As fall season heats up, athletic trainers debut new wet bulb globe temperature devices

By Mac Moore – KSHSAA Covered

In Kansas, high school coaches and student-athletes probably let out a sigh of relief when they checked the weather for the first week of fall sports practices that started this week.

But the cooler temperatures are a short reprieve that will not take the autumn heat off the minds of athletic trainers across the state. In fact, many of those individuals will still show up with fancy new gadgets to track temperatures at their facilities.

Thanks to a grant from the National Federation of State High School Associations announced back in February, all 354 Kansas State High School Activities Association members will be equipped with a wet bulb globe temperature (WBGT) device at no cost to the school.

These devices are electronic meters that provide a more precise measurement of apparent temperature than heat indices by accounting for environmental factors such as humidity, wind speed and solar radiation.

With the opportunity for all KSHSAA member schools to have access to this device, the KSHSAA Sports Medicine Advisory Committee provided an updated version of the organization’s recommended activity modification policy with WBGT values replacing the heat index values. The KSHSAA Executive Board approved the new version of the policy during its April meeting.

By using these devices and the WBGT ranges outlined in the activity modification policy, member schools will have a chance to improve player safety and protect them from heat illness. 

According to the National Weather Service, heat caused more fatalities than any other type of inclement weather. A study from the Center for Disease Control also found heat to be a contributing factor in 1,577 deaths in 2021, a 56% increase from the total in 2018.

The fall sports season is often when these precautions against heat are needed most, with reports of heat illness highest during the first few weeks of practice in August.

Wayne Harmon, Olathe North athletic trainer and a member of the Kansas Athletic Trainers’ Society, helped promote the use of WBGT devices by high schools in Kansas.

 “I think this year’s going to be a learning curve for a lot of places to think about not only the health of the kids, but the longevity of the sports,” Harmon said. 

Harmon said that he’s been using various WBGT devices for the last 15 years. He first learned about them when he was a college student at Wichita State in the late 1970s, using it on the sidelines at practices in much the same way he is now.

But Harmon said the use of WBGT devices did not start to really pick up until 2010 after the creation of the Korey Stringer Institute, a non-profit organization dedicated to the prevention of sudden death in sports and beyond. Korey Stringer was an offensive tackle for the NFL before dying of complications brought on by heat stroke during the Minnesota Vikings training camp in 2001.

“We all think we’re pretty much indestructible in athletics and sometimes we’re not,” Harmon said.

Harmon said football requires extra attention in regards to heat, humidity and wind for a few reasons. The first is the increased use of turf fields, which often produce a 10-plus degree increase in apparent temperature compared to grass fields. The second is the uniform.

“When you’re wearing football gear, you’re not dissipating heat very clearly,” Harmon said.

Harmon said that Olathe is hoping to determine its own policy within the next week or so. The five athletic trainers in Olathe are taking readings from the first days of fall practice and reporting them to Matthew Johnson, the director of athletics and activities for the Olathe Public Schools.

Harmon and his fellow Olathe athletic trainers will have less of a learning curve than others around the state.

Harmon said that more than a decade ago, a school board member in his district asked the athletic trainers to start tracking the difference in standard temperatures vs. apparent temperatures from the WBGT devices. The goal was to figure out how much practice time would be lost if they followed the activity modification procedure with the more precise temperature figure.

Based on the data at the time, Harmon said his school district did not lose too much practice time, but there were a few more days in the fall that climbed into the red or black zone of the current activity modification policy.

Harmon said he’s interested in seeing how different districts will adopt or modify the zone ranges recommended by KSHSAA. In Olathe, he sees the possibility for multiple schools to be in the different ranges of the WBGT zones on the same day. Harmon said he’ll have his eyes on different districts around the state to see if they will adopt or modify the KSHSAA policy.

“It’s going to be really interesting to see if everybody wants to follow (the policy) because every coach will tell you they want what the others want,” Harmon said. “If the other teams get to practice, then they should get to practice, no matter what the temperature ranges are.”

Harmon said that although the use of WBGT devices to help determine adjustments to practice on hot days is new, the changes meant to improve player safety have been a continual process of the last four or five decades.

“Until 40 years ago, a lot of times (football teams) didn’t have water on the field for the kids to practice and drink water,” Harmon said. “You may have had a water fountain on the side and they’d give you a couple minutes to get over there. You’d have 40 or 50 kids trying to hit the water fountain, so not everybody got water.”

Harmon said the issue often boils down to habits, old school vs. new school. He pointed to the opposition to the development of football helmets in the early 20th century, going from leather to padded plastic to adding face masks. Harmon also pointed to the increase in strength training for college athletes in recent years to demonstrate how coaching approaches can change.

“Thirty years ago, a basketball coach would not allow a kid to touch a weight all-year long,” Harmon said. “Now if they’re not in the weight room, they’re not physical enough to block out on the box.”

Harmon said the nature of change is slow to show the positive, but once everybody starts to see it, they begin to follow it “rabidly.”

“It’s a good change,” Harmon said. “It’s a quality change that helps protect our kids, but also makes our kids better for the long run.”

For more safety tips, Harmon and some of his KATS colleagues helped create a series of videos including a tutorial on how to use the Kestrel device and multiple rapid cooling techinques. Those are available on KSHSAA’s YouTube page here.


Activity Modification
WBGT Level/Zones

< 79.9° F 

• Normal activities
• Provide at least 3 separate rest breaks each hour with a minimum duration of 3 minutes each.

80° – 84.6° F 

• MINIMUM 3 separate rest breaks each hour with a minimum duration of 4 minutes each.
• Cold water immersion tub or other rapid cooling method should be prepared and ready.

84.7° – 87.7° F

•  MINIMUM 4 separate rest breaks each hour with a minimum duration of 4 minutes each.
• 2 HOUR MAXIMUM length of practice (not including rest breaks)
• Cold water immersion tub or other rapid cooling method prepared and ready
• Consider competition alterations
  • Coordinate with contest officials to allow for additional breaks
  • Shorten length of sub-varsity competitions
  • Shorten length of course (Cross Country)
• Football specific:
  • Protective equipment should be limited to helmets and shoulder pads, and these should be removed for conditioning.
  • If practice begins in a cooler range (green or yellow), but increases to orange during practice, players may continue practice in full protective gear.

87.8° – 89.7° F

• 1 HOUR MAXIMUM length of practice (not including rest breaks)
• MINIMUM 20 minutes of rest breaks distributed throughout the 1 hour of practice
• Cold water immersion tub or other rapid cooling method prepared and ready
• Consider competition alterations
  • Coordinate with contest officials to allow for additional breaks
  • Shorten length of sub-varsity competitions
  • Shorten length of course (Cross Country)
• Consider delaying practice/competitions until a cooler WBGT is reached
• Football specific:
  • No protective equipment should be worn.
  • No conditioning activities

> 89.8° F 

• No outdoor workouts. Delay practice/competitions until a cooler WBGT is reached.