Sexual Dimorphic Association Between Cardiorespiratory Fitness And Cardiac Autonomic Responses To Mental Challenge

Abstract

Cardiovascular and autonomic reactivity to psychological or behavioral challenges have long been used as putative risk factors for disease pathophysiology, including coronary heart disease and essential hypertension. The model of stress reactivity has also been used in an attempt to clarify the underlying cardioprotective mechanisms of aerobic fitness. However, it remains unclear whether enhanced aerobic fitness attenuates cardiovascular and autonomic responses to stress and if these reductions are specific to distinct populations. In order to advance this area, it is critically important to understand individual differences in these complex psychobiological responses and, in particular, whether there are sex differences in the relationship between aerobic fitness and cardiac autonomic responses to stress. Gender or sex has been identified as an important determinant of psychological stress responses and recent studies have pointed to sexually dimorphic effects of aerobic fitness and acute exercise on a number of health outcomes. PURPOSE: To examine the sexual dimorphic patterns between cardiorespiratory fitness and cardiovascular and autonomic responses to laboratory stressors. METHODS: Fifty participants (24 females, age = 21.0 ± 1.1 years) initially completed a maximal aerobic fitness test for the determination of peak oxygen consumption (VO2 peak). On a subsequent day participants completed a laboratory-based stress reactivity protocol consisting of a 6-min serial subtraction task and a 6-min modified Stroop task with false feedback. Measures of heart rate (HR), autonomic balance (RSA and PEP), and systolic and diastolic blood pressure (SBP and DBP) were assessed during baseline, stress, and recovery periods. RESULTS: Findings revealed that higher cardiorespiratory fitness levels were associated with lower HR, DBP, and RSA responses to the laboratory stressors only for females, ps<.05, with no such relation observed for males. CONCLUSION: These findings reveal new evidence that cardiorespiratory fitness is selectively related to more adaptive stress responses for college-aged females. Future research should explore these sexually dimorphic responses and examine both developmental influences as well as patterns of change across the menstrual cycle.