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1.
Front Bioeng Biotechnol ; 9: 636960, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34336797

RESUMO

Background: At the beginning of a sprint, the acceleration of the body center of mass (COM) is driven mostly forward and vertically in order to move from an initial crouched position to a more forward-leaning position. Individual muscle contributions to COM accelerations have not been previously studied in a sprint with induced acceleration analysis, nor have muscle contributions to the mediolateral COM accelerations received much attention. This study aimed to analyze major lower-limb muscle contributions to the body COM in the three global planes during the first step of a sprint start. We also investigated the influence of step width on muscle contributions in both naturally wide sprint starts (natural trials) and in sprint starts in which the step width was restricted (narrow trials). Method: Motion data from four competitive sprinters (2 male and 2 female) were collected in their natural sprint style and in trials with a restricted step width. An induced acceleration analysis was performed to study the contribution from eight major lower limb muscles (soleus, gastrocnemius, rectus femoris, vasti, gluteus maximus, gluteus medius, biceps femoris, and adductors) to acceleration of the body COM. Results: In natural trials, soleus was the main contributor to forward (propulsion) and vertical (support) COM acceleration and the three vasti (vastus intermedius, lateralis and medialis) were the main contributors to medial COM acceleration. In the narrow trials, soleus was still the major contributor to COM propulsion, though its contribution was considerably decreased. Likewise, the three vasti were still the main contributors to support and to medial COM acceleration, though their contribution was lower than in the natural trials. Overall, most muscle contributions to COM acceleration in the sagittal plane were reduced. At the joint level, muscles contributed overall more to COM support than to propulsion in the first step of sprinting. In the narrow trials, reduced COM propulsion and particularly support were observed compared to the natural trials. Conclusion: The natural wide steps provide a preferable body configuration to propel and support the COM in the sprint starts. No advantage in muscular contributions to support or propel the COM was found in narrower step widths.

2.
Abdom Radiol (NY) ; 46(12): 5746-5757, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34448024

RESUMO

PURPOSE: To retrospectively compare the efficacy and safety of prostatic artery embolization (PAE) combined with transurethral resection of the prostate (TURP) and simple TURP in treating large (> 100 mL) benign prostatic hyperplasia (BPH). METHODS: We retrospectively analyzed the clinical data of 13 and 17 patients with large BPH who underwent TURP and PAE + TURP, respectively, from January 2016 to January 2020. The changes in various indices before and after surgery were compared between the two groups. RESULTS: In the PAE + TURP group, the operation time (OT), intraoperative blood loss (BL), postoperative bladder flushing time (PBFT), and postoperative catheter retention time (PCRT) were lower, and the speed of the excised lesion (SEL) was higher than that in the TURP group (P < 0.05). Following-up for 12 months, the prostatic volume (PV), maximum urinary flow rate (Qmax), postvoid residual volume (PVR), International Prostate Symptom Score (IPSS), quality of life (QoL) score, total prostate-specific antigen (T-PSA), and free prostate-specific antigen (F-PSA) in each group improved as compared to before the surgery (P < 0.05), and the above improved indicators, IPSS ratio, and obstructive symptoms in the PAE + TURP group were higher than those in the TURP group (P < 0.05). The incidence of postoperative complications in the PAE + TURP group was lower than that in the TURP group. We obtained the pathological picture of a prostate biopsy after PAE for the first time. CONCLUSION: Compared to TURP alone, PAE + TURP should be promoted, because of its greater efficacy and safety in treating large BPH and fewer post-surgical complications.


