Warming up with an ice vest: core body temperature before and after cross-country racing.

CONTEXT Athletes running in a hot, humid environment may have an increased risk of heat illness. In the 2004 Olympic Games, American and Australian athletes were provided with ice vests designed to cool their bodies before performance. The vest appeared to be effective in keeping body temperatures down and improving the performance of the marathoners. However, body temperatures have not been reported when the vest was used before an actual competition. OBJECTIVE To determine if wearing the Nike Ice-Vest decreased core temperature (Tc) before and during athletic performance in warm (26 degrees C to 27 degrees C), humid (relative humidity = 50% to 75%) conditions. DESIGN A 2 x 3 mixed-model design was used to compare groups (ice vest, no ice vest) across changes in temperature from baseline (10 minutes and 1 minute before the race and immediately after the race). SETTING 2005 Big Wave Invitational 4-km race in Hawaii and 2005 Great American 5-km race in North Carolina. PATIENTS OR OTHER PARTICIPANTS Eighteen women from a National Collegiate Athletic Association Division I cross-country team who participated in either the Big Wave Invitational or the Great American Race. INTERVENTION(S) Four hours before the start of the race, the athletes ingested radiotelemetry temperature sensors. One hour before the start of the race, Tc was recorded, and half of the athletes donned a Nike Ice-Vest, which was removed immediately before the race. MAIN OUTCOME MEASURE(S) Additional Tc readings were taken at 10 minutes and 1 minute before the start of the race and immediately after the race. RESULTS Ten minutes before the start of the race, Tc was elevated by 0.84 degrees C +/- 0.37 degrees C in the no-vest group, compared with 0.29 degrees C +/- 0.56 degrees C in the ice-vest group ( P < .01). This difference in Tc persisted at 1 minute before the start. Immediately after the finish, the increase in Tc averaged 2.75 degrees C +/- 0.62 degrees C in the no-vest group and 2.12 degrees C +/- 0.62 degrees C in the ice-vest group ( P < .01). CONCLUSIONS Wearing an ice vest before cross-country performance in warm, humid conditions allowed athletes to start and finish the competition with a lower Tc than did those who did not wear a vest.