Pre-cooling is a temperature regulation strategy whereby core temperature (Tc) is lowered prior to exercise, and has been consistently shown to improve endurance capacity and athletic performance. However, pre-cooling protocols such as water immersion and cold air exposure are time consuming, logistically demanding and in some instances may result in adverse thermal responses, making these conventional methods impractical as a pre-event strategy. Endogenous cooling methods (i.e. fluid ingestion) have been shown to attenuate the rise in Tc during exercise. Despite the positive effects of fluid ingestion on Tc responses to exercise, the effect of fluid temperature has been less established. As such, it was the purpose of this study to examine the effect of crushed ice ingestion as a pre-cooling method on body temperature response and cycling time-trial performance. Seven trained male athletes completed a familiarisation, and two experimental 40 km cycling time trials (CTT) on a wind-braked cycle ergometer in a climate controlled chamber, set to 30oC and 75% relative humidity. The two experimental CTT included one trial preceded by a 30 min period of thermoneutral (26.8 ± 1.3°C) water consumption (CON), and the other by a 30 min period of pre-cooling via crushed ice (1.4 ± 1.1°C) consumption (ICE). The fluid volumes in each trial amounted to 6.8 g•kg-1 body mass. The order of trial completion was randomised, counterbalanced and completed within 14 days following the initial session. Each 40 km CTT required athletes to complete 1200 kJ of work in the fastest time possible. During the CTT, skin temperature (Tsk), Tc, cycling performance time, power output, heart rate (HR), blood lactate (BLa), and ratings of perceived exertion (RPE) / thermal sensation (RPTS) were measured at set intervals of work. Pre-cooling lowered the Tc after ICE (36.74 ± 0.67°C) significantly more than CON (37.27 ± 0.24°C), (p>0.05). This difference remained evident until 200 kJ of work was completed on the bike (ICE: 37.43 ± 0.42°C, CON: 37.64 ± 0.21°C). The CTT completion time was 6.5% faster in ICE when compared to CON (p<0.05). No significant differences existed between conditions at any time point of the CTT for Tsk,, HR or RPE (p>0.05). The RPTS was significantly higher in CON at 200 kJ of cycling compared to ICE (p<0.05). Ice ingestion was effective in lowering Tc and improved subsequent 40 km cycling performance in a hot / humid environment. A reduced thermal strain was evident in ICE compared to CON at the start of the CTT. Interestingly, split time data indicated that the latter parts of the CTT (900-1100 kJ) were significantly faster in ICE compared to CON despite no significant differences in HR, BLa, Tc, RPE and RPTS. The lower thermal strain evident in ICE compared to CON at the start of the CTT may have provided a greater heat storage capacity and muscle energy reserve that was used towards the end of the CTT, resulting in an enhanced time trial performance.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Veröffentlicht von The Norwegian School of Sport Sciences. Alle Rechte vorbehalten.