 Gait choice can have effects beyond immediate changes in limb movement and speed, notably in terms of ventilation.Because they lack a diaphragm, lizards and salamanders must expand and contract their body wall in order to force air in and out of their lungs, but these are the same muscles used to laterally undulate the body during locomotion.Thus, they cannot move and breathe at the same time, a situation called Carrier's constraint, though some, such as monitor lizards, can circumvent this restriction via buccal pumping.