[Effects of gravity-vector changing for endothelial (correction of endotherial) cells].
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Actins↗
SEARCH · PubMed Health
Results for “Gravity, Altered”
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[Usefulness and limitations of clinostats].
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Cell Division↗
Optokinetic nystagmus, vection, and motion sickness.
BACKGROUND: Two current theories concerning the etiology of motion sickness (MS)-the eye movement hypothesis and sensory conflict theory-were evaluated under conditions that manipulated the degree of optokinetic nystagmus (OKN) and/or vection. METHOD: Eye movement and perceptual responses were elicited with whole field stimulation in a vertically striped rotating drum and modulated with fixation and/or a restriction of the field of view (FOV). Measures of OKN, vection, and MS were recorded under the various conditions. RESULTS: Both visual field restriction and/or fixation diminished circular vection, OKN, and MS. Conditions involving both fixation and restricted FOV resulted in greater reductions in MS than did either restriction alone. CONCLUSIONS: These findings lend support to a multi-factor explanation of MS, involving both sensory conflict and eye movement.
Aerospace Medicine↗
Biomechanics of locomotion in subgravity.
The speed of walking or running on the moon as compared with earth is appreciably reduced, in spite of mechanisms of compensation taking place such a forward leaning of the body and an increase of the horizontal component of the push of the foot on the ground. However on the moon the same speed of locomotion as on earth can be reached by shifting to a different mechanism of locomotion, i. e. progression by jumps, which becomes possible on the moon because of the reduction of the body weight. The energy cost of locomotion is certainly less on the moon than on earth, about 1/6. Were the subject not restrained by the space suit, progression by jumps at 20 km hr-1 on the moon would cost no more than 10 ml kg-1 min-1 of oxygen, the same as walking on earth at 6 km hr-1. Maximal acceleration of the body as in sprinting, or deceleration as in stopping, attains much higher values on earth than on the moon. While sprinting on earth may involve the maximal muscular power, sprinting or progressing at the highest speed on the moon involves only a fraction of the maximal power, mainly because of the reduced maximal frequency of the steps (or jumps). The maximal height of the jump on both feet on the moon could attain 4 m in the unrestricted subject. An analysis is wanted on the restriction of the movements brought about by the space suit and on the energy cost of progression.
Biomechanical Phenomena↗
Modern view on the short-arm centrifuge as a potential generator of artificial gravity in piloted missions.
The problem of artificial gravity (AG) in long-term missions is one of the hottest, as the existing countermeasures do not fully cope with the negative consequences of weightlessness. From two variants of AG creation--rotation of space systems around of their mass center or short radius centrifuge (SAC)--the preference is given to SAC, as technically easier variant for realization. However, the rotation of a person on SAC can cause not only positive, but also negative effects. The purpose of the present study was to perform the analysis of data of researches on a problem of AG generated by a of SAC, executed in Russia during last 20 years, and to state modern views on application of SAC as a mean of AG creation in long piloted missions.
Adaptation, Physiological↗
Effects of graded load of artificial gravity on cardiovascular functions in humans.
An artificial gravity and ergometric exercise loading device for human use was manufactured. It has the capacity of a max 2 G-load at the heart level, and a max 150 W of work-load. Eight subjects (six completed) were subjected to four repeated trials with or without 20 W ergometric exercise. Anti-G score, defined as the G-load x running time to the endpoint, was significantly higher in the exercise trials than standing trials. Heart rate (HR), mean arterial pressure (MAP), thoracic fluid index (TFI) were significantly superior during the exercise trials. Artificial gravity by centrifuge at 1.2 or 1.4 G with 40 or 60 W of ergometric workload may be an excellent countermeasure against cardiovascular deconditioning after long exposure to microgravity.
Adult↗
Daily head-up tilt, standing or centrifugation can prevent vasoreactivity changes in arteries of simulated weightless rats.
Artificial gravity will be considered for long-duration spaceflight missions. Recent studies have shown that continuous exposure to gravity does not appear necessary to prevent the adverse effects of weightlessness, instead intermittent exposure may suffice. Vernikos et al reported that 1 G intermittent exposures with and without walking exercise was effective in preventing physiologic deconditioning with 4-d, -6 degrees bedrest, and standing at 1 G was most effective in preventing orthostatic intolerance. Our previous work has demonstrated differential adaptational changes in structure, function, and innervation state of arterial vasculature in different body regions of rat during simulated weightlessness and further suggested that these changes might be one of the most important mechanisms accounting for postflight orthostatic intolerance. We therefore designed the present study involving a comprehensive evaluation of the effect of intermittent G exposure in preventing the differential functional changes of the arteries at the end of 3-wk head-down tail suspension in rats to answer the following questions: (1) do intermittent G exposure have counteracting effect in preventing differential functional changes in arterial vasculature with tail-suspension? (2) among the treatments used in the present study, i.e., head-up tilt (HUT), standing (STD), and centrifugation (CEN), what kind of exposure is more effective? (3) how much time in daily 1 G exposure is needed to maintain the normal (1 G) vascular responsiveness?
