Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

B. Don Franks


Poor heart rate variability (HRV) among patients with coronary artery disease (CAD) is predictive of future incidence of sudden arrhythmic and all-cause death. Furthermore, mental stress appears to further depress HRV in these patients. Chronic aerobic activity level appears to be positively related to HRV among the general population; however, the extent to which this relationship exists among patients with CAD is not clear. Therefore, this study investigated the association between level of chronic aerobic activity and HRV among CAD patients during conditions of paced respiratory control and during the Stroop Color-Word Conflict Test (CWCT). CAD patients were assigned to one of three groups based on their documented volume of aerobic activity: low = 240-630 kcals/week; mod = 720-920 kcals/week; and high = 1020-1800 kcals/week. These groups did not differ in age, Body-Mass-Index, or score on the Minnesota Multiphasic Personality Inventory for Overcontrolled Hostility. Time and frequency domain measures of HRV were derived from ECG data obtained during 10 minutes of paced respiratory control and 5 minutes of performing the CWCT. There was a main effect of activity level (p $<$.05) on the standard deviation of R-R intervals (SDrr) and the total spectral power (TP) such that these dependent variables were greater in the high group than in the low or mod group. There were no differences in normalized units for high-frequency or low-frequency power (HF and LF, respectively). Furthermore, there was a main effect of the test condition on SDrr and TP, both of which were lower during the CWCT as compared to the paced respiratory control condition. There were no differences in normalized units of HF or LF power as a result of the CWCT. The results indicate that, among patients with CAD, a high level of chronic aerobic activity is associated with higher HRV and potentially, therefore, better health outcomes. However, there were no differences in HRV reactivity to mental effort associated with activity level.