Risk of Hypothermia in a New Olympic Event: the 10-km Marathon Swim

Abstract

o C). The highest ranked elite open-water swimmers in Brazil (7 men, 5 women; ages 21±7 years old) were submitted to anthropometrical measurements on the day before competition. All but one athlete took maltodextrine ad libitum during the competition. Core temperature and capillary glycemia data were obtained before and immediately after the race. RESULTS: Most athletes (83%) finished the race with mild to moderate hypothermia (core temperature <35 o C). The body temperature drop was more pronounced in female athletes (4.2±0.7 o C vs. male: 2.7±0.8 o C; p=0.040). When data from the athlete who did not take maltodextrine was excluded, capillary glycemia increased among athletes (pre 86.6±8.9 mg/dL; post 105.5±26.9 mg/ dL; p=0.014). Time to complete the race was inversely related to pre-competition body temperature in men (r=-0.802; p=0.030), while it was inversely correlated with the change in capillary glycemia in women (r=-0.898; p=0.038). CONCLUSION: Hypothermia may occur during open-water swimming events even in elite athletes competing in relatively warm water. Thus, core temperature must be a chief concern of any physician during an open-water swim event. Capillary glycemia may have positive effects on performance. Further studies that include more athletes in a controlled setting are warranted.

Effects of three different water temperatures on dehydration in competitive swimmers

“…None of the subjects were affected by hypothermia at the end of the three trials, although it is common in swimmers competing in an open water swimming event [2,3,[16][17][18]. Thereby, the 27 and 32…”

“…Open water swimmers perform races in a wide range of environmental conditions, such as cold/hot water temperature, high/low water salinity, high/low altitudes and high/low wave height. Hypothermia and dehydration are the most common medical problems during open water events [2,3]. Open water swimming is a widespread aquatic sport performed also by the master swimmers globally [4].…”

Nutrition Considerations in Special Environments for Aquatic Sports

“…Thermal conductivity is approximately 25 times greater in the water than in the air, so water even marginally colder than body temperature is a significant heat sink and has the potential to cause hypothermia. Given that the normal human body temperature is about 37 °C, even swimming in 21 °C (~16 °C differential or heat sink) for a prolonged time can cause hypothermia (Brannigan et al, 2009;Castro et al, 2009). Conversely, 20 min of swimming at approximately 50% VO 2max in 34 °C water (still a ~3 °C heat sink) yielded an esophageal temperature increase of only 1 °C, whereas 20 min of running at approximately 50% VO 2max at a much cooler temperature (21 °C) drove esophageal temperature to 39 °C (Holmér & Bergh, 1974).…”

“…This study also demonstrated that decreased heart rates in cold-water swimming were entirely compensated for by an increased cardiac stroke volume (McArdle et al, 1976), possibly the result of increased peripheral and cutaneous vasoconstriction causing an even greater increase in central blood volume and venous return. Taken together, not only do swimmers have a completely different mechanism for heat dissipation than terrestrial athletes, many complex factors also affect individual temperature regulation, including water temperature, prone position while swimming, physique of the athlete, length and intensity of the swimming, acclimatization, and individual responses (Brannigan et al, 2009;Castro et al, 2009;Gerrard, 1999;Holmér & Bergh, 1974;Macaluso et al, 2013;McArdle et al, 1976).…”

“…The wide range of water temperatures encountered by swimmers in training and OWS competition is the primary influence on deviations in core body temperature (Brannigan et al, 2009;Castro et al, 2009). Thus, it is important to recognize that the FINA OWS World Championship features race distances of 5 k, 10 k, and 25 k, which take elite athletes approximately 1 hr, 2 hr, and 5.5-6 hr, respectively.…”