scholarly journals Variability in the Center of Mass State During Initiation of Accurate Forward Step Aimed at Targets of Different Sizes

2021 ◽  
Vol 3 ◽  
Author(s):  
Hiroki Yamada ◽  
Masahiro Shinya
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Body Height ◽  
The Body ◽  
Target Condition ◽  
Large Target ◽  
Step Initiation ◽  
Task Requirements ◽  
The Central Nervous System ◽  
Stepping Accuracy

Motor control for forward step initiation begins with anticipatory postural adjustments (APAs). During APAs, the central nervous system controls the center of pressure (CoP) to generate an appropriate center of mass (CoM) position and velocity for various task requirements. In this study, we investigated the effect of required stepping accuracy on the CoM and CoP parameters during APA for a step initiation task. Sixteen healthy young participants stepped forward onto the targets on the ground as soon as and as fast as possible in response to visual stimuli. Two target sizes (small: 2 cm square and large: 10 cm square) and two target distances (short: 20% and long: 40% of the body height) were tested. CoP displacement during the APA and the CoM position, velocity, and extrapolated CoM at the timing of the takeoff of the lead leg were compared among the conditions. In the small condition, comparing with the large condition, the CoM position was set closer to the stance limb side during the APA, which was confirmed by the location of the extrapolated center of mass at the instance of the takeoff of the lead leg [small: 0.09 ± 0.01 m, large: 0.06 ± 0.01 m, mean and standard deviation, F(1, 15) = 96.46, p < 0.001, η2 = 0.87]. The variability in the mediolateral extrapolated center of mass location was smaller in the small target condition than large target condition when the target distance was long [small: 0.010 ± 0.002 m, large: 0.013 ± 0.004 m, t(15) = 3.8, p = 0.002, d = 0.96]. These findings showed that in the step initiation task, the CoM state and its variability were task-relevantly determined during the APA in accordance with the required stepping accuracy.

scholarly journals Can Muscle Stiffness Alone Stabilize Upright Standing?

1999 ◽  
Vol 82 (3) ◽  
pp. 1622-1626 ◽  
Author(s):  
Pietro G. Morasso ◽  
Marco Schieppati
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Muscle Stiffness ◽  
The Body ◽  
Ankle Muscles ◽  
Upright Standing ◽  
Stiffness Control ◽  
Control Patterns ◽  
Physiological Values

A stiffness control model for the stabilization of sway has been proposed recently. This paper discusses two inadequacies of the model: modeling and empiric consistency. First, we show that the in-phase relation between the trajectories of the center of pressure and the center of mass is determined by physics, not by control patterns. Second, we show that physiological values of stiffness of the ankle muscles are insufficient to stabilize the body “inverted pendulum.” The evidence of active mechanisms of sway stabilization is reviewed, pointing out the potentially crucial role of foot skin and muscle receptors.

Attributes of Quiet Stance in the Chronic Spinal Cat

1999 ◽  
Vol 82 (6) ◽  
pp. 3056-3065 ◽  
Author(s):  
Joyce Fung ◽  
Jane M. Macpherson
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Close Relation ◽  
Daily Basis ◽  
The Body ◽  
Spinal Reflexes ◽  
Emg Activity ◽  
Axis Orientation ◽  
Dynamic Task ◽  
Horizontal Orientation

Standing is a dynamic task that requires antigravity support of the body mass and active regulation of the position of the body center of mass. This study examined the extent to which the chronic spinal cat can maintain postural orientation during stance and adapt to changes in stance distance (fore-hindpaw separation). Intact cats adapt to changes in stance distance by maintaining a constant horizontal orientation of the trunk and changing orientation of the limbs, while keeping intralimb geometry constant and aligning the ground reaction forces closely with the limb axes. Postural adaptation was compared in four cats before and after spinalization at the T6 level, in terms of the forces exerted by each paw against the support, body geometry (kinematics) and electromyographic (EMG) activity recorded from chronic, indwelling electrodes, as well as the computed net torques in the fore and hindlimbs. Five fore-hindpaw distances spanning the preferred distance were tested before spinalization, with a total range of 20 cm from the shortest to the longest stance. After spinalization, the cats were trained on a daily basis to stand on the force platform, and all four cats were able to support their full body weight. Three of the four cats could adapt to changes in stance distance, but the range was smaller and biased toward the shorter distances. The fourth cat could stand only at one stance distance, which was 8 cm shorter than the preferred distance before spinalization. All cats shifted their center of pressure closer to the forelimbs after spinalization, but the amount of shift could largely be accounted for by the weight loss in the hindquarters. The three cats that could adapt to changes in stance distance used a similar strategy as the intact cat by constraining the trunk and changing orientation of the limb axes in close relation with the forces exerted by each limb. However, different postures in the fore- and hindlimbs were adopted, particularly at the scapula (more extended) and pelvis (tipped more anteriorly). Other changes from control included a redistribution of net extensor torque across the joints of the forelimb and of the hindlimb. We concluded that the general form of body axis orientation is relatively conserved in the spinal cat, suggesting that the lumbosacral spinal circuitry includes rudimentary set points for hindlimb geometry. Both mechanical and neural elements can contribute toward maintaining body geometry through stiffness regulation and spinal reflexes.

