scholarly journals Analysis of Postural Instability in the Upright Position on Narrow Platforms and the Interactions with Postural Constraints

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3909
Author(s):  
Atsushi Sugama ◽  
Akihiko Seo
Keyword(s):  
Postural Balance ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Upright Position ◽  
Pendulum Model ◽  
Working Postures ◽  
Loss Of Balance ◽  
Highly Correlated ◽  
Anterior Posterior

Background: Loss of balance is a considerable risk factor for workers while using ladders, because they are required to maintain static postural balance on platforms of a restricted size. This study observed center of mass (CoM) and center of pressure (CoP) behaviors and evaluated the effects of the platform depth (anterior–posterior length) and working postures. Methods: Eleven male participants stood on four platforms with depths ranging from 6 to 15 cm and maintained their positions for 60 s while performing or not performing other tasks (object holding, upward viewing, or both simultaneously). The kinematics were analyzed on the sagittal plane based on the inverse pendulum model. Results: The absolute moving range for the CoP–CoM linearly increased with the decreasing platform depth, and the working postures affected the slopes of the linear fits. The relative range of CoP–CoM displacement on narrow platforms was highly correlated with the subjective sense of instability. Conclusions: Monitoring the CoP is effective for a better understanding and evaluation of static postural balance. This study’s findings contribute to improving the design of work equipment through the use of wider platforms that are robust against the effects of working postures.

Comparing Standing Balance at Real and Virtual Elevated Environments

2002 ◽  
Vol 46 (26) ◽  
pp. 2169-2173
Author(s):  
Peter Simeonov ◽  
Hongwei Hsiao ◽  
Brian Dotson ◽  
Douglas Amnions
Keyword(s):  
Postural Balance ◽  
Occupational Safety ◽  
Center Of Pressure ◽  
Ground Level ◽  
Occupational Safety And Health ◽  
Visual Simulation ◽  
Mean Velocity ◽  
Deformable Surfaces ◽  
Safety And Health ◽  
Anterior Posterior

The study evaluated the efficacy of a surround-screen virtual reality (SSVR) system in simulating heights for studying human postural balance at elevation. Twenty four subjects performed standing tasks at 9-m elevation and ground level, on firm and deformable surfaces, in a real environment (RE) and a comparable virtual environment (VE). The RE was the interior of the high-bay laboratory at the National Institute for Occupational Safety and Health (NIOSH) in Morgantown, West Virginia; the VE simulated this environment in the SSVR system. Medial-lateral and anterior-posterior body sways and mean velocity of the human center-of-pressure displacement were collected using a force platform. The results indicated that the sway parameters were similar in VE and RE at elevation on both firm and deformable surfaces. At ground level, the sway parameters were significantly increased in the VE compared to the RE on a deformable surface, but not on a firm surface. It appears that visual simulation of elevated environments within a SSVR is adequate for studying the risk factors leading to losing balance and fall incidents.

AGE-RELATED DIFFERENCE IN DYNAMIC POSTURAL BALANCE AGAINST TILTING PERTURBATION IN MEN AND WOMEN

2017 ◽  
Vol 17 (07) ◽  
pp. 1740038 ◽  
Author(s):  
JI-WON KIM ◽  
YU-RI KWON ◽  
GWANG-MOON EOM
Keyword(s):  
Outcome Measures ◽  
Postural Balance ◽  
Elderly Women ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Dynamic Balance ◽  
Age And Gender ◽  
Related Difference ◽  
Age Related ◽  
And Gender

The aim of this study was to investigate how age and gender affect the dynamic postural balance during tilting perturbation. Fifty healthy subjects (15 young men, 13 young women, 11 elderly men and 11 elderly women) performed balance test on a movable force plate that tilted toe-up and toe-down. As outcome measures, maximum excursion and fluctuation were calculated from center of pressure (COP) data in the sagittal plane (anteroposterior). Two-way analysis of variance (ANOVA) and post-hoc comparisons were performed for the outcome measures with the independent factors of age and gender. The elderly had a greater COP maximum excursion as compared to the young during both perturbations ([Formula: see text]). COP fluctuation showed significant interaction of age and gender only in toe-up perturbation ([Formula: see text]). Especially, age-related difference existed only in women ([Formula: see text]). These results suggest that elderly women have dynamic balance strategy with great and fluctuated sway in response to toe-up perturbation. The age-related changes in dynamic balance among women may be related to the greater fall rate of elderly women.

