There are 3 moments during which an athlete can cool his body: pre-cooling (before a race/training), per-cooling (during exercise) or post-cooling (after the training/race). All 3 are effective, but there are important differences.
The effects of different pre-cooling techniques on exercise performance were examined within various ambient conditions and using different exercise protocols (i.e., endurance exercise vs. (intermittent) sprint exercise). It is demonstrated in a meta-analysis that pre-cooling improves exercise performance in the heat (ambient temperature >30°C) with 5.7% (± 0.9%). (*9)
The benefits of pre-cooling are larger for endurance athletes than for (intermittent) sprint athletes (*7).
Ninety minutes of cold air (0–18°C) / (32-64°F) exposure prior to exercise in moderate ambient conditions of 18°C (64°F) resulted in an increased time to exhaustion and an increased 1 hour work rate: 172 Watt with pre-cooling vs. 161 Watt without pre-cooling. (*8)
Athletes who began exercise at cooler body temperatures accumulated lactate more slowly, maintaining their lactate threshold by 15-20% longer. A later study found that pre-cooling reduced blood lactate levels by around 10-12% during high-intensity exercise, allowing athletes to maintain aerobic metabolism longer. This decrease in lactate accumulation was associated with lower core temperatures, helping athletes delay anaerobic fatigue and maintain steady performance. (*59), (*60)
Pre-cooling works, in both warm ánd moderate ambient temperatures. Especially in combination with cooling DURING training or race, see the next chapter as well.