The Experts below are selected from a list of 172821 Experts worldwide ranked by ideXlab platform
James M Wakeling - One of the best experts on this subject based on the ideXlab platform.
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does a two element Muscle Model offer advantages when estimating ankle plantar flexor forces during human cycling
Journal of Biomechanics, 2018Co-Authors: Adrian Lai, Allison S Arnold, Andrew A Biewener, Taylor J M Dick, James M WakelingAbstract:Traditional Hill-type Muscle Models, parameterized using high-quality experimental data, are often "too weak" to reproduce the joint torques generated by healthy adults during rapid, high force tasks. This study investigated whether the failure of these Models to account for different types of motor units contributes to this apparent weakness; if so, Muscle-driven simulations may rely on excessively high Muscle excitations to generate a given force. We ran a series of forward simulations that reproduced measured ankle mechanics during cycling at five cadences ranging from 60 to 140 RPM. We generated both "nominal" simulations, in which an abstract ankle Model was actuated by a 1-element Hill-type plantar flexor with a single contractile element (CE), and "test" simulations, in which the same Model was actuated by a 2-element plantar flexor with two CEs that accounted for the force-generating properties of slower and faster motor units. We varied the total excitation applied to the 2-element plantar flexor between 60 and 105% of the excitation from each nominal simulation, and we varied the amount distributed to each CE between 0 and 100% of the total. Within this test space, we identified the excitation level and distribution, at each cadence, that best reproduced the plantar flexor forces generated in the nominal simulations. Our comparisons revealed that the 2-element Model required substantially less total excitation than the 1-element Model to generate comparable forces, especially at higher cadences. For instance, at 140 RPM, the required excitation was reduced by 23%. These results suggest that a 2-element Model, in which contractile properties are "tuned" to represent slower and faster motor units, can increase the apparent strength and perhaps improve the fidelity of simulations of tasks with varying mechanical demands.
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does a two element Muscle Model offer advantages when estimating ankle plantar flexor forces during human cycling
Journal of Biomechanics, 2017Co-Authors: Allison S Arnold, Andrew A Biewener, Taylor J M Dick, James M WakelingAbstract:Abstract Traditional Hill-type Muscle Models, parameterized using high-quality experimental data, are often “too weak” to reproduce the joint torques generated by healthy adults during rapid, high force tasks. This study investigated whether the failure of these Models to account for different types of motor units contributes to this apparent weakness; if so, Muscle-driven simulations may rely on excessively high Muscle excitations to generate a given force. We ran a series of forward simulations that reproduced measured ankle mechanics during cycling at five cadences ranging from 60 to 140 RPM. We generated both “nominal” simulations, in which an abstract ankle Model was actuated by a 1-element Hill-type plantar flexor with a single contractile element (CE), and “test” simulations, in which the same Model was actuated by a 2-element plantar flexor with two CEs that accounted for the force-generating properties of slower and faster motor units. We varied the total excitation applied to the 2-element plantar flexor between 60 and 105% of the excitation from each nominal simulation, and we varied the amount distributed to each CE between 0 and 100% of the total. Within this test space, we identified the excitation level and distribution, at each cadence, that best reproduced the plantar flexor forces generated in the nominal simulations. Our comparisons revealed that the 2-element Model required substantially less total excitation than the 1-element Model to generate comparable forces, especially at higher cadences. For instance, at 140 RPM, the required excitation was reduced by 23%. These results suggest that a 2-element Model, in which contractile properties are “tuned” to represent slower and faster motor units, can increase the apparent strength and perhaps improve the fidelity of simulations of tasks with varying mechanical demands.
Athanase Benetos - One of the best experts on this subject based on the ideXlab platform.
