[Effects of orthostatism on heart rate and arterial pressure in sedentary subjects and in those in good physical condition].

Heart rate (HR), Systolic (SBP), Diastolic (DBP), and Mean Blood Pressures (MBP), were evaluated during a resting sitting and during upright moveless positions, in fifty seven highly trained runners with a maximal oxygen consumption equal or superior to 55 ml/kg. min. (VO2 max greater than or equal to 55 ml/kg . min., group I), and in fifty seven sedentary untrained men (group II). During sitting position the members of group I, had a significantly lower DBP and MBP than the members of group II. In the members of group II the assumption of upright posture did not produce significant changes in blood pressure, whereas subjects of group I showed a significantly drop in SBP, DBP and MBP. The results of this investigation indicated that in human, vigorous physical activity produce lower values of arterial blood pressure, and might be of value in the prevention of high blood pressure. On the other hand, the observed responses in group I during orthostatism, reveal a different regulation of the cardiovascular system. Changes in sympathetic and parasympathetic nervous system, venous compliance and plasma volume are designated as responsible of observed differences. This finding might also support the tendency to faintness reported by some authors in athletes.