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Milos R Popovic - One of the best experts on this subject based on the ideXlab platform.
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corrigendum to smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway gait posture 33 2010 14 17
Gait & Posture, 2012Co-Authors: Kei Masani, Albert H Vette, Kimitaka Nakazawa, Milos R PopovicAbstract:Corrigendum Corrigendum to ‘‘Smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway’’ [Gait Posture 33 (2010) 14–17] Kei Masani *, Albert H. Vette , Masaki O. Abe , Kimitaka Nakazawa , Milos R. Popovic a,b Rehabilitation Engineering Laboratory, Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada Rehabilitation Engineering Laboratory, Lyndhurst Centre, Toronto Rehabilitation Institute, 520 Sutherland Drive, Toronto, Ontario M4G 3V9, Canada Action Lab, Department of Biology, Northeastern University, 134 Mugar Life Science Building, 360 Huntington Avenue, Boston, MA 02115, USA Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
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smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway
Gait & Posture, 2011Co-Authors: Kei Masani, Albert H Vette, Kimitaka Nakazawa, Milos R PopovicAbstract:Abstract In previous studies, it was found using cross-correlation analysis that the modulation of the Motor Command to the calf muscles largely precedes body sway during quiet standing. The purpose of this study was to investigate whether this preceding time is correlated with an improved stabilization of the body. 26 young and 23 elderly healthy subjects were asked to stand quietly. Body sway was measured using a laser displacement sensor, and the electromyogram of the right soleus was measured as a representative of the Motor Command. The correlation and the time shift between Motor Command and body sway were estimated by means of cross-correlation analysis. We found that sway size was correlated with the identified time shift: that is, a smaller sway size was associated with a longer preceding time. The obtained results suggest that a control strategy generating a larger preceding time can stabilize the body more effectively. This result was found in both the young and elderly, suggesting that the particular control aspect associated with the time shift is a common feature in both age groups.
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controlling balance during quiet standing proportional and derivative controller generates preceding Motor Command to body sway position observed in experiments
Gait & Posture, 2006Co-Authors: Kei Masani, Albert H Vette, Milos R PopovicAbstract:To compensate for significant time delays in the control of human bipedal stance, it was suggested that a feed-forward control mechanism is needed to generate a preceding Motor Command to the body sway position observed in quiet standing. In this article, we present evidence that a feedback proportional-derivative (PD) controller can effectively generate a desired preceding Motor Command. We also discuss the following characteristics of the proposed PD controller: (1) the level of robustness of the controller with respect to neurological time delays and (2) how well the controller replicates the system's dynamics observed in experiments with able bodied subjects, i.e. how well the controller generates the observed preceding Motor Command. Human quiet stance was simulated using an inverted pendulum model regulated by a PD controller. The simulations were used to calculate the center of mass (COM) position and velocity data, and the Motor Command (ankle joint torque) data as a function of time. These data and the data obtained in the experiments were compared using cross-correlation functions (CCFs). The results presented herein imply that a PD feedback controller is capable of ensuring balance during human bipedal quiet stance, even if the neurological time delays are considerable. The proposed feedback controller can generate the preceding Motor Command that was observed in the experiments. Therefore, we conclude that a feed-forward mechanism is not necessary to compensate for the long closed-loop time delay in human bipedal stance as suggested in recent literature, and that the PD controller is a good approximation of the control strategy applied by able bodied subjects during quiet stance.
Kei Masani - One of the best experts on this subject based on the ideXlab platform.
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center of pressure velocity reflects body acceleration rather than body velocity during quiet standing
Gait & Posture, 2014Co-Authors: Kei Masani, Albert H Vette, Masaki O Abe, Kimitaka NakazawaAbstract:The purpose of this study was to test the hypothesis that the center of pressure (COP) velocity reflects the center of mass (COM) acceleration due to a large derivative gain in the neural control system during quiet standing. Twenty-seven young (27.2±4.5 years) and twenty-three elderly (66.2±5.0 years) subjects participated in this study. Each subject was requested to stand quietly on a force plate for five trials, each 90 s long. The COP and COM displacements, the COP and COM velocities, and the COM acceleration were acquired via a force plate and a laser displacement sensor. The amount of fluctuation of each variable was quantified using the root mean square. Following the experimental study, a simulation study was executed to investigate the experimental findings. The experimental results revealed that the COP velocity was correlated with the COM velocity, but more highly correlated with the COM acceleration. The equation of motion of the inverted pendulum model, however, accounts only for the correlation between the COP and COM velocities. These experimental results can be meaningfully explained by the simulation study, which indicated that the neural Motor Command presumably contains a significant portion that is proportional to body velocity. In conclusion, the COP velocity fluctuation reflects the COM acceleration fluctuation rather than the COM velocity fluctuation, implying that the neural Motor Command controlling quiet standing posture contains a significant portion that is proportional to body velocity.
