Assessment of male spinal alignment, while sleeping on side posture on soft, firm and custom made mattresses

Ergonomic factors in sleep designing system will have direct effects on maintaining the spinal alignment during sleep. Studies show that a mattress with uniform stiffness cannot preserve the spine's natural posture. Using a mattress made of components with different stiffness can be considered as a solution for this problem. In this study, male spinal alignment has been assessed and compared on the hard and soft mattress along with a new type of mattress with different stiffness. The aim of this study was to evaluate the performance of this new type of mattress and determination of specific layout for each volunteer. After obtaining the dimensional survey data, 25 male volunteers were asked to take the side sleeping position on soft and very firm surfaces, with specific stiffness based on a predetermined protocol. The location coordinates of markers installed on the spinous process by optical detection methods were obtained in frontal plane. In the next step, spring-foam elements were arranged in a frame for each volunteer so that their spinal frontal plane can be close to their natural alignment. In side sleeping posture a c formed curvature appeared along the spinal frontal plane on stiff surface due to lack of support of the spine, and on the soft mattress, softness caused further sinking in the area of pelvis and loss of natural posture. But the arrangement of elements with different stiffness (custom made mattresses) maintained the natural posture of spine. The specific layouts for each volunteer were extracted. The results of this study showed that use of mattresses with custom arrangement is an appropriate way for maintaining optimum spinal alignment during sleep. Common mattresses with uniform stiffness do not have the ability to maintain the spine in a natural position during sleep. Determination of specific arrangements for side sleeping posture can help predict layout required for every individual in the future studies without performing a test.