Effects of warm-up and precooling on endurance performance in the heat

Objective

To examine the effects of different thermoregulatory preparation procedures (warm‐up (WU), precooling (PC), control (C)) on endurance performance in the heat.

Methods

20 male subjects completed three treadmill runs to exhaustion (5 days apart). In each session, all subjects performed an incremental running test after WU (20 min at 70% maximum heart rate (HR)), after PC (wearing a cooling vest (0°C–5°C) for 20 min at rest) or without particular preparation (C). After a 5‐min break, the exercise protocol commenced at a workload of 9 km/h and was increased by 1 km/h every 5 min until the point of volitional fatigue. Running performance, HR, blood lactate concentration, tympanic temperature and skin temperature were measured in each trial.

Results

In the PC condition, the running performance (32.5 (5.1) min; mean (SD)) was significantly (p<0.05) higher than in WU (26.9 (4.6) min) and in C conditions (30.3 (4.3) min). During the first 30 min of testing, HR, tympanic temperature and skin temperature were significantly (p<0.05) lower after PC than after WU. There were no significant differences in lactate concentration; however, there was a trend to lower values after WU.

Conclusions

The use of an ice‐cooling vest for 20 min before exercising improved running performance, whereas the 20 min WU procedure had a distinctly detrimental effect. Cooling procedures including additional parts of the body such as the head and the neck might further enhance the effectiveness of PC measures.It is well established that high ambient temperatures have a detrimental effect on endurance performance.^1,2 Compared with temperate conditions (20°C), an ambient temperature of 30°C brought about a decrease of 2.3% in the performance of a 10 min exercise bout.² The question, however, as to what strategies could be applied to compensate for this heat‐induced decrease in performance has been left largely unanswered. Sufficient fluid intake is a possible answer, and application of cold provides another one.^3,4 In the context of endurance in heat a further question arises—namely, whether warm‐up (WU; including the concomitant increase in core temperature (CT)) is a sensible measure, taking into consideration the additional thermal stress.⁵For this reason, it is useful to compare the effects of WU and precooling (PC) to optimise endurance performance. The practical relevance of the objective lies in the fact that competitions—for example, the Olympic Games 2008 in Beijing—will be held in high ambient temperatures, exceeding 30°C at all times of day, and there is no coherent (systematically and experimentally tested) position in the literature on the implications of WU^6,7 for endurance performance in such temperatures. Although PC has been discussed more widely during the last two decades,^8,9,10 it has not yet been studied in comparison with active WU.