I first came across the idea of Constructive Rest when reading about the semi-supine position in the Alexander technique. Imogen Regone explains that:
“Constructive Rest is a way of lying down in a semi-supine position (on the back with the knees bent, and feet flat on the floor) that promotes good spinal alignment and release of excess tension. […] Lying down in Constructive Rest is one of the quickest and simplest ways to restore our natural shape, and can be invaluable for people suffering from neck or back pain.”
This exercise is effective at helping the spine to realign itself by releasing muscular tension and allowing the back to decompress. It affirms the idea that the back is able to naturally correct itself when allowed to do so.
I personally have found this exercise effective so I was fascinated when I came across the same idea in relation to chair design in Galen Cranz’s book The Chair: Rethinking culture, body and design. One of Cranz’s favourite chairs is the Red and Blue Rietveld chair designed in 1919. She explains the chair is generally not viewed as comfortable but rather admired conceptually for its clarity. Why then does she find it so comfortable?
I think the answer lies in the similarity between the semi-supine exercise and the position encouraged by the Rietveld chair. It’s actually the same position, just tilted at a different angle. Despite the Rietveld chair not being horizontal it’s significant backward tilt means that gravity is pulling the sitters back towards the flat surface of the chair back. This has the combined effect of taking some of the weight off the back, allowing the spine to decompress, and encouraging the shoulders and the rib cage to open up against the flat surface.
In addition to this the angle of the person’s upper leg in relation to their back is the same in the semi-supine position as it is for the user of the Rietveld chair. This angle (roughly 100 degrees) helps the lower back to align itself to the flat surface of the floor and the chair back.
Rietveld actually designed his chair with this in mind, his idea was that the chair could be used to tone the body in relaxing and playful way after a hard days work.