Function of the Axial Musculoskeletal System in Locomotion and Ventilation

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9807534 Carrier Vigorous activity requires elevated rates of metabolism. Thus, for an animal to sustain rapid locomotion, it must breathe as it runs. Although humans take breathing during locomotion for granted, there is increasing evidence that the ability to run and breathe at the same time is a derived condition among terrestrial vertebrates. analysis of fishes and amphibians clearly shows that the original function of the muscles of the abdomen and thorax was locomotion rather than lung ventilation. The significance of this is apparent in lizards in which the muscles that produce ventilation also have a role in locomotion. In these lizards, the locomotor function of the axial muscles predominates over their ventilatory function. Consequently, in some species, the locomotor actions of the trunk muscles interfere with breathing to such an extent that and both lung ventilation and oxygen consumption decline as speed increases. Similarly, in dogs, the locomotor function of the axial muscles appears to be dominate over the ventilatory function of these muscles. When trotting dogs uncouple their breathing from the locomotor cycle, activity of all but one or two of the trunk muscles stays locked to the stride cycle. This suggests that tetrapods will either be unable to run and breathe at the same time, or their ventilation must in some way be integrated with their locomotion. The research described in this proposal is intended to increase our understanding of the mechanical linkage between the locomotor and ventilatory systems by investigating the role the axial muscle-skeletal system plays in running and breathing. It has two goals. First Dr. Carrier will use electromyography and manipulation of locomotor forces to test specific hypotheses of locomotor function for the axial muscles in both lizards and mammals. Second, by comparing the intensity of muscle activity when ventilation is coupled versus not coupled to the locomotor cycle, the PI will determine whether locomotor-venti latory coupling decreases the conflict between running and breathing in mammals. This study will contribute to our understanding of the ways in which the oxygen cascade is maintained in the face of conflicting demands resulting from locomotion; and it will help clarify differences between lizards and mammals which may help explain the reliance of running lizards on anaerobic metabolism and the ability of mammals to sustain vigorous locomotion aerobically.