scholarly journals The onset time of balance control during walking is phase-independent, but the magnitude of the response is not

2019 ◽  
Author(s):  
Hendrik Reimann ◽  
Tyler Fettrow ◽  
David Grenet ◽  
Elizabeth D. Thompson ◽  
John J. Jeka
Keyword(s):  
Nervous System ◽  
Gait Cycle ◽  
Center Of Pressure ◽  
Body Movement ◽  
Reaction Force ◽  
The Body ◽  
Upper Body ◽  
Whole Body ◽  
Lower Body ◽  
The Central Nervous System

AbstractThe human body is mechanically unstable during walking. Maintaining upright stability requires constant regulation of muscle force by the central nervous system to push against the ground and move the body mass in the desired way. Activation of muscles in the lower body in response to sensory or mechanical perturbations during walking is usually highly phase-dependent, because the effect any specific muscle force has on the body movement depends upon the body configuration. Yet the resulting movement patterns of the upper body after the same perturbations are largely phase-independent. This is puzzling, because any change of upper-body movement must be generated by parts of the lower body pushing against the ground. How do phase-dependent muscle activation patterns along the lower body generate phase-independent movement patterns of the upper body? We hypothesize that in response to a perceived threat to balance, the nervous system generates a functional response by pushing against the ground in any way possible with the current body configuration. This predicts that the changes in the ground reaction force patterns following a balance perturbation should be phase-independent. Here we test this hypothesis by disturbing upright balance using Galvanic vestibular stimulation at three different points in the gait cycle. We measure the resulting changes in whole-body center of mass movement and the location of the center of pressure of the ground reaction force. We find that the whole-body balance response is not phase-independent as expected: balance responses are initiated faster and are smaller following a disturbance late in the gait cycle. Somewhat paradoxically, the initial center of pressure changes are larger for perturbations late in the gait cycle. The onset of the center of pressure changes however, does not depend on the phase of the perturbation. The results partially support our hypothesis of a phase-independent functional balance response underlying the phase-dependent recruitment of different balance mechanisms at different points of the gait cycle. We conclude that the central nervous system recruits any available mechanism to push against the ground to maintain balance as fast as possible in response to a perturbation, but the different mechanisms do not have equal strength.

Biomechanics of Step Initiation After Balance Recovery With Implications for Humanoid Robot Locomotion

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Christine Miller Buffinton ◽  
Elise M. Buffinton ◽  
Kathleen A. Bieryla ◽  
Jerry E. Pratt
Keyword(s):  
Humanoid Robot ◽  
Center Of Mass ◽  
Human Motion ◽  
Single Step ◽  
The Body ◽  
Balance Recovery ◽  
Joint Torques ◽  
Double Support ◽  
Step Initiation ◽  
Capture Point

Balance-recovery stepping is often necessary for both a human and humanoid robot to avoid a fall by taking a single step or multiple steps after an external perturbation. The determination of where to step to come to a complete stop has been studied, but little is known about the strategy for initiation of forward motion from the static position following such a step. The goal of this study was to examine the human strategy for stepping by moving the back foot forward from a static, double-support position, comparing parameters from normal step length (SL) to those from increasing SLs to the point of step failure, to provide inspiration for a humanoid control strategy. Healthy young adults instrumented with joint reflective markers executed a prescribed-length step from rest while marker positions and ground reaction forces (GRFs) were measured. The participants were scaled to the Gait2354 model in opensim software to calculate body kinematic and joint kinetic parameters, with further post-processing in matlab. With increasing SL, participants reduced both static and push-off back-foot GRF. Body center of mass (CoM) lowered and moved forward, with additional lowering at the longer steps, and followed a path centered within the initial base of support (BoS). Step execution was successful if participants gained enough forward momentum at toe-off to move the instantaneous capture point (ICP) to within the BoS defined by the final position of both feet on the front force plate. All lower extremity joint torques increased with SL except ankle joint. Front knee work increased dramatically with SL, accompanied by decrease in back-ankle work. As SL increased, the human strategy changed, with participants shifting their CoM forward and downward before toe-off, thus gaining forward momentum, while using less propulsive work from the back ankle and engaging the front knee to straighten the body. The results have significance for human motion, suggesting the upper limit of the SL that can be completed with back-ankle push-off before additional knee flexion and torque is needed. For biped control, the results support stability based on capture-point dynamics and suggest strategy for center-of-mass trajectory and distribution of ground force reactions that can be compared with robot controllers for initiation of gait after recovery steps.

