Whole-body pre-cooling can improve endurance exercise performance in the heat (2, 3); however there are logistical limitations that restrict the use of various pre-cooling strategies prior to actual competition. Pre-cooling is proposed to collectively reduce deep body and skin temperature and in effect, increase the heat storage capacity of the athlete, thereby allowing a greater amount of work to be completed prior to attainment of a critical core temperature (4). While there is a sound theoretical basis for implementing pre-cooling to improve cycling time trial (TT) performance in the heat, the practicalities of employing effective pre-cooling strategies are yet to be investigated. The purpose of this investigation was to identify a pre-cooling strategy that would be both practical and effective in achieving a reduction in rectal temperature (Trec) prior to a cycling race. Furthermore, the effectiveness of this novel strategy will be compared against the industry standard pre-cooling technique in enhancing performance of a cycling protocol simulating the 2008 Beijing Olympic cycling TT event. Methods The pre-cooling strategy used in this study was selected following extensive pilot work examining a variety of popular and novel techniques. Pilot work involved four subjects who completed eight different cooling strategies and a control condition (no treatment) in a counterbalanced experimental design. Trials were completed in a standardised hot environment (32-35ºC; 50-60% r.h.) and involved a 90 min period which included 30 min seated rest (heat stabilisation), 30 min pre-cooling and a 30 min structured cycling warm-up. Results of the pilot study identified the ingestion of a slushie and application of iced towels as a novel, practical and effective approach to pre-cooling. The main study consisted of a randomised controlled trial in which eleven male cyclists underwent three counterbalanced experimental interventions including no intervention (CON), the industry standard of plunge and ice jacket (STD COOL) and the combination of slushie and iced towels (NEW COOL). Subjects were provided with 9 g/kg BM CHO, 1.5 g/kg BM protein, 1.5 g/kg BM fat with a total energy goal of 230 kJ/kg BM and refrained from strenuous training 24 h prior to each trial. Trials were completed in a standardised hot environment (32-35ºC; 50-60% r.h.) and involved a ~3 ½ hr period including 60 min seated rest, 30 min pre-cooling; 20 min structured cycling warm-up and 10 min to make final preparations. At 120 min, the individual TT commenced and cyclists were required to complete 2 laps of a 23.2 km hilly circuit on the Velotron cycle ergometer (RacerMate Inc., Seattle, USA), fitted with an SRM cycling power meter (Jülich, Germany). Measurement of cyclist`s body mass, Trec, heart rate, thermal comfort, stomach fullness, blood lactate concentration and cycling performance were recorded at regular intervals and . Subjective ratings and perceptions were recorded after each TT completion. A two-way ANOVA (treatment × time) was conducted to determine differences between variables at each time point, with Newman-Keuls posthoc analyses performed if a main effect was identified. Magnitude-based inferences and 90% confidence limits for cycling performance were determined based on guidelines outlined by Hopkins (1). Results Monitoring of the heat chamber showed that all trials were carried out in similar conditions. The notable results are detailed in Table 1. In addition, stomach fullness tended to be greater as a result of slushie ingestion; however, this was not statistically significant. During the TT, Trec, heart rate and thermal comfort were significantly elevated above baseline with no difference between treatments. There was a trend for lactate concentrations to mirror the course profile, being slightly higher at the top of each climb and lower at the end of climb 1. The volume of sports drink consumed during the TT was 630 ± 70 g for all trials which provided a CHO intake of ~38 g (0.5g/kg BM). There was no effect of any treatment on subjective ratings of effort given, sensation, motivation and comfort reported at the completion of each TT. Discussion/Conclusion This study showed that a novel pre-cooling strategy, combining the internal consumption of a slushie made from sports drink and external application of iced towels enhanced the performance of a laboratory cycling protocol simulating the Beijing Olympic Games TT in hot and humid conditions. In contrast, pre-cooling with a cold water plunge followed by the use of an ice jacket produced unclear results. The benefits of the NEW COOL strategy were most evident in the second half of the TT in both the climb and descent potions of the laboratory protocol. The mechanism of the benefits seen with the NEW COOL strategy may involve small benefits to, hydration and CHO status as well as cooling. In summary, it represents an effective and practical technique that could be used by cyclists in preparation for races of similar characteristics to the Beijing Olympic TT course that are undertaken in hot and humid conditions.
© Copyright 2009 National Elite Sports Council 2009 Athlete Services Forum - High Performance Programming for Success - 11-12th November - Satellite Program - Applied Physiology Conference 2009 - Australian Institute of Sport, Canberra - 10th, 11th and 13th November. Alle Rechte vorbehalten. / Übersetzt mit https://www.DeepL.com/Translator