We examined the influence of mattress firmness on the spinal curve, sleep quality, and subjective evaluations in healthy subjects. The firmness of the three equal parts of air /mattress was controlled by the air pressure in each part. In Experiment 1,...
We examined the influence of mattress firmness on the spinal curve, sleep quality, and subjective evaluations in healthy subjects. The firmness of the three equal parts of air /mattress was controlled by the air pressure in each part. In Experiment 1, we created nine air mattress conditions by setting the air pressure of each of the upper and middle parts at 4, 6, or 8 kPa, and that of the lower part at 6 kPa. We measured the spinal curves of 10 healthy young male subjects from the coccyx to the 7th cervical vertebra by a fiber optic-based 3D bend and twist sensor, while they laid down on their right side with the angle of the trunk and thigh at 135º (abbreviated as lying135º) and when they laid supine, in each of the nine mattress conditions. We found that the spinal curve during supine position with the conditions of lower part: 6 kPa, middle: 4 kPa, and upper: 6 kPa (6:4:6) was the most similar to that during lying135º, which makes the spinal curve natural. However, the subjective evaluation of comfort of the mattress by a visual analog scale (VAS) scored highest in the 6:4:8 condition.