Spatial Orientation and Posture During and Following Weightlessness: Human Experiments on Spacelab Life Sciences 1

Abstract

The 4 payload crew members of the Spacelab Life Sciences 9-day space flight in 1991 were subjected to limited vestibular testing in flight as well as pre and post flight. Major differences in individual “perceptual style” appeared in their reaction to the visual-vestibular stimuli in the rotating dome experiment, and especially in the extent to which nondirectional tactile cues served to anchor the subjective vertical and body postural reactions. The ability of subjects to point to remembered target positions was degraded in space, which produced a tendency to point low in some subjects in flight. The eye movements and subjective response to sudden stops and head pitching following continuous spinning (dumping) were measured both in space and on the ground. Although subjective duration of inflight rotation for the dumping tests was shorter than that for the preflight tests, the postrotatory nystagmus, with or without head pitch, was lengthened in time constant relative to preflight. Ground tests, in addition to the flight experiments, investigated the changes following in subjective and oculomotor reactions to whole body tilt, the ability to balance with eyes open and closed; leg muscle strength and stamina as related to posture; visual field dependence; and the perceptual and oculomotor reactions to horizontal linear acceleration. Several of these tests, as well as postflight measures of motion sickness susceptibility, revealed subtle evidence of neurovestibular alterations that lasted a week or more following the 10-day orbital exposure.

A haptic illusion created by gravity

“…Future work could test the respective contributions of shoulder, elbow, wrist, and finger muscles to LF estimation, with the use of ballasts, elastic chords, and counterweights attached to various points of the arm during isometric force production. Such experiments can allow the effects of muscle activity to be distinguished from other effects specific to the conditions of microgravity and hypergravity, conditions that also affect vestibular inputs, postural control 35,36 , spatial orientation [54][55][56] , limb position sense [57][58][59] , and stress 60 . Our protocol did not allow us to probe the participants' conscious perception of forces.…”

A haptic illusion created by gravity

“…One could also test the impact of hand posture (e.g., flipping the hand 180°) on LF reproduction to control for biomechanical asymmetries. These experiments can be performed on the ground and allow the effects of muscle activity to be distinguished from other effects specific to the conditions of microgravity and hypergravity, conditions that also affect vestibular inputs, postural control, 37 , 38 spatial orientation, 65 , 66 , 67 limb position sense, 68 , 69 , 70 and stress. 71 Besides, our protocol did not allow us to probe the participants’ conscious perception of forces.…”

Effects of simulated hypo-gravity on lower limb kinematic and electromyographic variables during anti-gravitational treadmill walking

“…Previous work has demonstrated that human proprioception diminishes in hypogravity; limb matching tasks are less effectively completed ( Lackner and DiZio, 1992 ) as well as approximations of limb position ( Bringoux et al, 2012 ; Young et al, 1993 ). Mouchnino et al (1996) found that anticipatory postural adjustments were notably absent below standard Earth gravity.…”

“…To examine this, previous investigations have focused on manipulating the gait characteristics of an individual within an Earth-like environment. Few studies have sought to examine hysteresis in human gait through manipulation of the environment itself ( Bringoux et al, 2012 ; Ivanenko et al, 2002 ; Young et al, 1993 ). Yet even a brief consideration of the ontology of gait reveals the absolute importance of environmental conditions to human locomotion.…”