Why measuring Core Body Temperature for Sport Performance Evaluation?
This short note introduces the reader to the use of Core Body Temperature for Sport Performance Evaluation. greenTEG launched in 2019, a venture named CORE (www.corebodytemp.com) specialised in the use of Core Body Temperature monitoring for Sport Performance. Find out more here!
What is Core Body Temperature?
Core body temperature is one of the four primary vital signs of our body. Core body temperature refers to the temperature of the body’s organs.
It fluctuates following physiological processes, such as circadian cycles, menstruation, illness or physical activity.
Therefore, it can allow to gain more insight about the internal or external parameters affecting those natural mechanisms.
Many devices on the market attempt to estimate core body temperature via skin surface temperature. Due to the complexity of thermal regulation and environmental conditions, this estimate does not come close to the accuracy and reliability of greenTEG’s Core Body Temperature Sensor. greenTEG offers the first solution to monitor core body temperature continuously and non-invasively. The sensor can be easily integrated into any wearable device with skin contact.
This short video explains the benefits of monitoring core body temperature in sports. In the following, scientific findings will illustrate the link between core body temperature and sports performance. The ability of monitor core body temperature to help athletes perform better and longer will be exposed.
How Core Body Temperature monitoring can help improving Sport Performance ?
Based on a study by Gonzalez-Alonso et al. (1999), athletes performing in hot environments all fatigued at a core body temperature between 40°C and 41°C, despite different initial body temperatures (Fig. 1). 
Previous studies observed the same results, the only difference being the core body temperature levels at which the subjects fatigued.
This difference is down to the different fitness levels of the participants across the studies.
A high aerobic fitness usually leads to a better heat tolerance. Some trained athletes can perform with core body temperatures exceeding the 41°C mark.
The results mentioned above suggest that there is a certain critical core body temperature at which the performance of an athlete collapses. Another intriguing finding was that the time to fatigue was longer when the initial body temperature of the athlete was lower.
This makes sense when considering that the core body temperature rises linearly with respect to the workload and intensity.
The study concludes that a high core body temperature per se causes fatigue in athletes.
Heat-induced Fatigue: An explanation
A physiological explanation for heat-induced fatigue is offered by Julien Périard .
Firstly, a high core body temperature causes an increased cardiovascular strain due to the additional skin blood flow required to dissipate the excessive heat.
The subsequent heart rate increase can lead to the maximal heart rate being reached at lower workloads.
Secondly, reaching this critical core body temperature leads to a reduction in central neural drive to the muscles. In other words, your brain stops you performing to avoid further overheating.
Monitoring to avoid performance break-down
It becomes evident, that monitoring your core body temperature during performances, especially in the heat, has undeniable advantages.
The ability to perform just under this critical core body temperature and therefore avoid a performance breakdown is vital.
Furthermore, monitoring the core body temperature during an acclimatization program can help athletes keep their initial core body temperature low and hence prolong their time to fatigue.
What are the advantages of CORE Body Temperature monitor for Sport Performance Evaluation ?
- Direct connection via ANT+ to a range of sporting hardware including Garmin, Wahoo and COROS computers and watches (Garmin and iWatch).
- Real-time core body temperature data can be viewed and on devices that record sports activities.
- Coaching & Training made easy: the FIT file data can easily be accessed by popular training software including Today’s Plan, TrainingPeaks and Golden Cheetah.
- greenTEG also provides third party OEM integration with its CALERA(R) Technology.
- Public Statement regarding the accuracy claims of greenTEG’s CORE Body Temperature Monitor.
Are you interested in using CORE for your own training ?
Check our practical to learn more about how to use CORE body temperature monitor available here!
For which Sport, Core Body Temperature monitoring can be used?
The following Sports activities are suited to employ Core Body Temperature monitoring to analyze and optimize performances:
The following Sports activities are still currently being evaluated for their potential as Use Case for Core body temperature monitoring. Contact us to discover more!
 González-Alonso J. et al.(1999): “Influence of body temperature on the development of fatigue during prolonged exercise in the heat”, Journal of Applied Physiology Vol. 86 (3). Full document available here.
 Périard J. (1999): “Prolonged exercise in heat”, Sports Science. Full document available here.
 Périard J.: Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports.
 Racinais S.: Core temperature up to 41.5ºC during the UCI Road Cycling World Championships in the heat;