Ten male oarsmen performed a 6-min bout of "all-out" exercise on a rowing ergometer in the laboratory. Intraarterial blood pressure was recorded from a catheter inserted percutaneously into the radial artery. Mean arterial pressure increased only modestly from 110 +/- 13 to 122 +/- 24 mm Hg (P < 0.05). Large fluctuations in pressure were superimposed on the normal blood pressure waveform during rowing. These rhythmic pressure fluctuations exhibited a one-to-one coupling with stroke rate and were 2-3 times the magnitude of the normal pulse pressure. Thus, the effective pulse pressure during the 1st minute of rowing (112 +/- 11 mm Hg) was markedly higher (P < 0.01) than the pulse pressure at rest (45 +/- 5 mm Hg) and remained so throughout the exercise bout. In five additional subjects in which central venous pressure (CVP) was measured, large stroke-related fluctuations in pressure were also seen in the CVP waveform. Similar fluctuations in blood pressure were observed during repetitive Valsalva maneuvers. These results suggest that the blood pressure response to rowing is principally influenced by a Valsalva-like maneuver performed at the catch of each stroke. The observed arterial pressure fluctuations may explain the degree of myocardial hypertrophy that occurs in the hearts of rowers.