Date of Award

2005

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Computing, Health and Science

First Advisor

Dr Paul B. Laursen

Second Advisor

Dr David T. Martin

Abstract

Previous research using athletes has documented that precooling can improve endurance performance, especially in warm conditions. However, research comparing performance following different cooling techniques which are incorporated into a prerace routine is rare. Purpose: The purpose of this study was to compare the effects of two precooling techniques on cycling time trial performance in warm conditions. Methods: Six endurance trained, regionally competitive cyclists completed one maximal graded exercise test (V02peak 71.4 ±3.2 ml’kg-1min-1) and four ~40 min laboratory cycling time trials in a heat chamber (34.3 ± 1.1°C; 41.2 ± 3.0% relative humidity (rh)) using a fixed power-variable power format. After familiarisation, cyclists prepared for the time trial using two different precooling strategies and a control condition administered in a counterbalanced order. The three trials included: 1) no cooling (Control), 2) cooling jacket for 40 min (Jacket) or 3) 30 min water immersion (29°C to 24°C at a rate of 0.2°C'min-1 ) followed by cooling jacket for 40 min (Combination). Comparisons were made using a two-way ANOV A with repeated measures and Student's paired t-tests where appropriate. Results: Rectal temperature (Tre) prior to the time trial was 37.8 ± 0.1°C in Control, similar in Jacket (37.8 ± 0.3°C) and significantly lower in Combination (37.1 ±0.2"C, p < 0.01). Blood lactate during each treatment was similar except for the final readings (Control = 15.8 ± 4.4 mM, Jacket = 19.8 ± 4.3 mM and Combination = 17.5 ± 4.0 mM, p < 0.005). Heart rate was similar throughout the time trial for each treatment. Compared to the Control trial, performance time was similar for Jacket (-16 ± 36s, -1.5%; p = 0.34) but faster for Combination (-42 ± 25s, -3.8%; p = 0.01). The pacing strategy for Control and Combination were similar (gradually reducing split times) but unique for Jacket (started with a fast split time followed by a temporary increase in split times). Conclusions: A combination precooling strategy incorporating immersion in cool water followed by the use of a cooling jacket can: 1) produce decreases in Tre that persist throughout a warm up and 2) improve laboratory cycling time trial performance. The effects of a cooling jacket alone on Tre 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 during time trials performed in the heat.

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