3. Height adjustment range
- Many chairs do not lower enough to accommodate employees with shorter than average legs.
- When the chair’s seat pan does not lower enough, the employee cannot keep his/her knees at 90˚ of flexion with his/her feet flat on the floor. This is the optimal posture for the back and the legs. In this posture the back is the correct biomechanical position reducing back strain and the legs are relieved of the pressure that would be present should the feet not be supported on the floor.
- The seat pan should lower to 18” above the floor or lower.
4. Backrest height
- Some chairs have backrests with a small surface area.
- Too small of a backrest does not support the employee’s upper back. This can cause an increase in muscle tension, possibly resulting in overuse of the muscles and consequent upper back discomfort.
- The backrest should be at least 24” high.