Dear race director friends:
I understand you have undertaken a thankless job. You put in countless hours to assure your event is well-organized. I also understand you receive a slew of dumbass requests. Hopefully some of you will consider this request even though it directly contradicts the accepted logic most runners ascribe to.
Please stop distributing moisture-wicking tech shirts.
Why you ask?
Quite simply, they’re endangering the lives of runners that falsely believe their clothing will help keep them cool in hot weather. Many runners believe the tech fabric’s ability to transport sweat away from the skin helps cool the underlying skin.
In reality, it robs their bodies of the evaporative cooling effect, thus raising their body temperature instead of lowering it. Sweat evaporating off the surface of the shirt doesn’t cool the skin under the shirt with nearly as much efficiency as naked skin.
In short, most runners don’t understand how their body thermoregulates.
To combat this overheating, many runners will attempt to drink more water or sports drink which increases the danger of hyponatremia.
I’ve done several reviews of the literature to find any empirical evidence that moisture-wicking fabric actually lowers core body temperature. Not surprisingly, none apparently exists.
There are studies measuring perceived comfort where tech clothing is rated as more comfortable than natural fibers like cotton, but the research is silent on the issue of thermoregulation. Yet clothing manufacturers continue to churn out moisture-wicking clothing with the implied or expressed promise it will “keep you cool.”
In reality, moisture-wicking clothing was developed for low-intensity cold weather activities that required frequent stops (i.e., hiking.) For that purpose, it works wonderfully. It also works well for areas that remain covered, thus preventing air circulation (think socks and underwear.) For hot-weather exercise, it’s flat-out dangerous. Not only will hyperthermia reduce performance, it can lead to heat stroke and eventual death.
Race directors can help correct this deception by refraining from distributing moisture-wicking clothing, especially in hot-weather races. Please stop contributing to the idea that this clothing will keep you cool. You could potentially save the lives of your fellow runners.
Thank you for your time, I know it is valuable.
Runner friends: Please help me spread this important message and forward this post to any race directors you may know.