Ratio of Shear to Load Ground-Reaction Force May Underlie the Directional Tuning of the Automatic Postural Response to Rotation and Translation

2004 ◽  
Vol 92 (2) ◽  
pp. 808-823 ◽  
Author(s):  
Lena H. Ting ◽  
Jane M. Macpherson
Keyword(s):  
Ground Reaction Force ◽  
Center Of Pressure ◽  
Full Range ◽  
Center Of Mass ◽  
Reaction Force ◽  
Postural Response ◽  
Directional Tuning ◽  
Automatic Postural Response ◽  
Consistent Feature ◽  
Perturbation Direction

This study sought to identify the sensory signals that encode perturbation direction rapidly enough to shape the directional tuning of the automatic postural response. We compared reactions to 16 directions of pitch and roll rotation and 16 directions of linear translation in the horizontal plane in freely standing cats. Rotations and translations that displaced the center of mass in the same direction relative to the feet evoked similar patterns of muscle activity and active ground-reaction force, suggesting the presence of a single, robust postural strategy for stabilizing the center of mass in both rotation and translation. Therefore we postulated there should be a common sensory input that encodes the direction of the perturbation and leads to the directional tuning of the early electromyographic burst in the postural response. We compared the mechanical changes induced by rotations and translations prior to the active, postural response. The only consistent feature common to the full range of rotation and translation directions was the initial change in ground-reaction force angle. Other variables including joint angles, ground-reaction force magnitudes, center of pressure, and center of mass in space showed opposite or nonsignificant changes for rotation and translation. Change in force angle at the paw reflects the ratio of loading force to slip force, analogous to slips during finger grip tasks. We propose that cutaneous sensors in the foot soles detect change in ground-reaction force angle and provide the critical input underlying the directional tuning of the automatic postural response for balance.

Changes in Gait Characteristics due to Outsole Structure of Shoe

2015 ◽  
Vol 775 ◽  
pp. 28-33 ◽  
Author(s):  
Jin Seung Choi ◽  
Dong Won Kang ◽  
Jeong Woo Seo ◽  
Ju Young Kim ◽  
Seung Tae Yang ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Ankle Joint ◽  
Ground Reaction Force ◽  
Loading Rate ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Reaction Force ◽  
Long Term Effects ◽  
Vertical Ground Reaction Force ◽  
Gait Characteristics

The purpose of this study was to evaluate changes in kinematic and kinetic gait characteristics due to outsole structure of the shoe. In this experiment, cushioning shoe having cushion for heel (BOSS Corps., Korea) which is designed as a lever, MBT having an unstable rounded shoe (Masai Barefoot Technology, MBT, Swiss) and normal running shoe (Adidas, Germany) were compared. The experiment was performed walking on the straight walkway (10m x 3m) five times with preferred walking speed. 3D motion capture system was used to acquire kinematic and kinetic data using six infrared cameras and two force plates. For comparison among shoes, walking velocity, hip, knee and ankle joint angles (range of motion, trajectory), ground reaction force (loading rate, the decay rate, maximal vertical ground reaction force), and center of mass - center of pressure inclination angle (COM-COP angle) were used. The results showed that there were different effects of types of shoe on lower extremities. Joint angle trajectory of ankle, joint range of motion (ROM) of the hip, and peak force were significantly different among shoe types. MBT provided a decreased impact force. Cushioning shoe provided increased progressive force, decreased loading rate, and decreased COM-COP angle. For further study, it is necessary to analyze additional subjects (i.e., elderly) and long-term effects.

Mechanical power output during running accelerations in wild turkeys

2002 ◽  
Vol 205 (10) ◽  
pp. 1485-1494 ◽  
Author(s):  
Thomas J. Roberts ◽  
Jeffrey A. Scales
Keyword(s):  
Power Output ◽  
Ground Reaction Force ◽  
Center Of Mass ◽  
Reaction Force ◽  
Mechanical Power ◽  
Force Vector ◽  
Instantaneous Power ◽  
Hindlimb Muscle ◽  
Wild Turkeys ◽  
Running Mechanics

