Part I - why is everyone measuring body temperature?
Until recently, determining your internal temperature in real time required swallowing a thermetric pill then using a gadget to track your temperature as it worked its way through your body. But this has been made a thing of the past with the introduction of Core's new sensor which monitors your core body temperature by tracking thermal energy transfer (not just from an equation derived from your skin temperature) for incredibly accurate readings.
This is a graph of how accurate the CORE device is as compared to a thermetric pill
The unit itself is pretty simple, it pairs with most modern blue tooth devices to give real time data so you can make more informed choices during your training or racing. You just have to attach it to your heart rate monitor strap or stick it on with a special waterproof sticker then use its propriatary app to analyse the data or through your the platform that your device uploads to (ie Garmin Connect)
Before the delve in to how can monitoring your core body temperature be used to make you a better athlete, lets back up a little and look at...
What is Heat Training?
"Heat Training" describes heat related athletic training which is incorporated into an established training program. To get started with heat training there is usually an initial Heat Training block to trigger adaptation and subsequently followed by regular heat training workouts to maintain its benefits. The idea is not to complete heat training for every workout, but to adapt and maintain as best you can.
Heat Training can be focussed on Heat Acclimation aimed at improve performance in specific hot environments (ie in the lead up to a big race that you know will be hot ) or It can also with the intention of improving performance in any weather due to the body adaption to the heat (more on this later)
Your "Heat Training Zone" is the core body temperature range which is optimal for heat training Workouts. If you are training too low, you will not effectively get the physiological benefits and if you are training too hot, it can be counter-productive and dangerous.
Your heat training zone is usually around 38.5C but it can be more accurately determined with a Heat Ramp Test.
So what triggered all the recent attention to monitoring body temperature?
Actively monitoring your Core body temperature has recently been brought to the fore due to a study by physiologist Dr Chris Minson who was training an athlete for the 2008 Beijing Olympics marathon.
They were preparing with the expectation that it’d be really hot on the day of the marathon, but then Minson had an Oh Crap moment: What if it wasn't actually hot on race day? Would all that heat training actually make performance worse? So they conducted a study (Lorenzo S, Halliwill JR, Sawka MN, Minson CT. Heat acclimation improves exercise performance. J Appl Physiol (1985). 2010 Oct) that concluded that athletes who acclimatised with heat training would still perform better even when during cooler conditions.
What they did was study the impact of heat acclimation on improving exercise performance in both cool and hot environments. They took a group of well trained cyclists and performed tests of maximal aerobic power (V̇o2max), time-trial performance, and lactate threshold, in both cool and hot environments before and after a 10-day heat acclimation program.
I'm going to give these one bullet point each because they came to some pretty incredible conclusions:
- increased V̇o2max by 5% in cool and by 8% in hot conditions.
- improved time-trial performance by 6% in cool and by 8% in hot conditions.
- increased power output at lactate threshold by 5% in cool and by 5% in hot conditions.
- increased plasma volume and maximal cardiac output in both cool and hot conditions.
thats' crazy! how is that possible?
It is pretty well understood that as body temperature rises above approximately 40C, your performance declines as a result of the increased demand on the cardiovascular system for heat dissipation as well as oxygen transportation. In laymans terms means the body diverts blood to the skin and other vital organs to cool them which takes it away from the muscles where it is needed for performance.
However heat training at approximately 38.5C , the heat stress encourages the body to produce more plasma to help with the delivery of the oxygen carrying hemoglobin in the red blood cells to the muscles. With this increase in plasma brings a reduction of hematocrit level as hematocrit is the percentage or plasma to red blood cells which provokes haemoglobin production and increased blood volume. The increased blood means that there is more oxygen being provided to your muscles which corellates to increased power or longer sustainable power output.
This is why there have been comparisons of heat training to the similar benefits of altitude training.
Heat training also helps the body function more efficiently through ‘vascular coordination’ as you’ll start sweating sooner as your body will have adapted to more efficiently keeping your body temperature lower.
Monitoring your core temperature in real time helps athletes understand when they are approaching their upper limits to avoid the possibility of overheating.
The reason why more and more teams and professional athletes are actively monitoring their core temperature is simple... overheating will result in power loss so once the athlete is coming close to overheating they can make an informed choice, do they try to actively cool themselves down by external means like drinking more or unzipping a layer... or do they back off the intensity so they body will not work as hard and not overheat.
After heat training your perception of temperature will also change as you will be accostomed to training in the elevated temperature conditions so you won’t feel as "hot" at a given level of heat. The perception of how hot you are is important as with other training methods, if you have tollerated it during past training sessions you will better understand sort of level of intensity you can sustain at any given heat come race day.
So what teams in the World Tour are wearing CORE?
Well about half the teams in the men’s pro peloton are using it, including Deceuninck-QuickStep, Movistar, Astana-PremierTech and Bora-Hansgrohe have official partnerships with CORE.
In the lead up to the 2020 Tokyo Olympics road race, both gold medalists Anna Kiesenhofer and Richard Carapaz were training with CORE sensors. Anna did heat training at 38.7ºC with a CORE sensor and Richard Carapaz’s CORE unit could be seen when he won gold for Ecuador in a hot and humid race .
Warning: Please take note of the risks of Heat Training and seek guidance from a health professional or an accredited and experienced coach.
Next: Part II - getting started with your device and how to use it to train at heat.