For example, some boas and pythons bend the neck vertically around prey whereas many colubrid snakes, such as gopher and king snakes, bend the body sideways around the prey. Constriction postures seem to be more stereotyped in boas and pythons than in colubrids, which have highly variable constriction postures. This suggests that the epaxial muscles participate in constriction but are not the only muscles used in constriction. Although these long muscles and tendons are probably not the most important constricting muscles, they do not interfere with constriction. Which other muscles are involved in constriction is not yet known.
Constriction appears to involve continuous squeezing, but often is actually intermittent.
Muscles use a lot of energy when they exert force, so by squeezing intermittently only when necessary, the snakes probably save a lot of energy. Holding the constriction posture even when not squeezing allows a snake to squeeze again very quickly if the prey starts to move again. Constriction is usually assumed to kill prey by suffocation because the forces exerted appear to interfere with breathing in the prey. However, constriction often kills small mammals faster than would be expected if suffocation were the immediate cause of death. In many snakes, constriction may be strong enough to collapse the blood vessels in small prey, which in turn would quickly stop the heart from working and lead to heart attack and stroke.