EFFECT OF RELAXATION TRAINING ON CARDIAC PARASYMPATHETIC TONE

To examine the hypothesis that the relaxation response is associated w ith an increase in cardiac parasympathetic tone, the frequency compone nts of heart rate variability during relaxation training were investig ated in 16 college students. Electrocardiograms and pneumograms were r ecorded during a 5-min baseline period followed by three successive 5- min sessions of the autogenic training (relaxation) or by the same per iods of quiet rest (control), while subjects breathed synchronously wi th a visual pacemaker (0.25 Hz). Although neither the magnitude nor th e frequency of respiration showed a significant difference between rel axation and control, the amplitude of the high-frequency component of heart rate variability increased only during relaxation (p =.008). The re was no significant difference in the ratio of the low-frequency (0. 04-0.15 Hz) to the high-frequency amplitudes. The increased high-frequ ency amplitude without changes in the respiratory parameters indicates enhanced cardiac parasympathetic tone. Thus, our results support the initial hypothesis of this study. Enhanced cardiac parasympathetic ton e may explain an important mechanism underlying the beneficial effect of the relaxation response.