Adaptation, Physiological↗
Elaboration of on-board automated training system.
UNLABELLED: Long-term space flight requires regular controlling of crewmembers physical state and exercise training to prevent negative effect of microgravity. Considering a limited telecommunication we suppose on-board automated training system to become an effective alternative of on-earth mission teams. THE PURPOSE: to elaborate an expert system software permitting to automate the process of solution elaboration to estimate cosmonaut current psycho-physiological state and to form an individual program of physical training to prevent negative effects of long-term space flight. The first problem--to develop a formalized algorithm for expert evaluation of physical working capability basing the results of on-board compulsory running test MC 108-2.
Adult↗
[The 16th annual meeting of Japanese Society for Biological Sciences in Space. Proceedings].
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Adaptation, Physiological↗
[Effects of centrifugation-related artificial gravity on the human organism. Positive and negative effects].
Data of investigations of the artificial gravity issues in centrifuge experiments in Russian, USA and Japan over the past 40 years were analyzed. Periodic +Gz centrifugation was used to prevent or eliminate body deconditioning after 3- to 56-d simulated microgravity, and to increase the body functional reserve (orthostatic stability) in ordinary life. Positive effects included prevention of a decline of gravitational stability and reduction or averting the negative effects of simulated microgravity on various physiological systems. Better results can be achieved by combining artificial g-loads with the well-proven methods of combating deconditioning, i.e. physical training on bicycle ergometer and induced hydration. Human tolerance of g-loads on a short-arm centrifuge with a high (100%) gravitational gradient was found no worse than on a mid-arm centrifuge with a lower (20%) gravitational gradient. Negative effects of +Gz on a short-arm centrifuge were revealed and counteracting measures were determined.
Centrifugation↗
[Development and application of self-powered short arm human centrifuge].
OBJECTIVE: To present the development and application of a self-powered short arm human centrifuge. METHOD: Self-powered short arm human centrifuge consisted of human power, adjustable resistance trig, short arm and supporting construction parts. It was driven by human power. The short arm turned around the supporting part so artificial gravity is produced. The physical load can be adjusted by the adjustable resistance part. G-level depends on the rotative velocity of the central shaft. Nine healthy male volunteers received self-powered short arm human centrifuge training for 5 min per day with rotative velocity of 30-34 r min-1 for 7 d. Cardiac pumping function was measured before and after training. RESULT: Heart rate (HR) decreased significantly while left ventricular ejection time (LVET) increased significantly after 3 d training, and HR and LVET changed further after 7 d training. Stroke volume increased significantly only after 7 d training. CONCLUSION: Self-powered short arm human centrifuge combines artificial gravity and exercise and included other advantages of safety and economy of construction. Cardiac pumping function could be improved by 7 d training. It may be used for anti-G physiological training or as a countermeasure to counteract the effect of microgravity.
Adaptation, Physiological↗
The space elevator: a new tool for space studies.
The objective has been to develop a viable scenario for the construction, deployment and operation of a space elevator using current or near future technology. This effort has been primarily a paper study with several experimental tests of specific systems. Computer simulations, engineering designs, literature studies and inclusion of existing programs have been utilized to produce a design for the first space elevator. The results from this effort illustrate a viable design using current and near-term technology for the construction of the first space elevator. The timeline for possible construction is within the coming decades and estimated costs are less than $10 B. The initial elevator would have a 5 ton/day capacity and operating costs near $100/lb for payloads going to any Earth orbit or traveling to the Moon, Mars, Venus or the asteroids. An operational space elevator would allow for larger and much longer-term biological space studies at selectable gravity levels. The high-capacity and low operational cost of this system would also allow for inexpensive searches for life throughout our solar system and the first tests of environmental engineering. This work is supported by a grant from the NASA Institute for Advanced Concepts (NIAC).
Acceleration↗
Sensorimotor aspects of high-speed artificial gravity: I. Sensory conflict in vestibular adaptation.
Short-radius centrifugation offers a promising and affordable countermeasure to the adverse effects of prolonged weightlessness. However, head movements made in a fast rotating environment elicit Coriolis effects, which seriously compromise sensory and motor processes. We found that participants can adapt to these Coriolis effects when exposed intermittently to high rotation rates and, at the same time, can maintain their perceptual-motor coordination in stationary environments. In this paper, we explore the role of inter-sensory conflict in this adaptation process. Different measures (vertical nystagmus, illusory body tilt, motion sickness) react differently to visual-vestibular conflict and adapt differently. In particular, proprioceptive-vestibular conflict sufficed to adapt subjective parameters and the time constant of nystagmus decay, while retinal slip was required for VOR gain adaptation. A simple correlation between the strength of intersensory conflict and the efficacy of adaptation fails to explain the data. Implications of these findings, which differ from existing data for low rotation rates, are discussed.
