Why does muscle spasms happen?

Overuse or injury: A muscle spasm is the body's method of naturally bracing injured structures. Muscle spasms in the back can be caused by a muscle strain, a sprained muscle, or an underlying condition. Many treatments such as physical therapy, wearing a brace short term, short term use of muscle relaxants, inversion tables, and massage can help.

Options: Either from muscle fatigue, an electrolyte abnormality or from an irritated or inflamed nerve.

For many number of: Reasons, including stress, anxiety, sleep deprivation, electrolyte imbalances, dehydration, overexertion .. anything that can lead to neuromuscular instability.