Assuntos
Embolização Terapêutica , Hiperplasia Prostática , Ressecção Transuretral da Próstata , Artérias , Humanos , Masculino , Hiperplasia Prostática/cirurgia , Hiperplasia Prostática/terapia , Qualidade de Vida , Estudos Retrospectivos , Resultado do Tratamento
3.
Artigo em Inglês | MEDLINE | ID: mdl-34097615

RESUMO

Detecting human movement intentions is fundamental to neural control of robotic exoskeletons, as it is essential for achieving seamless transitions between different locomotion modes. In this study, we enhanced a muscle synergy-inspired method of locomotion mode identification by fusing the electromyography data with two types of data from wearable sensors (inertial measurement units), namely linear acceleration and angular velocity. From the finite state machine perspective, the enhanced method was used to systematically identify 2 static modes, 7 dynamic modes, and 27 transitions among them. In addition to the five broadly studied modes (level ground walking, ramps ascent/descent, stairs ascent/descent), we identified the transition between different walking speeds and modes of ramp walking at different inclination angles. Seven combinations of sensor fusion were conducted, on experimental data from 8 able-bodied adult subjects, and their classification accuracy and prediction time were compared. Prediction based on a fusion of electromyography and gyroscope (angular velocity) data predicted transitions earlier and with higher accuracy. All transitions and modes were identified with a total average classification accuracy of 94.5% with fused sensor data. For nearly all transitions, we were able to predict the next locomotion mode 300-500ms prior to the step into that mode.


Assuntos
Intenção , Dispositivos Eletrônicos Vestíveis , Adulto , Eletromiografia , Humanos , Locomoção , Músculos , Caminhada
4.
Front Neurorobot ; 15: 620928, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33762922

RESUMO

Exoskeletons are increasingly used in rehabilitation and daily life in patients with motor disorders after neurological injuries. In this paper, a realistic human knee exoskeleton model based on a physical system was generated, a human-machine system was created in a musculoskeletal modeling software, and human-machine interactions based on different assistive strategies were simulated. The developed human-machine system makes it possible to compute torques, muscle impulse, contact forces, and interactive forces involved in simulated movements. Assistive strategies modeled as a rotational actuator, a simple pendulum model, and a damped pendulum model were applied to the knee exoskeleton during simulated normal and fast gait. We found that the rotational actuator-based assistive controller could reduce the user's required physiological knee extensor torque and muscle impulse by a small amount, which suggests that joint rotational direction should be considered when developing an assistive strategy. Compared to the simple pendulum model, the damped pendulum model based controller made little difference during swing, but further decreased the user's required knee flexor torque during late stance. The trade-off that we identified between interaction forces and physiological torque, of which muscle impulse is the main contributor, should be considered when designing controllers for a physical exoskeleton system. Detailed information at joint and muscle levels provided in this human-machine system can contribute to the controller design optimization of assistive exoskeletons for rehabilitation and movement assistance.

5.
Biomed Res Int ; 2021: 8899699, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33628828

RESUMO

The in vivo characterization of the passive mechanical properties of the human triceps surae musculotendinous unit is important for gaining a deeper understanding of the interactive responses of the tendon and muscle tissues to loading during passive stretching. This study sought to quantify a comprehensive set of passive muscle-tendon properties such as slack length, stiffness, and the stress-strain relationship using a combination of ultrasound imaging and a three-dimensional motion capture system in healthy adults. By measuring tendon length, the cross-section areas of the Achilles tendon subcompartments (i.e., medial gastrocnemius and soleus aspects), and the ankle torque simultaneously, the mechanical properties of each individual compartment can be specifically identified. We found that the medial gastrocnemius (GM) and soleus (SOL) aspects of the Achilles tendon have similar mechanical properties in terms of slack angle (GM: -10.96° ± 3.48°; SOL: -8.50° ± 4.03°), moment arm at 0° of ankle angle (GM: 30.35 ± 6.42 mm; SOL: 31.39 ± 6.42 mm), and stiffness (GM: 23.18 ± 13.46 Nmm-1; SOL: 31.57 ± 13.26 Nmm-1). However, maximal tendon stress in the GM was significantly less than that in SOL (GM: 2.96 ± 1.50 MPa; SOL: 4.90 ± 1.88 MPa, p = 0.024), largely due to the higher passive force observed in the soleus compartment (GM: 99.89 ± 39.50 N; SOL: 174.59 ± 79.54 N, p = 0.020). Moreover, the tendon contributed to more than half of the total muscle-tendon unit lengthening during the passive stretch. This unequal passive stress between the medial gastrocnemius and the soleus tendon might contribute to the asymmetrical loading and deformation of the Achilles tendon during motion reported in the literature. Such information is relevant to understanding the Achilles tendon function and loading profile in pathological populations in the future.