Adaptation, Physiological↗
Sensorimotor aspects of high-speed artificial gravity: II. The effect of head position on illusory self motion.
The effects of cross-coupled stimuli on the semicircular canals are shown to be influenced by the position of the subject's head with respect to gravity and the axis of rotation, but not by the subject's head position relative to the trunk. Seventeen healthy subjects made head yaw movements out of the horizontal plane while lying on a horizontal platform (MIT short radius centrifuge) rotating at 23 rpm about an earth-vertical axis. The subjects reported the magnitude and duration of the illusory pitch or roll sensations elicited by the cross-coupled rotational stimuli acting on the semicircular canals. The results suggest an influence of head position relative to gravity. The magnitude estimation is higher and the sensation decays more slowly when the head's final position is toward nose-up (gravity in the subject's head x-z-plane) compared to when the head is turned toward the side (gravity in the subject's head y-z-plane). The results are discussed with respect to artificial gravity in space and the possible role of pre-adaptation to cross-coupled angular accelerations on earth.
Adolescent↗
Sensorimotor aspects of high-speed artificial gravity: III. Sensorimotor adaptation.
As a countermeasure to the debilitating physiological effects of weightlessness, astronauts could live continuously in an artificial gravity environment created by slow rotation of an entire spacecraft or be exposed to brief daily "doses" in a short radius centrifuge housed within a non-rotating spacecraft. A potential drawback to both approaches is that head movements made during rotation may be disorienting and nauseogenic. These side effects are more severe at higher rotation rates, especially upon first exposure. Head movements during rotation generate aberrant vestibular stimulation and Coriolis force perturbations of the head-neck motor system. This article reviews our progress toward distinguishing vestibular and motor factors in side effects of rotation, and presents new data concerning the rates of rotation up to which adaptation is possible. We have studied subjects pointing to targets during constant velocity rotation, because these movements generate Coriolis motor perturbations of the arm but do not involve unusual vestibular stimulation. Initially, reaching paths and endpoints are deviated in the direction of the transient lateral Coriolis forces generated. With practice, subjects soon move in straighter paths and land on target once more. If sight of the arm is permitted, adaptation is more rapid than in darkness. Initial arm movement trajectory and endpoint deviations are proportional to Coriolis force magnitude over a range of rotation speeds from 5 to 20 rpm, and there is rapid, complete motor adaptation at all speeds. These new results indicate that motor adaptation to high rotation rates is possible. Coriolis force perturbations of head movements also occur in a rotating environment but adaptation gradually develops over the course of many head movements.
Adaptation, Physiological↗
Understanding and treating "pusher syndrome".
"Pusher syndrome" is a clinical disorder following left or right brain damage in which patients actively push away from the nonhemiparetic side, leading to a loss of postural balance. The mechanism underlying this disorder and its related anatomy have only recently been identified. Investigation of patients with severe pushing behavior has shown that perception of body posture in relation to gravity is altered. The patients experience their body as oriented "upright" when the body actually is tilted to the side of the brain lesion (to the ipsilesional side). In contrast, patients with pusher syndrome show no disturbed processing of visual and vestibular inputs determining visual vertical. These new insights have allowed the authors to suggest a new physical therapy approach for patients with pusher syndrome where the visual control of vertical upright orientation, which is undisturbed in these patients, is the central element of intervention.
Accidental Falls↗
Proceedings of the 17th annual meeting of Japanese Society for Biological Sciences in Space.
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Adaptation, Physiological↗
[The problem of creation of artificial gravity with the use of a short-radius centrifuge for medical support of interplanetary piloted missions].
On the evidence of orbital flights, the system of countermeasures against the effects of microgravity does not fully make for deconditioning of a number of human organs and systems and recovery of preflight physical status and working ability of members of long-term missions takes 1.5 to 2 mos. of the post-flight rehabilitation. In order to maintain the physical form, health and performance of crews in future interplanetary missions, we should be ready to offer them a novel countermeasure, i.e. regular sessions of artificial gravity generated by a short-radius centrifuge (SRC) on board vehicles. The articles presents the substantiation and concept of ground-based simulation studies of health benefits from SRC in interplanetary missions. Of primary concern is development of SRC regimens that will put up a strong opposition to microgravity, assure crew safety, and reduce to the minimum time to fulfill the in-flight countermeasure program. Answers to arising questions can be found by consolidation of the expertise and resources of the countries willing to meet this challenge.
Adaptation, Physiological↗