On the Measurement of Dynamic Stability of Human Locomotion

1994 ◽  
Vol 116 (1) ◽  
pp. 30-36 ◽  
Author(s):  
Yildirim Hurmuzlu ◽  
Cagatay Basdogan
Keyword(s):  
Dynamic Stability ◽  
Complex Dynamics ◽  
Stability Index ◽  
Normal Subjects ◽  
Human Locomotion ◽  
Heel Strike ◽  
Analytical Methodology ◽  
Gait Patterns ◽  
Kinematic Data ◽  
The Stability

The main focus of the present investigation is the development of quantitative measures to assess the dynamic stability of human locomotion. The analytical methodology is based on Floquet theory, which was developed to investigate the stability of nonlinear oscillators. Here the basic approach is modified such that it accommodates the study of the complex dynamics of human locomotion and differences among various individuals. A quantitative stability index has been developed to characterize the ability of humans to maintain steady gait patterns. Floquet multipliers of twenty normal subjects were computed from the kinematic data at Poincare´ sections taken at four instants of the gait cycle, namely heel strike, foot flat, heel off, and toe off. Then, an averaged stability index was computed for each subject. Statistical analysis was performed to demonstrate the utility of the stability indices as quantitative measures of dynamic stability of gait for the subject population tested during the present study.

Development of a Dynamic Stability Simulator for Articulated and Conventionaltractors Useful for Real-Time Safety Devices

2013 ◽  
Vol 394 ◽  
pp. 546-553 ◽  
Author(s):  
Fabrizio Mazzetto ◽  
Marco Bietresato ◽  
Renato Vidoni
Keyword(s):  
Real Time ◽  
Dynamic Stability ◽  
Stability Problem ◽  
Stability Index ◽  
Real Field ◽  
Circular Trajectory ◽  
Safety Devices ◽  
Test Platform ◽  
Agricultural Tractors ◽  
The Stability

The safety of agricultural tractors drivers is a very actual topic, especially when tractors operate on side slopes, such as in terraced vineyards. This work approaches the stability problem of articulated tractors by modelling, simulating and quantifying the safety of the driver with respect to both roll and pitch overturns. First of all, an articulated tractor has been modelled and simplified, after that a stability index has been defined and calculatedin several simulated slope conditions when the tractor travels along a circular trajectory; then, the obtained results have beencompared with respect to a conventional tractor. This work is a preliminary studyfor a tilting test platform for real vehicles, capable to reproduce real field conditions (slope, obstacles, roughness). Finally, some directives on how exploiting the obtained results for real-time safety devices have been formulated.

scholarly journals Repeatability of kinetic and kinematic measurements in gait studies of the lower limb amputee

1987 ◽  
Vol 11 (2) ◽  
pp. 55-64 ◽  
Author(s):  
M. S. Zahedi ◽  
W. D. Spence ◽  
S. E. Solomonidis ◽  
J. P. Paul
Keyword(s):  
Lower Limb ◽  
Normal Subjects ◽  
Human Locomotion ◽  
Computational Method ◽  
Research Use ◽  
Clinical Use ◽  
Kinematic Data ◽  
Lower Limb Amputee ◽  
Biomechanical Evaluation

During the last few years considerable attention has been given to the use of gait analysis as a tool for clinical use. The instrumentation for measurement of the kinetics and kinematics of human locomotion was originally designed for research use. Extension of its use into the clinical field calls for simplified methodology and clearly defined protocols with precise identification of the relevant parameters for the analysis. Force platforms, TV-computer and pylon transducer systems were used for collection of kinetic and kinematic data of five normal subjects, 10 below-knee, 10 above-knee and one hip disarticulation amputee. The repeatability tests showed significant differences in the measured parameters. These variations are attributed to the methodology of the analysis and the step to step variation of the subjects' gait. Differences in the degree of step to step variation between various amputee and normal subjects are quantified. In this presentation the capability of present day systems to perform repeatable gait measurements is discussed. A computational method for determination of representative measurements for the purposes of biomechanical evaluation and comparison as well as quantification of the degree of repeatability is described.

