
There is a specific vocabulary used in Pilates to explain the alignment of the spine during certain exercises. Neutral refers to the natural curvature of the spine, usually referencing the lumbar spine and pelvis, but also includes the thoracic and cervical spine. Neutral addresses the entire alignment of the spine, with all the curvatures included, depending on the exercise.
Imprint and Supported are used interchangeably in the respect that the words are addressing the abdominal connection needed to protect the low/lumbar spine. If an exercise is too challenging for an individual to maintain “neutral” spine. Then the instructor will give the direction for the client or group class to "engage the abdominals" or "scoop the belly", and tuck pelvis under, so that the lumbar spine is supported during the movement. If there is a weak abdominal connection when lifting legs into a hovered position, the lumbar spine can arch up away from the mat. This position will create excess tension in the low back. Common words like tuck, tilt, and curl, are imagery cues that help students visualize the shape of the spinal position. This tucked, tilted, imprinted, or supported position will protect the lumbar spine so the exercise can be executed efficiently, as well as keeping the instruction delivery more interesting.
When imprinting or supporting the lumbar spine it is important to recognize that not every individuals low back needs to touch the mat in order to be in a "supported" position. Not everyone needs the same degree of tuck or tilt. All you need is enough of a curl in the low spine so that your abdominals can remain engaged and not "pop" out in a dome. The degree to which any client needs to imprint the lumbar spine will vary from person to person.