Comparing real-life and laboratory-induced stress reactivity on cardio-respiratory parameters: differentiation of a tonic and a phasic component.

To recreate stress in laboratory conditions, the nature of the elicited physiological reactions to the presentation of mental tasks has been extensively studied. However, whether this experimental response is equivalent to real-life stress reactivity is still under debate. We investigated cardio-respiratory reactivity to a sequential protocol of different mental tasks of varying difficulties, some of them involving emotional material, and repeated the measures in a baseline and in a real-life stress situation. R-R interval (RRI), breathing frequency and volumes, and respiratory sinus arrhythmia (RSA) were computed. Baseline results showed a superior sensitivity of respiratory parameters to mental task load over RRI and RSA, no effect of task difficulty or emotional material, and a habituation response of all parameters along the protocol. Stress results showed a dual effect: first, a decreased RRI and RSA in rest values, and second, a decreased reactivity in RRI in response to mental tasks. These findings are discussed through the interaction of activation, considered to be a tonic variable, and arousal, as a phasic response. Copyright 2010 Elsevier Inc. All rights reserved.