Physical jerks are a type of involuntary muscle movement that can be caused by a variety of medical conditions. Spasms are one type of physical jerk, which is an uncontrolled contraction of a muscle or group of muscles. These spasms can be painful and can last for a few seconds or minutes. They can also be caused by stress, fatigue, or dehydration. Treatment for physical jerks usually involves rest, stretching, and medications.