C-28: Free Communication/Poster – Heat Stress Physiology: THURSDAY, JUNE 2, 2005 9:00 AM - 12:00 PM: ROOM: Ryman C2
Previous research using athletes has documented that precooling can improve endurance performance, especially in warm conditions. However, research comparing performance following different cooling techniques that are compatible with pre-race routines is rare.
The purpose of this study was to compare the effects of two precooling techniques on cycling time-trial performance in warm conditions.
Six endurance trained, regionally competitive cyclists completed one maximal graded exercise test (VO2pk: 71.4±3.2 ml.kg−1·min−1) and four ∼40min laboratory cycling time trials (TT) in a heat chamber (34.3±1.1°C; 41.2±3.0% rh) using a fixed power-variable power format. After familiarization, cyclists prepared for the TT using three different precooling techniques prior to the warm-up administered in a counterbalanced order: 1) no cooling (CONTROL), 2) cooling jacket for 40min (JACKET) or 3) 30min water immersion (29°C to 24°C; 0.2°C·min−1) followed by cooling jacket for 40min (COMBO). Comparisons were made using a two-way ANOVA with repeated measures.
Rectal temperature (Trec) prior to the TT was 37.8±0.1°C in CONTROL, similar in JACKET (37.8±0.3°C) and lower in COMBO (37.1±0.2°C, p <.01). At the end of the fixed power output component of the TT, blood lactate was 4.3±1.2 mM in CONTROL, similar in JACKET (4.3±1.1 mM) and lower in COMBO (3.4±1.0 mM, p = .05). Heart rate was similar throughout the TT for each treatment. Compared to the CONTROL trial, TT performance was similar for JACKET (−15± 36s, –0.7%, p = .35) but faster for COMBO (−42±25s, −1.8%, p = .01). Pacing strategy for CONTROL and COMBO were similar (gradual increases in power) but unique for JACKET (aggressive start followed by a temporary decrease in power).
A combination precooling strategy that involves immersion in cool water followed by use of a cooling jacket can 1) produce decreases in Trec that persist throughout a warm up and 2) improve laboratory cycling time trial performance. Effects of a cooling jacket alone on Trec are subtle and do not appear to persist throughout a warm-up. Further research is required to understand the influence of cooling jackets on pacing strategy adopted during time trials performed in the heat. Supported by University of Ballarat, Cycling Australia and an Australian Sports Commission Grant