scholarly journals Postural and Trunk Responses to Unexpected Perturbations Depend on the Velocity and Direction of Platform Motion

2016 ◽  
pp. 769-776
Author(s):  
E. ZEMKOVÁ ◽  
Z. KOVÁČIKOVÁ ◽  
M. JELEŇ ◽  
K. NEUMANNOVÁ ◽  
M. JANURA
Keyword(s):  
Center Of Pressure ◽  
Peak Velocity ◽  
Center Of Mass ◽  
Lateral Direction ◽  
Physically Active ◽  
Platform Motion ◽  
Trunk Motion ◽  
Posterior Direction ◽  
Highly Correlated ◽  
Postural Perturbations

This study compares postural and trunk responses to translating platform perturbations of varied velocities and directions. A group of 18 young and physically active subjects were exposed to a set of postural perturbations at varied velocities (5, 10, 15, and 20 cm/s) and directions of platform movement (forward, backward, left-lateral, and right-lateral). The center of pressure (CoP) displacement measurement, in addition to the trunk motion (representing the center of mass (CoM) displacement), were both monitored. Results identified that the CoP displacement increased from slow to faster velocities of platform motion more widely in both anterior and posterior directions (50.4 % and 48.4 %) as compared to the CoM displacement (17.8 % and 14.9 %). However a greater increase in the peak CoM velocity (70.3 % and 69.6 %) and the peak CoM acceleration (60.5 % and 53.1 %) was observed. The values in the anterior and posterior direction only differed significantly at the highest velocity of platform motion (i.e. 20 cm/s). A similar tendency was observed in the medio-lateral direction, but there were no significant differences in any parameter in the left-lateral and right-lateral direction. The velocity of the platform motion highly correlated with peak velocity (r=0.92-0.97, P<0.01) and moderately with amplitude of trunk displacement (r=0.56-0.63, P<0.05). These findings indicate that the velocity of perturbation alters peak CoM velocity rather than the magnitude of CoM displacement. The effect of the direction of perturbations on the trunk response emerges only at a high velocity of platform motion, such that the peak CoM velocity and peak CoM acceleration are significantly greater in anterior than posterior direction.

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 The Relationships Among Sagittal-Plane Lower Extremity Moments: Implications for Landing Strategy in Anterior Cruciate Ligament Injury Prevention

2009 ◽  
Vol 44 (1) ◽  
pp. 33-38 ◽  
Author(s):  
Yohei Shimokochi ◽  
Sae Yong Lee ◽  
Sandra J. Shultz ◽  
Randy J. Schmitz
Keyword(s):  
Anterior Cruciate Ligament ◽  
Lower Extremity ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Cruciate Ligament ◽  
Center Of Mass ◽  
Knee Extensor ◽  
Whole Body ◽  
Plantar Flexor ◽  
Anterior Cruciate

Abstract Context: Excessive quadriceps contraction with insufficient hamstrings muscle cocontraction has been shown to be a possible contributing factor for noncontact anterior cruciate ligament (ACL) injuries. Assessing the relationships among lower extremity internal moments may provide some insight into avoiding muscle contraction patterns that increase ACL injury risk. Objective: To examine the relationships of knee-extensor moment with ankle plantar-flexor and hip-extensor moments and to examine the relationship between knee moment and center of pressure as a measure of neuromuscular response to center-of-mass position. Design: Cross-sectional study. Setting: Applied Neuromechanics Research Laboratory. Patients or Other Participants: Eighteen healthy, recreationally active women (age  =  22.3 ± 2.8 years, height  =  162.5 ± 8.1 cm, mass  =  57.8 ± 9.3 kg). Intervention(s): Participants performed a single-leg landing from a 45-cm box onto a force plate. Kinetic and kinematic data were collected. Main Outcome Measure(s): Pearson product moment correlation coefficients were calculated among the net peak knee-extensor moment (KEMpk), sagittal-plane ankle (AM) and hip (HM) net internal moments, and anterior-posterior center of pressure relative to foot center of mass at KEMpk (COP). Results: Lower KEMpk related to both greater AM (r  =  −0.942, P &lt; .001) and HM (r  =  −0.657, P  =  .003). We also found that more anterior displacement of COP was related to greater AM (r  =  −0.750, P &lt; .001) and lower KEMpk (r  =  0.618, P  =  .006). Conclusions: Our results suggest that participants who lean the whole body forward during landing may produce more plantar-flexor moment and less knee-extensor moment, possibly increasing hip-extensor moment and decreasing knee-extensor moment production. These results suggest that leaning forward may be a technique to decrease quadriceps contraction demand while increasing hamstrings cocontraction demand during a single-leg landing.

