Well known to athletes are the negative effects of heat on performance during prolonged exercise. It there is a way to reduce these effects, an athlete should be interested in trying it out. One strategy is pre-cooling and several studies have found a positive effect from it. Precooling methods have included ice vests, cold towels, cold water spray, cold showers or immersions, and cold rooms; and the longer and larger the cooling stimulus, the greater the improvements in performance. How these methods affect exercise performance appear to be associated with reduced cardiovascular strain, improvements in oxygen supply, and reduction in the accumulation of anaerobic metabolic byproducts, chemicals that can increase muscular fatigue.
A recent study in Medicine and Science in Sports and Exercise attempted to test the benefits of precooling on self-paced endurance performance in male cyclists. This type of protocol allows the athlete to determine his or her own pace with the intention of completing a specific distance or amount of time. In other words, it simulates a race, but does so in a controlled lab environment. Two randomly-ordered 40-min time trials were completed on separate days in a 91º (50% humidity) environment. On one of those days, athletes immersed their lower body to hip level in 57º water (sounds painful to me!) for 20 min prior to the time trial.
What they found
Precooling resulted in the following:
- increased power output during the 40-min time trial, especially during the final 10 min of the ride, resulting in a greater estimated distance covered (19.3 km vs 18.0 km)
- lower skin and core (rectal) temperatures during the first 15 min of the time trial
- no change in heart rate or rating of perceived exertion, but a lower thermal sensation
What does this mean for you? Physiologically, precooling had no profound effects except for a lower body temperature which would be expected. Cardiovascular response was not changed, nor was the muscle’s ability to contract. However, performance was improved and isn't that what it's all about? Although the improvement was not huge, any amount will benefit the athlete and even a small improvement can make the difference between first and second place.
How does one precool? When I lived in Tucson, I would soak my cotton t-shirt in cold water before putting it on just before a run. It really helped keep me cool, despite the fact that it would be completely dry within 15 minutes of dry desert air exposure. For a kayaker, it may be as simple as water immersion prior to paddling. The athletes in this study were immersed up to their hips. The authors didn’t mention whether or not they were wearing shorts. I suspect not. If the direct benefits are dependent on which muscle groups are immersed, than it makes sense that a kayaker will want to immerse his or her upper body. In which case, wet clothing may be the downside of doing this. Regardless, if precooling is possible before exercising in the heat and you can do it without too much discomfort (i.e., wet clothes), go for it. It can’t hurt you, unless you give yourself frostbite from rubbing ice cubes on your skin.
Reference: Duffield et al, Med Sci Sports Exerc. 42, 2010
