ABSTRACT
The biomechanical interactions among lower spinal column, pelvic girdle, and thigh and knee angles were also investigated in the middle of the 20th centry. The pelvis also rotates forward and lumbar lordosis increases when the knees drop below the height of the tuberosities. However, muscles that span the hip joint may affect pelvis and spine positions: the effect of opening the hip angle on the lumbar spine depends on whether muscle tension is present. Experimental studies treat body postures as independent variables. Attitudes about proper working postures and office work tasks are changing rapidly. Backrests shall be high enough to support the whole back and even neck and head. The backrest shall be able to decline so far that the user can truly rest on it. Traditional sciences like orthopaedics, anatomy, physiology and medicine provide clear clues for healthy work postures. Re-evaluation of traditional axioms and establishment of new physiological and psychological assessment methods are needed.
