When crewmembers make the transition from Earth's gravity to the near weightlessness of space, they face another major adaptation: how will they maneuver in space and how will they determine their orientation as they move around? Normal activity on Earth, such as walking, standing, sitting and working with the hands requires the brain to interpret and integrate information coming from all the body's senses (touch, hearing, sight, etc.) This information, once processed by the brain, gives feedback to the body on how the limbs are positioned, how the entire body is oriented (up or down, right or left), and which muscles should be moved to reorient the body.
In space, the eyes, inner ears, muscles, joints, and skin cannot rely on gravity as a constant indicator of position and orientation. The brain must learn to rearrange the relationships among the signals from these sensory systems when processing the information in order to produce correct responses. This rearrangement requires a period of adaptation. Before adaptation occurs, crewmembers often experience space motion sickness (SMS), difficulty determining orientation and controlling motion, and the illusion that the body or environment is moving even when both are stationary. Many of these same problems recur upon return to Earth, since another period of adaptation is needed to readjust the body back to the sensation of gravity. Length of recovery time is related to the duration of the mission.
Alterations in Postural Equilibrium Control Associated with Long-Duration Space Flight
Anticipatory Postural Activity (Posa) - Phase 1A
Anticipatory Postural Activity (Posa)
Biomechanics of Movement during Locomotion
The Effects of Long-Duration Space Flight on Eye, Head and Trunk Coordination during Locomotion
The Effects of Long-Duration Space Flight on Gaze Control
Eye-Head Coordination during Target Acquisition
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Page last updated: 07/16/1999