Simple SummaryThe body’s response initiated by apnea and cooling the face through contact with cold water consists of the simultaneous activation of the sympathetic and parasympathetic division of the autonomic nervous system (ANS) in the so-called diving response. As a result, the heart rate (HR) slows down, systemic circulation vessels constrict, and blood with its oxygen supply is redistributed to cells that are particularly sensitive to hypoxia. The response is adaptive, preferentially protecting brain tissue from the effects of apnea-induced hypoxia. On the other hand, strong stimulation of the intracardiac vagus nerve can cause bradycardia and even a few seconds of asystole. A possible demonstration that basal HR assessed before face immersion can determine the course of the reflex response of the heart would be of prognostic importance and would open the field for practical applications in the prevention of an unfavorable course of cardiodepressive responses.AbstractThe regular cardiac response to immersion of the face in cold water is reduction in heart rate (HR). The highly individualized and unpredictable course of the cardiodepressive response prompted us to investigate the relationship between the cardiac response to face immersion and the resting HR. The research was conducted with 65 healthy volunteers (37 women and 28 men) with an average age of 21.13 years (20–27 years) and a BMI of 21.49 kg/m2(16.60–28.98). The face-immersion test consisted of stopping breathing after maximum inhaling and voluntarily immersing the face in cold water (8–10 °C) for as long as possible. Measurements included determination of minimum, average, and maximum HR at rest and minimum and maximum HR during the cold-water face-immersion test. The results indicate a strong relationship between the cardiodepressive reaction of the immersion of the face and the minimum HR before the test, as well as a relationship between the maximum HR during the test and the maximum HR at rest. The results also indicate a strong influence of neurogenic HR regulation on the described relationships. The parameters of the basal HR can, therefore, be used as prognostic indicators of the course of the cardiac response of the immersion test.