SUMMARYWe tested the hypothesis that the hindlimb muscles of wild turkeys(Meleagris gallopavo) can produce maximal power during running accelerations. The mechanical power developed during single running steps was calculated from force-plate and high-speed video measurements as turkeys accelerated over a trackway. Steady-speed running steps and accelerations were compared to determine how turkeys alter their running mechanics from a low-power to a high-power gait. During maximal accelerations, turkeys eliminated two features of running mechanics that are characteristic of steady-speed running: (i) they produced purely propulsive horizontal ground reaction forces, with no braking forces, and (ii) they produced purely positive work during stance, with no decrease in the mechanical energy of the body during the step. The braking and propulsive forces ordinarily developed during steady-speed running are important for balance because they align the ground reaction force vector with the center of mass. Increases in acceleration in turkeys correlated with decreases in the angle of limb protraction at toe-down and increases in the angle of limb retraction at toe-off. These kinematic changes allow turkeys to maintain the alignment of the center of mass and ground reaction force vector during accelerations when large propulsive forces result in a forward-directed ground reaction force. During the highest accelerations, turkeys produced exclusively positive mechanical power. The measured power output during acceleration divided by the total hindlimb muscle mass yielded estimates of peak instantaneous power output in excess of 400 W kg-1 hindlimb muscle mass. This value exceeds estimates of peak instantaneous power output of turkey muscle fibers. The mean power developed during the entire stance phase increased from approximately zero during steady-speed runs to more than 150 W kg-1muscle during the highest accelerations. The high power outputs observed during accelerations suggest that elastic energy storage and recovery may redistribute muscle power during acceleration. Elastic mechanisms may expand the functional range of muscle contractile elements in running animals by allowing muscles to vary their mechanical function from force-producing struts during steady-speed running to power-producing motors during acceleration.

scholarly journals Gutenberg Gait Database, a ground reaction force database of level overground walking in healthy individuals

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Fabian Horst ◽  
Djordje Slijepcevic ◽  
Marvin Simak ◽  
Wolfgang I. Schöllhorn
Keyword(s):  
Ground Reaction Force ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Three Dimensional ◽  
Human Gait ◽  
Healthy Individuals ◽  
Overground Walking ◽  
Gait Patterns ◽  
Specific Factors ◽  
Gait Database

AbstractThe Gutenberg Gait Database comprises data of 350 healthy individuals recorded in our laboratory over the past seven years. The database contains ground reaction force (GRF) and center of pressure (COP) data of two consecutive steps measured - by two force plates embedded in the ground - during level overground walking at self-selected walking speed. The database includes participants of varying ages, from 11 to 64 years. For each participant, up to eight gait analysis sessions were recorded, with each session comprising at least eight gait trials. The database provides unprocessed (raw) and processed (ready-to-use) data, including three-dimensional GRF and two-dimensional COP signals during the stance phase. These data records offer new possibilities for future studies on human gait, e.g., the application as a reference set for the analysis of pathological gait patterns, or for automatic classification using machine learning. In the future, the database will be expanded continuously to obtain an even larger and well-balanced database with respect to age, sex, and other gait-specific factors.

scholarly journals Active foot placement control ensures stable gait: Effect of constraints on foot placement and ankle moments

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0242215
Author(s):  
A. M. van Leeuwen ◽  
J. H. van Dieën ◽  
A. Daffertshofer ◽  
S. M. Bruijn
Keyword(s):  
Steady State ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Reaction Force ◽  
Stride Frequency ◽  
Tight Control ◽  
Foot Placement ◽  
Ankle Moment ◽  
Reaction Forces ◽  
Moment Control

Step-by-step foot placement control, relative to the center of mass (CoM) kinematic state, is generally considered a dominant mechanism for maintenance of gait stability. By adequate (mediolateral) positioning of the center of pressure with respect to the CoM, the ground reaction force generates a moment that prevents falling. In healthy individuals, foot placement is complemented mainly by ankle moment control ensuring stability. To evaluate possible compensatory relationships between step-by-step foot placement and complementary ankle moments, we investigated the degree of (active) foot placement control during steady-state walking, and under either foot placement-, or ankle moment constraints. Thirty healthy participants walked on a treadmill, while full-body kinematics, ground reaction forces and EMG activities were recorded. As a replication of earlier findings, we first showed step-by-step foot placement is associated with preceding CoM state and hip ab-/adductor activity during steady-state walking. Tight control of foot placement appears to be important at normal walking speed because there was a limited change in the degree of foot placement control despite the presence of a foot placement constraint. At slow speed, the degree of foot placement control decreased substantially, suggesting that tight control of foot placement is less essential when walking slowly. Step-by-step foot placement control was not tightened to compensate for constrained ankle moments. Instead compensation was achieved through increases in step width and stride frequency.

scholarly journals Dynamic Balancing Responses in Unilateral Transtibial Amputees Following Outward-Directed Perturbations During Slow Treadmill Walking Differ Considerably for Amputated and Non-Amputated Side

2021 ◽  
Author(s):  
Andrej Olenšek ◽  
Matjaž Zadravec ◽  
Helena Burger ◽  
Zlatko Matjačić
Keyword(s):  
Stance Phase ◽  
Center Of Pressure ◽  
Center Of Mass ◽  
Reaction Force ◽  
Dynamic Balancing ◽  
Transtibial Amputation ◽  
Control Subjects ◽  
Foot Strike ◽  
Transtibial Amputees ◽  
Proprioceptive Function