Assuntos
Tendão do Calcâneo/fisiologia , Fenômenos Biomecânicos/fisiologia , Músculo Esquelético/fisiologia , Adulto , Articulação do Tornozelo/fisiologia , Eletromiografia , Feminino , Humanos , Masculino , Amplitude de Movimento Articular/fisiologia , Torque
6.
Gait Posture ; 80: 7-13, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32464538

RESUMO

BACKGROUND: Flatfoot has a very high incidence of obese children. Functional parameters such as plantar pressures and center of pressure (COP) are sensitive to foot type. However, previous foot biomechanical studies of obese children rarely excluded the flatfoot as a prerequisite of the participants involved. RESEARCH QUESTION: This study aimed to determine whether it is essential to define flatfoot as a subject screening criterion in the foot biomechanical study for obese children. METHODS: Foot types were classified by arch index (AI). Totally 21 obese children with flatfoot (OF group) along with matched control groups of obese children with normal foot (ON group) and normal-weighted children with flatfoot (NF group) were selected from our database. Barefoot walking trails were conducted using Footscan® plate system. Peak force (PF), peak pressure (PP), pressure-time integral (PTI), contact area (CA) and COP data were recorded. Independent t-test and effect size were used to compare the data between the study group and the control groups. Intraclass correlation coefficient was used to measure the between-trail reliability for the dependent variables. RESULTS: In comparison with the OF group, an upward trend for PF, PP and PTI was found for the ON group, while an opposite tendency for the NF group. The OF group displayed a significant larger CA under the midfoot region than the NF group even if there is no significant difference for AI. The OF group displayed a more medial shift of COP progression compared to the ON group. But no significant differences were found for COP parameters between the OF group and the NF group. SIGNIFICANCE: This study provided substantial evidence to support that prospective foot biomechanical research on the obese group needs to identify the flatfoot as one of the subject screening criteria to carry out more reliable results without producing confounding effects.


Assuntos
Pé Chato/fisiopatologia , Pé/fisiopatologia , Obesidade Pediátrica/fisiopatologia , Pressão , Caminhada , Adolescente , Fenômenos Biomecânicos , Peso Corporal , Estudos de Casos e Controles , Criança , Feminino , Humanos , Masculino , Estudos Prospectivos , Reprodutibilidade dos Testes
7.
Artigo em Inglês | MEDLINE | ID: mdl-32167889

RESUMO

Tracking the myotendinous junction (MTJ) in consecutive ultrasound images is crucial for understanding the mechanics and pathological conditions of the muscle-tendon unit. However, the lack of reliable and efficient identification of MTJ due to poor image quality and boundary ambiguity restricts its application in motion analysis. In recent years, with the rapid development of deep learning, the region-based convolution neural network (RCNN) has shown great potential in the field of simultaneous objection detection and instance segmentation in medical images. This article proposes a region-adaptive network (RAN) to localize MTJ region and to segment it in a single shot. Our model learns about the salient information of MTJ with the help of a composite architecture. Herein, a region-based multitask learning network explores the region containing MTJ, while a parallel end-to-end U-shaped path extracts the MTJ structure from the adaptively selected region for combating data imbalance and boundary ambiguity. By demonstrating the ultrasound images of the gastrocnemius, we showed that the RAN achieves superior segmentation performance when compared with the state-of-the-art Mask RCNN method with an average Dice score of 80.1%. Our proposed method is robust and reliable for advanced muscle and tendon function examinations obtained by ultrasound imaging.


