Search results for "Space Flight"

Does the centre of mass remain stable during complex human postural equilibrium tasks in weightlessness?

2001

In normal gravity conditions the execution of voluntary movement involves the displacement of body segments as well as the maintenance of a stable reference value for equilibrium control. It has been suggested that centre of mass (CM) projection within the supporting base (BS) is the stabilised reference for voluntary action, and is conserved in weightlessness. The purpose of this study was to determine if the CM is stabilised during whole body reaching movements executed in weightlessness. The reaching task was conducted by two cosmonauts aboard the Russian orbital station MIR, during the Franco-Russian mission ALTAIR, 1993. Movements of reflective markers were recorded using a videocamera…

Comparison of actual and imagined execution of whole-body movements after a long exposure to microgravity

2003

Five cosmonauts were tested 30 days before a six-month space flight and also on the 2nd and the 6th day after their return to Earth. Cosmonauts performed and imagined a task that involved climbing two stairs to step onto a platform, jumping down with both feet and walking normally for a distance of 4 m. Durations of actual and imagined movements were measured by an electronic stopwatch. Results indicated that cosmonauts performed actual and imagined movements with similar durations before and after the space flight. However, the 2nd day after their return to Earth, cosmonauts significantly increased the durations of both actual and imagined movements. The durations of the imagined and actua…

European vestibular experiments on the Spacelab-1 mission: 4. Thresholds of perception of whole-body linear oscillation.

1986

Thresholds for the detection of linear oscillatory motion at 0.3 Hz in the X, Y and Z body axes were determined during the flight of Spacelab-1 and on the ground pre- and post-flight, using the method of limits with a single staircase procedure. Pre-flight, Z axis thresholds (mean 0.077 ms-2) were significantly higher than X and Y thresholds (mean 0.029 ms-2). Measures obtained on three crew members in-flight exhibited thresholds greater, by a factor of 1.5-4.3, than those obtained pre-flight. Post-flight, two crew members had significantly elevated X and Y axis thresholds whereas the other two crew members had lowered thresholds in X, Y and Z axes. In general, thresholds had returned to pr…

General remarks on the role of the vestibular system in weightlessness

1987

Different methods are described to experimentally achieve weightlessness. Since the function of the otolith system depends on the presence of contact forces opposing gravity, it is disabled in weightlessness and may send misleading positional information to the brain. Without the contributions of the otolith system it is difficult in space to distinguish self-motion from object motion. Furthermore, the disintegration of information from the neck position receptors from those of the otolith system can lead to additional illusory positional sensations. Since the function of the semicircular canal system in previous space flights was found to be essentially undisturbed, the vestibular experime…

Responses to eccentric rotation in two space-bound subjects

1993

Two subjects were rotated eccentrically in the manner described previously. In contrast to a normal control group, settings of a luminous line to the subjective vertical were almost unrelated to the gravitoinertial vector before, and totally so shortly after, space flight. Only 3 days postflight did a clear relation to the gravitoinertial vector re-establish itself in the one subject who actually flew. The correspondence became normal 5 days after the flight. Since there were no clinical abnormalities evident in the subjects, it is suggested that both subjects suppressed their vestibular information, presumably as an effect of vestibular deconditioning training before the flight. In additio…

Effects of rectilinear acceleration and optokinetic and caloric stimulations in space.

1984

During the flight of Spacelab 1 the crew performed a number of experiments to explore changes in vestibular function and visual-vestibular interactions on exposure to microgravity. Measurements were made on the threshold for detection of linear oscillation, vestibulo-ocular reflexes elicited by angular and linear movements, oculomotor and posture responses to optokinetic stimulations, and responses to caloric stimulation. Tests were also conducted on the ground, during the 4 months before and on days 1 to 6 after flight. The most significant result was that caloric mystagmus of the same direction as on the earth could also be evoked in the weightless environment.

European vestibular experiments on the Spacelab-1 mission: 1. Overview.

1986

During the flight of Spacelab-1 a series of vestibular experiments was performed on the crew by a group of European investigators. Control experiments were carried out on the same subjects pre- and postflight. The tests included caloric stimulation of the ears, threshold measurements of response to linear acceleration, motion sickness provocative stimuli, vestibulo-ocular reflexes during linear and angular stimulation, estimation of the subjective vertical (luminous line measurements) and static ocular counterrotation at various tilt angles. The caloric experiment proved the existence of a nonthermoconvective mechanism of caloric nystagmus in space. Most of the other test results point to a…

SPACE FLIGHT AND LOSS OF STRENGTH IN UPPER LIMB MUSCLES

2008