Practical precooling: Effect on cycling time trial performance in warm conditions

The purpose of this study was to compare the effects of two practical precooling techniques (skin cooling vs. skin+core cooling) on cycling time trial performance in warm conditions. Six trained cyclists completed one maximal graded exercise test ([Vdot]O2peak 71.43.2 mlkg-1min-1) and four 40min laboratory cycling time trials in a heat chamber (34.3C1.1C; 41.2%3.0% rh) using a fixed-power/variable-power format. Cyclists prepared for the time trial using three techniques administered in a randomised order prior to the warm-up: (1) no cooling (control), (2) cooling jacket for 40min (jacket) or (3) 30-min water immersion followed by a cooling jacket application for 40min (combined). Rectal temperature prior to the time trial was 37.8C0.1C in control, similar in jacket (37.8C0.3C) and lower in combined (37.1C0.2C, P0.01). Compared with the control trial, time trial performance was not different for jacket precooling (-1636s, -0.7%; P=0.35) but was faster for combined precooling (-4225s, -1.8%; P=0.009). In conclusion, a practical combined precooling strategy that involves immersion in cool water followed by the use of a cooling jacket can produce decrease in rectal temperature that persist throughout a warm-up and improve laboratory cycling time trial performance in warm conditions.