Plateau in Muscle Blood Flow during Prolonged Exercise in Miniature Swine

摘要

Cardiovascular, metabolic and thermoregulatory responses were studied in eight male miniature swine during a prolonged treadmill run. Each animal underwent 8 to 10 weeks of exercise regimen enabled the animals to run at 65% of the heart rate range for approximately 100 minutes. Skin wetting and a fan were used to cool the pigs during the run. Regional blood flow was significantly altered with the onset of exercise; however, hindlimb muscle and total gastrointestinal blood flow were unchanged throughout the exercise period. Compared with five minute values, heart rate and cardiac output were significantly elevated. Core temperatures increased between 5 and 30 minutes of exercise but then remained unchanged to the end of exercise. Mean arterial pressure oxygen consumption and blood lactate did not change during the exercise bout. These data indicate that limiting increases in core temperature during prolonged exercise was associated with a plateau in active muscle blood flow. The cardiovascular drift observed after the plateau in core temperature probably reflected an increased skin blood flow since cooling procedures effectively limited the thermal stress during prolonged exercise. (aw)