Reduce muscle spasm
Muscle spasm is often a response to pain. The muscles surrounding the injury contract to protect it. This is known as muscle guarding and it aims to prevent further damage. Ice, being useful for pain relief is therefore beneficial in reducing muscle spasms.
However it is also thought that muscle spasms which are not caused by acute injury but more muscle overuse or imbalances can also be reduced through the use of cold therapy. This is not fully understood but is thought to be due to ice slowing the conduction velocity of sensory and motor nerves, as well as the activity of muscle spindle cells which are responsible for muscle tone, resulting in a decrease in motor activity.