Flexibility is the ability to bend with injuring or breaking. Flexibility is a key component of physical exercise because having functional range of motion at all joints of the musculoskeletal system helps and ensures proper body movement. Flexibility is a joint specific characteristic. For example, someone who has been in ballet their entire lives will have greater flexibility than somebody of the same age and same sex. Having a good range of motion at the hip joint has been associated with good lower back function. There are many factors that affect range of motion such as age, sex, genetics, and posture.