Forty minutes. That’s roughly how long it took me to get my teammate from the training pitch to the nearest A&E that Saturday afternoon, weaving through traffic instead of waiting for what felt like an eternity for an ambulance. I thought I was doing the sensible thing, the fast thing. The registrar who met us at the door had a different view entirely, and what she explained about core temperature thresholds has stayed with me ever since.
He’d collapsed near the end of a punishing five-a-side session, temperatures nudging the high twenties, humidity thick enough to chew. Confused, stumbling, oddly aggressive when we tried to help him into the car. None of us clocked it as anything more than dehydration. It wasn’t.
Key takeaways
- A teammate’s collapse from heat stroke revealed why the first 10 minutes matter infinitely more than the destination
- Beyond 40.5°C, the body isn’t just uncomfortable — it’s suffering cellular-level damage that compounds every minute
- The difference between life and permanent injury comes down to cold water and a phone call, not car keys
What actually happens once the body crosses 40.5°C
Exertional heat stroke is defined by a combination of dangerously high core temperature and disrupted brain function, and while 40°C is often cited as a rough marker, clinicians are increasingly clear that there’s no single magic number. Although a core temperature of 40°C is included in the definition, there is no universal threshold, as severe complications can occur at lower temperatures depending on individual susceptibility. Some elite athletes tolerate readings above that without any neurological symptoms at all, which is precisely why doctors look for confusion, agitation or loss of coordination alongside the thermometer reading, not instead of it.
But the 40.5°C figure keeps appearing in emergency medicine literature for a reason. Exertional heat stroke is a medical emergency involving life-threatening hyperthermia with central nervous system dysfunction, and the longer a patient’s temperature stays above the critical threshold of 40 to 40.5°C, the greater the possibility of long-term sequelae or death. Beyond that point, the damage stops being reversible fatigue and starts being cellular injury. Sustained elevation of core temperature causes cytotoxic injury through direct damage to macromolecules and cellular structures, including protein and DNA denaturation and lipid membrane instability. That’s not a metaphor. That’s your teammate’s kidneys, liver and clotting system taking a battering while everyone around him is still arguing about whether he needs water or an ambulance.
Why the clock Matters More Than the destination
This is the part that genuinely unsettled me. Sports medicine researchers have found that outcomes hinge almost entirely on how quickly cooling begins, not on how quickly a patient reaches a hospital bed. Exertional heat stroke has had a 100% survival rate when immediate cooling via cold water immersion or aggressive whole body cold water dousing was initiated within 10 minutes of collapse. Ten minutes. We spent four times that just getting through traffic, without so much as a bag of ice on him.
The reason speed trumps everything else is that damage accumulates the whole time the body stays hot, regardless of where the patient physically is. Recovery from exertional heat stroke and heat injury is related to the duration of core temperature elevation above the critical level of approximately 40.5°C; the longer a patient’s core temperature remains above this level, the greater the risk of severe morbidity and mortality, and the longer the period needed for recovery. A recent UK consensus statement on pre-hospital heat illness management reinforces the same point, noting that severe cases are commonly defined by a core temperature above 40.5°C, though the precise threshold remains debated and individual susceptibility varies considerably. Several organisations define the threshold for severe exertional heat illness as a core temperature above 40.5°C, though a lower threshold of 40°C is also commonly reported, and there is a risk of significant harm if the diagnosis is overlooked when core temperature is below 40.5°C.
The mortality gap between the two main types of heat stroke also puts things in perspective. Mortality rates are around 26.5% for exertional heat stroke and 63.2% for classic heat stroke. The exertional kind, the sort hitting fit young athletes on a pitch or a running track, is survivable in the vast majority of cases, provided cooling starts almost immediately. That’s a big provided.
Cooling first, hospital second
What I should have done, and what I now tell anyone who’ll listen at the club, is start cooling on the spot before even thinking about a car journey. Rectal thermometry is the gold standard for confirming the diagnosis in a clinical setting, but on a pitch or in a car park, nobody has that kit handy, so cooling begins based on symptoms alone: confusion, hot skin, collapse, a heart rate that won’t settle. Whole-body immersion in cold water works fastest. Whole-body immersion in ice water, with the head kept above water, achieves the fastest reduction in core temperature, at least 0.15°C per minute, and cooling should stop when the core temperature reaches approximately 38°C.
Nobody carries an ice bath to five-a-side, obviously. But cold water poured over the neck, armpits and groin, wet towels swapped constantly, removing kit and clothing straight away, all of it buys precious minutes while someone else calls 999. The NHS’s own first aid guidance for heat-related illness follows the same logic of acting on the spot rather than rushing to move the person. Move them to a cool place, remove unnecessary clothing, give them fluids if they’re conscious enough to drink safely, and cool their skin by spraying or sponging with cool water and fanning, with cold packs wrapped in a cloth placed under the armpits or on the neck. Crucially, if someone shows signs of heat stroke rather than heat exhaustion, confusion, seizures, loss of consciousness, that’s a 999 call, not a lift in your Vauxhall.
Warning signs rarely arrive without notice, either, even if they’re easy to dismiss mid-match: irritability that seems out of character, glassy confusion, stumbling that looks more like poor balance than injury. Catch that window and a phone call to 999 while cooling begins on the spot does more good than any amount of determined driving.
My teammate recovered, thankfully, though it took him the better part of two months before his GP cleared him to train properly again, and he still notices he overheats faster than he used to on warm days, something clinicians studying return-to-play cases have observed can persist long after the initial emergency has passed.
This article is for general information and does not replace professional medical advice. If you suspect heat stroke, call 999 immediately and begin cooling while you wait, and always speak to your GP about any lasting symptoms following a heat-related illness.
Sources : fphc.rcsed.ac.uk | sciencedirect.com