ABSTRACT
The environments produced by accelerating a human body are grouped into three main categories: (1) transient, (2) sustained and (3) chronic. Acceleration takes place when the velocity of a body changes either in magnitude or direction. Changes in acceleration that last 1 or 2 s and do not achieve steady-state are termed transient, abrupt or impact. Sustained acceleration is usually a steady-state environment with short periods of changing accelerations at the beginning (onset) and ending (offset) of the acceleration environment. The duration of this exposure is usually 1 h. Chronic acceleration is a steady-state exposure that lasts for several hours, days or even years. Not surprisingly with these types of definitions that rely on the duration of exposure, there are not clear distinctions where transient acceleration ends and sustained acceleration begins. The same can be said about sustained and chronic accelerations. Because of the very short duration of transient acceleration, the environment is developed using sleds or drop towers. This article deals with sustained acceleration that uses the centrifuge to provide the acceleration as does chronic acceleration studies.
