The Effect of Water Temperature on Heart Rate Variability and Cognition

Heart rate variability (HRV) is a key indicator of fitness, and stress resilience. Previous research has shown that HRV decreases under mental workload, including during tasks that require strict attention. Studies also show that temperature exposure affects attention: cold increases the stress response while warm water has a calming effect. Very few studies combine thermal exposure with cognitive testing, and no controlled trials have investigated whether water temperature modulates HRV responses specifically during cognitive demand.