microgravity

1. A condition in which there is very little net gravitational force, as of a free-falling object, an orbit, or interstellar space.
2. A minute shift in gravity that can occur through geologic factors in a region, such as the movement of the earth's crust along fault lines.

An environment, such as a spacecraft, in which gravitational forces exerted on the body are less than normal. Prolonged exposure to microgravity results in effects similar to detraining in athletes (e.g. loss of muscle and bone mass). These changes can present problems when returning to a normal gravity. Regular in-flight exercise, including resistance training and aerobic activities, may counteract some of these effects.