Dr Mandal, balanced sitting posture on
forward sloping seat #2
A seat that tilts forward encourages "Balanced Seating" (Dr. A.C. Mandal). Opposing trunk muscle groups are balanced and normal lumbar curve is preserved producing balanced seating in which the back is straight, the joint angles are open and the muscles are relaxed. This position provides greater mobility and relieves pressure on the lungs and stomach. Children will often tilt forward on the legs of their chair to relieve back pressure. By tilting their chairs forward they avoid bending their backs, allowing the front and back muscles to relax, and thereby sitting in a more comfortable position with a straight back. (Fig.4)
While riding a horse, the rider sits upright, yet maintains a lumbar lordosis (low back S-curve) because the thighs are sloping downwards. This is exactly the same position as the neutral resting position, or sitting on a chair seat that tilts forward. This means the rider is in the perfect position for "Balanced Seating" (Fig.5). To further evaluate the effect a forward tilting seat has on the flexion, forward bending, of the back, Dr. A.C. Mandal conducted an experiment to document the results. To record the changes in the flexion of the various parts of the body, the anatomical points were marked at the knee joints, hip joints, 4th lumbar (low back) disc and shoulder joints. The participant was seated at a fixed height for the seat and work surface, but the feet were placed incrementally in three different positions in order to simulate different work heights, and the seat and work surface were tilted. To begin with, the girl was positioned at the conventional right angle (Fig.6), whereupon the chair seat and work surface were tilted incrementally and the position of the feet lowered to simulate an increase in the chair and work surface heights (Fig.7 & 8). Fifty photographs of each of 3 positions were taken during a period of 10 days to record the changes in the flexion. The findings were significant. Flexion, forward bending, in the hip-joint and back was greatly reduced, preserving lordosis in the lumbar (S-curve in the low back) region. The final position (Fig. 8) with feet lowered simulating even higher seat and work surface, is exactly the same as the natural resting position where the muscles are relaxed and the body is in a perfect posture for "Balanced Seating", the most suitable position for long periods of sitting. Front seat tilt and higher work surfaces are valuable alternatives that can eliminate lower back strain and ultimately prevent chronic back pain. In this half standing position the disc pressure will of course be very low. Furniture should be designed to accommodate the natural resting position, in which opposing muscles are well balanced. The resulting posture will enhance the performance, efficiency and well-being of employees.