By Jay Gormley & Arezow Doost, CBS 11 News

DALLAS (CBSDFW.COM) – At James Madison High School in south Dallas, even the young are feeling a bit old.

“I come to practice in the morning,” said defensive lineman, DeAndrew Hill. “Then I go to work and then I come back to practice. I’m tired.”

If Hill, a high school senior, is tired, what about his coaches who are in their forties and fifties? The question crossed the mind of Madison head coach, Ronald Johnson. “One of the first things in our meeting that we (the coaches) talked about was taking care of ourselves. We’re not as young as we used to be.”

Johnson’s concerns come one day after Prestonwood Christian Academy’s 55-year-old assistant coach, Wade McLain passed out during football practice and later died. With the tragedy fresh on his mind, Coach Johnson told his assistants to wear hats and drink plenty of water.

Critics say the real issue is establishing a hard weather number which all coaches in Texas can follow to protect themselves and their players from heat-related illness or death. Dr. Terry Madsen of Forest Park Medical Center says the number is simple: “I think a heat index of 105 is appropriate,” he said.

Heat index is what the body actually feels. Dr. Madsen, who specializes in sports medicine, believes if the heat index is at or above 105, players should not practice outdoors. “It could be a temperature as low as 80 degrees with a humidity of 40 percent or 50 percent.”

Dr. Madsen agrees that coaches are more susceptible to the heat because they’re older and some are out of shape.  However, he also warns that the excessive heat can take a toll on the best of athletes. “They’re not out wearing bathing suits and dipping in the pool,” said Dr. Madsen. “They’re wearing layers of clothing and layers of padding.”

U.I.L. Rules ban players from wearing pads the first four days of practice. But soon the pads will be on and so will the pressure to avoid another heat-related tragedy.

 Experts say those not on a football field should also be mindful of the high temperatures.

“In this kind of heat, people just need to take cover,” said Dr. Keto Trivedi, the medical director of Methodist Mansfield Medical Center. “Forty minutes to an hour, just go inside. You can probably tolerate more, but you don’t want to wait until you get weak and pass out.”

Charlie Sanchez, a firefighter and paramedic in North Richland Hills, isn’t always afforded this possibility. Sanchez, 36, was battling a fire several weeks ago when he said he became overcome by the heat.

“Getting really dizzy, light-headed, tunnel vision,” he said, describing his symptoms. “I could feel my heart just, pounding.”

But Janice Womble, a Mansfield resident, just enjoys spending time on her 23 acres. That fact got her in trouble last week.

“It was very cloudy, and I thought I would do the mowing,” Womble said. “I usually have no problem doing anything like that and staying outside for long periods of time.”

She has a warning,which that now mimics professional opinion: Don’t underestimate the heat.

“I’m pretty healthy and it just knocked me flat,” she said. “I spent three days in the hospital.”

Learn more about heat exhaustion here, complete with tips from the Mayo Clinic.