A muscle spasm, also known as a cramp, twitch or charley horse, is the sudden, involuntary forced contraction of a muscle. Here are the main causes.

Muscle cramps are involuntary, sudden, and painful contractions of one or more muscles. Causes include dehydration, mineral loss, muscle overuse or injury during exercise, and pregnancy.

Medically reviewed by Smita Patel, DO Hypnic jerks, also known as sleep starts or hypnagogic jerks, are abrupt muscle contractions or twitches that happen as soon as you fall asleep. Up to 70% of ...

What causes muscle twitching? Our body's nervous system is constantly telling our muscles what to do without our having to consciously thinking about each action.

But the causes of leg cramps are wide-ranging. Need a break? Play the USA TODAY Daily Crossword Puzzle. Muscle cramping can be a sign that there are imbalances in your body’s levels of certain ...

Though many people experience muscle twitching, it's often incorrectly identified as a muscle spasm. While both are involuntary contractions of a muscle, muscle spasms and muscle twitching aren't ...

Clonus reflex is a set of rhythmic, involuntary muscle contractions. Learn about the causes, symptoms, and treatment options for this condition today.

Running coach Tom Craggs explains what causes delayed onset muscle soreness (DOMS), what to do once it kicks in and how to reduce your risk of getting it.

Can't straighten arms after exercising? Learn about causes like inflammation and muscle damage, and discover treatment and prevention tips for faster recovery.

Dystonia is an involuntary muscle contraction that causes abnormal posture. People may experience twisted and repetitive movements that can affect any muscle in the body.

Platysmal bands are caused by aging and thickening of two edges of the neck muscles. There are many causes, including age, genetics, and muscle activity.