Cold water immersion (CWI) is a ‘hot topic’ at the moment. In many countries, there has been an explosion in the number of individuals undertaking CWI for anecdotally claimed mental and physical health-related benefits.1 These immersions range from static immersions in home-based ice baths and cold showers, to open water swims and dips. Associated with this, in 2021 Her Majesty’s Coastguard in the UK reported a 52% increase in call-outs associated with swimming and dipping and, between 2018 and 2021, there was a 79% increase in open-water swimming deaths (34–61 deaths) in the UK.2
For tropical animals such as humans, immersion in cold water is stressful and carries a significant risk of respiratory, cardiovascular and, possibly, peripheral neurovascular injury. The most dangerous response associated with CWI is ‘cold shock’.3 4 It is initiated by a rapid fall in skin temperature and includes gasping, hyperventilation, release of stress hormones, hypertension and arrhythmias. The loss of control of breathing…