WHOOP could use its PowerPack to estimate core body temperature

WHOOP may have found another job for the little battery pack you slide over its tracker. Instead of just charging the device, it could help WHOOP work out your core body temperature, something its current bands don’t offer.

The idea comes from a US patent application published on October 22, 2026, titled “Core Body Temperature”. It sounds a bit strange at first, but there is some clever thinking behind it. And no – it doesn’t involve wearing the charger all day.

Your charger plays a central role

Measuring temperature at your wrist is easy enough, many wearables do that. But figuring out what is happening deeper inside your body is much harder.

Skin temperature changes with the room, your clothing, sweat and all sorts of other things. So WHOOP is looking at how heat moves through the skin and the wearable, rather than relying on a skin temperature reading alone.

WHOOP’s patent describes a system using multiple temperature sensors. One would measure temperature near the skin, while another would sit inside the removable PowerPack. Additional sensors could measure temperatures at other points in the device.

During charging, the PowerPack would provide a controlled amount of heat. By measuring how temperatures change, WHOOP could build a better picture of the thermal properties of the wearable and the body underneath it.

That’s the real trick here. The charger isn’t somehow measuring the temperature inside your body directly; it’s helping WHOOP work out how to interpret the temperatures its sensors can actually measure. The system would then combine skin temperature, estimated heat flow and the calibrated thermal model to estimate core body temperature.

You wouldn’t need to keep the charger attached

Most people only put the PowerPack on when the battery needs topping up. And the filing does account for that. It specifically describes gathering useful temperature information during ordinary charging, without asking the wearer to do anything special.

The PowerPack could be used for calibration, with the resulting parameters stored to support later core-temperature estimates. In other words, charging could double as an opportunity for WHOOP to learn more about the heat passing through the device.

Our takeaway

WHOOP currently reports skin temperature, usually in the context of overnight trends and your personal baseline. A reliable core-temperature estimate could add another piece of information about the body’s daily temperature rhythm.

Other wearables are already experimenting with this. I recently tested the Speediance Strap Pro, which also estimates core body temperature, although it uses a different combination of heat-flow sensing, skin temperature and modelling.

The obvious use is exercise, particularly during longer sessions and training in hot conditions. Core temperature could give WHOOP another way to understand physiological strain beyond heart rate, HRV and the other signals it already uses.

There are possible uses outside exercise as well. Core temperature changes throughout the day and is linked with circadian rhythms, so it could potentially add another layer to sleep and recovery tracking.