Mobility refers to the ability to move freely in one's environment. Several factors can affect mobility, including age, health conditions, disabilities, pain, and fear. Those at high risk of mobility issues include people who are poorly nourished, have decreased sensation, cardiovascular or respiratory problems, or neuromuscular disorders. Casts are used to immobilize and support broken or injured bones and apply compression to tissues. Different types of casts are used depending on the location of injury, such as short arm casts for forearm fractures or walking casts to allow limited mobility. Common casting materials include plaster of paris.