Chest straps are commonly used for heart rate monitors and the CORE sensor. However, some women find these chest straps uncomfortable or even painful. Thankfully, a number of alternatives allow the use of CORE without a chest strap:
Attach the CORE sensor to the bra band on the side or the back of the body. The black plastic clip that helps secure the sensor may or may not be needed, depending on the width and the material of the bra band.
Wear the CORE sensor on your arm using an arm strap. Please note that accuracy can be lower than when CORE is positioned on the torso.
For sports usage, CORE needs data from a heart rate monitor for its algorithm to deliver the most accurate core body temperature. This heart rate data can come from a number of sources:
A traditional heart rate monitor that uses electrocardiography (ECG) sensors. This provides the most accurate data and is typically worn on a separate strap. However, we know a number of women who have sewn small sleeves on the front band of their sports bras to house the monitor. This allows full functioning of the monitor without the discomfort of a separate chest strap.
A PPG (photoplethysmography) heart rate monitor integrated into a smart watch. These monitors use light pulses to measure heart rate and are not as accurate as the ECG monitors. The CORE sensor will work with them, but the accuracy of temperature measurements may decline.
A PPG heart rate monitor worn on an arm band. While still not as accurate as an ECG sensor, the arm placement delivers much more accurate data than the wrist sensor.
The CORE sensor can also be worn outside of sports activity without a heart rate monitor to continually track basal body temperature. Basal temperature can help predict fertility and provide an early indicator of pregnancy.