Use of graded exercise to evaluate physiological hyperreactivity to mental stress.

Physiological hyperreactivity (i.e., response in excess of metabolic requirements) to mental stress has been implicated in the etiology of coronary heart disease. This study evaluated potential hyperreactivity of cardiovascular, pulmonary, and biochemical variables to mental stress. Thirty healthy males, 19-36 yr, performed a mental arithmetic task and cycle ergometry at three powerloads. Linear regressions were calculated for each of 17 dependent variables during exercise, with oxygen uptake (VO2) serving as the independent variable. Ten variables were significantly correlated (P less than 0.003) with VO2 during exercise and, therefore, were predicted at the VO2 observed during the arithmetic task. The actual level of each variable observed during the arithmetic task was compared with the level predicted from the exercise by paired t-tests. Heart rate, systolic and diastolic blood pressure, rate-pressure product, minute ventilation, respiratory frequency, and respiratory exchange ratio were significantly greater (7-32%, P less than 0.005) during the arithmetic task than predicted from the exercise at an equivalent VO2. Plasma cortisol and serum lipid variables were not useful for evaluating hyperreactivity. Results demonstrated that graded aerobic exercise can serve as a reference for evaluating physiological hyperreactivity to mental stress for a group of ten variables which were significantly correlated with VO2 during graded exercise.