scholarly journals Gait transitions in simulated reduced gravity

2011 ◽  
Vol 110 (3) ◽  
pp. 781-788 ◽  
Author(s):  
Yuri P. Ivanenko ◽  
Francesca Sylos Labini ◽  
Germana Cappellini ◽  
Velio Macellari ◽  
Joseph McIntyre ◽  
...  
Keyword(s):  
Inverted Pendulum ◽  
Abrupt Change ◽  
The Body ◽  
Reduced Gravity ◽  
Altered Gravity ◽  
Transition Speed ◽  
Simulation Techniques ◽  
Significant Prolongation ◽  
Gait Parameters ◽  
Gait Transitions

Gravity has a strong effect on gait and the speed of gait transitions. A gait has been defined as a pattern of locomotion that changes discontinuously at the transition to another gait. On Earth, during gradual speed changes, humans exhibit a sudden discontinuous switch from walking to running at a specific speed. To study the effects of altered gravity on both the stance and swing legs, we developed a novel unloading exoskeleton that allows a person to step in simulated reduced gravity by tilting the body relative to the vertical. Using different simulation techniques, we confirmed that at lower gravity levels the transition speed is slower (in accordance with the previously reported Froude number ∼0.5). Surprisingly, however, we found that at lower levels of simulated gravity the transition between walking and running was generally gradual, without any noticeable abrupt change in gait parameters. This was associated with a significant prolongation of the swing phase, whose duration became virtually equal to that of stance in the vicinity of the walk-run transition speed, and with a gradual shift from inverted-pendulum gait (walking) to bouncing gait (running).

scholarly journals Effect of reduced gravity on the preferred walk-run transition speed.

1997 ◽  
Vol 200 (4) ◽  
pp. 821-826 ◽  
Author(s):  
R Kram ◽  
A Domingo ◽  
D P Ferris
Keyword(s):  
Froude Number ◽  
Inverted Pendulum ◽  
Center Of Mass ◽  
Reduced Gravity ◽  
Leg Length ◽  
Pendulum System ◽  
Transition Speed ◽  
Inverted Pendulum Model ◽  
Inverted Pendulum System ◽  
Pendulum Model

We investigated the effect of reduced gravity on the human walk-run gait transition speed and interpreted the results using an inverted-pendulum mechanical model. We simulated reduced gravity using an apparatus that applied a nearly constant upward force at the center of mass, and the subjects walked and ran on a motorized treadmill. In the inverted pendulum model for walking, gravity provides the centripetal force needed to keep the pendulum in contact with the ground. The ratio of the centripetal and gravitational forces (mv2/L)/(mg) reduces to the dimensionless Froude number (v2/gL). Applying this model to a walking human, m is body mass, v is forward velocity, L is leg length and g is gravity. In normal gravity, humans and other bipeds with different leg lengths all choose to switch from a walk to a run at different absolute speeds but at approximately the same Froude number (0.5). We found that, at lower levels of gravity, the walk-run transition occurred at progressively slower absolute speeds but at approximately the same Froude number. This supports the hypothesis that the walk-run transition is triggered by the dynamics of an inverted-pendulum system.

scholarly journals Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

1999 ◽  
Vol 86 (1) ◽  
pp. 383-390 ◽  
Author(s):  
Timothy M. Griffin ◽  
Neil A. Tolani ◽  
Rodger Kram
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Gravitational Potential Energy ◽  
Reduced Gravity

Walking humans conserve mechanical and, presumably, metabolic energy with an inverted pendulum-like exchange of gravitational potential energy and horizontal kinetic energy. Walking in simulated reduced gravity involves a relatively high metabolic cost, suggesting that the inverted-pendulum mechanism is disrupted because of a mismatch of potential and kinetic energy. We tested this hypothesis by measuring the fluctuations and exchange of mechanical energy of the center of mass at different combinations of velocity and simulated reduced gravity. Subjects walked with smaller fluctuations in horizontal velocity in lower gravity, such that the ratio of horizontal kinetic to gravitational potential energy fluctuations remained constant over a fourfold change in gravity. The amount of exchange, or percent recovery, at 1.00 m/s was not significantly different at 1.00, 0.75, and 0.50 G (average 64.4%), although it decreased to 48% at 0.25 G. As a result, the amount of work performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

Pectoral fin locomotion in the striped surfperch. I. Kinematic effects of swimming speed and body size

1996 ◽  
Vol 199 (10) ◽  
pp. 2235-2242 ◽  
Author(s):  
E Drucker ◽  
J Jensen
Keyword(s):  
Body Size ◽  
Swimming Speed ◽  
Beat Frequency ◽  
Limited Range ◽  
The Body ◽  
Small Fish ◽  
Large Fish ◽  
Pectoral Fin ◽  
Transition Speed ◽  
Speed Up