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corrigendum to smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway gait posture 33 2010 14 17
Gait & Posture, 2012Co-Authors: Kei Masani, Albert H Vette, Kimitaka Nakazawa, Milos R PopovicAbstract:Corrigendum Corrigendum to ‘‘Smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway’’ [Gait Posture 33 (2010) 14–17] Kei Masani *, Albert H. Vette , Masaki O. Abe , Kimitaka Nakazawa , Milos R. Popovic a,b Rehabilitation Engineering Laboratory, Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada Rehabilitation Engineering Laboratory, Lyndhurst Centre, Toronto Rehabilitation Institute, 520 Sutherland Drive, Toronto, Ontario M4G 3V9, Canada Action Lab, Department of Biology, Northeastern University, 134 Mugar Life Science Building, 360 Huntington Avenue, Boston, MA 02115, USA Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
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smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway
Gait & Posture, 2011Co-Authors: Kei Masani, Albert H Vette, Kimitaka Nakazawa, Milos R PopovicAbstract:Abstract In previous studies, it was found using cross-correlation analysis that the modulation of the Motor Command to the calf muscles largely precedes body sway during quiet standing. The purpose of this study was to investigate whether this preceding time is correlated with an improved stabilization of the body. 26 young and 23 elderly healthy subjects were asked to stand quietly. Body sway was measured using a laser displacement sensor, and the electromyogram of the right soleus was measured as a representative of the Motor Command. The correlation and the time shift between Motor Command and body sway were estimated by means of cross-correlation analysis. We found that sway size was correlated with the identified time shift: that is, a smaller sway size was associated with a longer preceding time. The obtained results suggest that a control strategy generating a larger preceding time can stabilize the body more effectively. This result was found in both the young and elderly, suggesting that the particular control aspect associated with the time shift is a common feature in both age groups.
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controlling balance during quiet standing proportional and derivative controller generates preceding Motor Command to body sway position observed in experiments
Gait & Posture, 2006Co-Authors: Kei Masani, Albert H Vette, Milos R PopovicAbstract:To compensate for significant time delays in the control of human bipedal stance, it was suggested that a feed-forward control mechanism is needed to generate a preceding Motor Command to the body sway position observed in quiet standing. In this article, we present evidence that a feedback proportional-derivative (PD) controller can effectively generate a desired preceding Motor Command. We also discuss the following characteristics of the proposed PD controller: (1) the level of robustness of the controller with respect to neurological time delays and (2) how well the controller replicates the system's dynamics observed in experiments with able bodied subjects, i.e. how well the controller generates the observed preceding Motor Command. Human quiet stance was simulated using an inverted pendulum model regulated by a PD controller. The simulations were used to calculate the center of mass (COM) position and velocity data, and the Motor Command (ankle joint torque) data as a function of time. These data and the data obtained in the experiments were compared using cross-correlation functions (CCFs). The results presented herein imply that a PD feedback controller is capable of ensuring balance during human bipedal quiet stance, even if the neurological time delays are considerable. The proposed feedback controller can generate the preceding Motor Command that was observed in the experiments. Therefore, we conclude that a feed-forward mechanism is not necessary to compensate for the long closed-loop time delay in human bipedal stance as suggested in recent literature, and that the PD controller is a good approximation of the control strategy applied by able bodied subjects during quiet stance.
Albert H Vette - One of the best experts on this subject based on the ideXlab platform.