Assuntos
Aprendizado Profundo , Interpretação de Imagem Assistida por Computador/métodos , Músculo Esquelético/diagnóstico por imagem , Tendões/diagnóstico por imagem , Ultrassonografia/métodos , Adulto , Articulação do Tornozelo/diagnóstico por imagem , Feminino , Humanos , Masculino , Adulto Jovem
8.
Sci Rep ; 9(1): 11836, 2019 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-31413264

RESUMO

Skeletal muscle architecture significantly influences the performance capacity of a muscle. A DTI-based method has been recently considered as a new reference standard to validate measurement of muscle structure in vivo. This study sought to quantify muscle architecture parameters such as fascicle length (FL), pennation angle (PA) and muscle thickness (tm) in post-stroke patients using diffusion tensor imaging (DTI) and to quantitatively compare the differences with 2D ultrasonography (US) and DTI. Muscle fascicles were reconstructed to examine the anatomy of the medial gastrocnemius, posterior soleus and tibialis anterior in seven stroke survivors using US- and DTI-based techniques, respectively. By aligning the US and DTI coordinate system, DTI reconstructed muscle fascicles at the same scanning plane of the US data can be identified. The architecture parameters estimated based on two imaging modalities were further compared. Significant differences were observed for PA and tm between two methods. Although mean FL was not significantly different, there were considerable intra-individual differences in FL and PA. On the individual level, parameters measured by US agreed poorly with those from DTI in both deep and superficial muscles. The significant differences in muscle parameters we observed suggested that the DTI-based method seems to be a better method to quantify muscle architecture parameters which can provide important information for treatment planning and to personalize a computational muscle model.


Assuntos
Imagem de Tensor de Difusão , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/patologia , Acidente Vascular Cerebral/diagnóstico por imagem , Sobreviventes , Ultrassonografia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
9.
Front Neurol ; 10: 736, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31354610

RESUMO

This study aims to quantify passive muscle stiffness of spastic wrist flexors in stroke survivors using shear wave elastography (SWE) and to correlate with neural and non-neural contributors estimated from a biomechanical model to hyper-resistance measured during passive wrist extension. Fifteen hemiplegic individuals after stroke with Modified Ashworth Scale (MAS) score larger than one were recruited. SWE were used to measure Young's modulus of flexor carpi radialis muscle with joint from 0° (at rest) to 50° flexion (passive stretch condition), with 10° interval. The neural (NC) and non-neural components i.e., elasticity component (EC) and viscosity component (VC) of the wrist joint were analyzed from a motorized mechanical device NeuroFlexor® (NF). Combining with a validated biomechanical model, the neural reflex and muscle stiffness contribution to the increased resistance can be estimated. MAS and Fugl-Meyer upper limb score were also measured to evaluate the spasticity and motor function of paretic upper limb. Young's modulus was significantly higher in the paretic side of flexor carpi radialis than that of the non-paretic side (p < 0.001) and it increased significantly from 0° to 50° of the paretic side (p < 0.001). NC, EC, and VC on the paretic side were higher than the non-paretic side (p < 0.05). There was moderate significant positive correlation between the Young's Modulus and EC (r = 0.565, p = 0.028) and VC (r = 0.645, p = 0.009) of the paretic forearm flexor muscle. Fugl-Meyer of the paretic forearm flexor has a moderate significant negative correlation with NC (r = -0.578, p = 0.024). No significant correlation between MAS and shear elastic modulus or NF components was observed. This study demonstrated the feasibility of combining SWE and NF as a non-invasive approach to assess spasticity of paretic muscle and joint in stroke clinics. The neural and non-neural components analysis as well as correlation findings of muscle stiffness of SWE might provide understanding of mechanism behind the neuromuscular alterations in stroke survivors and facilitate the design of suitable intervention for them.

