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Factors Predictive of Human One‐Kilometer Ice Swimming Race Time Performance

Ice swimming is a popular sport under consideration as a possible Winter Olympic Event. Swimming in water that is ≤5°C brings inherent risks such as hypothermia and factors that influence swimming performance are poorly understood in this regard. This study evaluated International Ice Swimming Association data for one‐kilometer ice swimming performance that included swimmer age, sex (144 male; 75 female), height/weight for body mass index (BMI) calculation, swim time, swim stroke, and swim conditions for 177 swimmers who (without wetsuits) performed 219 different ice swimming races on 9 different times and locations (December 19, 2015–August 10, 2016). Swimmers using the crawl stroke required 19.38 ± 0.27 minutes for these one‐kilometer swims. Four factors were highly predictive of swim time. Age is most predictive, air temperature and gender are moderately predictive, and BMI is least predictive. As age increases, swim time gets significantly slower. Warmer air temperature was surprisingly associated with slower swim time. Males were faster than females. In many sports decreased BMI is predictive of improved fitness, however increased BMI is also associated with improved thermal conservation, a factor that could be important for ice swimming. A BMI of 20 was the absolute lower observed limit for ability to complete these one‐kilometer swims, increasing BMI was associated with increases in race time, and gender specific BMI differences were not statistically significant. When swimmers completed more than one race, the second swim was significantly faster than the first. Water temperature did not significantly impact swim times. The physiology of cold‐water exposure can be applied to athletes, survival situations, the military, and the medical field. This study provides data that increases the understanding of the human body's physiological reaction when exposed to cold conditions, specifically in water, and provides a framework that allows for the prediction of ice water swim times.