Cycling has recently become fertile ground for all types of scientific applications resulting in gadgets. One of these that has recently carved out its own space is the body temperature sensor. And here we deal with what was first proposed to the general public with a mature product: the CORE body temperature sensor.
This sensor is used by numerous professionals in training and racing. As regards the use of these athletes during racing, the use of this sensor responds to a very specific need, namely that of monitoring body temperature since if this is too high there is a drop in power expressed on the pedals .
The correlation between body temperature and drop in power has been studied and proven and is quite precise, i.e. for an increase of 1° in body temperature there is a drop until 5% expressible power and up to 16% reduction in V02max. It goes without saying that for a running pro (who however also uses sensors to swallow, to have a more precise measurement) having this data at hand, also obtained over months of use of the sensor in various conditions, is useful for implementing strategies for cool the core of your reactor, thanks to cold drinks provided by the flagship for example, or with the well-known vests with pockets for ice before a time trial. Given that this is not generally feasible for amateurs (but you never know…) what is a sensor of this kind actually used for?
Beyond the curiosities, it must be said right from the start that it is an expensive product, dedicated to very advanced amateurs, who take care of every single aspect of their preparation. So those who love “bread and salami” cycling can move on immediately. In particular, the CORE sensor is useful for those who include sessions in their training routine Heat, that is, they try to artificially raise the temperature of their “core”, or the internal part of the body. This type of training is not only used to create an adaptation to the hot and/or humid climate (in case one has to suddenly move from one climate to a very different one for some reason), but is used to make real physiological changes, such as increasing the rate of sweating to dissipate heat from the body, reducing the concentration of electrolytes in sweat, increasing the volume of blood plasma to provide nutrients and help the body cool, reducing resting body temperature and reducing of heart rate. In particular, the increase in blood plasma leads to an increase in blood volume, and this would lead to greater efficiency in cooling the inside of the body and therefore minimizing the loss of power in the heat.
To do this, there are various “protocols” ranging from dressing in winter clothes while doing the rollers, without a fan and with the heating “full”, up to doing the rollers in the bathroom after having taken a hot shower, with the environment saturated of humidity. Returning to the sensor, this is used to monitor the temperature during these training sessions, both to avoid exaggerating (with unpleasant consequences in theory) and because to do things precisely and correctly the cyclist needs a certain level to obtain these physiological adaptations of exposure to heat for certain periods of time.
Having made this long but necessary premise, the CORE sensor looks like a small square (15g in weight) of white plastic which must be installed on the heart rate monitor, the latter necessary for its operation. Or attached to the body with the supplied stickers. The sensor has a small charging port, which must be done with the supplied cable. The charging time is quite slow considering the size of the object, about 4 hours from fully discharged to fully charged. The duration is given as approximately 6 days of use, but it clearly depends on how much you use it.
The CORE sensor is not a simple thermometer, but is based on a Seebeck sensor. For those interested This is the CORE supplier link. The sensor itself is only part of the package, as the CORE app is fundamental and is necessary for reading the data. Once downloaded and also connected to the heart rate monitor and sensor (via ANT+ or BT), on Garmin, Wahoo, Suunto, Hammerhead and Coros you can also install the widget to have the CORE field on a data page and keep an eye on it during an outing/workout.
Once worn, an intermittent green light indicates that the sensor is active and begins to record. From the app you can see the relevant graph, with various data fields, such as skin temperature, caloric stress index (Heat Strain Index), or the progress of the physiological process to cool the body, the temperature zones and the time spent in each of them (cumulatively in hours, days, weeks, months). This data can then also be viewed on popular training software such as TrainingPeaks and Golden Cheetah, to monitor its progress and/or evolution over time and not lose the adaptations obtained.
However, recording data is only the basis of using the CORE sensor. Once everything has been installed correctly you need to establish your own temperature zones, and to do this you need to do a heat ramp testi.e. a test that must be carried out on the rollers, dressed as much as possible and without a fan, in order to reach a high temperature in the shortest possible time.
By monitoring the heart rate, as well as the cadence, regardless of the increase in power, we notice that at a certain point with a constant heart rate the power drops as the internal body temperature increases. Then, after an initial warm-up, slowly increasing the power reaches what CORE calls the “control point”, which is a temperature of 38ºC. At this point the heart rate must be kept stable during the test. As a consequence, the body temperature continues to increase, while it is necessary to regulate the power output to keep the heart rate constant. Inevitably, after a more or less long time, the power will decrease. When the power drops to 80% of the initial one or you are exhausted and unable to continue, the test should be stopped. The heart rate will obviously drop instantly, while the body temperature will not, as the cooling takes a time that varies from subject to subject. In this way, the critical temperature is identified, the one in which power drops with a stable heart rate and consequently the body temperature zones for training are identified, which are therefore subjective.
The ideal area forHeat Training it is the high 3/low 4 zone, in which most of the training time must be spent to have the desired physiological adaptations. I will not go into the merits of what the ideal training strategies are, such as the frequency and duration of Heat Training sessions, because these are subjective and should probably be discussed with coaches trained to prescribe them.
In any case, this is the theory and practice behind the use of a sensor like the CORE. Clearly the effectiveness or otherwise of this sensor is linked to the performance of the relevant training sessions. Workouts that I personally find terrible to do: dressed heavily, on rollers, without a fan, the sensations are anything but pleasant and you need great motivation to do them. In any case, for those who aim to improve their performance at any cost, this sensor can provide a plethora of data to analyze, but above all to make training sessions repeatable with precision. Out of curiosity I tried to monitor my temperature during one of these sessions on the rollers with an “ear” thermometer, the kind that measures the ear temperature, and even when I was about to melt the temperature never rose even to 37°, at faced with a temperature measured by the sensor of over 38°. Clearly I can’t tell if this means the sensor is imprecise or truly precise. There are those who have done serious studies on the matter, always for those interested.
Getting to the point, it is difficult to recommend a product of this type or not, as it is aimed at a possible clientele who is probably already very oriented towards instruments of this type, who does not mind expenses, given that the price of the sensor is 270euand who above all must have the desire and motivation to train according to the Heat protocols, given that, otherwise, the sensor itself is not of great use if used during “traditional” training or laps.
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