of antagonistic and stabilizer muscles. Neck pain pilots displayed lower specific tension of neck muscles during side-bending contractions likely related to neuromuscular and morphological differences of lateral neck muscle s such as the splenius capitis. The second part of the study revealed that muscles responses were different across gender; the women showing higher levels of muscle activity during sustained head-neck posture under Gz loading and particularly when helmet with mounted display was tested. In addition, 3D-kinematics analysis showed that neck pain pilots displayed lower coupled motions and lower joint position sense. Furthermore, during actual moderate flight, this type of helmet altered the strength of neck muscles even in asymptomatic pilot s. These findings underscore the potential higher risk of injury in women compared with men when helmet mounted display are used during flight and the need to improve the neck strength and CSA in women and/or weak pilots.PARIS-Arts et Métiers (751132303) / SudocSudocFranceF

Comput Methods Biomech Biomed Engin

The tearing of a muscle-tendon complex (MTC) is caused by an eccentric contraction; however, the structures involved and the mechanisms of rupture are not clearly identified. The passive mechanical behavior the MTC has already been modeled and validated with the discrete element method. The muscular activation is the next needed step. The aim of this study is to model the muscle fiber activation and the muscular activation of the MTC to validate their active mechanical behaviors. Each point of the force/length relationship of the MTC (using a parabolic law for the force/length relationship of muscle fibers) is obtained with two steps: 1) a passive tensile (or contractile) test until the desired elongation is reached and 2) fiber activation during a position holding that can be managed thanks to the Discrete Element model. The muscular activation is controlled by the activation of muscle fiber. The global force/length relationship of a single fiber and of the complete MTC during muscular activation is in agreement with literature. The influence of the external shape of the structure and the pennation angle are also investigated. Results show that the different constituents of the MTC (extracellular matrix, tendon), and the geometry, play an important role during the muscular activation and enable to decrease the maximal isometric force of the MTC. Moreover, the maximal isometric force decreases when the pennation angle increases. Further studies will combine muscular activation with a stretching of the MTC, until rupture, in order to numerically reproduce the tearing of the MTC

Interactions between fascicles and tendinous tissues in gastrocnemius medialis and vastus lateralis during drop landing

International audienceAnimal tendons have been shown to act as shock absorbers to protect muscle fascicles from exercise‐induced damage during landing tasks. Meanwhile, the contribution of tendinous tissues to damping activities such as landing has been less explored in humans. The aim of this study was to analyze in vivo fascicle‐tendon interactions during drop landing to better understand their role in energy dissipation. Ultrafast ultrasound images of the gastrocnemius medialis (GM) and vastus lateralis (VL), lower limb electromyographic activity, 2‐D kinematics, and ground reaction forces were collected from twelve participants during single‐ and double‐leg drop landings from various heights. For both muscles, length changes were higher in tendinous tissues than in fascicles, demonstrating their key role in protecting fascicles from rapid active lengthening. Increasing landing height increased lengthening and peak lengthening velocity of VL fascicle and GM architectural gear ratio, whereas GM fascicle displayed similar length and velocity patterns. Single‐leg landing lengthens the tendinous tissues of GM and, to a greater degree, VL muscles, without affecting the fascicles. These findings demonstrate the adjustment in fascicle‐tendon interactions to withstand mechanical demand through the tendon buffer action and fascicle rotation. The higher VL fascicle contribution to negative work as the drop height increases would suggest muscle‐specific damping responses during drop landing. This can originate from the distal‐to‐proximal sequence of joint kinetics, from differences in muscle and tendon functions (one‐ and two‐joint muscles), architectural and morphological properties (eg, tendon stiffness), as well as from the muscle activity of the GM and VL muscles