Heart rate response to psychological stressors of individuals possessing resting bradycardia.

The authors examined the relation between trained and inherent bradycardia and heart rate (HR) and T-wave amplitude response to psychological stressors. They compared cardiac responses to two psychological stressors of 10 trained male runners (MVo2max = 75 mL/kg-1 min-1) possessing low resting heart rate (M = 58 bpm), 10 untrained men (MVo2max = 58 mL/kg-1 min-1) with inherently low resting heart rate (M = 58 bpm), and 10 unconditioned men (MVo2max = 51 mL/kg-1 min-1) with normal resting heart rate (M = 69 bpm). All participants completed a maximal oxygen consumption treadmill test, an easy and a hard mental arithmetic task, and the Stroop Color and Word Test. Their analysis of the data revealed no significant differences in relative heart rate response or T-wave amplitude between groups during or after any stressor. In contrast, absolute heart rates during and after mental arithmetic and during the Stroop test were significantly lower for both the trained and inherently low groups compared with the control group. These findings suggest that the lower absolute HR response during and after stressors was influenced by both aerobic training and genetic inheritance.