Instructed heart rate control in the presence and absence of a distracting task: the effects of biofeedback training.

Twenty volunteers participated in a single-session experiment in which bi-directional heart rate (HR) control was assessed before and after brief unidirectional HR biofeedback. Subjects attempted to raise (INC) and lower (DEC) HR while performing mental arithmetic, as well as in no-task conditions. Biofeedback training was also carried out in the presence and absence of mental arithmetic. Subjects were divided into two groups on the basis of initial HR reactivity to mental arithmetic. Group U received feedback and instructions to raise HR during the training period, while group D attempted to lower HR. Significant differences in HR modifications during INC and DEC trials were observed prior to any biofeedback training in no-task conditions. Following training, however, ability to raise HR deteriorated in group D, while HR decelerations were impaired in group U. Unidirectional training in HR control thus handicapped subsequent attempts to modify HR in the reverse direction. The pattern of HR change was generally paralleled by respiration rate. Subjects were also able to influence the cardiac reactions to mental arithmetic even before the administration of biofeedback. The data nevertheless suggest that training affects the magnitude of HR reactions after the biofeedback is withdrawn. In the biofeedback phase itself, the HR increases and decreases produced by groups U and D, respectively, were diminished on simultaneous mental arithmetic performance.