Evaluation of Static and Dynamic Stability of Spinal Cord Injuries: What Are the Gaps

2020 ◽  
Vol 22 (1) ◽  
pp. 1-5
Author(s):  
Hussein Asiabi ◽  
Mokhtar Arazpour ◽  
Mahmoud Bahramizadeh ◽  
Mohammad Taghi Karimi
Keyword(s):  
Spinal Cord ◽  
Dynamic Stability ◽  
Normal Subjects ◽  
Assistive Devices ◽  
Quiet Standing ◽  
Stability Parameters ◽  
Cord Injury ◽  
Lesion Level ◽  
The Stability ◽  
Improve Stability

Background. Depending on the level of lesion, spinal cord injury (SCI) individuals have limited ability to stand and walk. They have to use various assistive devices to restore their abilities. The aim of this study was to evaluate the stability of SCI individuals during walking and quiet standing. Material and methods. Three groups: normal subjects and SCI individuals with complete and incomplete lesions, were enrolled. Stability of the subjects was evaluated based on center of pressure (COP) sways in quiet standing and spatiotemporal gait parameters in walking. The difference between the stability of normal and SCI subjects was determined by use of the two-sample t test. The correlation between the mean values of stability parameters in standing and walking and lesion level was determined by use of Pearson’s correlation. Results. The stability of SCI subjects during quiet standing was better than that of normal subjects. How­ever, their dynamic stability was significantly less than normal subjects. The dynamic stability of complete and incomplete SCI subjects did not differ significantly (P-value<0.05). There was no correlation between lesion level and stability parameters. Conclusion. 1. SCI individuals suffer mostly from lack of dynamic stability, which does not depend on their lesion levels. 2. It seems that this problem may be due to rehabilitation methods used to improve stability in these patients. 3. It is recommended that new methods of rehabilitation or assistive devices should be used to improve stability of these individuals.

Effects of Nonslip Socks on the Gait Patterns of Older People When Walking on a Slippery Surface

2013 ◽  
Vol 103 (6) ◽  
pp. 471-479 ◽  
Author(s):  
Anna L. Hatton ◽  
Daina L. Sturnieks ◽  
Stephen R. Lord ◽  
Joanne C.M. Lo ◽  
Hylton B. Menz ◽  
...  
Keyword(s):  
Older People ◽  
Step Length ◽  
Heel Strike ◽  
Test Time ◽  
Clinical Effects ◽  
Timed Up And Go ◽  
Gait Patterns ◽  
Kinematic Data ◽  
Gait Parameters ◽  
Slippery Surface

Background: Slips are a common cause of falls, and nonslip socks have been marketed to prevent slips in older people. However, few studies have investigated the biomechanical and clinical effects of walking in nonslip socks. This study aimed to examine gait parameters in older people walking on a slippery surface wearing nonslip socks compared with standard sock and barefoot conditions. Methods: Fifteen older people completed five trials of the fast-paced Timed Up and Go test while barefoot and while wearing standard socks and nonslip socks. Kinematic data (step length, heel horizontal velocity at heel strike, and foot-floor angle at heel strike) and clinical data (total Timed Up and Go test time, total number of steps, number of steps in turn, and observed slips, trips, or falls) were collected. Results: Performance on the Timed Up and Go test did not differ between the barefoot and nonslip sock conditions; however, participants walked more slowly and took shorter steps when wearing standard socks. Participants rated nonslip socks to feel less slippery than barefoot and standard socks. Conclusions: Compared with wearing standard socks, wearing nonslip socks improves gait performance and may be beneficial in reducing the risk of slipping in older people. (J Am Podiatr Med Assoc 103(6): 471–479, 2013)

Evaluation of Static and Dynamic Stability of Spinal Cord Injuries: What Are the Gaps?

2020 ◽  
Vol 22 (1) ◽  
pp. 1-6
Author(s):  
Hussein Asiabi ◽  
Mokhtar Arazpour ◽  
Mahmoud Bahramizadeh ◽  
Mohammad Taghi Karimi
Keyword(s):  
Spinal Cord ◽  
Dynamic Stability ◽  
Normal Subjects ◽  
Assistive Devices ◽  
Quiet Standing ◽  
Stability Parameters ◽  
Cord Injury ◽  
Lesion Level ◽  
The Stability ◽  
Improve Stability

Summary Background. Depending on the level of lesion, spinal cord injury (SCI) individuals have limited ability to stand and walk. They have to use various assistive devices to restore their abilities. The aim of this study was to evaluate the stability of SCI individuals during walking and quiet standing. Material and methods. Three groups: normal subjects and SCI individuals with complete and incomplete lesions, were enrolled. Stability of the subjects was evaluated based on center of pressure (COP) sways in quiet standing and spatiotemporal gait parameters in walking. The difference between the stability of normal and SCI subjects was determined by use of the two-sample t test. The correlation between the mean values of stability parameters in standing and walking and lesion level was determined by use of Pearson’s correlation. Results. The stability of SCI subjects during quiet standing was better than that of normal subjects. How­ever, their dynamic stability was significantly less than normal subjects. The dynamic stability of complete and incomplete SCI subjects did not differ significantly (P-value<0.05). There was no correlation between lesion level and stability parameters. Conclusions. 1. SCI individuals suffer mostly from lack of dynamic stability, which does not depend on their lesion levels. 2. It seems that this problem may be due to rehabilitation methods used to improve stability in these patients. 3. It is recommended that new methods of rehabilitation or assistive devices should be used to improve stability of these individuals.

