Abstract

Objective: To examine the effects of different thermoregulatory preparation procedures (warm-up, precooling, control) on the endurance performance in the heat.

Methods: Twenty male subjects completed three treadmill runs to exhaustion (5 days apart). In each session, all subjects performed an incremental running test either after warm-up (20 min at 70% HRmax), after precooling (wearing an ice cooling vest [0 - 5°C] for 20 min at rest) or without particular preparation (control). 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 till the point of volitional fatigue. Running performance, heart rate, blood lactate concentration, tympanic temperature, and skin temperature were measured in each trial.

Results: In the precooling condition, the running performance (32.5 (5.1) min) was significantly (p<.05) higher than in warm-up (26.9 (4.6) min) and in control conditions (30.3 (4.3) min). During the first 30 min of testing, heart rate, tympanic temperature, and skin temperature were significantly (p<.05) lower after precooling than after warm-up. There were no significant differences in lactate concentration, however, there was a trend to lower values after warm-up.

Conclusions: The use of an ice cooling vest for 20 min prior to exercising improved running performance, whereas the 20-min-warm-up procedure had a distinctly detrimental effect. Cooling procedures including additional parts of the body like the head and the neck might further enhance the effectiveness of precooling measures.