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response by benetos et al to letter regarding article short leukocyte telomere length precedes clinical expression of atherosclerosis the blood and Muscle Model
Circulation Research, 2018Co-Authors: Athanase Benetos, Simon Verhulst, Jeremy D Kark, Simon Toupance, Abraham AvivAbstract:Converging evidence suggests that the hematopoietic system is a key player in the telomere length (TL)–atherosclerosis connection. The hematopoietic system and the vascular endothelium, where atherosclerosis begins, share a common embryonic precursor—the hemogenic endothelium, which gives birth not only to the vascular endothelium but also to hematopoietic stem cells that build the hematopoietic system.1 This shared embryonic history and perpetual interactions between the hematopoietic system and the vascular endothelium prompted the proposal to unite the 2 systems into a singular entity coined the hemothelium.2 We draw on the hemothelium paradigm in responding to the letter by De Meyer about the meaning of the findings presented in our article.3 De Meyer rightfully focuses on the vascular endothelium as a key player in the TL–atherosclerosis connection but provides little evidence to support his idea that as expressed in leukocyte TL (LTL), the hematopoietic system has a minimal role in this connection. To build his case, De Meyer cites a study showing shorter TL in vascular endothelial cells from 11 patients who died from atherosclerotic cardiovascular disease (ACVD) than that in 22 individuals who died from other causes with no TL overlap between the 2 groups and between endothelial cells derived from atherosclerotic regions than nonatherosclerotic regions in the coronary arteries.4 He notes, in contrast, that although LTL is slightly shorter in patients with ACVD than in their peers without the disease, there is considerable overlap between the 2 groups. De Meyer …
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short leukocyte telomere length precedes clinical expression of atherosclerosis the blood and Muscle Model
Circulation Research, 2017Co-Authors: Athanase Benetos, Carlos Labat, Masayuki Kimura, Simon Toupance, Sylvie Gautier, Pascal Rossi, Nicla Settembre, J Hubert, Luc Frimat, Baptiste BertrandAbstract:Rationale: Short telomere length (TL) in leukocytes is associated with atherosclerotic cardiovascular disease (ASCVD). It is unknown whether this relationship stems from having inherently short leukocyte TL (LTL) at birth or a faster LTL attrition thereafter. LTL represents TL in the highly proliferative hematopoietic system, whereas TL in skeletal Muscle represents a minimally replicative tissue. Objective: We measured LTL and Muscle TL (MTL) in the same individuals with a view to obtain comparative metrics for lifelong LTL attrition and learn about the temporal association of LTL with ASCVD. Methods and Results: Our Discovery Cohort comprised 259 individuals aged 63±14 years (mean±SD), undergoing surgery with (n=131) or without (n=128) clinical manifestation of ASCVD. In all subjects, MTL adjusted for Muscle biopsy site (MTL A ) was longer than LTL and the LTL-MTL A gap similarly widened with age in ASCVD patients and controls. Age- and sex-adjusted LTL ( P =0.005), but not MTL A ( P =0.90), was shorter in patients with ASCVD than controls. The TL gap between leukocytes and Muscle (LTL-MTL A ) was wider ( P =0.0003), and the TL ratio between leukocytes and Muscle (LTL/MTL A ) was smaller ( P =0.0001) in ASCVD than in controls. Findings were replicated in a cohort comprising 143 individuals. Conclusions: This first study to apply the blood-and-Muscle TL Model shows more pronounced LTL attrition in ASCVD patients than controls. The difference in LTL attrition was not associated with age during adulthood suggesting that increased attrition in early life is more likely to be a major explanation of the shorter LTL in ASCVD patients. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02176941.
Masayuki Kimura - One of the best experts on this subject based on the ideXlab platform.
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telomere length dynamics in early life the blood and Muscle Model
The FASEB Journal, 2018Co-Authors: Sanjeev Sabharwal, Simon Verhulst, George Guirguis, Jeremy D Kark, Carlos Labat, Natalie Roche, Kristina Martimucci, Krunal Patel, Debra S Heller, Masayuki KimuraAbstract:Telomere length (TL) trajectories in somatic tissues during human growth and development are poorly understood. We examined a blood-and-Muscle Model during early life, focusing on TL trajectories in leukocytes, representing the highly proliferative hematopoietic system, and skeletal Muscle, a minimally proliferative tissue. Leukocyte TL (LTL) and skeletal Muscle TL (MTL) were measured in 28 fetuses and 73 children. LTL and MTL were highly variable across individuals (sd: fetal LTL = 0.72 kb, MTL = 0.72 kb; children LTL = 0.81 kb, MTL = 0.82 kb) but were highly correlated within individuals (fetuses, r = 0.76, P < 0.0001; children, r = 0.87, P < 0.0001). LTL was shorter than MTL in fetuses (10.63 vs. 11.01 kb; P = 0.0004) and children (8.46 vs. 9.40 kb; <0.0001). The LTL-MTL gap was smaller in fetuses than children. TL in children was inversely correlated with body mass index (BMI) (LTL: -0.047 ± 0.016 kb/BMI, P < 0.005; MTL: -0.037 ± 0.017 kb/BMI, P = 0.03). We conclude that variations in TL across adults and differences in TL between somatic tissues are largely established in early life. Because TL plays a significant role in aging-related diseases, insight into the factors that fashion TL in somatic tissues during early development should contribute to an understanding of the relationship of TL with these disease and longevity in humans.-Sabharwal, S., Verhulst, S., Guirguis, G., Kark, J. D., Labat, C., Roche, N. E., Martimucci, K., Patel, K., Heller, D. S., Kimura, M., Chuang, D., Chuang, A., Benetos, A., Aviv, A. Telomere length dynamics in early life: the blood-and-Muscle Model.
