[The relationships between sympathetic and parasympathetic tones and cardiovascular responses during active coping]

The relationships between sympathetic and parasympathetic tones and a variety of cardiovascular measures were examined in 27 male college students subjected to an active coping, namely a reaction time task, for five minutes. The results demonstrated an enhanced sympathetic tone during the first one minute (P1), indicating the decreases of pre-ejection period (PEP), left ventricular ejection time, and electromechanical systole (QS2), and the increase of QT/QS2. The reactivities of QT/QS2 and PEP defined by mean changes in the P1 period differed in their relationship with cardiovascular responses in the last four minutes. Although the PEP reactivity was associated with the cardiac performance (stroke volume and PEP/LVET), the QT/QS2 reactivity was correlated with the mean blood pressure (MBP). The reactivities of respiratory sinus arrhythmia (RSA) were defined by the residual difference obtained by subtracting values estimated by baseline RSAs from the mean value of changes during five minutes period. Subjects with high RSA reactivity (vagal withdrawal) showed higher heart rate and MBP than those with low RSA reactivity. The results are discussed with respect to the cardiac loading factors and hemodynamics.