Cardiac electrical and functional activity following an outdoor cold-water swimming event.

AIMS: Participation in outdoor cold-water swimming (OCWS) events combines endurance exercise and cold exposure. Concerns have emerged about the potential risk of acute adverse cardiac events during OCWS, particularly during endurance events. We analysed the effect of prolonged OCWS on cardiac function in trained athletes. METHODS: The swimming event consisted of laps over a 1000-m course, for up to 6 h, in water at 15 °C. Twenty participants (11 males, 47.3 ± 8.6 years old) were included. Core temperature (Tcore) was monitored using an ingestible temperature sensor during and up to 1 h after the swim. Body composition, blood pressure, electrocardiogram (ECG), and transthoracic echocardiography were assessed 1 day before the event and within the first hour upon completion of the swim. RESULTS: Mean body mass index was 27.1 ± 5.1 kg/m2 and fat mass was 25.2 ± 9.1 %. Mean duration of swimming was 214 ± 115 min. Minimum Tcore was 35.6 ± 1.3 °C. A significant lengthening of the QT interval corrected (QTc) for heart rate was observed post-exercise (437.7 ± 27.7 vs. 457.2 ± 35.9 ms, p = 0.012), with 5 participants exhibiting post-exercise QTc >500ms. OCWS did not alter the biventricular systolic function and left ventricular relaxation. No correlation was observed between ΔQTc and ΔTcore. CONCLUSION: OCWS seemed to acutely delay post-exercise cardiac repolarization without alteration of cardiac function in a healthy trained population. Additional investigations would be warranted to explore the clinical implications of QT lengthening and its relationship with autonomic nervous system regulation during OCWS.

Analysis of Factors Associated With Continued Cooling of Core Temperature After Prolonged Cold-Water Swimming.

PURPOSE: To assess the factors associated with continued cooling duration of core temperature (Tcore°) after prolonged outdoor cold-water swimming. METHODS: We designed a cohort study among swimmers participating in an outdoor cold-water swim during qualifying for the English Channel Swim. The day before the event, the participants completed a demographic questionnaire, and body composition was measured using bioelectrical impedance analysis (mBCA 525, Seca). The swimming event consisted of laps over a 1000-m course, for up to 6 hours, in water at 12.5 to 13 °C. Tcore° was measured using an ingestible temperature sensor (e-Celsius, BodyCap) during and up to 1 hour after the swim. RESULTS: A total of 14 participants (38 [11] y; N = 14, n = 11 males, n = 8 in swimming costume and n = 6 in wetsuit) were included. Before swimming, Tcore° was 37.54 (0.39) °C. The participants swam for an average of 194.00 (101.94) minutes, and mean Tcore° when exiting the water was 35.21 (1.30) °C. The duration of continued cooling was 25 (17) minutes with a minimum Tcore° of 34.66 (1.26) °C. Higher body mass index (r = .595, P = .032) and fat mass (r = .655, P = .015) were associated with longer continued cooling, independent of wetsuit wear. Also, the rate of Tcore° drop during swimming (-1.22 [1.27] °C/h) was negatively correlated with the rate of Tcore° gain after swimming (+1.65 [1.23] °C/h, r = -.682, P = .007). CONCLUSION: Increased body mass index and fat mass were associated with Tcore° continued cooling duration after prolonged outdoor cold-water swimming at 12.5 to 13 °C. The rate of Tcore° drop during swimming was negatively correlated with the rate of rewarming.