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center of pressure velocity reflects body acceleration rather than body velocity during quiet standing
Gait & Posture, 2014Co-Authors: Kei Masani, Albert H Vette, Masaki O Abe, Kimitaka NakazawaAbstract:The purpose of this study was to test the hypothesis that the center of pressure (COP) velocity reflects the center of mass (COM) acceleration due to a large derivative gain in the neural control system during quiet standing. Twenty-seven young (27.2±4.5 years) and twenty-three elderly (66.2±5.0 years) subjects participated in this study. Each subject was requested to stand quietly on a force plate for five trials, each 90 s long. The COP and COM displacements, the COP and COM velocities, and the COM acceleration were acquired via a force plate and a laser displacement sensor. The amount of fluctuation of each variable was quantified using the root mean square. Following the experimental study, a simulation study was executed to investigate the experimental findings. The experimental results revealed that the COP velocity was correlated with the COM velocity, but more highly correlated with the COM acceleration. The equation of motion of the inverted pendulum model, however, accounts only for the correlation between the COP and COM velocities. These experimental results can be meaningfully explained by the simulation study, which indicated that the neural Motor Command presumably contains a significant portion that is proportional to body velocity. In conclusion, the COP velocity fluctuation reflects the COM acceleration fluctuation rather than the COM velocity fluctuation, implying that the neural Motor Command controlling quiet standing posture contains a significant portion that is proportional to body velocity.
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corrigendum to smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway gait posture 33 2010 14 17
Gait & Posture, 2012Co-Authors: Kei Masani, Albert H Vette, Kimitaka Nakazawa, Milos R PopovicAbstract:Corrigendum Corrigendum to ‘‘Smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway’’ [Gait Posture 33 (2010) 14–17] Kei Masani *, Albert H. Vette , Masaki O. Abe , Kimitaka Nakazawa , Milos R. Popovic a,b Rehabilitation Engineering Laboratory, Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada Rehabilitation Engineering Laboratory, Lyndhurst Centre, Toronto Rehabilitation Institute, 520 Sutherland Drive, Toronto, Ontario M4G 3V9, Canada Action Lab, Department of Biology, Northeastern University, 134 Mugar Life Science Building, 360 Huntington Avenue, Boston, MA 02115, USA Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
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smaller sway size during quiet standing is associated with longer preceding time of Motor Command to body sway
Gait & Posture, 2011Co-Authors: Kei Masani, Albert H Vette, Kimitaka Nakazawa, Milos R PopovicAbstract:Abstract In previous studies, it was found using cross-correlation analysis that the modulation of the Motor Command to the calf muscles largely precedes body sway during quiet standing. The purpose of this study was to investigate whether this preceding time is correlated with an improved stabilization of the body. 26 young and 23 elderly healthy subjects were asked to stand quietly. Body sway was measured using a laser displacement sensor, and the electromyogram of the right soleus was measured as a representative of the Motor Command. The correlation and the time shift between Motor Command and body sway were estimated by means of cross-correlation analysis. We found that sway size was correlated with the identified time shift: that is, a smaller sway size was associated with a longer preceding time. The obtained results suggest that a control strategy generating a larger preceding time can stabilize the body more effectively. This result was found in both the young and elderly, suggesting that the particular control aspect associated with the time shift is a common feature in both age groups.
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controlling balance during quiet standing proportional and derivative controller generates preceding Motor Command to body sway position observed in experiments
Gait & Posture, 2006Co-Authors: Kei Masani, Albert H Vette, Milos R PopovicAbstract:To compensate for significant time delays in the control of human bipedal stance, it was suggested that a feed-forward control mechanism is needed to generate a preceding Motor Command to the body sway position observed in quiet standing. In this article, we present evidence that a feedback proportional-derivative (PD) controller can effectively generate a desired preceding Motor Command. We also discuss the following characteristics of the proposed PD controller: (1) the level of robustness of the controller with respect to neurological time delays and (2) how well the controller replicates the system's dynamics observed in experiments with able bodied subjects, i.e. how well the controller generates the observed preceding Motor Command. Human quiet stance was simulated using an inverted pendulum model regulated by a PD controller. The simulations were used to calculate the center of mass (COM) position and velocity data, and the Motor Command (ankle joint torque) data as a function of time. These data and the data obtained in the experiments were compared using cross-correlation functions (CCFs). The results presented herein imply that a PD feedback controller is capable of ensuring balance during human bipedal quiet stance, even if the neurological time delays are considerable. The proposed feedback controller can generate the preceding Motor Command that was observed in the experiments. Therefore, we conclude that a feed-forward mechanism is not necessary to compensate for the long closed-loop time delay in human bipedal stance as suggested in recent literature, and that the PD controller is a good approximation of the control strategy applied by able bodied subjects during quiet stance.