Instant 99mTc-Labelled Glucoheptonate Kit for Kidney Imaging

1983 ◽  
Vol 22 (05) ◽  
pp. 246-250 ◽  
Author(s):  
M. Al-Hilli ◽  
H. M. A. Karim ◽  
M. H. S. Al-Hissoni ◽  
M. N. Jassim ◽  
N. H. Agha
Keyword(s):  
Sodium Hydroxide Solution ◽  
Normal Subjects ◽  
Organ Distribution ◽  
Stable Complex ◽  
Scintillation Camera ◽  
Ph Adjustment ◽  
The Mean ◽  
The Stability ◽  
Kidney Imaging ◽  
Mean Concentration

Gelchromatography column scanning has been used to study the fractions of reduced hydrolyzed 99mTc, 99mTc-pertechnetate and 99mTc-chelate in a 99mTc-glucoheptonate (GH) preparation. A stable high labelling yield of 99mTc-GH complex in the radiopharmaceutical has been obtained with a concentration of 40-50 mg of glucoheptonic acid-calcium salt and not less than 0.45 mg of SnCl2 2 H2O at an optimal pH between 6.5 and 7.0. The stability of the complex has been found significantly affected when sodium hydroxide solution was used for the pH adjustment. However, an alternative procedure for final pH adjustment of the preparation has been investigated providing a stable complex for the usual period of time prior to the injection. The organ distribution and the blood clearance data of 99mTc-GH in rabbits were relatively similar to those reported earlier. The mean concentration of the radiopharmaceutical in both kidneys has been studied in normal subjects for one hour with a scintillation camera and the results were satisfactory.

A FORECAST OF PRODUCTIVE LONGEVITY OF HOLSTEIN COWS BY INDIRECT SIGNS

2020 ◽  
Author(s):  
З.С. САНОВА
Keyword(s):  
Correlation Coefficient ◽  
Aging Process ◽  
Direct Relationship ◽  
Stability Index ◽  
Age At First Calving ◽  
Group I ◽  
Predicted Values ◽  
The Stability ◽  
Relationship Of ◽  
The Relationship

В статье представлены материалы о взаимосвязи продолжительности продуктивного использования коров с характеристикой устойчивости к деградации, с возрастом отела и удоем. В исследованной, разнородной по происхождению, группе животных для прогноза продуктивного периода коров, обусловленного устойчивостью к деградации и возрастом первого отела, пригодно уравнение регрессии, аргументами в котором являются индекс устойчивости, возраст первого отела в первой и второй степенях. Коэффициент корреляции межу предсказанными значениями продуктивного периода и его фактическими величинами в I группе составляет 0,502, во II - 0,604. При этом крайние варианты прогнозируются со статистическими ошибками 5 мес при оценке индекса устойчивости по 2 лактациям и 4,1 мес по 3, а средние варианты, соответственно, 1,6 и 1,51 мес. Индекс устойчивости к процессу старения является важной характеристикой биологических особенностей коров, определяющий их продуктивное долголетие. Его оценка по первым 2 и 3 лактациям имеет прямолинейную связь с продуктивным периодом (r=0,4109 и r=0,5270), соответственно. Зависимость продуктивного периода от возраста первого отела криволинейная — с увеличением возраста первого отела сокращается срок продуктивного использования, при возрасте первого отела более 1400 дней срок продуктивного использования колеблется от 1,33 до 1,41 лактации. Коэффициент корреляции между этими характеристиками коров составляет - 0,2164 в I и - 0,2620 во II группах. The article presents materials about the relationship of the duration of productive use of cows with the characteristic of resistance to degradation, with the age of calving and milk yield. In the studied group of animals, which is heterogeneous in origin, the regression equation is suitable for predicting the productive period of cows due to resistance to degradation and the age of the first calving, the arguments of which are the stability index, the age of the first calving in the first and second degrees. The correlation coefficient between the predicted values of the productive period and its actual values in group I is 0.502, in group II - 0.604. At the same time, the extreme variants are predicted with statistical errors of 5 months when evaluating the stability index for 2 lactations and 4.1 months for 3, and the average variants, respectively, are 1.6 and 1.51 months. The index of resistance to the aging process is an important characteristic of the biological characteristics of cows, which determines their productive longevity. Its estimate for the first 2 and 3 lactations has a direct relationship with the productive period (r=0.4109 and r=0.5270), respectively. The dependence of the productive period age at first calving curvilinear with increasing age at first calving reduces the time to productive use, while age at first calving of more than 1400 days, the period of productive use ranges from 1.33 to 1.41 lactation. The correlation coefficient between these characteristics of cows is-0.2164 in I and-0.2620 in II groups.

