A back spasm involves a sudden, involuntary muscle contraction that can be set off by something as routine as lifting a bag or sitting for too long. Muscle fatigue, dehydration, and nerve irritation ...

Back spasms are involuntary muscle contractions. They can happen because of muscle weakness, overuse, or injury. Muscle strains can cause sudden pain and spasms, often occurring in the lower back from ...

Add Yahoo as a preferred source to see more of our stories on Google. Many of us have felt a muscle in some part of our body suddenly and involuntarily tighten, causing a twitch or even severe cramp.