CHANGES IN BLOOD FLOW OF COMMON CAROTID ARTERY AND MIDDLE CEREBRAL ARTERY DURING EXERCISE

877 The purpose of this study was to estimate cerebral blood flow during exercise. Eleven healthy males aged 25.6±3.7 yrs (mean±SD) performed an incremental bicycle ergometer exercise at 60 watts for 3 minutes, 120 watts for 3 minutes and 180 watts for 6 minutes. We measured the mean flow velocity of the right common carotid artery (MVca) and right middle cerebral artery (MVmc) simultaneously using Doppler ultrasound (HP Inc.). We used a 7.5MHz liner probe for measuring MVca and a 1.9MHz PWD pencil probe for MVmc. The heart rate was 70±8.3 bpm at rest and up to 166±113 bpm at the peak of exercise. MVca was 34.8±9.8 cm/sec at rest and increased with increasing exercise intensities and reached 40.1±12.5 cm/sec at peak of exercise. It further increased to 49.7±13.1 cm/sec at immediately after exercise. MVmc was 53.9±9.8 cm/sec at rest and reached its peak value of 79.2±14.3 cm/sec at 120 watts exercise and fell to 67.0±12.5 cm/sec at peak exercise. The MVmc/MVca ratio was 1.58±0.38 at rest and increased to its peak value of 2.21±0.39 at 120 watts exercise. It then fell to 1.69±0.30 at peak exercise. We found that MVca increased 15% from resting value during the highest intensity of exercise, while MVmc increased 47% at a moderate intensity. These results indicate that an increase in blood flow to the external carotid artery was larger than that of the internal carotid artery during the highest intensity of exercise. Thus, it is suggested that cerebral blood flow increased during exercise and reached its peak value at a moderate exercise intensity.