scholarly journals Transition versus Continuous Slope Walking: Adaptation to Change Center of Mass Velocity in Young Men

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Yoon No Gregory Hong ◽  
Jinkyu Lee ◽  
Choongsoo S. Shin
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Force Plate ◽  
Human Locomotion ◽  
The Body ◽  
Initial Contact ◽  
Horizontal Distance ◽  
Downhill Walking ◽  
Walking Adaptation ◽  
Propulsion Phase

During continuous uphill walking (UW) or downhill walking, human locomotion is modified to counteract the gravitational force, aiding or impeding the body’s forward momentum, respectively. This study aimed at investigating the center of mass (COM) and center of pressure (COP) velocities and their relative distance during the transition from uphill to downhill walking (UDW) to determine whether locomotor adjustments differ between UDW and UW. Fourteen participants walked on a triangular slope and a continuous upslope of 15°. The kinematics and COPs were obtained using a force plate and a motion capture system. The vertical velocity of the COM in the propulsion phase, the horizontal distance between the COM and COP at initial contact, and the duration of the subphases significantly differed between UDW and UW (all p<0.05). Compared with the results of UW, longer durations and the deeper downward moving COM in the propulsion phase were observed during UDW (all p<0.05). Additionally, a shorter horizontal distance between the COM and COP at initial contact was associated with a slower vertical COM velocity in the propulsion phase during UDW. The reduced velocity is likely a gait alteration to decrease the forward momentum of the body during UDW.

scholarly journals An exploration of strategies used by dressage horses to control moments around the center of mass when performing passage

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3866 ◽  
Author(s):  
Hilary M. Clayton ◽  
Sarah Jane Hobbs
Keyword(s):  
Sagittal Plane ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Force Production ◽  
The Body ◽  
Camera Motion ◽  
Slow Speed ◽  
Moment Arms ◽  
Trunk Posture ◽  
The Moment

BackgroundLocomotion results from the generation of ground reaction forces (GRF) that cause translations of the center of mass (COM) and generate moments that rotate the body around the COM. The trot is a diagonally-synchronized gait performed by horses at intermediate locomotor speeds. Passage is a variant of the trot performed by highly-trained dressage horses. It is distinguished from trot by having a slow speed of progression combined with great animation of the limbs in the swing phase. The slow speed of passage challenges the horse’s ability to control the sagittal-plane moments around the COM. Footfall patterns and peak GRF are known to differ between passage and trot, but their effects on balance management, which we define here as the ability to control nose-up/nose-down pitching moments around the horse’s COM to maintain a state of equilibrium, are not known. The objective was to investigate which biomechanical variables influence pitching moments around the COM in passage.MethodsThree highly-trained dressage horses were captured by a 10-camera motion analysis system (120 Hz) as they were ridden in passage over four force platforms (960 Hz). A full-body marker set was used to track the horse’s COM and measure balance variables including total body center of pressure (COP), pitching moments, diagonal dissociation timing, peak force production, limb protraction–retraction, and trunk posture. A total of twenty passage steps were extracted and partial correlation (accounting for horse) was used to investigate significant (P < 0.05) relationships between variables.ResultsHindlimb mean protraction–retraction correlated significantly with peak hindlimb propulsive forces (R = 0.821;P < 0.01), mean pitching moments (R = 0.546,P = 0.016), trunk range of motion, COM craniocaudal location and diagonal dissociation time (P < 0.05).DiscussionPitching moments around the COM were controlled by a combination of kinematic and kinetic adjustments that involve coordinated changes in GRF magnitudes, GRF distribution between the diagonal limb pairs, and the moment arms of the vertical GRFs. The moment arms depend on hoof placements relative to the COM, which were adjusted by changing limb protraction–retraction angles. Nose-up pitching moments could also be increased by providing a larger hindlimb propulsive GRF.

scholarly journals Improvement of Gender Balance Based on the Real-Time Visual Feedback System of the Pressure Center of Smart Wearable Devices: A Case Control Study

2020 ◽  
Author(s):  
I-Lin Wang ◽  
Li-I Wang ◽  
Shi-Jie Xue ◽  
Rui Hu ◽  
Yu Su ◽  
...  
Keyword(s):  
Real Time ◽  
Visual Feedback ◽  
Center Of Pressure ◽  
Balance Control ◽  
Center Of Mass ◽  
Physical Stability ◽  
Feedback System ◽  
Wearable Devices ◽  
The Body ◽  
Smart Wearable

