MUSCLE SPASMS?

There are a variety of causes of muscle spasms, and each depends upon predisposing factors, the part of the body involved, and the environment that the body is in.

Spasms may occur when a muscle is overused and tired, particularly if it is overstretched or if it has been held in the same position for a prolonged period of time. In effect, the muscle cell runs out of energy and fluid and becomes hyperexcitable, resulting in a forceful contraction. This spasm may involve part of a muscle, the whole muscle, or even adjacent muscles.

Overuse as a cause of skeletal muscle spasm is often seen in athletes who are doing strenuous exercise in a hot environment. This is also an occupational issue with construction workers or others working in a hot environment. Usually, the spasms will occur in the large muscles that are being asked to do the work. When this occurs associated with heat exposure, the condition is also known as heat cramps.

Overuse can also occur with routine daily activities like shoveling snow, or mowing or raking grass, causing muscle spasms of the neck, shoulder, and back. Chronic neck and back pain can lead to recurrent muscles spasms. Large muscle groups make up the trunk, including the neck, chest wall, upper back, and lower back. Spasms in these muscles can be a result of an injury or they may develop over time because of arthritic changes in the spine.

Reference: http://www.medicinenet.com/muscle_spasms/page6.htm