抄録
In earlier studies, we have shown that the ratio of the first derivative (dP/dt) of carotid artery pulse (CAP) to the blood pressure (P), CAP (dP/dt)/P, is an easily measurable, noninvasive index of cardiac contractility even in moderate exercise (Ifuku et al. 1994). Using this cardiac index, we aimed to examine the regulatory mechanism of cardiac function during a cold pressor test in athletes. Seventeen healthy subjects (9 athletes, 8 untrained subjects) were subjected to the cold pressor test according to Hines and Brown's method, which required them to immerse the right hand in chilly water (4°C) for 1 min. Although the mean blood pressure increased significantly during cold stress in both athletes and untrained subjects (P<0.05), the cardiac function of different groups changed in different manners. In athletes, the cardiac index and heart rate increased significantly (P<0.05), so that resultant cardiac outputs increased significantly (P<0.05). However, in untrained subjects, the index tended to decrease and heart rate decreased significantly (P<0.05), so that cardiac outputs decreased significantly (P<0.05). After the offset of immersion, the index and heart rate decreased significantly in untrained subjects (P<0.05). These findings suggest that the cardiac contractility and heart rate during a cold pressor test are enhanced in athletes, but depressed in untrained subjects. [Jpn J Physiol 55 Suppl:S223 (2005)]
