9318610 Bramble The project will investigate the complex interactions between forces that result from locomotor activity and the mechanics of the respiratory system in mammals. Traditionally, mammalian locomotion and respiratory physiology have been studied as discretely different phenomena, but recently acquired evidence supports the view that the chest of mammals has evolved to integrate these activities, both structurally and functionally, in a manner that previously has not been understood. Bramble and Jenkins (Science, 262:235-240) demonstrated that inertial displacements of the abdominal viscera in trotting dogs passively drive the diaphragm independent of diaphragmatic contractions, which primarily serve to modulate visceral motion. Visceral displacements and the loading of the anterior chest walls by the forelimbs are among the factors producing asynchronous ventilation of the lungs and the recycling of air between their lobes. The present project is designed to further explore these complex interactions, specifically by documenting (in several mammalian species that exhibit different locomotor styles) the interrelationships of visceral and diaphragmatic kinematics induced by different gaits and speeds, the activity of the primary respiratory muscles, and the ventilation patterns within the lungs. The resultant data still substantially contribute to a better understanding of the functional design of the mammalian respiratory system. ***
