By doing so, you will be able to better mood for a new day. Formula 41 Extreme When we use our muscles that can be controlled voluntarily (arms and legs), they contract and relax alternately as we move our arms and legs. Similarly, the muscles that support our head, neck, neck and trunk are synchronized to hold our posture. When a muscle or just a few fibers of it that contracts involuntarily, it is called a spasm, and if this is forceful and sustained, it turns into a cramp.