Abstract BackgroundDue to disrupted motor and proprioceptive function lower limb amputation imposes considerable challenges associated with balance and greatly increases risk of falling in case of perturbations during walking. The aim of this study was to investigate dynamic balancing responses in unilateral transtibial amputees when they were subjected to perturbing pushes to the pelvis in outward direction at the time of foot strike on non-amputated and amputated side during slow walking.MethodsFourteen subjects with unilateral transtibial amputation and nine control subjects participated in the study. They were subjected to perturbations that were delivered to the pelvis at the time of foot strike of either the left or right leg. We recorded trajectories of center of pressure and center of mass, durations of in-stance and stepping periods as well as ground reaction forces. Statistical analysis was performed to determine significant differences in dynamic balancing responses between control subjects and subjects with amputation when subjected to outward-directed perturbation upon entering stance phases with non-amputated or amputated side.ResultsWhen outward-directed perturbations were delivered at the time of foot strike of the non-amputated leg, subjects with amputation were able to modulate center of pressure and ground reaction force similarly as control subjects which indicates application of in-stance balancing strategies. On the other hand, there was a complete lack of in-stance response when perturbations were delivered when the amputated leg entered the stance phase. Subjects with amputations instead used the stepping strategy and adjusted placement of the non-amputated leg in the ensuing stance phase to make a cross-step. Such response resulted in significantly higher displacement of center of mass. ConclusionsResults of this study suggest that due to the absence of the COP modulation mechanism, which is normally supplied by ankle motor function, people with unilateral transtibial amputation are compelled to choose the stepping strategy over in-stance strategy when they are subjected to outward-directed perturbation on the amputated side. However, the stepping response is less efficient than in-stance response. To improve their balancing responses to unexpected balance perturbation people fitted with passive transtibial prostheses should undergo perturbation-based balance training during clinical rehabilitation.

Effect of Hopping Frequency on Bilateral Differences in Leg Stiffness

2013 ◽  
Vol 29 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Hiroaki Hobara ◽  
Koh Inoue ◽  
Kazuyuki Kanosue
Keyword(s):  
Ground Reaction Force ◽  
Center Of Mass ◽  
Reaction Force ◽  
Human Movement ◽  
Vertical Ground Reaction Force ◽  
Mass Model ◽  
Lower Extremity Injuries ◽  
Leg Stiffness ◽  
Significant Difference ◽  
Bilateral Differences

Understanding the degree of leg stiffness during human movement would provide important information that may be used for injury prevention. In the current study, we investigated bilateral differences in leg stiffness during one-legged hopping. Ten male participants performed one-legged hopping in place, matching metronome beats at 1.5, 2.2, and 3.0 Hz. Based on a spring-mass model, we calculated leg stiffness, which is defined as the ratio of maximal ground reaction force to maximum center of mass displacement at the middle of the stance phase, measured from vertical ground reaction force. In all hopping frequency settings, there was no significant difference in leg stiffness between legs. Although not statistically significant, asymmetry was the greatest at 1.5 Hz, followed by 2.2 and 3.0 Hz for all dependent variables. Furthermore, the number of subjects with an asymmetry greater than the 10% criterion was larger at 1.5 Hz than those at 2.2 and 3.0 Hz. These results will assist in the formulation of treatment-specific training regimes and rehabilitation programs for lower extremity injuries.

EVALUATION OF A COMPUTER-SIMULATION MODEL FOR HUMAN AMBULATION ON STILTS

2004 ◽  
Vol 04 (03) ◽  
pp. 283-303 ◽  
Author(s):  
CHRISTOPHER S. PAN ◽  
KIMBERLY M. MILLER ◽  
SHARON CHIOU ◽  
JOHN Z. WU
Keyword(s):  
Computer Simulation ◽  
Ground Reaction Force ◽  
Center Of Mass ◽  
Reaction Force ◽  
Construction Workers ◽  
Whole Body ◽  
Vertical Ground Reaction Force ◽  
Actual Measurement ◽  
Increased Risk ◽  
Vertical Ground

Stilts are elevated tools that are frequently used by construction workers to raise workers 18 to 40 inches above the ground without the burden of erecting scaffolding or a ladder. Some previous studies indicated that construction workers perceive an increased risk of injury when working on stilts. However, no in-depth biomechanical analyses have been conducted to examine the fall risks associated with the use of stilts. The objective of this study is to evaluate a computer-simulation stilts model. Three construction workers were recruited for walking tasks on 24-inch stilts. The model was evaluated using whole body center of mass and ground reaction forces. A PEAK™ motion system and two Kistler™ force platforms were used to collect data on both kinetic and kinematic measures. Inverse- and direct-dynamics simulations were performed using a model developed using commercial software — ADAMS and LifeMOD. For three coordinates (X, Y, Z) of the center of mass, the results of univariate analyses indicated very small variability for the mean difference between the model predictions and the experimental measurements. The results of correlation analyses indicated similar trends for the three coordinates. Plotting the resultant and vertical ground reaction force for both right and left feet showed small discrepancies, but the overall shape was identical. The percentage differences between the model and the actual measurement for three coordinates of the center of mass, as well as resultant and vertical ground reaction force, were within 20%. This newly-developed stilt walking model may be used to assist in improving the design of stilts.

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