Stress reactivity: hemodynamic adjustments in trained and untrained humans.

There is mounting evidence to suggest a relationship between heightened cardiovascular (CV) and sympathetic nervous system (SNS) reactivity to behaviorally stressful situations and cardiovascular pathology. Exercise training has been suggested as a non-pharmacological, therapeutic intervention technique to counter behaviorally induced CV and SNS reactivity. This approach is based on well-documented adaptations in CV and SNS functioning that result from exercise training. However, the theoretical basis for the relationship between physical fitness and stress reactivity has not been fully explored. Additionally, there are methodological and design considerations that inhibit comparison and interpretation of research studies regarding the role of physical fitness or exercise training and cardiovascular and SNS reactivity during behavioral stress. The focus of our laboratory studies has been to more fully described the CV and SNS responses to behaviorally challenging novel and learned tasks in highly fit, exercise trained, and untrained college-age males. The results from these studies suggest that highly fit and untrained males exhibit similar CV and SNS responses to a novel task. However, upon repeated exposure to the task, fit individuals exhibit attenuated mean arterial pressure and cardiac output responses. The data from the longitudinal studies suggest that there is an exercise training induced attenuation in the cardiac output response to behavioral challenge and that this is at least partially the result of an attenuated stroke volume response to the task. Thus, exercise training does appear to alter cardiovascular functioning during familiar, behaviorally challenging situations.