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short leukocyte telomere length precedes clinical expression of atherosclerosis the blood and Muscle Model
Circulation Research, 2017Co-Authors: Athanase Benetos, Carlos Labat, Masayuki Kimura, Simon Toupance, Sylvie Gautier, Pascal Rossi, Nicla Settembre, J Hubert, Luc Frimat, Baptiste BertrandAbstract:Rationale: Short telomere length (TL) in leukocytes is associated with atherosclerotic cardiovascular disease (ASCVD). It is unknown whether this relationship stems from having inherently short leukocyte TL (LTL) at birth or a faster LTL attrition thereafter. LTL represents TL in the highly proliferative hematopoietic system, whereas TL in skeletal Muscle represents a minimally replicative tissue. Objective: We measured LTL and Muscle TL (MTL) in the same individuals with a view to obtain comparative metrics for lifelong LTL attrition and learn about the temporal association of LTL with ASCVD. Methods and Results: Our Discovery Cohort comprised 259 individuals aged 63±14 years (mean±SD), undergoing surgery with (n=131) or without (n=128) clinical manifestation of ASCVD. In all subjects, MTL adjusted for Muscle biopsy site (MTL A ) was longer than LTL and the LTL-MTL A gap similarly widened with age in ASCVD patients and controls. Age- and sex-adjusted LTL ( P =0.005), but not MTL A ( P =0.90), was shorter in patients with ASCVD than controls. The TL gap between leukocytes and Muscle (LTL-MTL A ) was wider ( P =0.0003), and the TL ratio between leukocytes and Muscle (LTL/MTL A ) was smaller ( P =0.0001) in ASCVD than in controls. Findings were replicated in a cohort comprising 143 individuals. Conclusions: This first study to apply the blood-and-Muscle TL Model shows more pronounced LTL attrition in ASCVD patients than controls. The difference in LTL attrition was not associated with age during adulthood suggesting that increased attrition in early life is more likely to be a major explanation of the shorter LTL in ASCVD patients. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02176941.
Baptiste Bertrand - One of the best experts on this subject based on the ideXlab platform.
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short leukocyte telomere length precedes clinical expression of atherosclerosis the blood and Muscle Model
Circulation Research, 2017Co-Authors: Athanase Benetos, Carlos Labat, Masayuki Kimura, Simon Toupance, Sylvie Gautier, Pascal Rossi, Nicla Settembre, J Hubert, Luc Frimat, Baptiste BertrandAbstract:Rationale: Short telomere length (TL) in leukocytes is associated with atherosclerotic cardiovascular disease (ASCVD). It is unknown whether this relationship stems from having inherently short leukocyte TL (LTL) at birth or a faster LTL attrition thereafter. LTL represents TL in the highly proliferative hematopoietic system, whereas TL in skeletal Muscle represents a minimally replicative tissue. Objective: We measured LTL and Muscle TL (MTL) in the same individuals with a view to obtain comparative metrics for lifelong LTL attrition and learn about the temporal association of LTL with ASCVD. Methods and Results: Our Discovery Cohort comprised 259 individuals aged 63±14 years (mean±SD), undergoing surgery with (n=131) or without (n=128) clinical manifestation of ASCVD. In all subjects, MTL adjusted for Muscle biopsy site (MTL A ) was longer than LTL and the LTL-MTL A gap similarly widened with age in ASCVD patients and controls. Age- and sex-adjusted LTL ( P =0.005), but not MTL A ( P =0.90), was shorter in patients with ASCVD than controls. The TL gap between leukocytes and Muscle (LTL-MTL A ) was wider ( P =0.0003), and the TL ratio between leukocytes and Muscle (LTL/MTL A ) was smaller ( P =0.0001) in ASCVD than in controls. Findings were replicated in a cohort comprising 143 individuals. Conclusions: This first study to apply the blood-and-Muscle TL Model shows more pronounced LTL attrition in ASCVD patients than controls. The difference in LTL attrition was not associated with age during adulthood suggesting that increased attrition in early life is more likely to be a major explanation of the shorter LTL in ASCVD patients. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02176941.
