Baseline and Rest: A Need for Conceptual Clarity When Measuring Parasympathetic Reactivity and Recovery

Parasympathetic nervous system (PNS) activity has widespread research applications but poses measurement challenges due to its high sensitivity to environmental conditions and immediate demands. While standardised methods exist for measuring PNS reactivity and recovery in response to stressors, the selection of appropriate baseline and resting states is often overlooked. This commentary argues that a clearer conceptual distinction between baseline, a research construct for comparing values, and rest, a psychophysiological state of low arousal and cognitive engagement, is crucial for data interpretation. This includes a need for explicitly justifying baseline conditions in relation to research goals and validating rest conditions. By improving the clarity and rigour of baseline and rest, researchers can enhance the interpretability of PNS reactivity and recovery measures, supporting integration of research findings across studies.