HEART-RATE RESPONSE TO PSYCHOLOGICAL STRESSORS OF INDIVIDUALS POSSESSING RESTING BRADYCARDIA

The authors examined the relation between trained and inherent bradyca rdia and heart rate (HR) and T-wave amplitude response to psychologica l stressors. They compared cardiac responses to two psychological stre ssors of 10 trained male runners (MV02max = 75 mL/kg-1 min-1) possessi ng low resting heart rate (M = 58 bpm), 10 untrained men (MV02max = 58 mL/kg-1 min-1) with inherently low resting heart rate (M = 58 bpm), a nd 10 unconditioned men (MV02max = 51 mLkg-1 min-1) with normal restin g 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 World Test. Their analysis of the data reve aled no significant differences in relative heart rate response or T-w ave amplitude between groups during or after any stressor. In contrast , absolute heart rates during and after mental arithmetic and during t he Stroop test were significantly lower for both the trained and inher ently low groups compared with the control group. These findings sugge st that the lower absolute HR response during and after stressors was influenced by both aerobic training and genetic inheritance.