Neutral spine

A Neutral Spine or "good posture" refers to the "three natural curves [that] are present in a healthy spine."

Posture
The word "posture" comes from the Latin verb "ponere" which is defined as "to put or place." The general concept of human posture refers to "the carriage of the body as a whole, the attitude of the body, or the position of the limbs (the arms and legs)."

Good posture is the stance which is attained, "when the joints are not bent and the spine is aligned and not twisted." In this position, a person is thus able to completely and optimally attain balance and proportion of the body mass and framework. Good posture optimizes breathing and affects the circulation of bodily fluids. Padmasana or the Lotus Position is a central stance in yoga which is used to enhance breathing through good posture. The word padmasana is a combination of the sanskrit words padma (lotus) and asana (posture).

Neutral spine
In medicine and occupations concerned with physical fitness, the concept of good posture is referred to as "Neutral Spine." In this context, proper posture or "Neutral Spine,"
 * is the proper alignment of the body between postural extremes. In its natural alignment, the spine is not straight. It has curves in the thoracic (upper) and lumbar (lower) regions. There is a slight forward curve in the lumbar region (lordosis), a slight backward curve in the thorasic region (kyphosis) and a slight extension in the tiny cervical vertebra at the top of the spine. In addition, the ears, shoulders, hips, knees and ankles are aligned as if a plumb line was running from the ears down through the torso into the legs and the feet. In neutral posture, the body is able to function in its strongest, most balanced position. Stress to the joints, muscles, vertebrae and tissue is minimized.

In contrast, a non-neutral spine leads to "improper posture, [that] especially when walking, puts increased stress on your back and causes discomfort and damage." A non-neutral spine develops as the result of a person's lifestyle. People who sit for long hours on the job are susceptible to a number of misalignments."

"Neutral Spine" is ideally maintained while sitting, standing, and sleeping.