CORE body temp sensor

Anyone else order one of these?

They’re shipping once the tour de france is over.

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I have one on order, but more from a professional curiousity side…we manufacture medical thermometers so I want to check this out.

I’m a little dubious as to their claims…extrapolating core temp from surface measurements has never been very accurate. We’ll see…

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I have one. I’m interested to review the data over longer / hotter rides indoors and out. The ConnectIQ data field is really handy for display/recording. Is the data useful though…? I really don’t know at this point.


I’m interested in it not just for crazy hot days where my power is garbage and my HR is high, but also on extended climbs where I suffer, I think because at 7mph there is very little airflow. It will be interesting to see the numbers.

Shane how are you validating the accuracy? How you cross referencing against another thermometer?

I’m not. I draw the line with shoving things into dark places verify anything for this sport… or ingesting some kind of pill. I’m interested to see if there is any difference in core body temp observed and if that data can be used in a meaningful way. I have my doubts.

Maybe it’s technology that could be incorporated directly into HR straps in the future.


No sense of adventure. :stuck_out_tongue_winking_eye::stuck_out_tongue_winking_eye::stuck_out_tongue_winking_eye:

Thanks for the feedback…agreed that there is some question about actionable data from this.


yesterday before sleeping i seen this thread, i am very interest in this topic, is it possible to merge with this thread:

So my pre-ordered unit arrived this week. Will be starting to play around with it this weekend.

I remain somewhat skeptical about being able to measure actual “core” body temp via an on-skin unit, but we’ll see.

Also skeptical about whether it has any useful function during an activity…

I’ve used it on three rides so far, and even if there is no actionable data, I consider it an interesting look inside the machine. What I am seeing so far is that it takes a VERY long time for core temp to increase, and also decrease. Yesterday in Chicago it was finally a little warm at 73-75 degrees, but I wore the same exact clothes I wore for a ride at 50 degrees (LS jersey and a noninsulated but thicker vest). Same route, tried to do same intensity, and the core temp max for ride at 50 was 100.4, and at 75 degrees it was 101.1

See two screenshots from Garmin Connect. One is of the ride, and then the other is me just sitting down still for 30 minutes in the same kit outside on my porch having a NA beer while waiting to see how long it took for the core temp to come down. I can’t get Garmin Connect (web) to show in fahrenheit, sorry.

A few things:

Update the firmware using the iOS app. It’s easy in settings, automatically checks.

Put the sensor on a good 10 minutes or so before riding. It takes no time at all to get the skin temp, but core temp takes time to get the first measurement. On my Garmin 1030, it doesn’t wait around long to receive the core temp number before giving up. Turn your Garmin on only after you get a core temp reading in the iOS app. If you don’t you will have to reboot your garmin.

History in the iOS app can be reset, if you get a weird reading (like when you take it off and rinse it) and your Y axis will go nuts making the history tab absolutely useless. To erase the history, swipe the magnetic charger back and forth on the back side of the core (part that touches your skin) and the core will light up green to indicate you’ve erased the history.

Pairing it with a HRM will yield quicker results, according to one of the core team members. You’re probably already doing that.

Don’t bother wearing it overnight for some sort of insight. It’s a really boring result.

Interested to hear what you think when you get a ride in.

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Based on the review below, neither of those observations seem correct.

“During muscular exercise, core temperature initially increases rapidly and subsequently increases at a reduced rate”

“During muscular exercise, the magnitude of core temperature elevation is largely independent of the environmental condition

In particular, it seems that only above about 75-80 degrees F is core temperature elevated compared to cooler conditions.

So no diurnal variation?

I wonder if it could it be used to detect ovulation for those using the rhythm method of birth control?

Kinda doubt it…our basal therms go to the hundredths for additional specificity.

At this point, it appears the CORE uses skin temp as a surrogate for core temp (base don an algorithm). I don’t think you could rely on that for ovulation measurements.

This is just my initial read of it, so I could be wrong…

Very little variation

And I seriously doubt most TR users need to worry about birth control.

Well, my observations are only what the device is showing. But a fast rise in temp (accumulation of heat) doesn’t seem to make sense to me (a non scientist) unless the body intended to do it, which makes no sense because it works so hard to keep itself cool while exercising. Guess it depends on what quickly means.

I found the first article by googling “time course of changes in core temperature during exercise”. It was the first study that popped up. The third one includes this diagram.

The X axis isn’t labeled, but the text says “heat balance is achieved within 30 – 45 min of steady-state exercise, with the greatest rate of body heat storage, and therefore increase in core temperature, occurring in the first 15–20 min (46) (Fig. 1).” Your CORE data seems to lag about 20-30 minutes behind that expected time course.

In any case, I don’t think that the body “means” for core temperature to go up during exercise - it just seems that it can’t fully prevent it, because based on the figure at least it takes a while before heat dissipation increases enough to match heat production.

CORE uses a thermal energy transfer sensor which we make in Zurich. It is not a ’skin temperature’ measurement (although we can also record this as well).

There are details about this sensor works on our website here: The technology behind CORE

It is nice to see the graphics and a suggestion is to do some hill climbs and map the core body temperature against the elevation.

The ’speed’ of core body temperature metrics is a slow moving metric, especially when you consider that power and HR can change rapidly. Core body temperature is tracked in real-time with live data and when you analyse the data you will see that the human body continually tries to regulate (e.g. with sweat) and aide cooling. Many factors impact the core body temperature of a person and our data from over 5 years of R&D shows that ‘effort’ intrinsically impacts core body temperature.

For example, we can see the rider data collected during the Tour de France and the Giro de Italia that show when cycling uphill, the rider effort increases and core body temperature increases. When the rider effort drops the core body temperature follows. A rider can cycle with high intensity downhill which would keep their core body temperature high though the wind and cooling effect would make it less like that they cross their threshold.

Regarding ‘actionable data’, this is a good question. Athletes will use core body temperature data for training (heat-block-training) which stresses/conditions the body for improved competitive performance. While racing, there can be different approaches to interpret the data. For example, athletes participating in extreme endurance events can use core body temperature data as a guide (like FTP or HR) and manage their temperature so they don’t exceed their threshold which would put them at risk of heat-stress and degraded performance/recovery. In a stage race, a lead-out rider in a group can use the data as a guide and switch turns in good time. Riders can also ‘actively cool’ which could be reducing power, pouring water over their body or opening up the jersey to increase wind-flow.

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Those of you that have been using this device - how are you getting on @GPLama @chiefhiawatha

I’m waiting for mine to arrive from Switzerland (@GPLama - you’re in Oz too aren’t you, what sort of shipping time was it for you?).

I’m pretty excited about using it, particularly over here in the summer heat. I expect I’ll be using it retrospectively in the first instance but I see there is a developing area of using it to guide training which looks cool.