Cardiovascular and Perceptual Responses to an Open Water Channel Swim: A Case Study

Abstract

PURPOSE: Channel swimming presents many challenges, including duration, hypothermia, and exhaustion. Little research focuses on physiological function and perceptual responses of this unique sport. The purpose of this case study was to describe the cardiovascular and perceptual responses during an open water channel swim. METHODS: One female (age = 24, height = 158.4 cm, mass = 58.2 kg, body fat = 25.0%) participated as she swam 21 miles from Doctor's Cove (Catalina Island) to Palos Verdes, California. The subject observed Catalina Channel Swimming Federation Rules which prevent 1) the use of insulating or buoyant material (e.g. wetsuits), and 2) unnatural assistance to the swimmer (e.g. drafting, touching a kayak). A telemetric monitor recorded heart rate (HR) at five second intervals. At 24 minute intervals, the subject rested and refueled for one minute, during which she reported perceived pain (0-10), rate of perceived exertion (RPE, 6-20), perceived thermal sensation (0-8), and perceived thirst (1-9). Investigators tracked air and water temperature, distance remaining (DR), and average velocity at identical intervals. RESULTS: The subject completed the swim in 9:02:48; water temperature averaged 19.1 °C (66.4 °F) and air temperature averaged 18.6 °C (65.5 °F). Heart rate and thermal sensation remained consistent across the channel, ranging from 148-155 bpm and 3-4, respectively. Pain inconsistently varied from 0-5 during the swim. RPE remained between 12-14 for the first eight hours, but increased dramatically in the final 40 minutes, reaching 18 at swim completion. Thirst sensation steadily increased throughout the swim, again reaching maximal values upon completion. Physiologically and statistically significant correlations existed between thirst and DR (r = -0.905), RPE and HR (r = 0.741), RPE and DR (r = -0.694), and pain and DR (r = -0.671). CONCLUSIONS: Efforts to understand physiological and perceptual responses during endurance swimming might aid in preparation and performance of future channel swimmers.