Abstract Background: The body maintains stability by integrating inputs from the central nervous system of vision, hearing, proprioception, and multiple senses. With the development of smart wearable devices, smart wearable devices can provide real-time center of pressure (COP) position-assisted balance control, which is beneficial to maintain physical balance.Methods: Forty healthy college students (20 male-20 female) participated in this study, and the posture balance actions of left-leg stance non-visual feedback, left -leg stance visual feedback, right-leg stance non-visual feedback, and right-leg stance visual feedback are performed. Visual feedback provides smart insoles matching Podoon APP on a tablet computer with the COP position displayed by a dot as real-time visual feedback. A mixed-design two-way ANOVA was performed and included the study.Results: The experimental results show that the displacement, velocity, radius, and area of the COP decreased significantly in the left-leg stance visual feedback/right-leg stance visual feedback, the test compared with the parameters in the eft-leg stance non-visual feedback/right-leg stance non-visual feedback (P < 0.05). Providing visual feedback through intelligent insoles can reduce the movement of the center of mass (COM) and maintain physical stability for healthy young people of different genders. In the one leg visual/non-visual in standing, the COP maximum anteroposterior displacement, COP anteroposterior velocity, COP radius, and COP area of women are significantly decreased than men (P < 0.05). Women have better real-time balance control ability than men with smart insoles.Conclusion: The simple intelligent wearable assisted devices can immediately increase the control ability in static stance of men and women, and women have better real-time balance control ability than men.

scholarly journals Unilateral Discomfort Increases the Use of Contralateral Side during Sit-to-Stand Transfer

2017 ◽  
Vol 2017 ◽  
pp. 1-7
Author(s):  
Simisola O. Oludare ◽  
Charlie C. Ma ◽  
Alexander S. Aruin
Keyword(s):  
Center Of Pressure ◽  
Center Of Mass ◽  
Biceps Femoris ◽  
Contralateral Side ◽  
The Body ◽  
Medial Gastrocnemius ◽  
Lower Limb Muscles ◽  
Sit To Stand ◽  
Left And Right ◽  
Movement Asymmetry

Individuals with unilateral impairment perform symmetrical movements asymmetrically. Restoring symmetry of movements is an important goal of rehabilitation. The aim of the study was to evaluate the effect of using discomfort-inducing devices on movement symmetry. Fifteen healthy individuals performed the sit-to-stand (STS) maneuver using devices inducing unilateral discomfort under the left sole and left thigh or right sole and right thigh and without them. 3D body kinematics, ground reaction forces, electrical activity of muscles, and the level of perceived discomfort were recorded. The center of mass (COM), center of pressure (COP), and trunk displacements as well as the magnitude and latency of muscle activity of lower limb muscles were calculated during STS and compared to quantify the movement asymmetry. Discomfort on the left and right side of the body (thigh and feet) induced statistically significant displacement of the trunk towards the opposite side. There was statistically significant asymmetry in the activity of the left and right Tibialis Anterior, Medial Gastrocnemius, and Biceps Femoris muscles when discomfort was induced underneath the left side of the body (thigh and feet). The technique was effective in causing asymmetry and promoted the use of the contralateral side. The outcome provides a foundation for future investigations of the role of discomfort-inducing devices in improving symmetry of the STS in individuals with unilateral impairment.

Cortical contributions to control of posture during unrestricted and restricted stance

2014 ◽  
Vol 111 (9) ◽  
pp. 1920-1926 ◽  
Author(s):  
Chantelle D. Murnaghan ◽  
Jordan W. Squair ◽  
Romeo Chua ◽  
J. Timothy Inglis ◽  
Mark G. Carpenter
Keyword(s):  
Muscle Activity ◽  
Critical Level ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Sensory Information ◽  
Upright Stance ◽  
Subcortical Structures ◽  
The Central Nervous System ◽  
The Relationship

There is very little consensus regarding the mechanisms underlying postural control. Whereas some theories suggest that posture is controlled at lower levels (i.e., brain stem and spinal cord), other theories have proposed that upright stance is controlled using higher centers, including the motor cortex. In the current investigation, we used corticomuscular coherence (CMC) to investigate the relationship between cortical and shank muscle activity during conditions of unrestricted and restricted postural sway. Participants were instructed to stand as still as possible in an apparatus that allowed the center of mass to move freely (“Unlocked”) or to be stabilized (“Locked”) without subject awareness. EEG (Cz) and electromyography (soleus and lateral/medial gastrocnemii) were collected and used to estimate CMC over the Unlocked and Locked periods. Confirming our previous results, increases in center of pressure (COP) displacements were observed in 9 of 12 participants in the Locked compared with Unlocked condition. Across these 9 participants, CMC was low or absent in both the Unlocked and Locked conditions. The results from the current study suggest that this increase is not associated with an increase in the relationship between cortical and shank muscle activities. Rather, it may be that increases in COP displacement with locking are mediated by subcortical structures as a means of increasing sway to provide the central nervous system with a critical level of sensory information.

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