The spine is the central axis of your body, through which the bulk of your nerves run down from your brain to the rest of your body. Maintaining the strength and suppleness of your spine is essential to living a long, and comfortable life. The spine has three natural curves: the cervical spine (your neck), the thoracic spine (your upper back), and the lumbar spine (your lower back). This "s" shape of the spine developed in response to the body's need to absorb shock and allow movement in the back. The cervical and lumbar segments of your spine arc in a concave curve, while the thoracic spine has a gentle convex shape.
When standing, sitting, or lying down, you should notice all three of these curves. Tight hips, chest, and shoulders, as well as poor posture due to lack of awareness, lack of core strength, and societal habits such as looking down at computer and cellphone screens, can cause the spine to be pulled out of alignment, either losing or overexaggerating the natural curves. Using ergodynamic chairs and pillows, and having awareness of the curves when walking and exercising, will help to maintain proper alignment.