scholarly journals The stability index of a cactus

1977 ◽  
Vol 24 (2) ◽  
pp. 170-183
Author(s):  
Douglas D. Grant ◽  
D. A. Holton
Keyword(s):  
Connected Graph ◽  
Stability Index ◽  
The Stability

AbstractWe show that ifGis a connected graph of ordernsuch that no line lies in more than one cycle (in other words,Gis a cactus of ordern), then the stability index ofGis one of the integers 0, 1,n−7,n−6,n−5,n−4 orn.

Features of pubertal patients with schizophrenia neurocognitive profile

2017 ◽  
Vol 41 (S1) ◽  
pp. S430-S431
Author(s):  
Y. Barylnik ◽  
S. Pakhomova ◽  
D. Samoylova ◽  
J. Abrosimova ◽  
E. Kolesnichenko ◽  
...  
Keyword(s):  
Stability Index ◽  
Neurocognitive Disorders ◽  
Motor Speed ◽  
Structuring Element ◽  
Test Part ◽  
Psychic Disorders ◽  
Competing Interest ◽  
Neurocognitive Profile ◽  
The Stability ◽  
High Level

Identifying the patterns of neurocognitive disorders in pubertal schizophrenia is actual.MethodsBenton Test of visual retention, methods of forward and reverse bills, Bourdon correction sample, Wechsler's subtests (subtest 11 – “Encryption”, subtest 12 – “Labyrinths” 1, 2, 3, 4, 5), Trail Creating a Test Part A.ResultsAll patients were divided into 3 groups. The first group (schizophrenia) and second group (other psychic disorders) showed the worst results than healthy subjects. Qualitative analysis of the “Benton Test” results showed similar variations of difficulty and types of errors in the subjects of the first and second groups – ignoring the number of the figure sides, as well as difficulties in the structuring element of the image corners. The “Methods of forward and reverse bills” demonstrated the fatigue and attention instability. “Bourdon test” showed a high level of the stability index (K = 0.09). Wechsler's subtest “Encryption B” obtained poor results, indicating a pathological decrease in visual-motor speed. During the subtest “Labyrinths 1, 2, 3, 4, 5” the subjects of first and second groups exceeded the allowable time limit, but the first group of schizophrenia patients allowed more blunders during pubertal study (ignored the walls of the maze, torn pencil despite the given instructions). The test groups 1 and 2 while passing “Trail Creating a Test Part A” have shown good results – job data did not cause difficulties and carried out in accordance with the specified instructions.ConclusionsNeurocognitive disorders allow to confirm the presence of morphological and functional brain changes when endogenous mental illness occurs.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Stability of slender inverted flags and rods in uniform steady flow

2016 ◽  
Vol 809 ◽  
pp. 873-894 ◽  
Author(s):  
John E. Sader ◽  
Cecilia Huertas-Cerdeira ◽  
Morteza Gharib
Keyword(s):  
Multiple Equilibria ◽  
Complex Dynamics ◽  
Flow Direction ◽  
Flow Speed ◽  
Uniform Flow ◽  
Biological Phenomena ◽  
Cantilever Length ◽  
The Stability ◽  
Elastic Sheets ◽  
Clamped Edge

Cantilevered elastic sheets and rods immersed in a steady uniform flow are known to undergo instabilities that give rise to complex dynamics, including limit cycle behaviour and chaotic motion. Recent work has examined their stability in an inverted configuration where the flow impinges on the free end of the cantilever with its clamped edge downstream: this is commonly referred to as an ‘inverted flag’. Theory has thus far accurately captured the stability of wide inverted flags only, i.e. where the dimension of the clamped edge exceeds the cantilever length; the latter is aligned in the flow direction. Here, we theoretically examine the stability of slender inverted flags and rods under steady uniform flow. In contrast to wide inverted flags, we show that slender inverted flags are never globally unstable. Instead, they exhibit bifurcation from a state that is globally stable to multiple equilibria of varying stability, as flow speed increases. This theory is compared with new and existing measurements on slender inverted flags and rods, where excellent agreement is observed. The findings of this study have significant implications to investigations of biological phenomena such as the motion of leaves and hairs, which can naturally exhibit a slender geometry with an inverted configuration.

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