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Trunk muscle co-activation using functional electrical stimulation modifies center of pressure fluctuations during quiet sitting by increasing trunk stiffness.

Milosevic M, Masani K, Wu N, McConville KM, Popovic MR - J Neuroeng Rehabil (2015)

Bottom Line: The experimental study involved 15 able-bodied individuals who were seated on an instrumented chair.During the experiment, COP of the body projected on the seating surface was calculated to compare sitting stability of participants during unsupported and FES-assisted quiet sitting.The analytical (simulation) study examined dynamics of quiet sitting using an inverted pendulum model, representing the body, and a proportional-derivative (PD) controller, representing the central nervous system control.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON, M5S 3G9, Canada. matija.milosevic@utoronto.ca.

ABSTRACT

Background: The purpose of this study was to examine the impact of functional electrical stimulation (FES) induced co-activation of trunk muscles during quiet sitting. We hypothesized that FES applied to the trunk muscles will increase trunk stiffness. The objectives of this study were to: 1) compare the center of pressure (COP) fluctuations during unsupported and FES-assisted quiet sitting - an experimental study and; 2) investigate how FES influences sitting balance - an analytical (simulation) study.

Methods: The experimental study involved 15 able-bodied individuals who were seated on an instrumented chair. During the experiment, COP of the body projected on the seating surface was calculated to compare sitting stability of participants during unsupported and FES-assisted quiet sitting. The analytical (simulation) study examined dynamics of quiet sitting using an inverted pendulum model, representing the body, and a proportional-derivative (PD) controller, representing the central nervous system control. This model was used to analyze the relationship between increased trunk stiffness and COP fluctuations.

Results: In the experimental study, the COP fluctuations showed that: i) the mean velocity, mean frequency and the power frequency were higher during FES-assisted sitting; ii) the frequency dispersion for anterior-posterior fluctuations was smaller during FES-assisted sitting; and iii) the mean distance, range and centroidal frequency did not change during FES-assisted sitting. The analytical (simulation) study showed that increased mechanical stiffness of the trunk had the same effect on COP fluctuations as the FES.

Conclusions: The results of this study suggest that FES applied to the key trunk muscles increases the speed of the COP fluctuations by increasing the trunk stiffness during quiet sitting.

No MeSH data available.


Related in: MedlinePlus

Block diagram of the model used in the simulation study. The feedback model included the neural controller with transmission delays (τ1, transmission time delay and τ2, feedback time delay) and the neuromusculoskeletal (NMS) torque-generation process, as well as mechanical stiffness (K) and passive damping (B) to control the inverted pendulum. The inverted pendulum was used to describe the mechanics of the quiet sitting. m is the moving mass, h is the height of center of mass (COM), and I is the moment of inertia of the inverted pendulum. KP and KD, are proportional and derivative gains of the proportional-derivative (PD) controller, respectively, used to emulate the neural controller. An inverted pendulum model of quiet sitting is represented, where yCOP is the center of pressure (COP) position, θ is the sway angle, and g is the acceleration of gravity. Gaussian random noise was inserted into the system to drive the simulations
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Fig2: Block diagram of the model used in the simulation study. The feedback model included the neural controller with transmission delays (τ1, transmission time delay and τ2, feedback time delay) and the neuromusculoskeletal (NMS) torque-generation process, as well as mechanical stiffness (K) and passive damping (B) to control the inverted pendulum. The inverted pendulum was used to describe the mechanics of the quiet sitting. m is the moving mass, h is the height of center of mass (COM), and I is the moment of inertia of the inverted pendulum. KP and KD, are proportional and derivative gains of the proportional-derivative (PD) controller, respectively, used to emulate the neural controller. An inverted pendulum model of quiet sitting is represented, where yCOP is the center of pressure (COP) position, θ is the sway angle, and g is the acceleration of gravity. Gaussian random noise was inserted into the system to drive the simulations

Mentions: We conducted an analytical (simulation) study to investigate the mechanism of changes of COP fluctuations in AP direction, which were observed in the experiments described in Section 2.1. The simulation study was performed using Matlab and Simulink (ver. R2011b, MathWorks, Inc., USA). A feedback model of the control system during quiet sitting was developed using: i) an inverted pendulum model to describe the mechanics of the quiet sitting; ii) a proportional-derivative (PD) controller to represent the neural controller of the central nervous system that regulates balance of the trunk; iii) motor and sensory command transmission delays; iv) a neuromusculoskeletal (NMS) torque-generation process, which was modeled using a second order dynamic equation; and v) mechanical stiffness and passive damping of the trunk. All components of the model are shown in Fig. 2. A detailed description follows.Fig. 2


Trunk muscle co-activation using functional electrical stimulation modifies center of pressure fluctuations during quiet sitting by increasing trunk stiffness.

