Hyperthermia during Olympic triathlon: influence of body heat storage during the swimming stage

The purpose of this project was to determine whether mild heat stress induced by wearing a wet suit while swimming in relatively warm water (25.4 +/- 0.1 degrees C) increases the risk of heat injury during the cycling and running stages of an International distance triathlon in a hot and humid environment (32 degrees C and 65% RH). Five male triathletes randomly completed two simulated triathlons (swim = 30 min; bike = 40 km; run = 10 km) in the laboratory using a swimming flume, cycle ergometer, and running treadmill. In both trials, all conditions were identical, except for the swimming portion in which a neoprene wet suit was worn during one trial (WS) and a swimming suit during the other (SS). The swim portion consisted of a 30-min standardized swim in which oxygen consumption ((V)over dot O-2) was replicated, regardless of WS or SS. During the cycling and running stages, however, the subjects were asked to complete the distances as fast as possible. Core temperature (T-c) was not significantly different between the SS and WS trials at any time point during the triathlon. However, mean skin temperature (T-sk) and mean body temperature (T-b) were higher (P < 0.05) in the WS at 15 (T-sk = +4.1 degrees C, T-b = +1.5 degrees C) and 30 min (T-sk = +4 degrees C, T-b = +1.6 degrees C) of the swim. These T-sk and T-b differences were eliminated by 15 min of the cycling stage and remained similar (P > 0.05) through the end of the triathlon. Moreover, there were no differences (P > 0.05) in (V)over dot O-2, heart rate (HR), rating of perceived exertion (RPE), or thermal sensation (TS) between the WS and SS. Additionally, no significant differences were found in cycling (SS = 1:14:46 +/- 2:48 vs WS = 1:14:37 +/- 2:54 min), running (SS = 55:40 +/- 1:49 vs WS = 57:20 +/- 4:00 min), or total triathlon times (SS = 2:40:26 +/- 1:58 vs WS = 2:41:57 +/- 1:37 min). These data indicate that wearing a wet suit during the swimming stage of an international distance triathlon in 25.4 degrees C water does not adversely affect the thermoregulatory responses of the triathlete on the subsequent cycling and running stages.