Swimming trials at increasing velocity were used to determine the effects of steady swimming speed on pectoral fin kinematics for an ontogenetic series of striped surfperch Embiotoca lateralis, ranging from 6 to 23 cm in standard length (SL). The fin stroke cycle consisted of a propulsive period, the duration of fin abduction and adduction, and a 'refractory' period, during which the fin remained adducted against the body. Pectoral fin-beat frequency (fp) measured as the inverse of the entire stride period, as in past studies, increased curvilinearly with speed. Frequency, calculated as the reciprocal of the propulsive period alone, increased linearly with speed, as shown previously for tail-beat frequency of fishes employing axial undulation. Fin-beat amplitude, measured as the vertical excursion of the pectoral fin tip during abduction, increased over a limited range of low speeds before reaching a plateau at 0.35­0.40 SL. Pectoral fin locomotion was supplemented by intermittent caudal fin undulation as swimming speed increased. At the pectoral­caudal gait transition speed (Up-c), frequency and amplitude attained maxima, suggesting that the fin musculature reached a physiological limit. The effects of body size on swimming kinematics differed according to the method used for expressing speed. At a given absolute speed, small fish used higher stride frequencies and increased frequency at a faster rate than large fish. In contrast, the relationship between fp and length-specific speed (SL s-1) had a greater slope for large fish and crossed that for small fish at high speeds. We recommend that comparisons across size be made using speeds expressed as a percentage of Up-c, at which kinematic variables influencing thrust are size-independent.

scholarly journals The gravitational imprint on sensorimotor planning and control

2020 ◽  
Vol 124 (1) ◽  
pp. 4-19 ◽  
Author(s):  
O. White ◽  
J. Gaveau ◽  
L. Bringoux ◽  
F. Crevecoeur
Keyword(s):  
Internal Representation ◽  
The Body ◽  
Altered Gravity ◽  
Partial Adjustment ◽  
Gravitational Forces ◽  
Planning And Control ◽  
Biomechanical Constraints ◽  
And Control ◽  
Future Work ◽  
The Impact

Humans excel at learning complex tasks, and elite performers such as musicians or athletes develop motor skills that defy biomechanical constraints. All actions require the movement of massive bodies. Of particular interest in the process of sensorimotor learning and control is the impact of gravitational forces on the body. Indeed, efficient control and accurate internal representations of the body configuration in space depend on our ability to feel and anticipate the action of gravity. Here we review studies on perception and sensorimotor control in both normal and altered gravity. Behavioral and modeling studies together suggested that the nervous system develops efficient strategies to take advantage of gravitational forces across a wide variety of tasks. However, when the body was exposed to altered gravity, the rate and amount of adaptation exhibited substantial variation from one experiment to another and sometimes led to partial adjustment only. Overall, these results support the hypothesis that the brain uses a multimodal and flexible representation of the effect of gravity on our body and movements. Future work is necessary to better characterize the nature of this internal representation and the extent to which it can adapt to novel contexts.

COAGULATION ABNORMALITIES IN LEAD EXPOSED RATS

1987 ◽  
Author(s):  
Narendra Kumar Satija ◽  
Har Bhajan Singh ◽  
Anjana Grover ◽  
Ram Mohan Rai
Keyword(s):  
Modern Technology ◽  
Environmental Pollutant ◽  
The Body ◽  
Albino Rats ◽  
Thrombin Time ◽  
Significant Prolongation ◽  
Lysis Time ◽  
Industrial Material ◽  
Euglobulin Lysis Time ◽  
Plasma Recalcification Time

The accelerated rate of development of modern technology has greatly expanded the range of health hazards. Lead, a widely used industrial material, is a significant environmental pollutant that contaminates food, water, soil and air. Although much progress has been made in elucidating its adverse effects on various systems of the body like hepatic, CNS, renal etc., its effect on coagulation remains to be established. In view of this an experimental study was carried out in animals to understand how lead influences hemostasis.Male albino rats were exposed to lead either acutely by administering 20 mg lead acetate per kg body weight daily i.p. for 3 days or chronically by administering lead through drinking water containing 5 ppm lead for 150 days. Acute exposure to lead caused severe coagulopathy characterized by significant prolongation of plasma recalcification time, decrease in platelet count and decreased wall adherence of blood, decreased fibrinogen and euglobulin lysis time and significant increase in prothrombin time, thrombin time, and partial thromboplastin time. Similar observations were found in chronically exposed animals. It is concluded that exposure to heavy metals like lead may lead to a state of hypocoagulability.

Reduced-Gravity Human Factors Research with Aircraft

1969 ◽  
Vol 11 (5) ◽  
pp. 463-471 ◽  
Author(s):  
Michael J. Moran
Keyword(s):  
Human Factors ◽  
Space Flight ◽  
Gravity Data ◽  
Parabolic Flight ◽  
Gravity Level ◽  
Reduced Gravity ◽  
Low Gravity ◽  
Simulation Techniques ◽  
Space Experiments ◽  
Actual Space

Human factors in a low-gravity environment became important with the beginning of manned space flight programs. The costs and dangers associated with actual space experiments necessitated the development of reduced-gravity simulation techniques. Since parabolic flight is the only way to produce approximately the same physical conditions as orbital space flight, it is the only technique acceptable for many human factors studies. However, the shortness of periods at the desired gravity level and the high gravity levels of the pre- and post-parabola flight compromise the effectiveness of the technique. In spite of its faults, this technique has been used to produce many meaningful studies. These studies have done much to increase our limited knowledge of reduced-gravity human factors. It appears that this technique will continue to be a main source of low-gravity data, until the era of manned orbiting laboratories.

