Firefighters' basal cardiac autonomic function and its associations with cardiorespiratory fitness.

Background: Firefighters' activities require constant adjustments of the cardiovascular system with cardiac autonomic function (CAF) playing an important role. Despite the crucial role of CAF in regulating stress response, little is known about firefighters' CAF.

Objective: We aimed to characterize the resting on-duty and off-duty CAF of male firefighters, in association with cardiorespiratory fitness (CRF).