Having provided first aid and medical teams for hundreds of endurance events Lucas Trihey considers the dangers of heat stroke.

March 2016

As a race organiser and responder, heat stroke is the injury that worries me most. When it strikes a runner down things need to happen quickly to save the person from serious organ damage or death. In hot conditions many runners find it difficult to anticipate and prevent.


High temperatures with high humidity is the worst combination. According to the American College of Sports Medicine (ACSM) a sunny day with a temp of 29C and 75% humidity with little wind is hot and sticky enough to place people undertaking “continuous activity” at high risk of heat stroke.

In hot, low-humidity conditions runners can cope quite well and avoid heat injury because the body is able to shed heat to the (drier) environment using our body’s wonderful cooling system. But when it’s hot AND humid it’s harder to shed heat and we start to cook.

So while participants in Death Valley (USA) or across the Simpson Desert (Australia) often run in safety in 40+C temps due to the low humidity a day of moderate temps and high humidity will see runners in other areas struggling to stay cool and some will suffer heat injury.

HOT AND DRY = OFTEN OKAY – Body can usually shed heat

WARM/HOT AND HUMID = DANGEROUS – Body can’t shed heat


  • When you exercise, heat is generated as a by-product of muscles working and if you can’t shed this heat to the environment your temperature will rise.
  • If your temperature rises you will get sick, if it rises far enough your organs will start to cook and fairly quickly will stop working – this is life threatening.
  • To avoid heat injury you need to avoid getting too hot. You need to help your body shed the heat that your muscles are producing, protect yourself from radiant heat and if you find yourself getting hot you need to slow down and find ways to cool your body.


Be aware that hydration actually has little to do with preventing heat stress. There are many examples of well-hydrated runners and trekkers getting heat stroke. What you need to do is to cool your body. Encouraging people to over-hydrate in an attempt to prevent heat stroke is misguided and is likely to lead to over-hydration and illness (hyponatraemia). As always, the best hydration advice is to “drink to your thirst”.

Read about Austrian tourist Caroline Grossmueller who died at Lake Eyre in 1998 of heatstroke with plenty of water remaining:


Over the years I’ve been at events and have treated runners with heat stroke who have done permanent damage to their organs. I have also researched events where participants have died or received severe brain or organ damage. See the CASE STUDIES below.

After studying these incidents I sought advice from experts including Associate Professor of Physiology, Martin Thompson (Sydney University) and papers from the American College of Sports Medicine. The following guidelines come from this research and should help runners and event organisers to reduce the chances of heat stroke.



  • Wear loose, light coloured clothing. Avoid black lycra.
  • Use ice water and ice packs to keep your cool. Lots of events provide these items now.
  • Tip iced water over your head, torso and limbs at regular intervals.
  • Put small ice packs under your cap, against your neck (carotid area), under arms and down your shorts to rest against your inner groin/thigh – all these parts of the body have good blood supply and are a great way to cool you down.
  • If possible run in the shade rather than full sun.
  • If possible run in places that catch a breeze rather than in a still, humid valley.
  • If the heat is bothering you take regular rests in the shade.
  • Have a good supply of fluids with you and drink if thirsty – but don’t overhydrate.
  • If feeling the heat stop at an aid station to get help rather than pushing on to collapse somewhere remote.


  • Provide ice water dousing buckets around the course.
  • Provide ice packs (party ice in a small freezer bag) for runners.
  • Prepare your marshals so they know how to recognise heat injury and help runners on hot days.
  • In dangerously hot/humid conditions organisers should be prepared to shorten, re-route or cancel the event.
  • Use the WBGT index to help evaluate conditions (see the section on WBGT)
  • Advise your marshals and aid stations not to encourage over-drinking. Simply filling your stomach with too much water will not prevent over-heating and may make them ill with the effects of sodium dilution (hyponatraemia).


The Wet Bulb Globe Thermometer (WBGT) is an index value derived from a combination of temp in the shade, temp in the sun, wind (or lack of) and humidity. WBGT is recognised internationally as offering event organisers and managers an appropriate tool to make informed decisions about the risk of heat stress for individuals exerting themselves in the heat.

Local WBGT values are available for some Australian locations via the BOM website:

We use a hand-held WBGT meter at all warm weather events.