Control of Body's Center of Mass Motion During Level Walking and Obstacle-Crossing in Older Patients with Knee Osteoarthritis

2010 ◽  
Vol 26 (2) ◽  
pp. 229-237 ◽  
Author(s):  
W.-C. Hsu ◽  
T.-M. Wang ◽  
M.-W. Liu ◽  
C.-F. Chang ◽  
H.-L. Chen ◽  
...  
Keyword(s):  
Knee Osteoarthritis ◽  
Dynamic Stability ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Mass Motion ◽  
Obstacle Crossing ◽  
Knee Oa ◽  
Level Walking ◽  
Increased Risk

AbstractKnee osteoarthritis (OA) has been reported to affect the performance of ambulation, including unobstructed and obstructed gait. An increased risk of falling in patients with knee OA during obstaclecrossing, as opposed to unobstructed level walking, may be explained by the difference in the control of the body's center of mass (COM) with respect to the center of pressure (COP) while trying to ensure sufficient foot clearance. The purpose of the study was to investigate the dynamic stability in patients with knee OA during level walking and obstacle-crossing. The COM-COP inclination angles and angular velocities, as well as temporal-spatial variables, from eleven patients with bilateral knee OA and eleven normal controls were obtained during level walking and obstacle-crossing using a three-dimensional motion analysis system and forceplates. Demands in the control of the COM relative to the COP were found to be greater during obstacle-crossing in both subject groups. While less stable COM control was found around the end stage of double stance phase during obstacle-crossing when compared to level walking, patients with knee OA successfully acquired strategies in the sagittal plane to maintain close-tonormal stable COM control with normal toe clearances during both level walking and obstacle-crossing. They achieved stable transitions from single limb stance (SLS) to double limb stance (DLS) through a reduced anterior inclination angle and from DLS to SLS through increased anterior angular velocity. It is suggested that assessment of the ability to control dynamic stability in patients with knee OA should consider both the positions and velocities of the COM and COP.

Changes in Postural Sway and Its Fractions in Conditions of Postural Instability

2006 ◽  
Vol 22 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Luis Mochizuki ◽  
Marcos Duarte ◽  
Alberto Carlos Amadio ◽  
Vladimir M. Zatsiorsky ◽  
Mark L. Latash
Keyword(s):  
Average Velocity ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Force Plate ◽  
Control Mechanisms ◽  
Mean Square ◽  
Loss Of Balance ◽  
Eyes Open ◽  
Support Area ◽  
Anterior Posterior

We investigated changes in postural sway and its fractions associated with manipulations of the dimensions of the support area. Nine healthy adults stood as quietly as possible, with their eyes open, on a force plate as well as on 5 boards with reduced support area. The center of pressure (COP) trajectory was computed and decomposed into rambling (Rm) and trembling (Tr) trajectories. Sway components were quantified using RMS (root mean square) value, average velocity, and sway area. During standing on the force plate, the RMS was larger for the anterior-posterior (AP) sway components than for the mediolateral (ML) components. During standing on boards with reduced support area, sway increased in both directions. The increase was more pronounced when standing on boards with a smaller support area. Changes in the larger dimension of the support area also affected sway, but not as much as changes in the smaller dimension. ML instability had larger effects on indices of sway compared to AP instability. The average velocity of Rm was larger while the average velocity of Tr was smaller in the AP direction vs. the ML direction. The findings can be interpreted within the hypothesis of an active search function of postural sway. During standing on boards with reduced support area, increased sway may by itself lead to loss of balance. The findings also corroborate the hypothesis of Duarte and Zatsiorsky that Rm and Tr reveal different postural control mechanisms.