Measures of dynamic balance during level walking in healthy adult subjects: Relationship with age, anthropometry and spatio-temporal gait parameters

2019 ◽  
Vol 234 (2) ◽  
pp. 131-140 ◽  
Author(s):  
Tiziana Lencioni ◽  
Ilaria Carpinella ◽  
Marco Rabuffetti ◽  
Davide Cattaneo ◽  
Maurizio Ferrarin
Keyword(s):  
Motor Control ◽  
Body Mass ◽  
Healthy Subjects ◽  
Normative Data ◽  
Dynamic Balance ◽  
Frontal Plane ◽  
The Body ◽  
Heel Strike ◽  
Gait Parameters ◽  
Spatio Temporal

The maintenance of balance in dynamic conditions (e.g. during walking) is a necessary requirement that motor control must reach to avoid falls. However, this is a challenging situation, since to ensure the forward progression of the body, the center of mass must stay outside the base of support in the sagittal plane, and simultaneously remain inside the lateral borders in the frontal plane. Deviation from normative data of healthy subjects in dynamic balance could be used to quantify gait stability, fall risk and to provide hints for rehabilitation. However, normative data can be influenced by age, sex, anthropometry and spatio-temporal gait parameters, and such differences among subjects and leg side can hamper accurate assessment. The aims of this study were to investigate, in a group of healthy subjects: (1) possible asymmetry in dynamic balance maintenance strategies between leg sides, (2) the influence of age, sex and anthropometry on stability and (3) its dependence by spatio-temporal gait parameters. A total of 34 healthy subjects aged between 21 and 71 years, and ranging from 50.1 to 101.6 kg of body mass and from 155.0 to 188.9 cm of height were assessed on spatio-temporal and dynamic balance parameters (Foot Placement Estimator at heel strike and Margin of Stability at mid-stance) during self-selected gait. No parameter showed differences between legs. Dynamic balance parameters were influenced by sex, age, body mass and height mainly in the frontal plane. These measures were also correlated with gait speed and stride length both in the antero-posterior and medio-lateral directions. In addition also cadence and step width influenced the stability in the sagittal and frontal planes, respectively. The findings of this study confirm the symmetry in motor control of dynamic balance during self-selected gait in healthy subjects. Sex, anthropometry and spatio-temporal gait parameters have a significant effect on stability parameters, and this should be taken into account in dynamic balance studies.

Dynamic Modeling of Quadrupedal Running Gaits Using a Simple Template With Asymmetrical Body Mass Distribution

2004 ◽  
Author(s):  
Hong Zou ◽  
James P. Schmiedeler
Keyword(s):  
Mass Distribution ◽  
Inverted Pendulum ◽  
Equal Mass ◽  
The Body ◽  
Robotic Systems ◽  
Energy Losses ◽  
Slip Model ◽  
Additional Energy ◽  
Quadruped Robots ◽  
Key Characteristics

Most quadruped robots capable of running have employed bounding gaits at speeds far below those at which an animal of equal mass would gallop, which is a similar gait. This paper extends the spring-loaded inverted pendulum (SLIP) model to capture the key characteristics of trotting and galloping in biological systems. The objective is to establish a tool that will aid in determining the speed at which bounding or galloping is efficient for robotic systems. The SLIP model includes a linear damper in the legs to model all energy losses in a stride, and in the case of bounding, the body is taken to have an asymmetrical mass distribution. Results indicate that the model exhibits biological characteristics for both trotting and galloping, although duty factors are unrealistically low. Including leg mass in the models to account for additional energy loss does not offer improvement over the use of a linear damper alone.

scholarly journals Benchmark: Reachability on a model with holes

10.29007/cv59 ◽  
2018 ◽  
Author(s):  
Thomas Heinz ◽  
Jens Oehlerking ◽  
Matthias Woehrle
Keyword(s):  
Inverted Pendulum ◽  
The Body ◽  
System Model ◽  
Motion Trajectories ◽  
Pursuit Evasion ◽  
Specific Behaviour ◽  
Safety Property ◽  
Input Signals ◽  
Wheeled Robot ◽  
Line Following

The benchmark presented in this paper is an example for verification of a hybrid system model with so-called holes, i.e. part of the system behaviour is not specified. Verification of such a model allows 3rd parties to plug a specific behaviour into a hole without changing desirable properties of the system. The particular example is based on an open-source robotics application, namely a self-balancing two-wheeled robot which is essentially modeled as an inverted pendulum. The balance controller provides two input signals for translational (forward/backward) and rotational (left/right turn) motion which can be driven by arbitrary path planning applications. Examples for such applications are line following and pursuit-evasion algorithms as well as a remote control which allows trajectories to be defined externally. These motion trajectories may or may not yield a state from which the balance controller is unable to recover, which means that the robot falls over. Hence, the verification goal is to prove the safety property that the body pitch angle is bounded under motion trajectories.

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