Glossary
Lumbar support
Support for the natural inward curve of the lower back, built into a chair's backrest or added afterward with a cushion.
Lumbar support is padding or a shaped backrest section designed to fill the natural inward curve of the lower spine while seated. Without it, most people slump as they get tired, flattening that curve and shifting load onto the lower back muscles and discs instead of letting the spine's natural shape carry some of it.
Office chairs handle this in a few ways: a fixed curved backrest, an adjustable pad that moves up, down, and sometimes in and out, or mesh backrests that flex to follow the spine. Adjustable lumbar support tends to suit a wider range of body types and torso heights than a fixed curve built into the shell.
A lumbar support pillow is a common and inexpensive fix for chairs that lack built-in support, including many chairs used at kitchen tables or borrowed dining chairs pressed into home office duty. The main mistake is positioning it too high, against the mid or upper back, when it needs to sit against the lower back curve just above the belt line to do its job.