Aerobic Fitness Impacts Cardiorespiratory And Stress Hormone Responses To Concurrent Mental And Physical Stress

Abstract

Studies have demonstrated that a combination of mental and physical challenge can elicit exacerbated cardiorespiratory (CR) and stress hormone responses above a single stimulus. However, an analysis of the effects of aerobic fitness on the CR and neuroendocrine responses to concurrent mental and physical stress between below average (Low-fit) and above average (High-fit) fitness individuals, has not been conducted. PURPOSE: To examine the effect of aerobic fitness on cardiorespiratory and stress hormone (cortisol [CORT], epinephrine [EPI], and norepinephrine [NE]) responses to concurrent mental and physical stress. METHODS: Eight above average (high-fit [HF], VO2max = 51.18 ± 2.09 ml·kg·min-1) and eight below-average fitness (low-fit [LF], VO2max = 36.58 ± 3.36 ml·kg·min-1) participants completed two experimental conditions. An exercise-alone condition (EAC) consisted of cycling at 60% VO2max for 37 minutes, while a dual-stress condition (DSC) included concurrent participation in a mental challenge for 20 minutes while cycling. RESULTS: Heart rate, respiration rate, minute ventilation, and ventilatory efficiency were exacerbated in the DSC. The DSC elicited greater overall CORT, EPI, and NE responses. Additionally, LF participants had a greater overall release of CORT in the DSC. However, HF demonstrated greater EPI and NE responses, paralleled with elevated cardiorespiratory responses. DISCUSSION: LF individuals seem to demonstrate unnecessary and possibly unfavorable CORT responses to the DSC compared to HF individuals. The higher levels of EPI and NE in HF participants may explain the elevated cardiorespiratory responses compared to LF participants.