In a subacute experiment 7 apparently healthy volunteers received a daily oral dose of 5 mg nebivolol for seven days, followed by a seven-day washout period with placebo. From the first day during treatment with nebivolol, peak exercise heart rate and systolic blood pressure, as measured during a standardized submaximal treadmill exercise, significantly decreased by 15% and 19% respectively. A prolonged treatment for one week did not further increase the response of exercise heart rate and systolic blood pressure to nebivolol. However, the ratio of preejection period (PEPc) to left ventricular ejection time (LVETc), an indirect and valuable measure of left ventricular performance, progressively and significantly decreased during the seven-day treatment period with nebivolol from a mean value of 0.37 +/- 0.012 to 0.31 +/- 0.009. The improvement of systolic time intervals resulted from a shortening of the PEPc and a lengthening of the LVETc. At rest, heart rate did not change significantly with nebivolol, whereas both systolic and diastolic blood pressure gradually and significantly lowered. The postexercise LVETc significantly shortened during treatment with nebivolol, and this shortening was more pronounced after seven days of treatment. After discontinuation of treatment with nebivolol, all these effects persisted for more than thirty hours after the last intake and gradually returned to pretreatment values thereafter. From these data it appears that nebivolol effectively reduces blood pressure at rest and during exercise in healthy volunteers, beneficially influencing preload and afterload, as measured by systolic time intervals.(ABSTRACT TRUNCATED AT 250 WORDS)