The purpose of this investigation was to evaluate the cardiovascular responses to rowing. In the first part of the study, heart rate (HR) and cardiac output (Q) were measured at rest and at three steady-state exercise levels on the variable-resistance rowing ergometer in 10 female and 11 male subjects. Q was determined non-invasively by the equilibration method of CO2 re-breathing, and stroke volume (SV) was calculated. Subjects varied in rowing ability from healthy, inexperienced rowers to competitive athletes. The linear relationships between Q and oxygen consumption for the women (r = 0.57; P less than 0.001; slope = 5.2 +/- 1.1) (mean +/- SD) and the men (r = 0.58; P less than 0.001; slope = 6.1 +/- 1.4) were similar to published values for other types of upright exercises. For both mean and women, SV increased from rest to the first level of exercise, and then reached a plateau at or before the second exercise intensity. Between the second and third levels of exercise, SV decreased significantly in the female subjects (107 +/- 18 vs 94 +/- 16 ml; P less than 0.05), but not in the male subjects (128 +/- 1 1 vs 126 +/- 15 ml; P = not statistically significant). In the second part of the study, HR, Q, and SV were compared on the cycle and rowing ergometers on successive days in eight additional subjects. At similar levels of oxygen consumption and Q, HR was significantly higher, and SV was significantly lower during rowing exercise than with cycle exercise.(ABSTRACT TRUNCATED AT 250 WORDS)