Risk Factors and Predictors of Hypothermia and Dropouts During Open-Water Swimming Competitions

in International Journal of Sports Physiology and Performance
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Purpose: To measure core temperature (T core) in open-water (OW) swimmers during a 25-km competition and identify the predictors of T core drop and hypothermia-related dropouts. Methods: Twenty-four national- and international-level OW swimmers participated in the study. Participants completed a personal questionnaire and a body fat/muscle mass assessment before the race. The average speed was calculated on each lap over a 2500-m course. T core was continuously recorded via an ingestible temperature sensor (e-Celsius, BodyCap). Hypothermia-related dropouts (H group) were compared with finishers (nH group). Results: Average prerace T core was 37.5°C (0.3°C) (N = 21). 7 participants dropped out due to hypothermia (H, n = 7) with a mean T core at dropout of 35.3°C (1.5°C). Multiple logistic regression analysis found that body fat percentage and initial T core were associated with hypothermia (G 2 = 17.26, P < .001). Early T core drop ≤37.1°C at 2500 m was associated with a greater rate of hypothermia-related dropouts (71.4% vs 14.3%, P = .017). Multiple linear regression found that body fat percentage and previous participation were associated with T core drop (F = 4.95, P = .019). There was a positive correlation between the decrease in speed and T core drop (r = .462, P < .001). Conclusions: During an OW 25-km competition at 20°C to 21°C, lower initial T core and lower body fat, as well as premature T core drop, were associated with an increased risk of hypothermia-related dropout. Lower body fat and no previous participation, as well as decrease in swimming speed, were associated with T core drop.

Drigny and Rolland are with the University Hospital Center; Drigny, Lebreton, Moussay, and Mauvieux are with INSERM, COMETE, GIP CYCERON; and Chesneau, Marais, and Outin are with LMNO, Science 3, University of Caen Normandy, Caen, France. Pla is with the Research Dept, French Swimming Federation, Paris, France, and the Inst of Biomedical Research and Epidemiology of Sport, Paris, France. Racinais is with the Research and Scientific Support Dept, Aspetar Orthopedic and Sports Medicine Hospital, Doha, Qatar.

Drigny (j.drigny@gmail.com) is corresponding author.
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