Understanding the science
The nervous system is a complex network of neurons (nerve cells) transmitting information to and from different parts of the body. The nervous system is made up of the brain, spinal cord, and nerves. The spinal cord and nerves transmit information from different parts of the body to the brain and the brain then interprets the information and sends information back out to control movements of muscle, digestion or speech. The brain and spinal cord are protected by the skull and the vertebra and so will be protected from all but the most severe of injuries. The nerves exiting the spine, however, are vulnerable to irritation by tissue injury, leading to swelling and compression by adjacent structures such discs, joints or muscles.
Tissue injury can be caused by a single traumatic event, such as improper lifting of a heavy object, or through repetitive stresses, such as sitting in an awkward position with poor spinal posture for an extended period of time. In either case, injured tissues undergo physical and chemical changes that can cause inflammation, pain, and diminished function for an individual.
When nerves exiting the spine are irritated or compressed they can alter nerve impulses creating pain, altered movement patterns, or numbness. As nerves are irritated in the low back (lumbar spine) they can create local pain near the spine, but if the nerves are severely irritated it creates pain down the leg, commonly referred to as sciatica. The same can occur in the neck (cervical spine) where mild nerve compromise can create local pain but if it gets worse it can refer pain to the head (in the form of headaches) or down the arm.