Journal of Applied Physiology, Vol 74, Issue 3 1012-1015, Copyright © 1993 by American Physiological Society
Lack of heart rate variation between morning and afternoon exercise testing in coronary artery disease patients
J. D. Marriott, L. H. Hartley and J. Sherwood
Cardiac Rehabilitation Department, Brigham and Women's Hospital, Boston, Massachusetts 01125.
The purpose of this study was to investigate cardiovascular [heart rate
(HR), blood pressures, rate-pressure product (RPP)], physiological (oxygen
uptake), and metabolic (blood plasma lactic acid concentration) responses
during symptom-limited graded exercise testing (SL-GXT) during early
morning and late afternoon hours in an unmedicated, regularly exercising,
coronary artery disease population. Subjects, males ages 41-71 yr (n = 11),
underwent SL-GXT via cycle ergometry at 8:30 A.M. and 4:30 P.M. HR,
systolic blood pressure, diastolic blood pressure, and RPP were evaluated
at rest and at submaximal and peak work. Oxygen uptake and rate of
perceived exertion were also determined at submaximal and peak power
output, with blood plasma lactic acid concentration measured at peak work.
Data, analyzed by the paired t test, failed to demonstrate any significant
variation in HR, systolic blood pressure, diastolic blood pressure, RPP, or
blood plasma lactic acid responses during exercise at the two points used.
Oxygen uptake did not significantly change at any submaximal intensity.
Thus SL-GXT results obtained at early morning (8:30 A.M.) and late
afternoon (4:30 P.M.) are a reproducible, reliable means of prescribing
exercise HR and work intensities.