On a warm day in November 2012 I coordinated the first aid team at Glenbrook Marathon for 200 runners. Temps were mid 30s and humidity was around 70%. Late in the morning we heard reports that a runner had collapsed approx 150m from an aid station. Not long after collapsing this person was unconscious, fitting and having seizures, all signs that the brain was being damaged. We called an ambulance, got ice packs and cold water onto the person, and he spent three days in Nepean Hospital being treated for kidney damage. He was lucky the collapse was close to a road and we were able to get to him within 15 minutes, but even so he suffered life threatening heat stroke. It would have been far more dangerous if this collapse had occurred on a remote section of the course.


At a 15km beach run on Bribie Island in October 2013 a leading runner didn’t appear as expected at the finish. He was later found unconscious on a track among the dunes near the beach. Tragically this runner died. One possibility is that the runner began to suffer from heat stroke, became disoriented and left the beach. This thread on Cool Running has more information:


An Australian participant in the October 2011 event in Egypt suffered seizures and heat stroke that led to permanent brain damage. According to media reports the runner now needs 24/7 care and lives on a disability pension.

An American runner in the 2010 Gobi Desert event died from “complications due to… heatstroke”


American College of Sports Medicine (Position Stand)

Exertional Heat Illness during Training and Competition


Trek for Timor

Pleased to announce ESS will be providing first aid services and a radio network to the great team of volunteers organising Blue Mountains Trek for Timor in September 2016. This family-friendly, non-competitive trek is 50km with shorter distance options and is a fund raiser for great causes in one of our nearest and newest neighbouring nations. In the past funds have helped build schools and other important community initiatives.

Blood Analysis – on site / remote area

We are pleased to announce that our medical service now includes on-site blood analysis. This specialised equipment in the hands of our trained medical staff is a significant improvement and will allow us to make better informed decisions and deliver improved diagnostics and patient care. Particulary important for remote work, the equipment will be valuable at all events where our ability to test for electrolytes, creatinine, glucose, haemoglobin and troponin levels could save lives. A useful effect that blood analysis will provide is that it can be used to rule out options as well as diagnosing an illness and as such can greatly help a doctor to rule out a serious issue and allow a runner/trekker/expeditioner to continue.

Managing Heat

ESS has supported some pretty out there endurance events in hot conditions and are leaders in managing events, athletes and crew in hot and/or humid environments. We use the WBGT heat index to evaluate conditions and put in place strategies to avoid heat illness. As well as helping manage lots of summer endurance events, last year we advised Kirrily Dear and her crew about heat management for her 12-day, 860km in western NSW in a hot summer and we are working with Mina Guli as she prepares to run five marathons across the Tanami Desert in February.

Collapsed and unconscious = start simple CPR!

Members of the public and bystanders have little to fear from legal threats if attempting to provide CPR. Information on the Australian Emergency Law blog makes it clear that there has never been a successful law suit brought against a person for trying to revive someone using CPR. From a first aid perspective it’s simple: if a collapsed person is unconscious and not breathing – start CPR immediately and you dramatically raise their odds of survival. And CPR guidelines for the public have been simplified – compress the chest to 1/3 depth (whether for adult or child) and push to the beat of “stayin alive” by the Bee Gees. If there’s a defibrillator nearby send someone to get it – the defib will talk you though how to use it. Keep CPR going until an ambulance arrives.

With thanks to Dr Michael Eburn/Australian Emergency Law

Nicholas Gleeson blog

Nick lost his sight at the age of seven and is now an accessibility advocate and speaker. Nick’s Simpson trip with ESS went well with six days wandering in the area to the north of Poeppel Corner. Nick was joined by an old friend Vina from the USA, Sarah was the trekking guide and Lucas supported the small team. They experienced the natural world, Aboriginal sites, fauna and flora. Nick’s blog makes great reading

Blind trekker Nick Gleeson to Simpson Desert in 2015

Pleased to announce that ESS will guide blind adventurer Nick Gleeson on a 7-day, 120km remote trek across the Simpson Desert in July 2015. Lucas guided Nick up Kilimanjaro, at 5896m the highest mountain in Africa in 2001. Nick has just been named a recipient of an AMP Foundation Tomorrow Fund grant.

Mount Barney Skyrun

ESS is providing medical and safety teams, a radio network and input into course selection and mapping for the Mount Barney Skyrunning event will take place in southern Queensland in August 2015. Here, Race Director Sean Greenhill climbs the South Ridge on a recent recce trip with ESS where the course was checked out and a location for a radio repeater was established.

Satellite tracking of participants

Over two years ESS has worked with satellite tracking systems that follow individual runners or trekkers with on-screen updates at event HQ every ten minutes. These systems give event organisers excellent supervision of participants for safety purposes. They also have a HELP button for emergencies. This photo shows satellite tracking in use at the Big Red Run 2014.