The range of motion capable by a joint is its flexibility. Being able to do impressive moves such as splits is not as important as making sure that all the muscles involved in the articulation of a joint are balanced. Muscles exert a passive tension even when not engaged in exercise, in order to maintain posture. Therefore, it is important that muscles be balanced around a joint to avoid joint discomfort, pain, or decrease in range of motion. Being flexible is not about moving joints into hyperextension, but rather being able to move the joint in all planes that are available to it.