Swimming Three Ice Miles within Fifteen Hours

Ice Mile swimming (1608 m in water of below 5 °Celsius) is becoming increasingly popular. This case study aimed to identify body core temperature and selected haematological and biochemical parameters before and after repeated Ice Miles. An experienced ice swimmer completed three consecutive Ice Miles within 15 h. Swim times, body core temperatures, and selected urinary and haematological parameters were recorded. Body core temperature reached its maximum between 5, 8 and 15 min after immersion (37.7°C, 38.1°C, and 38.0°C, respectively). The swimmer suffered hypothermia during the first Ice Mile (35.4°C) and body core temperature dropped furthermore to 34.5°C during recovery after the first Ice Mile. He developed a metabolic acidosis in both the first and the last Ice Mile (pH 7.31 and pH 7.34, respectively). We observed hyperkalaemia ([K⁺] > 5.5 mM) after the second Ice Mile (6.9 mM). This was followed by a drop in [K⁺] to3.7 mM after the third Ice Mile. Anticipatory thermogenesis (i.e. an initial increase of body core temperature after immersion in ice cold water) seems to be a physiological response in a trained athlete. The results suggest that swimming in ice-cold water leads to a metabolic acidosis, which the swimmer compensates with hyperventilation (i.e. leading to respiratory alkalosis). The shift of serum [K⁺] could increase the risk of a cardiac arrhythmia. Further studies addressing the physiology and potential risks of Ice Mile swimming are required to substantiate this finding.