The spine is a complex arrangement of multiple units (bones, joints, discs, ligament and muscle attachment, etc.). Abnormal posture with chronic inappropriate loading and loss of strength and elasticity of muscles as we age causes the discs in our spine to lose fluid and flexibility as well as overloading the joints in the spine. This does not bode well when someone overstretches or does heavy lifting. It can cause a spasm, strain or sprain in the muscles and/or ligaments in the back thereby causing acute pain. A disc in the spine can actually bulge out or rupture if the spine is overly strained. Back pain can be due to injury or chronic overload (ie poor posture), which leads to degeneration (arthritis).