The present study investigated psychophysiological
responses to paced respiration of different frequencies.
Twenty men and 20 women (mean age: 24.3 years) underwent
five breathing conditions (paced with 0.15 Hz, 0.20 Hz,
0.25 Hz, 0.30 Hz, and unpaced), each lasting 5 min. As
dependent physiological measures heart period, and different
heart period variability (HPV) parameters were assessed.
Psychological variables consisted of mood estimates as
well as rated accuracy and effort to follow the pacing
rhythm. HPV decreased with higher breathing frequencies,
under paced and unpaced conditions, whereas mood ratings
did not change. Subjects indicated more effort and less
accuracy in following the pacing signal, the more its frequency
differed from their spontaneous breathing frequency. The
comparison of a spontaneous breathing condition with a
frequency-matched paced condition revealed that pacing
per se provoked a reduction in heart period. Because this
decrease was not accompanied by changes in any of the HPV
frequency components, their validity as measures of autonomic
control needs to be questioned.