Janet L Taylor - One of the best experts on this subject based on the ideXlab platform.
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signals of Motor Command bias joint position sense in the presence of feedback from proprioceptors
Journal of Applied Physiology, 2009Co-Authors: Janette L Smith, Matthew Crawford, Uwe Proske, Janet L TaylorAbstract:Joint position sense is believed to be mediated by muscle afferent signals. Because a “phantom” hand produced by a sensory and Motor nerve block appears to move in the direction of voluntary effort, signals of “Motor Command” or “effort” can influence perceived joint position. To determine whether this occurs when sensory signals are available, three studies assessed position sense when Motor Command and afferent signals were available, but joint movement was prevented. First, the hand was positioned to stop movement at the proximal joint of the middle finger, and movement at the distal joint was impossible because the muscles had been “disengaged”. Voluntary efforts produced illusory position changes in the direction of the effort (12.6 ± 2.0° distal joint; 12.3 ± 2.3° proximal joint for efforts at 30% maximum; means ± SD). Second, when subjects attempted to move the index finger under isometric conditions, the index finger appeared to move 7.4 ± 1.2° in the direction of efforts. These illusions graded with the level of effort (10 or 30% maximum) and far exceeded any real joint movement. Finally, because changes in muscle afferent feedback might have accompanied the voluntary efforts, all forearm and hand muscles were completely paralyzed by locally infused rocuronium. During paralysis, passive wrist position was signaled accurately, but, during attempted efforts (30% maximum), perceived wrist position changed by 9.7 ± 4.9°. Before paralysis, isometric efforts changed it by 6.7 ± 3.6°. Thus all studies concur: when joint movement is prevented, signals of Motor Command contribute to joint position sense.
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Signals of Motor Command bias joint position sense in the presence of feedback from proprioceptors.
Journal of Applied Physiology, 2008Co-Authors: Janette L Smith, Matthew Crawford, Uwe Proske, Janet L TaylorAbstract:Joint position sense is believed to be mediated by muscle afferent signals. Because a “phantom” hand produced by a sensory and Motor nerve block appears to move in the direction of voluntary effort...
Janette L Smith - One of the best experts on this subject based on the ideXlab platform.
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signals of Motor Command bias joint position sense in the presence of feedback from proprioceptors
Journal of Applied Physiology, 2009Co-Authors: Janette L Smith, Matthew Crawford, Uwe Proske, Janet L TaylorAbstract:Joint position sense is believed to be mediated by muscle afferent signals. Because a “phantom” hand produced by a sensory and Motor nerve block appears to move in the direction of voluntary effort, signals of “Motor Command” or “effort” can influence perceived joint position. To determine whether this occurs when sensory signals are available, three studies assessed position sense when Motor Command and afferent signals were available, but joint movement was prevented. First, the hand was positioned to stop movement at the proximal joint of the middle finger, and movement at the distal joint was impossible because the muscles had been “disengaged”. Voluntary efforts produced illusory position changes in the direction of the effort (12.6 ± 2.0° distal joint; 12.3 ± 2.3° proximal joint for efforts at 30% maximum; means ± SD). Second, when subjects attempted to move the index finger under isometric conditions, the index finger appeared to move 7.4 ± 1.2° in the direction of efforts. These illusions graded with the level of effort (10 or 30% maximum) and far exceeded any real joint movement. Finally, because changes in muscle afferent feedback might have accompanied the voluntary efforts, all forearm and hand muscles were completely paralyzed by locally infused rocuronium. During paralysis, passive wrist position was signaled accurately, but, during attempted efforts (30% maximum), perceived wrist position changed by 9.7 ± 4.9°. Before paralysis, isometric efforts changed it by 6.7 ± 3.6°. Thus all studies concur: when joint movement is prevented, signals of Motor Command contribute to joint position sense.
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Signals of Motor Command bias joint position sense in the presence of feedback from proprioceptors.
Journal of Applied Physiology, 2008Co-Authors: Janette L Smith, Matthew Crawford, Uwe Proske, Janet L TaylorAbstract:Joint position sense is believed to be mediated by muscle afferent signals. Because a “phantom” hand produced by a sensory and Motor nerve block appears to move in the direction of voluntary effort...