In addition to putting the spine in its best alignment, the reduction in force on the lower back occurs because some weight of the upper torso is supported by the back rest. Vertibrae distorted Muscles unbalanced As shown in the previous studies, the data suggest that the neutral posture is a semi-crouch position, not right angles. If you think about it, that's the posture the astronauts assume whent they are weightless. This study was evaluated a group of computer users for problems related to working in the same position all the time. Thus, the issues here are different from the strictly posture issues of the previously mentioned studies.
Static postures affect various parts of the body.
Conclusion Science does not support the recommendation of sitting at right angles. Rather, a semi-crouched position is better. Furthermore, instead of trying to find the perfect posture for yourself, you should shift and change. The way to think about it is that the rule can help you get in a starting position from which you can vary. You can optimize your position if you tilt the chair seat or by angling the back rest so that you maintain a semi-crouch position.