10.
Gait Posture ; 67: 257-261, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30396058

RESUMO

BACKGROUND: Children and adolescents with Juvenile Idiopathic Arthritis (JIA) exhibit deviations in ankle dynamic joint stiffness (DJS, or moment-angle relationship) compared to healthy peers, but the relationship between ankle DJS and self-reported walking impairments has not been studied. This secondary analysis aimed to investigate the relationship between ankle DJS and self-reported walking disability in juveniles with JIA, and to determine whether intraarticular corticosteroid foot injections (IACI) were associated with long term changes in ankle DJS. RESEARCH QUESTIONS: Is ankle DJS altered in children with JIA reporting walking difficulties compared to children with JIA reporting no walking difficulties? Are IACIs associated with persistent alterations in ankle DJS? METHODS: Gait dynamics (DJS), foot pain, and foot-related disability were assessed in 33 children with JIA before intraarticular corticoid foot injection (IACI), and three months after IACI. Using self-reported walking capacity scores, children were classified as either having no walking difficulties (ND) or having walking difficulties (WD). Inferential statistics were used to compare demographics, pain, impairment scores, and ankle DJS between the groups. RESULTS: Before treatment, in the WD group, ankle DJS was significantly decreased both in the early rising phase (ERP = 0.03+0.02 vs. 0.05+0.02 Nm(kg*deg)- 1) and late rising phase (LRP = 0.11+0.06 vs. 0.24+0.22 Nm(kg*deg)-1) compared to the ND group. At three months, the ERP was still significantly decreased in the WD group (ERP = 0.03+0.01 vs. 0.05+0.03 Nm(kg*deg)-1). SIGNIFICANCE: Among children and adolescents with JIA who reported walking difficulties prior to IACIs, alterations in DJS in early stance phase (decreased ERP) remained three months after IACI suggesting persistent gait adaptations, possibly related to pain. Pre-treatment gait analysis may aid in identifying children who will not have long term benefit from IACIs in terms of improved gait, and therefore, may be informed and have the choice to be spared the risk of side effects associated with this treatment.


Assuntos
Articulação do Tornozelo/fisiopatologia , Artrite Juvenil/tratamento farmacológico , Glucocorticoides/administração & dosagem , Limitação da Mobilidade , Caminhada/fisiologia , Adolescente , Artrite Juvenil/fisiopatologia , Criança , Pré-Escolar , Avaliação da Deficiência , Feminino , Pé/fisiopatologia , Análise da Marcha , Humanos , Injeções Intra-Articulares , Masculino , Dor/tratamento farmacológico , Dor/etiologia , Amplitude de Movimento Articular/efeitos dos fármacos , Amplitude de Movimento Articular/fisiologia , Autorrelato , Resultado do Tratamento
11.
Artigo em Inglês | MEDLINE | ID: mdl-29963551

RESUMO

Quantifying neural and non-neural contributions to the joint resistance in spasticity is essential for a better evaluation of different intervention strategies such as botulinum toxin A (BoTN-A). However, direct measurement of muscle mechanical properties and spasticity-related parameters in humans is extremely challenging. The aim of this study was to use a previously developed musculoskeletal model and optimization scheme to evaluate the changes of neural and non-neural related properties of the spastic wrist flexors during passive wrist extension after BoTN-A injection. Data of joint angle and resistant torque were collected from 21 chronic stroke patients before, and 4 and 12 weeks post BoTN-A injection using NeuroFlexor, which is a motorized force measurement device to passively stretch wrist flexors. The model was optimized by tuning the passive and stretch-related parameters to fit the measured torque in each participant. It was found that stroke survivors exhibited decreased neural components at 4 weeks post BoNT-A injection, which returned to baseline levels after 12 weeks. The decreased neural component was mainly due to the increased motoneuron pool threshold, which is interpreted as a net excitatory and inhibitory inputs to the motoneuron pool. Though the linear stiffness and viscosity properties of wrist flexors were similar before and after treatment, increased exponential stiffness was observed over time which may indicate a decreased range of motion of the wrist joint. Using a combination of modeling and experimental measurement, valuable insights into the treatment responses, i.e., transmission of motoneurons, are provided by investigating potential parameter changes along the stretch reflex pathway in persons with chronic stroke.

