Heat and humidity can be lethal for your players -- here's what to know

(Amid a summer in which several parts of the nation are experiencing record high temperatures and unusually high humidity values, we republish this article, which first appeared in the Youth Soccer Insider in 2018.)
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It can be OK to practice in 100-degree weather, or it could be dangerous. It depends on the humidity factor.

So impactful is humidity that, for example, 86-degree weather can be lethal if humidity is extremely high.

“Humidity is probably the key factor that could be the most difficult on the body with regards to exercise, because with the humidity, your body's ability to dissipate heat is stunted,” says Dr. George Chiampas, U.S. Soccer’s Chief Medical Officer. “You can’t sweat it off because the environment outside of you is hotter than yourself.”

Therefore, coaches must figure out the Wet Bulb Globe Temperature (WBGT) -- when deciding whether to cancel or delay training, or games.

If WBGT sounds complicated, it’s made comprehensible by U.S. Soccer’s “Heat Guidelines,” part of its Recognize to Recover Program overseen by Chiampas.

“WBGT is becoming a more and more a common term in youth sports and in sports in general,” he says.

The R2R “Heat Guidelines” provide a graph to estimate WBGT (for which there are also apps, such as WeatherFX, and WBGT monitors). Also included in the Guidelines is a list of indicators of heat-illness and heat stroke (which can be life-threatening), management and recovery information, acclimatization procedure, and work-to-rest ratio formulas.

Emphasized also is access to cooling and hydration resources.

“We’re understanding more and more in regards to heat and acclimatization,” Chiampas said. “We also see that there have been extremes in temperatures over the last 10 years.”

The Guidelines break the nation into three geographic parameters based on how acclimated players are to heat, because, "Players who are playing in the South are more acclimated to warmer weather compared to players who are playing the North," Chiampas says.

The main emphasis of the Guidelines is player safety, but they also serve to optimize performance.

“If as coach, you start learning more about exercising in the heat, this is gives you some insight into the importance of it and that it is a factor in the ability of your players to play at a high level,” Chiampas says. “It also gives you some action items of things that you can do, such as adjust your work-rest ratio. But I think most importantly it's providing coaches, parents and players, as well as referees, a user-friendly process to implement a very important safety component.”

The U.S. Soccer Federation R2R Guidelines are mandated for Development Academy clubs, serve as guidelines for USSF members, and meant as a resource for American soccer outside its membership.

For Heat Guidelines, go HERE.

The R2R home page is HERE.

2 comments about "Heat and humidity can be lethal for your players -- here's what to know".
  1. Bob Ashpole, July 22, 2019 at 6:04 p.m.

    Synthetic fields present a danger as well if field owners do not wet the fields periodically. (I have never known one to do so for youth matches.)

    The synthetic fields absorb heat in direct sunlight. The actual temperature on the field may be 20 degrees F higher than the ambient air temperature. The field surface may be hotter.

    Not only is there a greater risk of heat injury, but also a risk of blisters from the hot fields.

  2. R2 Dad, July 22, 2019 at 10:14 p.m.

    There is a youth soccer tournament near Sacramento every August, which never fails to be brain-melting hot. They call it a Blast--really more of a blast furnace.  The parents still send their kids, but none of the coastal teams do well. I never understood why that tourney was always so popular with the clubs--cheap entry?. It's 95F there today, 100F tomorrow--too hot for U9-U14 in my book even though matches start at 3pm. Is this really necessary? Can't they run matches 8-11am and 5-8pm instead? I guess they haven't had a kid drop dead yet.

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