For anyone spending long hours at a desk, finding a comfortable sitting position is a constant battle. The question of the ideal backrest angle is not just about comfort; it's a critical component of spinal health and productivity. Extensive ergonomic research points to a specific range as the optimal backrest angle for prolonged sitting: a recline of 100 to 110 degrees.

This recommendation is grounded in biomechanics. Sitting upright at a strict 90-degree angle places significant pressure on the lumbar discs and requires constant muscle activation to maintain posture, leading to fatigue and strain. By reclining slightly to 100-110 degrees, the body's weight is distributed more evenly between the backrest and the seat. This position reduces pressure on the intervertebral discs in the lower back and decreases the workload on the postural muscles in the back and neck.

However, the angle is only one part of the equation. This position is most effective when combined with proper lumbar support. A well-designed chair should have an adjustable lumbar cushion that maintains the spine's natural 'S' curve, preventing the pelvis from rotating backward and the lower back from flattening. Furthermore, effective reclining requires a synchronized tilt mechanism where the seat pan tilts slightly as you recline, keeping your feet firmly on the floor and maintaining a healthy angle behind your knees.

Simply setting your chair to 110 degrees is not a magic solution. Dynamic sitting—making small, frequent adjustments to your position—is essential. The optimal angle provides a healthy "home base," but you should move away from it and return throughout the day. Combine this reclined posture with regular breaks to stand, stretch, and walk. This approach mitigates the risks associated with any static posture, no matter how ergonomically perfect it seems. Ultimately, the 100-110 degree backrest angle is a powerful tool for enhancing comfort and protecting your spine during long periods of seated work.