12.
Biomed Res Int ; 2018: 3697835, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29750152

RESUMO

Displacement of the myotendinous junction (MTJ) obtained by ultrasound imaging is crucial to quantify the interactive length changes of muscles and tendons for understanding the mechanics and pathological conditions of the muscle-tendon unit during motion. However, the lack of a reliable automatic measurement method restricts its application in human motion analysis. This paper presents an automated measurement of MTJ displacement using prior knowledge on tendinous tissues and MTJ, precluding the influence of nontendinous components on the estimation of MTJ displacement. It is based on the perception of tendinous features from musculoskeletal ultrasound images using Radon transform and thresholding methods, with information about the symmetric measures obtained from phase congruency. The displacement of MTJ is achieved by tracking manually marked points on tendinous tissues with the Lucas-Kanade optical flow algorithm applied over the segmented MTJ region. The performance of this method was evaluated on ultrasound images of the gastrocnemius obtained from 10 healthy subjects (26.0 ± 2.9 years of age). Waveform similarity between the manual and automatic measurements was assessed by calculating the overall similarity with the coefficient of multiple correlation (CMC). In vivo experiments demonstrated that MTJ tracking with the proposed method (CMC = 0.97 ± 0.02) was more consistent with the manual measurements than existing optical flow tracking methods (CMC = 0.79 ± 0.11). This study demonstrated that the proposed method was robust to the interference of nontendinous components, resulting in a more reliable measurement of MTJ displacement, which may facilitate further research and applications related to the architectural change of muscles and tendons.


Assuntos
Músculo Esquelético/diagnóstico por imagem , Tendões/diagnóstico por imagem , Adulto , Algoritmos , Feminino , Humanos , Masculino , Ultrassonografia/métodos
13.
Int J Mol Sci ; 17(9)2016 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-27618015

RESUMO

The metanephric mesenchyme (MM) cells are a subset of kidney progenitor cells and play an essential role in mesenchymal-epithelial transition (MET), the key step of nephron generation. Six2, a biological marker related to Wnt signaling pathway, promotes the proliferation, inhibits the apoptosis and maintains the un-differentiation of MM cells. Besides, LiCl is an activator of Wnt signaling pathway. However, the role of LiCl in cellular regulation of MM cells remains unclear, and the relationship between LiCl and Six2 in this process is also little known. Here, we performed EdU assay and flow cytometry assay to, respectively, detect the proliferation and apoptosis of MM cells treated with LiCl of increasing dosages. In addition, reverse transcription-PCR (RT-PCR) and Western-blot were conducted to measure the expression of Six2 and some maker genes of Wnt and bone-morphogenetic-protein (BMP) signaling pathway. Furthermore, luciferase assay was also carried out to detect the transcriptional regulation of Six2. Then we found LiCl promoted MM cell proliferation at low-concentration (10, 20, 30, and 40 mM). The expression of Six2 was dose-dependently increased in low-concentration (10, 20, 30, and 40 mM) at both mRNA and protein level. In addition, both of cell proliferation and Six2 expression in MM cells declined when dosage reached high-concentration (50 mM). However, Six2 knock-down converted the proliferation reduction at 50 mM. Furthermore, Six2 deficiency increased the apoptosis of MM cells, compared with negative control cells at relative LiCl concentration. However, the abnormal rise of apoptosis at 30 mM of LiCl concentration implies that it might be the reduction of GSK3ß that increased cell apoptosis. Together, these demonstrate that LiCl can induce the proliferation and apoptosis of MM cells coordinating with Six2.


