Steel spent over a decade as a professional netball player — a version of basketball popular in Australia, England, and other countries — but her career ended that day in 2016.

Instead of hours of intense workouts, she can only walk or do light yoga. When her heart rate and body temperature start to rise, "my body sort of rebels against that, and it's all starts to shut down," Steel told Business Insider.

When the body temperature reaches 104 degrees Fahrenheit or higher, heat stroke can become deadly. For those who recover from the immediate danger, the effects on their hearts, kidneys, and immune systems can be long-lasting.

Steel showed some serious signs of heat stroke












Amy Steel was a professional netball player for over a decade.



Chris Hyde/Getty Images

Steel's professional netball career started at age 15. She traveled around Australia and to other countries, competing in championship games. "I had some really special career moments," she said.

She would train for five hours a day, balancing early morning and evening practices with a job in accounting.

The day Steel collapsed in 2016, the weather was over 102 degrees Fahrenheit. Steel's team was playing a preseason game in Shepparton, about 100 miles north of Melbourne. Officials took humidity and temperature readings in the stadium and deemed it safe to play. However, Steel said the readings were done before the room was packed with spectators and sweaty athletes.

Unlike basketball, netball has no dribbling and instead of a hoop with a backboard, there's a ring. But both are cardio-intense sports.

After the game, before her collapse, Steel noticed the ice bath she sat in felt hot. She tried to take a shower but couldn't figure out how to work the taps — mental confusion is a red flag for heat stroke.

"One of the main things that's critical with heat stroke is you start to see cognitive impairment," said Lacy Alexander, a kinesiology professor at Penn State University who wasn't involved in treating Steel. The brain is sensitive to high temperatures. When it gets too hot, "you start to get that cooking of brain and neural tissue," she said.

The long-term effects of heat stroke can be debilitating












Eight years after getting heat stroke, Amy Steel is still dealing with its effects.



Lewis Blaustein/EcoAthletes

Alexander said restricted blood flow to the gut during heat stroke can release bacteria into the bloodstream. This can cause a cytokine storm, similar to the way some people's immune systems overreact to COVID-19.

"You see this really huge response of the immune system to severe heat-related events," she said. This kind of overreaction can trigger a series of other illnesses long after a heat stroke.

Following her collapse and hospitalization, Steel, for example, developed tonsilitis though she'd had her tonsils removed. A bout of glandular fever she'd had in childhood reappeared. And her kidneys showed markers of inflammation for two years after she was first hospitalized.

Steel still struggles with fatigue. "I will quite regularly have to have, at a bare minimum, two sleeps to get through to the end of the day," she said.

Once while out driving on a hot day, Steel found herself drifting into oncoming traffic. When the temperature is in the mid-80s, she starts to feel cognitive effects from the heat.

Researchers aren't completely sure what causes this sensitivity, but Alexander said heat shock proteins, which help protect cells from stress, can become dysregulated. "This is potentially one reason that may put certain individuals at an increased propensity for not doing well in the heat in the future," she said.

With climate change increasing temperatures worldwide, Steel wants other athletes to be aware of some of the long-term effects of heat-related illnesses.

"It's certainly been quite debilitating and really life-changing in terms of being an elite athlete and really at my peak fitness to then having to basically rest for a bulk of the day," Steel said.