Philippe Poignet - One of the best experts on this subject based on the ideXlab platform.
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Exploring Peripheral Mechanism of Tremor on Neuromusculoskeletal Model: A General Simulation Study
IEEE Transactions on Biomedical Engineering, 2009Co-Authors: Dingguo Zhang*, Philippe Poignet, AntÔnio P. L. BoAbstract:This paper provides a general simulation study on tremor based on a modular neuromusculoskeletal Model. It focuses on the peripheral mechanism. It is known that the reflex loops in the peripheral nervous system have influences on the tremor. A neuromusculoskeletal Model with several reflex loops is developed to explore the dynamics of tremor. The Muscle Model is derived from a Hill-type Muscle Model. The reflex loops include the spindle organ, Golgi tendon organ, and Renshaw cell. Their effects are investigated quantitatively in detail. A two-Muscle (agonist/antagonist) system with interaction is further studied. Moreover, a Model in combination with the central oscillation and peripheral system is developed. Some results are in accordance with the previous research, whereas some new findings are proposed according to the simulation study.
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Nonlinear identification of skeletal Muscle dynamics with sigma-point kalman filter for Model-based FES
2008Co-Authors: Mitsuhiro Hayashibe, Philippe Poignet, David GuiraudAbstract:A Model-based FES would be very helpful for the adaptive movement synthesis of spinal-cord-injured patients. For the fulfillment, we need a precise skeletal Muscle Model to predict the force of each Muscle. Thus, we have to estimate many unknown parameters in the nonlinear Muscle system. The identification process is essential for the realistic force prediction. We previously proposed a mathematical Muscle Model of skeletal Muscle which describes the complex physiological system of skeletal Muscle based on the macroscopic Hill-Maxwell and microscopic Huxley concepts. It has an original skeletal Muscle Model to enable consideration for the muscular masses and the viscous frictions caused by the Muscle-tendon complex. In this paper, we present an experimental identification method of biomechanical parameters using sigma-point Kalman filter applied to the nonlinear skeletal Muscle Model. Result of the identification shows its effective performance. The evaluation is provided by comparing the estimated isometric force with experimental data with the stimulation of the rabbit medial gastrocnemius Muscle. This approach has the advantage of fast and robust computation, that can be implemented for online application of FES control.
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experimental identification of skeletal Muscle biomechanical parameters with sigma point kalman filter
IFESS: International Functional Electrical Stimulation Society, 2007Co-Authors: Mitsuhiro Hayashibe, David Guiraud, Christine Azevedo Coste, Philippe PoignetAbstract:This work establishes a computational identification of skeletal Muscle biomechanical parameters based on experiments. We previously proposed a mathematical Muscle Model which describes the complex physiological system of skeletal Muscle based on the macroscopic Hill and microscopic Huxley concepts. The original skeletal Muscle Model enables consideration for the muscular masses and the viscous frictions by Muscle tendon complex. In this paper, we present an experimental identification method of biomechanical parameters with Sigma-Point Kalman Filter under nonlinear differential equations of our Model. SPKF has higher accuracy and consistency for nonlinear estimation than extended kalman filter. Result of the estimation shows its effective performance.
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mathematical Muscle Model for functional electrical stimulation control strategies
International Conference on Robotics and Automation, 2004Co-Authors: H E Makssoud, David Guiraud, Philippe PoignetAbstract:In paraplegic patients with upper motor neuron lesions the signal path from the central nervous system to Muscles is interrupted. Functional Electrical Stimulation (FES) applied to the lower motor neurons can replace the lacking signals. A neuroprosthesis may be used to restore motor function in paraplegic patients on the basis of FES. The neuroprosthesic implant allows Muscles to be controlled with high accuracy, high selectivity and the repeatability of the Muscle's response can be achieved. The SUAW project succeeded in the implantation of an advanced neuroprosthetic device on two patients, but the movement generation remains open loop and is tuned empirically. The system is thus insufficient to enhance significantly the daily-life of the patient, nevertheless, the good results obtained give us the opportunity to envisage the system evolves towards the automatic synthesis of the stimulation patterns generating the desired movement and closed loop control. To achieve this goal, some preliminary researches have to be carried out; starting with a specific Modeling that can be used in the contest of FES. The main issues concern Muscle Modeling including FES parameters as inputs, fatigue, the interaction with the skeleton, and the identification of parameters. This paper describes the mathematical Modeling of the skeletal Muscle.