scholarly journals Characterizing the Validity of the Inverted Pendulum Model for Quiet Standing

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Jia-Li Sung ◽  
Chih-Yuan Hong ◽  
Chin-Hsuan Liu ◽  
Posen Lee ◽  
Lan-Yuen Guo ◽  
...  
Keyword(s):  
Human Body ◽  
Inverted Pendulum ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Reaction Force ◽  
Age Groups ◽  
Quiet Standing ◽  
Aging Effects ◽  
Vertical Projection

By assuming that the human body rotates primarily around the ankle joint in the sagittal plane, the human body has been modelled as a single inverted pendulum (IP) to simulate the human quiet stance. Despite its popularity, the validity of the IP model has been challenged in many studies. Rather than testing the validity of the IP model as a true or false question, this work proposes a feature to quantify the degree of validity of the IP model. The development of the proposed feature is based on the fact that the IP model predicts that the horizontal acceleration of COM is proportional to the COP error which is defined as the difference between the center of pressure (COP) and the vertical projection of the center of mass (COM). Since the horizontal components of the acceleration of COM and the ground reaction force (GRF) are always proportional, the proposed feature is the correlation coefficient between the anterior-posterior (AP) components of GRF and the COP error. The efficacy of the proposed feature is demonstrated by comparing its differences for individuals in two age groups (18–24 and 65–73 years) in quiet standing. The experimental results show that the IP model is more suited for predicting the motion of the older group than the younger group. Our results also show that the proposed feature is more sensitive to aging effects than one of the most reliable and accurate COP-based postural stability features.

scholarly journals State-Space Characterization of Balance Capabilities in Biped Systems with Segmented Feet

2021 ◽  
Vol 8 ◽  
Author(s):  
Carlotta Mummolo ◽  
Kubra Akbas ◽  
Giuseppe Carbone
Keyword(s):  
State Space ◽  
Trajectory Optimization ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Dynamic Balance ◽  
Center Of Mass ◽  
Whole Body ◽  
Stability Criteria ◽  
Reduced Order

The human ability of keeping balance during various locomotion tasks is attributed to our capability of withstanding complex interactions with the environment and coordinating whole-body movements. Despite this, several stability analysis methods are limited by the use of overly simplified biped and foot structures and corresponding contact models. As a result, existing stability criteria tend to be overly restrictive and do not represent the full balance capabilities of complex biped systems. The proposed methodology allows for the characterization of the balance capabilities of general biped models (ranging from reduced-order to whole-body) with segmented feet. Limits of dynamic balance are evaluated by the Boundary of Balance (BoB) and the associated novel balance indicators, both formulated in the Center of Mass (COM) state space. Intermittent heel, flat, and toe contacts are enabled by a contact model that maps discrete contact modes into corresponding center of pressure constraints. For demonstration purposes, the BoB and balance indicators are evaluated for a whole-body biped model with segmented feet representative of the human-like standing posture in the sagittal plane. The BoB is numerically constructed as the set of maximum allowable COM perturbations that the biped can sustain along a prescribed direction. For each point of the BoB, a constrained trajectory optimization algorithm generates the biped’s whole-body trajectory as it recovers from extreme COM velocity perturbations in the anterior–posterior direction. Balance capabilities for the cases of flat and segmented feet are compared, demonstrating the functional role the foot model plays in the limits of postural balance. The state-space evaluation of the BoB and balance indicators allows for a direct comparison between the proposed balance benchmark and existing stability criteria based on reduced-order models [e.g., Linear Inverted Pendulum (LIP)] and their associated stability metrics [e.g., Margin of Stability (MOS)]. The proposed characterization of balance capabilities provides an important benchmarking framework for the stability of general biped/foot systems.

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