Assuntos
Apoptose/genética , Proliferação de Células/genética , Proteínas de Homeodomínio/metabolismo , Cloreto de Lítio/farmacologia , Fatores de Transcrição/metabolismo , Animais , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células HEK293 , Proteínas de Homeodomínio/genética , Humanos , Camundongos , Fatores de Transcrição/genética , Via de Sinalização Wnt
14.
Gait Posture ; 39(3): 926-32, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24374063

RESUMO

Excessive co-contraction causes inefficient or abnormal movement in several neuromuscular pathologies. How synergistic muscles spanning the ankle, knee and hip adapt to co-contraction of ankle muscles is not well understood. This study aimed to identify the compensation strategies required to retain normal walking with excessive antagonistic ankle muscle co-contraction. Muscle-actuated simulations of normal walking were performed to quantify compensatory mechanisms of ankle and knee muscles during stance in the presence of normal, medium and high levels of co-contraction of antagonistic pairs gastrocnemius+tibialis anterior and soleus+tibialis anterior. The study showed that if co-contraction increases, the synergistic ankle muscles can compensate; with gastrocmemius+tibialis anterior co-contraction, the soleus will increase its contribution to ankle plantarflexion acceleration. At the knee, however, almost all muscles spanning the knee and hip are involved in compensation. We also found that ankle and knee muscles alone can provide sufficient compensation at the ankle joint, but hip muscles must be involved to generate sufficient knee moment. Our findings imply that subjects with a rather high level of dorsiflexor+plantarflexor co-contraction can still perform normal walking. This also suggests that capacity of other lower limb muscles to compensate is important to retain normal walking in co-contracted persons. The compensatory mechanisms can be useful in clinical interpretation of motion analyses, when secondary muscle co-contraction or other deficits may present simultaneously in subjects with motion disorders.


Assuntos
Articulação do Tornozelo/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Caminhada/fisiologia , Aceleração , Adulto , Fenômenos Biomecânicos , Eletromiografia , Humanos , Masculino
15.
J Electromyogr Kinesiol ; 23(4): 759-65, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23561824

RESUMO

This article introduces history-dependent effects in a skeletal muscle model applied to dynamic simulations of musculoskeletal system motion. Force depression and force enhancement induced by active muscle shortening and lengthening, respectively, represent muscle history effects. A muscle model depending on the preceding contractile events together with the current parameters was developed for OpenSim software, and applied in simulations of standing heel-raise and squat movements. Muscle activations were computed using joint kinematics and ground reaction forces recorded from the motion capture of seven individuals. In the muscle-actuated simulations, a modification was applied to the computed activation, and was compared to the measured electromyography data. For the studied movements, the history gives a small but visible effect to the muscular force trace, but some parameter values must be identified before the exact magnitude can be analysed. The muscle model modification improves the existing muscle models and gives a more accurate description of underlying forces and activations in musculoskeletal system movement simulations.


Assuntos
Articulações/fisiologia , Modelos Biológicos , Movimento/fisiologia , Contração Muscular/fisiologia , Amplitude de Movimento Articular/fisiologia , Adulto , Simulação por Computador , Feminino , Humanos , Masculino , Estresse Mecânico
16.
J Electromyogr Kinesiol ; 22(4): 566-74, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22572108

RESUMO

Moment-angle relationship (dynamic joint stiffness)--the relationship between changes in joint moment and changes in joint angle--is useful for demonstrating interaction of kinematics and kinetics during gait. However, the individual contributors of dynamic joint stiffness are not well studied and understood, which has thus far limited its clinical application. In this study, ankle dynamic joint stiffness was analyzed and decomposed into three components in thirty able-bodied children during the stance phase of the gait. To verify the accuracy of the decomposition, the sum of decomposed components was compared to stiffness computed from experimental data, and good to very good agreement was found. Component 1, the term associated with changes in ground reaction force moment, was the dominant contribution to ankle dynamic joint stiffness. Retrospective data from eight children with juvenile idiopathic arthritis and idiopathic toe-walking was examined to explore the potential utility of analytical decomposition in pathological gait. Compared to controls, component 1 was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two sub-components of component 1 which are based on magnitudes and rates of change of the ground reaction force and of its moment arm, and differences between the two patient groups and controls were most evident and interpretable here. Findings of the current study indicate that analytical decomposition can help identify the individual contributors to joint stiffness and clarify the sources of differences in patient groups.


