Muscle spasms frequently occur due to the overuse of muscles through repetitive exercise or physical activity or as a result of dehydration, according to MedicineNet. Muscle spasms can also result from medical conditions such as atherosclerosis, restless leg syndrome and dystonias.
When a muscle is overused or overextended, muscle cells are depleted of fluid and energy, and the muscle begins to contract forcibly under pressure. This is especially common in athletes and manual laborers, notes MedicineNet. Heat cramps can be exacerbated by hot weather, and severe heat may also contribute to dehydration, another cause of muscle spasms. Dehydration depletes the body of essential electrolytes and deprives cell proteins of the nutrients and minerals needed to facilitate an organized contraction.
Muscle spasms can also be caused by the narrowing of the arteries and inadequate blood supply that accompanies atherosclerosis. Restless leg syndrome is characterized by sporadic nocturnal leg cramps and is more prevalent with age. Finally, movement disorders called dystonias produce forceful contractions and twisting of muscles. Dystonias frequently contribute to uncontrollable movements such as torticollis, in which the head is forced to the side due to a neck spasm, or blepharospasms that result in uncontrollable blinking of the eyes. MedicineNet reports that dystonias are caused by abnormal neurotransmitter chemicals within the brain, and that dystonia symptoms may accompany a stroke.