Effects of long-distance swimming in cold water on temperature, blood pressure and stress hormones in winter swimmers

Abstract Long-distance swimmers swam in 10–14°C water on four days. Responses in blood pressure and rectal temperature were determined every day, and hormonal responses on the third day. Swimming time lengthened with the days and diastolic blood pressure after swimming was significantly lower on the fourth day than on the first day. In rectal temperatures there were great individual variations. Noradrenaline was elevated more in the thin swimmers. A lesser rise in diastolic blood pressure and the longer duration of swimming on the fourth day may point to habituation to the cold.