Let’s use an analogy to explain back pathologies caused by mechanical (movement) dysfunction. Imagine the intervertebral discs (those squishy, cushiony things in between each vertebrae) are jam-filled doughnuts. When we bend forward, pressure is applied onto the front part of each vertebrae as well as each disc. This is usually quite safe when we go about our day; however, if we are in this posture under load, the extra force increases the risk of compressing a disc on one side and causing it to burst and leak jam out. This can manifest as a disc bulge (where part of the doughnut bulges into the space where spinal nerves run but does not break open) or in more severe cases, a disc herniation (fully blown jam leakage). 

When a bulge or herniation occur, it can push up or rub against the nerve roots, causing pain, numbness and tingling. This in turn can cause muscles to tighten as a protective mechanism for affected areas, which unfortunately often manifests as more pain. The result is pain that can range from acute (lasting a few days) or chronic (lasting a few weeks or months), localised or referred, neural and/or muscular, and affect several structures.