Assuntos
Articulação do Tornozelo/fisiopatologia , Artrite Juvenil/fisiopatologia , Modelos Biológicos , Contração Muscular , Músculo Esquelético/fisiopatologia , Amplitude de Movimento Articular , Caminhada , Adolescente , Criança , Simulação por Computador , Módulo de Elasticidade , Feminino , Humanos , Masculino , Torque
17.
Gait Posture ; 34(1): 29-35, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21474318

RESUMO

The purpose of this study was to determine how gait deviation in one plane (i.e. excessive subtalar inversion/eversion) can affect the dynamic function of the tibialis anterior, gastrocnemius, and soleus to accelerate the subtalar, ankle, knee and hip joints, as well as the body center of mass. Induced acceleration analysis was performed based on a subject-specific three-dimensional linkage model configured by stance phase gait data and driven by one unit of muscle force. Eight healthy adult subjects were examined in gait analysis. The subtalar inversion/eversion was modeled by offsetting up to 20° from the normal subtalar angle while other configurations remained unaltered. This study showed that the gastrocnemius, soleus and tibialis anterior generally functioned as their anatomical definition in normal gait, but counterintuitive function was occasionally found in the bi-articular gastrocnemius. The plantarflexors play important roles in the body support and forward progression. Excessive subtalar eversion was found to enlarge the plantarflexors and tibialis anterior's function. Induced acceleration analysis demonstrated its ability to isolate the contributions of individual muscle to a given factor, and as a means of studying effect of pathological gait on the dynamic muscle functions.


Assuntos
Marcha/fisiologia , Músculo Esquelético/fisiologia , Articulação Talocalcânea/fisiologia , Adulto , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Feminino , Articulação do Quadril/fisiologia , Humanos , Articulação do Joelho/fisiologia , Masculino , Modelos Anatômicos , Músculo Esquelético/fisiopatologia , Articulação Talocalcânea/fisiopatologia
18.
Gait Posture ; 31(2): 234-40, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19942435

RESUMO

Ankle fractures are one of the most common lower limb traumas. Several studies reported short- and long-term post-operative results, mainly determined by radiographic and subjective functional evaluations. Three-dimensional gait analysis with a multi-segment foot model was used in the current study to quantify the inter-segment foot motions in 18 patients 1 year after surgically treated ankle fractures. Data were compared to that from gender- and age-matched healthy controls. The correlations between Olerud/Molander ankle score and kinematics were also evaluated. Patients with ankle fractures showed less plantarflexion and smaller range of motion in the injured talocrural joint, which were believed to be a sign of residual joint stiffness after surgery and immobilization. Moreover, the forefoot segment had smaller sagittal and transverse ranges of motion, less plantarflexion and the hallux segment had less dorsiflexion and smaller sagittal range of motion. The deviations found in the forefoot segment may contribute to the compensation mechanisms of the injured ankle joint. Findings of our study show that gait analysis with a multi-segment foot model provides a quantitative and objective way to perform the dynamic assessment of post-operative ankle fractures, and makes it possible to better understand not only how the injured joint is affected, but also the surrounding joints.


Assuntos
Traumatismos do Tornozelo/fisiopatologia , Traumatismos do Tornozelo/cirurgia , Fraturas Ósseas/fisiopatologia , Fraturas Ósseas/cirurgia , Marcha/fisiologia , Adolescente , Adulto , Análise de Variância , Traumatismos do Tornozelo/reabilitação , Fenômenos Biomecânicos , Estudos de Casos e Controles , Avaliação da Deficiência , Feminino , Seguimentos , Fraturas Ósseas/reabilitação , Humanos , Imageamento Tridimensional/instrumentação , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Amplitude de Movimento Articular/fisiologia
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