Milosevic M, Masani K, Wu N, McConville KM, Popovic MR - J Neuroeng Rehabil (2015)

Block diagram of the model used in the simulation study. The feedback model included the neural controller with transmission delays (τ1, transmission time delay and τ2, feedback time delay) and the neuromusculoskeletal (NMS) torque-generation process, as well as mechanical stiffness (K) and passive damping (B) to control the inverted pendulum. The inverted pendulum was used to describe the mechanics of the quiet sitting. m is the moving mass, h is the height of center of mass (COM), and I is the moment of inertia of the inverted pendulum. KP and KD, are proportional and derivative gains of the proportional-derivative (PD) controller, respectively, used to emulate the neural controller. An inverted pendulum model of quiet sitting is represented, where yCOP is the center of pressure (COP) position, θ is the sway angle, and g is the acceleration of gravity. Gaussian random noise was inserted into the system to drive the simulations
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4641430&req=5

Fig2: Block diagram of the model used in the simulation study. The feedback model included the neural controller with transmission delays (τ1, transmission time delay and τ2, feedback time delay) and the neuromusculoskeletal (NMS) torque-generation process, as well as mechanical stiffness (K) and passive damping (B) to control the inverted pendulum. The inverted pendulum was used to describe the mechanics of the quiet sitting. m is the moving mass, h is the height of center of mass (COM), and I is the moment of inertia of the inverted pendulum. KP and KD, are proportional and derivative gains of the proportional-derivative (PD) controller, respectively, used to emulate the neural controller. An inverted pendulum model of quiet sitting is represented, where yCOP is the center of pressure (COP) position, θ is the sway angle, and g is the acceleration of gravity. Gaussian random noise was inserted into the system to drive the simulations
Mentions: We conducted an analytical (simulation) study to investigate the mechanism of changes of COP fluctuations in AP direction, which were observed in the experiments described in Section 2.1. The simulation study was performed using Matlab and Simulink (ver. R2011b, MathWorks, Inc., USA). A feedback model of the control system during quiet sitting was developed using: i) an inverted pendulum model to describe the mechanics of the quiet sitting; ii) a proportional-derivative (PD) controller to represent the neural controller of the central nervous system that regulates balance of the trunk; iii) motor and sensory command transmission delays; iv) a neuromusculoskeletal (NMS) torque-generation process, which was modeled using a second order dynamic equation; and v) mechanical stiffness and passive damping of the trunk. All components of the model are shown in Fig. 2. A detailed description follows.Fig. 2

Bottom Line: The experimental study involved 15 able-bodied individuals who were seated on an instrumented chair.During the experiment, COP of the body projected on the seating surface was calculated to compare sitting stability of participants during unsupported and FES-assisted quiet sitting.The analytical (simulation) study examined dynamics of quiet sitting using an inverted pendulum model, representing the body, and a proportional-derivative (PD) controller, representing the central nervous system control.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, ON, M5S 3G9, Canada. matija.milosevic@utoronto.ca.

ABSTRACT

Background: The purpose of this study was to examine the impact of functional electrical stimulation (FES) induced co-activation of trunk muscles during quiet sitting. We hypothesized that FES applied to the trunk muscles will increase trunk stiffness. The objectives of this study were to: 1) compare the center of pressure (COP) fluctuations during unsupported and FES-assisted quiet sitting - an experimental study and; 2) investigate how FES influences sitting balance - an analytical (simulation) study.

Methods: The experimental study involved 15 able-bodied individuals who were seated on an instrumented chair. During the experiment, COP of the body projected on the seating surface was calculated to compare sitting stability of participants during unsupported and FES-assisted quiet sitting. The analytical (simulation) study examined dynamics of quiet sitting using an inverted pendulum model, representing the body, and a proportional-derivative (PD) controller, representing the central nervous system control. This model was used to analyze the relationship between increased trunk stiffness and COP fluctuations.

Results: In the experimental study, the COP fluctuations showed that: i) the mean velocity, mean frequency and the power frequency were higher during FES-assisted sitting; ii) the frequency dispersion for anterior-posterior fluctuations was smaller during FES-assisted sitting; and iii) the mean distance, range and centroidal frequency did not change during FES-assisted sitting. The analytical (simulation) study showed that increased mechanical stiffness of the trunk had the same effect on COP fluctuations as the FES.

Conclusions: The results of this study suggest that FES applied to the key trunk muscles increases the speed of the COP fluctuations by increasing the trunk stiffness during quiet sitting.

No MeSH data available.


Related in: MedlinePlus