Live core temperature measurement during exercise
During a ThermoClinic you measure your own core temperature live with a CORE sensor while you exercise. You see what exertion does to your body, and you learn how to recognise, treat and prevent heat illness.
Max 15 participants per clinic. Also on location for running groups and clubs.
The clinic
Not a dry presentation, but hands-on experience. You combine the latest science and lessons from elite sport with measurements of your own body, and go home with insights you can apply straight away.
How does your body regulate its temperature? Why do you perform worse in the heat? You learn to recognise, treat and prevent heat illness, with insights from research and elite sport.
You're given a CORE sensor and a sports watch for a run at your own pace. You see live how quickly your core temperature climbs towards 39°C.
We look at your temperature curve together. You see how your temperature lags behind your heart rate and even keeps rising after the run. That's how you translate the theory to your own races.
What you learn
What happens in your body during exertion and heat? Knowledge from scientific research, including the Department of Physiology at Radboudumc.
Practical cooling strategies from elite sport: arrive well prepared at the start, slow the rise of your body temperature and recover faster.
Recognise the signs of heat exhaustion and heatstroke, in yourself and in your fellow runners, and know what to do immediately. Acting fast can save lives.
Match your pace, ambition and drinking to the conditions. Heat illness can occur from a feels-like temperature of just 15°C.
Who it's for
Heatstroke often strikes precisely the fit, well-trained and motivated athletes. Awareness matters for every runner.
Sign up for a scheduled clinic. Ideal preparation for summer races such as the Dam tot Damloop or an autumn marathon.
€45 per participantFrom five participants we come to your club. Location, date and time by arrangement, including weekdays during the day or in the evening.
Group rate on requestPrepare your participants for hot editions and strengthen your safety policy. See also hittebewustsporten.nl for advice for organisations.
Tailored, by arrangementThe instructors
Every ThermoClinic is led by a regular team of instructors. Meet them here.
Ever since Arthur Fonville (24) died from heat stroke during the Dam tot Damloop in 2014, his father Joost has been dedicating himself to helping athletes. He aims to raise awareness about the body’s thermoregulation and the risks of overheating. He also teaches athletes how to recognize symptoms and what to do if things go wrong.
Daniëlle has been a physiotherapist for runners since 2004 and holds a master's in sports physiotherapy. She is a keen runner herself. A surprising number of her patients have experienced overheating and want information and practical guidance. Her thesis on this topic introduced her to Joost. In the ThermoClinics, she now shares her expertise as a physiotherapist and runner.
As a professional long-distance runner, Jasmijn has competed in many hot races and gained experience with heat acclimatisation and cooling strategies. While studying Biomedical Sciences at Radboud University, she specialised in thermoregulation in athletes, which brought her into contact with Joost. In the ThermoClinics, she combines practical experience with scientific knowledge so athletes can perform safely in the heat.
Jippe competed nationally in athletics for years and now does triathlon. As a biomedical scientist, he wrote his master's thesis on thermoregulation during and after exercise. He currently studies medicine. In the ThermoClinics, he combines his experience as an athlete with scientific and medical knowledge, so athletes, coaches and professionals know how to exercise in a heat-aware way.
Kjeld is a master's student in medicine at Erasmus University and a dedicated triathlete. After suffering heatstroke during his first marathon, he delved into heat and hydration. For his bachelor's research, he studied runners' risk behaviour at the Rotterdam Marathon. He qualified for the Ironman World Championship in Kona. In the ThermoClinics, he shares his knowledge and personal experience.
Scheduled clinics
The dates come live from our calendar. Don't see your date? Email us and we'll plan one by arrangement, including weekdays during the day or in the evening.
Maximum 15 participants per clinic. Once full, it's full.
Why this exists
In 2014 Arthur Fonville, 24, died of heatstroke at the finish of the Dam tot Damloop. His father Joost then started ThermoClinics with one goal: to prevent others from going through this.
In 2025 Joost co-founded the Heat-Aware Sports Foundation (Stichting Hittebewust Sporten). Its goal: to make athletes, organisers and healthcare professionals aware of the risks of exercising in the heat. Every year in the Netherlands, athletes end up in hospital with heat illness, while with good preparation this is almost always preventable. ThermoClinics is independent and supported by the foundation.
“I knew hot weather was tough. But only when I watched my own core temperature climb towards 39 degrees did I really get it.”
ThermoClinic participant
Done a clinic yourself? Share your experience
Practical
Don't see your preferred date, or coming as a group? Email info@thermoclinics.nl and we'll arrange a location and time together.
Go to the sign-up formFree web app
After the clinic you'll want to keep exploring your own data at home. The FIT File Viewer opens the FIT file from your sports watch and shows your core temperature, skin temperature, heart rate, pace and elevation together in one chart.
100% in your browser. Your FIT files never leave your device.
Tested with Garmin watches. FIT files from Coros watches do not show CORE temperature values, because Coros and/or CORE have not published which fields in the FIT file hold these values.
Open your own FIT file and analyse your run, just like during the clinic.
Open the FIT File Viewer