Aerobic fitness does not influence directly heart rate reactivity to mental stress.

Thirty-seven aerobically high and low fit male and female university students, selected on the basis of estimated aerobic capacity, completed a set of hard as well as a set of easy mental arithmetic tasks for 90 seconds in a counterbalanced order with a 10 min rest period between the tasks. Heart rate (HR) reactivity to either task was independent of aerobic fitness level. Although subjectively rated as more challenging, HR responses to the hard arithmetic task were not greater than that seen to the easy task. These results do not support the conjecture that aerobic fitness level may mediate HR response to acute mental challenge. The overall implications of these results are discussed in relation to the literature concerning aerobic fitness and mental stress.