| Abstract: | The present study measured somatic muscle, cardiovascular, and endocrine responses to an unsignalled, rewarded reaction time task and examined the relative contributions of heart rate reactivity and Type A behavior in accounting for variability in response to the task. Task responses were characterized by significant changes in muscle tension, heart rate, blood pressure, cardiac output, and plasma norepinephrine concentration. Subjects shown to be high heart rate reactors during an independent cold pressor test were found to produce the greatest changes in heart rate, systolic and diastolic blood pressures, ventricular ejection time, cardiac output, and rate-pressure product during the reaction time task. In contrast, Type As did not respond differently from Type Bs. The results indicate that heart rate reactivity is a relatively stable trait which generalizes from cold pressor to a nonaversive task and which accounts for much of the between-subject variability in cardiovascular response. |
