Exercise haemodynamics: field activities versus laboratory tests

BACKGROUND: The present knowledge on changes in blood pressure during athletics is based virtually entirely on the results of stress testing, owing to the inability to measure blood pressures during sports activities. However, everyday physical activities, as well as sports activities, differ in many respects from stress testing, so that a direct comparison cannot be made. OBJECTIVE: To study the effect of three different sports, track running, road cycling and weight lifting, on blood pressures recorded intra-arterially with the Oxford system and to compare the results with those obtained during traditional ergometry. METHODS: Blood pressure was recorded continuously in three groups of male athletes (22 joggers, 6 cyclists and 11 builders) by means of the intraarterial portablke Oxford method, through a catheter placed in the radial artery. RESULTS: During track running beat-by-beat analysis of the recordings showed a peculiar behaviour of the phasic pressure waves. Periodic oscillations of the pulse pressure, which varied in frequency in the range 4-28 cycles/min according to the velocity of running and heart rate, were observed nearly always. The frequency of the running-induced fluctuations in pulse pressure almost always equalled the difference between the heart rate and the stepping rate, suggesting that these oscillations were beats. The source of the stride-dependent wave was identified with the shaking of the aorta and the great vessels during the running. A weak correlation between the maximum blood pressure recorded during track running and the blood pressure recorded during treadmill or bicycle ergometry was found. Outdoor cycling caused a far higher increase in blood pressure than did bicycle ergometry, confirming that the response of the blood pressure to the laboratory test is not a good predictor of the changes in blood pressure which actually occur during outdoor activities. Weight lifting brought about noticeable elevations in blood pressure, to well above 300 mmHg. One main determinant of the blood pressure rises occurring during heavy-resistance exercise was found to be the increase in intrathoracic pressure. The simultaneous remarkable increases in abdominal pressure caused by isometric activities either with or without the Valsalva manoeuvre would on the contrary exert a protective effect on the cerebral vessels. In fact, the intra-abdominal pressure is immediately transmitted to the cerebrospinal fluid through the intervertebral foramina, thereby reducing the actual transmural pressure across the cerebral vessels. CONCLUSION: The present results indicate that the blood pressure variations recorded during athletics are not well reproduced by the laboratory tests. Many of the reported data are under-estimates of the blood pressure changes which actually occur during sports activities.