The slope of the simultaneously changing blood pressure with heart rate (baroreflex sensitivity - BRS) is supposed to be a measure of the quality of arterial pressure regulation. In an attempt to discover early mechanisms of cardiovascular alterations we monitored different parameters in healthy, young volunteers: physically trained (N = 24) and aged-matched sedentary controls (N = 35).

We measured ECG, systolic (SBP) and diastolic blood pressure (DBP), cardiac output (CO), stroke volume (SV), peripheral vascular resistance (SVR) and BRS first at rest and then during slow breathing. Slow breathing (6 breaths/min) is one of the manoeuvres that are believed to increase vagal tone.

A spectral analysis of RR intervals was done by the autoregression method. We determined the area under the power spectrum curves over the high frequency (HF) band (0.15–0.4 Hz) and the low frequency (LF) band (0.04–0.15 Hz).

RR intervals, SBP, DBP and BRS were nearly the same in trained and untrained volunteers at rest and during slow breathing. There were also no difference in heart rate variability parameters except the significant difference (p<0,05) between groups in LF/HF during slow breathing. The increase in this ratio was greater in physically trained than in untrained. CO (p<0,05) and SV (p<0,01) were significantly greater in trained individuals. SVR was constantly but insignificantly smaller in trained individuals.

The conclusion of our measurement is that physical training presumably changes CO, SV and SVR, but not BRS. Does that mean that BRS is not a valuable measure of the quality of blood pressure regulation?