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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

Experimental setup showing participant’s posture on a chair without back support during sitting balance assessments. The force plate was positioned on the seat surface, under the buttocks, to capture trunk sway, while the participant’s feet were not supported on the ground and the participants had their arms crossed on their chest. The figure also shows the: a front view of the participant illustrating the approximate location of the FES electrodes on the rectus abdominis (RA) muscle and; b back view of the participant illustrating the approximate location of the of the FES electrodes on the lumbar erector spinae (L3) muscle. The RA and L3 muscles were stimulated bilaterally and were activated simultaneously to generate co-activations
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Fig1: Experimental setup showing participant’s posture on a chair without back support during sitting balance assessments. The force plate was positioned on the seat surface, under the buttocks, to capture trunk sway, while the participant’s feet were not supported on the ground and the participants had their arms crossed on their chest. The figure also shows the: a front view of the participant illustrating the approximate location of the FES electrodes on the rectus abdominis (RA) muscle and; b back view of the participant illustrating the approximate location of the of the FES electrodes on the lumbar erector spinae (L3) muscle. The RA and L3 muscles were stimulated bilaterally and were activated simultaneously to generate co-activations

Mentions: Participants were asked to maintain an upright sitting posture on a height-adjustable instrumented chair without back support, such that their feet were not supported on the ground and with their arms crossed on their chest (Fig. 1). Participants maintained quiet sitting posture during: a) unsupported sitting; and b) FES-assisted sitting conditions. The order of the two sitting conditions was randomized between participants. Before data collection, participants were given an opportunity to become familiarized with FES-assisted sitting. For each condition, data was collected over two, 30 s trials.Fig. 1


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)

Experimental setup showing participant’s posture on a chair without back support during sitting balance assessments. The force plate was positioned on the seat surface, under the buttocks, to capture trunk sway, while the participant’s feet were not supported on the ground and the participants had their arms crossed on their chest. The figure also shows the: a front view of the participant illustrating the approximate location of the FES electrodes on the rectus abdominis (RA) muscle and; b back view of the participant illustrating the approximate location of the of the FES electrodes on the lumbar erector spinae (L3) muscle. The RA and L3 muscles were stimulated bilaterally and were activated simultaneously to generate co-activations
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: Experimental setup showing participant’s posture on a chair without back support during sitting balance assessments. The force plate was positioned on the seat surface, under the buttocks, to capture trunk sway, while the participant’s feet were not supported on the ground and the participants had their arms crossed on their chest. The figure also shows the: a front view of the participant illustrating the approximate location of the FES electrodes on the rectus abdominis (RA) muscle and; b back view of the participant illustrating the approximate location of the of the FES electrodes on the lumbar erector spinae (L3) muscle. The RA and L3 muscles were stimulated bilaterally and were activated simultaneously to generate co-activations
Mentions: Participants were asked to maintain an upright sitting posture on a height-adjustable instrumented chair without back support, such that their feet were not supported on the ground and with their arms crossed on their chest (Fig. 1). Participants maintained quiet sitting posture during: a) unsupported sitting; and b) FES-assisted sitting conditions. The order of the two sitting conditions was randomized between participants. Before data collection, participants were given an opportunity to become familiarized with FES-assisted sitting. For each condition, data was collected over two, 30 s trials.Fig. 1

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