Interrelationship of plasma cortisol and other activation indices during EMG biofeedback training

Plasma cortisol, cephalic electromyography (EMG), heart rate, fingertip vasoconstriction/dilation, respiration rate, self-reported anxiety, and target symptom severity were monitored in 24 human outpatients who volunteered to undergo the novel experience of an eight-session EMG biofeedback-based relaxation training program. Acute cortisol levels were generally found to be positively related to heart rate, degree of vasoconstriction, and self-reported anxiety but independent of cephalic EMG level and respiration rate. For the 12 participants above the median in initial trait anxiety, the mean reductions in cortisol were 22, 19, and 31% (relative to baseline) at the fourth, eighth, and 1-month follow-up sessions, respectively. Although there was some indication of the presence of a centrally integrated state of lowered neurophysiological arousal, the multiple dependent measures suggest that relaxation in this situation is not necessarily a simple unitary physiological and psychological event.The authors wish to thank David Greenwald and Daniel Klaus for assistance in collecting the data reported here. This research was partially supported by an award from the Roche Psychiatric Service Foundation, Stress Grants Program, and NIH Grant NS04095.