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

Abstract

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.