The effects of whole-body cold-water immersion on brain connectivity related to the affective state in adults using fMRI: a protocol of a pre-post experimental design

An emerging body of behavioural studies indicates that regular swimming in cold-water has positive effects on mental health and wellbeing, such as reducing fatigue, improving mood, and lessening depressive symptoms. Moreover, some studies reported the immediate effects of cold-water immersion (CWI) on elevating mood and increasing a positive emotional state. However, the neural mechanisms underlying these effects remain largely unknown. The lack of studies using neuroimaging techniques to investigate how a whole-body cold-water immersion affects neural processes, partly, resulted from the lack of a tested experimental protocol. Previous protocols administered tonic limb cooling (1 - 10°C) while recording functional magnetic resonance (fMRI) signals. However, using very low water temperature constitutes points of contrast to painful experiences that are different from what we experience after a whole-body head-out cold-water immersion. In our protocol, healthy adults unhabituated to cold water were scanned twice – immediately before (Pre-CWI) and after (Post-CWI) immersion in cold water (water temperature 20°C) for five-minutes. We recorded cardiac and ventilatory responses to CWI and assessed self-reported changes in positive and negative affects. Our protocol showed reliable changes in brain connectivity after the short exposure to cold water, thus enabling it’s use it as a tested experimental framework in future studies.