Cardiovascular Changes Associated with Treadmill Running

Six adult white Pekin ducks were trained to run on a treadmill for 10 min at a speed of 1 -43 km h". O2 consumption, CO2 production, breathing rate, blood gas tension and pH, sciatic and carotid blood flows and colonic and skin temperatures were measured in the experiments. A 2*6 times increase in oxygen consumption was observed when going from resting on the treadmill to exercise. The increased oxygen delivery was achieved by a 61% increase in cardiac output and a 51% increase in the arterio-venous oxygen content difference. Probably the reported resting oxygen consumption was higher than a true resting level causing the increment in oxygen consumption to be more correctly 3-6 times the resting level. Sciatic and carotid blood flow increased by 3-7 times and 2-3 times, respectively, during exercise. At cessation of exercise, the carotid blood flow decreased very rapidly, while the sciatic blood flow decreased more slowly. An increased web temperature above the exercise level was seen in the post-exercise period. The results suggest that the ducks prefer to use non-evaporative heat loss in the post-exercise period, respiratory evaporative cooling being of minor importance. This strategy may be correlated to the small internal heat load induced by the running (body temperature increased by only 0-3 °C).