AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 132-H141, Copyright © 1989 by American Physiological Society
Modulation of cardiac autonomic activity during and immediately after exercise
Y. Arai, J. P. Saul, P. Albrecht, L. H. Hartley, L. S. Lilly, R. J. Cohen and W. S. Colucci
Harvard University-Massachusetts Institute of Technology Division Health Sciences and Technology, Cambridge 02139.
Fluctuations in heart rate above 0.03 Hz reflect autonomic modulation of
sinoatrial node activity. To assess the dynamics of autonomic nervous
activity during and immediately after exercise, we determined the power
spectrum of heart rate and respiratory fluctuations in 43 normal subjects
without known cardiac disease, 8 patients with severe congestive heart
failure, and 6 patients status-post cardiac transplantation before, during,
and after graded-work load exercise on a cycle ergometer. Before exercise,
heart rate fluctuations (spectral power) at both high (0.15-0.80 Hz) and
low (0.03-0.15 Hz) frequencies were significantly higher in normal subjects
than in either heart failure or transplant patients but were not different
between the two groups with heart disease. During exercise, heart rate
power at all frequencies rapidly and progressively decreased in normal
subjects, until at peak exercise it was not different from the other two
groups. During recovery, heart rate power increased in normal subjects but
remained significantly below base line. The findings demonstrate a marked
reduction of autonomic modulation of heart rate in patients with heart
failure and after cardiac transplant and support a progressive withdrawal
of vagal activity during exercise with a gradual increase during recovery
in normal subjects.
