Interactions between locomotion and ventilation in tetrapods.

Interactions between locomotion and ventilation have now been studied in several species of reptiles, birds and mammals, from a variety of perspectives. Among these perspectives are neural interactions of separate but linked central controllers; mechanical impacts of locomotion upon ventilatory pressures and flows; and the extent to which the latter may affect gas exchange and the energetics of exercise. A synchrony, i.e. 1:1 pattern of coordination, is observed in many running mammals once they achieve galloping speeds, as well as in flying bats, some flying birds and hopping marsupials. Other, non-1:1, patterns of coordination are seen in trotting and walking quadrupeds, as well as running bipedal humans and running and flying birds. There is evidence for an energetic advantage to coordination of locomotor and respiratory cycles for flying birds and running mammals. There is evidence for a mechanical constraint upon ventilation by locomotion for some reptiles (e.g. iguana), but not for others (e.g. varanids and crocodilians). In diving birds the impact of wing flapping or foot paddling on differential air sac pressures enhances gas exchange during the breath hold by improving diffusive and convective movement of air sac oxygen to parabronchi. This paper will review the current state of our knowledge of such influences of locomotion upon respiratory system function.