Issues related to the influence of the work environment on workers' health are increasingly deserving the attention of researchers worldwide. Among the various work activities performed by individuals in different environments, data processing work deserves special attention, especially typing, which is carried out by individuals directly involved in entering data or information into computer equipment.

Typing work can be considered simple from an intellectual point of view, repetitive after learning, and often becomes automated, leading the individual who performs it to lose interest and lack motivation. It is important to emphasize that, no matter how small, there is always mental exertion required for the work to be executed with quality. This quality can be compromised if the environment is not suitable, leading to visual, postural, and muscular problems (MACIEL, 1985; PARAGUAY, 1987).

Focusing on postural problems, these can be caused by the adoption of inadequate posture during task execution or due to the use of inappropriate furniture. According to KNOPLICH (1989), every position the body assumes in space corresponds to a harmonic balance axis, through the constant action of the spine, which performs functions such as supporting the body's weight through bones (vertebrae and discs), moving the body through joints and muscles, and protecting the nervous cord. Specific muscle groups play a fundamental role in maintaining, supporting posture, and moving the spine; they act as points of support and reference for most of the forces coming to or from the body, in the relationship between man and the external world. The spine presents, in its anterior part, the vertebral bodies and intervertebral discs, which function as "mechanical shock absorbers" and weight support (BARREIRA, 1989).

Posture is defined by the American Academy of Orthopedics (apud BARREIRA, 1989) as the relative arrangement of body parts. Good posture is defined as the balance between the body's support structures, muscles, and bones. Poor posture occurs when there is a lack of relationship between various body parts, leading to body imbalance in its support bases. Poor posture leads to diseases and is associated with muscular and emotional problems. Posture is divided into dynamic and static. Dynamic posture is the appropriate balance in performing body movements without pain. When this occurs, vertebrae, discs, joints, and muscles perform this function without wear or damage. Static posture is defined as the organic balance of man in a stationary position (standing, sitting, or lying down), in a situation that does not cause damage to the mentioned structures or produce pain when this position is maintained for a long period of time. (KNOPLICH,1989). When developing work activities, individuals assume various postures. Specifically for typing activity, the seated position is adopted, which we will now discuss.

In the seated position, 50% of the individual's body weight falls on the ischial tuberosities, which are suitable for supporting high pressures when the body is in contact with the chair seat; 34% of the body weight falls on the posterior thigh region and 1% on the soles of the feet.

Based on this principle, the correct sitting position for work is considered to be achieved with the proper chair and posture, i.e., those that maintain the physiological curvatures of the spine with minimal overload on the intervertebral discs, avoiding venous retention in the lower limbs (KNOPLICH, 1989; COUTO, 1978). KNOPLICH (1989) recommends that in the seated position, both feet should be flat on the floor, the trunk straight, the head held high looking forward, and the back supported by the chair backrest. The author acknowledges that maintaining this position for prolonged periods is almost impossible; therefore, some measures should be taken to provide comfort to the worker. The ideal ergonomic conditions for sitting work according to COUTO (1978) are as follows: the chair should allow the body weight to be distributed more on the ischial tuberosity without significant overload on the posterior thigh; it should allow venous return from the popliteal fossa; it should not push the sacrum forward; it should not propel the individual forward or backward; it should provide proper back support; together with the chair arms, it should allow lateral movements; elbows should be at desk height; the chair and desk together should not limit the movements of the upper limbs.

Whenever a task can be performed in a seated position, the workstation can be planned or adapted for this position to provide the worker with conditions of good posture, adequate visualization, and operation for their best performance and productivity. The chair and desk should be compatible with the type of work to be performed; they should have a work area easily visible to the operator and dimensional characteristics that allow correct positioning and necessary movements for the operator's legs and feet. Regarding the chair, the mentioned standard establishes that the seats and backrests should not cause fatigue conditions for the individual and should have minimum comfort requirements, namely: adjustable height according to the worker's stature and nature of the function performed; foot support to keep them supported and legs at a right angle to the feet and thighs; little or no shaping at the base of the seat; backrest shape slightly adapted to the body to support the lumbar region; rounded front edge of the seat.