Postural Stasis Condition where a single body position is held for long periods of time. The health risks of postural stasis include restricted blood circulation, fewer nutrients to the intervertebral discs, and atrophy of muscle tissue. Posterior Alignment Semi-reclined posture often preferred by VDT workers, similar to that assumed by automobile drivers. Thighs are horizontal and the back is reclined about 10 degrees from vertical. Shearing Forces that act in opposite directions, such as the sliding that occurs when a body and its clothing come into contact with the surface of a chair.
Shear forces are minimal, which allows the sitter to recline without untucking a blouse or shirt.
Shear forces are high in a forward-sloping chair when clothing tends to stay with the seat while the body slides forward. Spinal Disc See intervertebral disc. Thrombosis Formation or presence of a blood clot within a blood vessel. Tilt Lock Device that freezes the tilting action of the seat pan. On some chairs, tilt lock can be used to lock the chair in any position between upright and full recline.