A pill that measures the temperature during running or cycling can prevent overheating: the main cause of death in extreme endurance sports.

In 2014, Arthur Fonville, a 24-year-old highly-trained medical student, is one of the 50,000 participants of the annual Dam to Dam run about 16.1 km from Amsterdam to Zaandam. A little pale, he reaches the finish line where he collapses and instantly dies due to a heat stroke. With 20 degrees Celsius, that day is not particularly warm. However, rescuers measure the student’s body temperature of 42 degrees at the finish line. At this temperature, enzymes lose their structure, which results in irreversible damage to vital organs.

Arthur Fonville
Dam to Dam run, 16.1 km.

Overheating of the body can be caused by an endogenous cause, and is then known as fever. The cause is usually an infection by a bacteria or a virus. An important feature is that the setting of the ‘thermostat’ in the hypothalamus has been changed. The ‘thermostat’ then adjusts to a higher level, above 38 degrees.

When exogenous overheating occurs, there is a disturbance of the balance between heat production and heat loss. The body cannot get rid of sufficient heatin an unchanged setting of the thermostat. In that case we don’t speak of fever but we speak of hyperthermia.


Hyperthermia is a condition of the body where there is an uncontrolled increase in temperature by a disturbance of the balance between heat production and heat loss. Body temperature will increase without an increase in the setting of the internal thermostat. This distinguishes hyperthermia from fever.

  • Heatstroke or heliosis by staying too long in the full sun, such as a kid left in a closed car in the sun.
  • Exercise in a very humid environment, by sweating the body can cool down insufficiently.
  • Delirium tremens, withdrawal syndrome by alcohol addiction.
  • Drug use: cocaine, amphetamines, MDMA, GHB.
  • Status epileptic, generalized seizures.
April 05, 2016

KHON KAEN: — A four-year-old died tragically at a funeral after being stuck in a car left in the blazing afternoon sun in the Northeast region of Thailand.
It appears the little girl was playing and climbing into the car unbeknownst to those at the funeral. When she was found to be missing,a search was made, but it was some hours before she was found dead in the back of a Toyota Corolla.
Sangharn Makaew, 53, a village elder in KhuaRiang district of Chumpae,took his granddaughter KanyaphatSunanon, 4, to a house in the village with his wife in the late morning. A funeral was being arranged and while the adults attended to matters several children played together nearby.
In the afternoon, when it was time to go home,Sangharn could not find his granddaughter and a search was made. It was not until 8pm when a villager found the lifeless body of the girl in the back of the car. They frantically tried to revive her but it was too late.
Police sent the body for detailed autopsy. They suspect that the girl was playing with other
children and climbed into the car and fell asleep and suffocated in the blazing heat of the afternoon.


Hyperthermia can quickly become life-threatening if nothing is done properly. Taking measures may include:

  • Stopping the triggering factors, such as a sun stroke. The victim must be moved to a cool place in the shadow.
  • Physical cooling with water and / or ice.
  • Specific therapy, such as medication.
  • Heat Cramps
  • Headache
  • Dizziness, weakness
  • Convulsions
  • Unconsciousness
  • Impaired breathing
  • Death

The pill that measures the core temperature of the body has about the size of an antibiotic capsule. That’s pretty big but inside there are a processor on a microchip and a battery. With a sip of water, you swallow the pill. Shortly after the pill arrives in the stomach, its connection with the ‘reader’, the band that you wear around your waist, starts. It measures the core temperature every 20 seconds using a magnetic field.

After walking for ten minutes and a spicy run by our experienced runner, the temperature rises from 37.4 to 38.6. In this case we are not talking of fever but of hyperthermia since the setting of the body ‘thermostat’ has not change.

Heat pill myTemp
Professor Maria Hopman

Professor Maria Hopman, a physiologist at the Radboud University in Nijmegen, is doing research in this field since 2006. She began to measure the core temperature in walkers because during a four-day walking event,two hikers deceased. Previously she used the CorTemp heat pill company HQ Inc., from America. This heat pill, which NASA has been used since the eighties, can be read only with an expensive device, a ‘reader’ in jargon. The disadvantage is that the core temperature of the person, who carries the pill, can only be measured at a standstill situation, not while walking, running or biking.

The special importance is how high and how fast the temperature rises during exercise. As this is clear measures can be taken in time.


Therefore, Hopmans started developing a heat pill that can measure continuously. She did that with Clemens Neervoort who invented the Champion Chip in the eighties, a household name in the running world.

Using a magnetic ‘tag’, such a chip measures intermediate and end times of runners in a race. Based on this technique, the development of the heat pill ‘myTemp’ was baptized. There is still the need of a computer in reading the data from a small box that is worn with a belt around the waist. In mid-2016 there will be an application for smartphones and smart watches, which the users of the heath pill will be informed of their core temperature while walking or cycling via Bluetooth. Bluetooth sensor is already built into the reader, but the software is not finished yet.

Do you need to drink to prevent dehydration? During a test with 250 runners using CorTemp pill, in a 15 km race, after finishing 15 percent of the runners showed a core temperature above forty degrees. At that rate of temperature a man may be unwell and get arrhythmias. If there are 50,000 runners, 7500 will be overheated at the finish.

CorTemp Applications
Sports Physiology

  • Monitor heat illness on the field, in the water, or on the racetrack
  • Measure core body temperature of players wearing uniforms
  • Compare brief high-intensity workouts to prolonged endurance training
  • Evaluate the effects of extreme environments on the body
  • Compare the productivity of players in hot and cold environments
  • Track changes of core body temperature during exercise and at rest
  • Monitor open-water swimmers who are exposed to cold water for longer period
  • Supervise new players for the first 14 days for full acclimatization to the heat

The new heat pill makes it finally possible to start a thorough investigation of overheating during exercise, the main cause of death among runners, because the fluctuations are monitored continuously. How quickly does the temperature of a runner increase and how long will this go on? And the next step: what is the explanation for that? Is it genetic predisposition or will fatigue plays a role during exercise, and how much do you need to drink to prevent dehydration and thus to keep your heat regulation under control?

All these questions are still waiting for answers.

It is intended that the my-Temp pill will cost only a few euro in the near future. In comparison, the CorTemp pill cost 90 dollar each and the reader 2500 dollar. The low cost of the Temp pill makes a large-scale survey among runners possible.

Most importantly, if my Temp pill in endurance athletes just becomes so ingrained as the heart rate monitor, tragic hyperthermia deaths like the case of Arthur Fonville can be prevented in the future. The Finnish company Polar known, inter alia, of their heart rate monitors, brings in the near future of a heart rate monitor in combination with a temperature gauge on the market, with which the temperature can be measured continuously.