Arm Strap

Regular price 13.95 CHF

CORE can be worn on the arm

Many people find the convenience of wearing CORE on the arm strap (compared to a chest strap) an acceptable trade-off.

Please note, when CORE is worn on the arm, the accuracy of the core body temperature measurements is lower as the thermoregulation of the arm can different from the torso/chest. 

When it is more convenient to use an arm strap and the level of accuracy from wearing CORE on the torso is not needed, the arm strap is made of a comfortable elastic material, perforated for improved breathability and with velcro for convenience and adjustability. 

The black arm strap is 'one size fits all' (as it can be adjusted to fit) and is designed to remain comfortable for sports and all-day use.

This includes ONLY the arm strap and the CORE device is not included and is shown in the photos for demonstration. 

**Please note that prices shown for customers from outside Switzerland and the EU exclude VAT or relevant import duties** 

Alternatively you can purchase through one of our official partners

Free shipping to the US, UK, Canada,
Mexico, and Europe on orders over CHF 249

Seamless connection with your training and racing tech

Product Description

Product Description

Train and perform at your absolute best with the most accurate non-invasive wearable device for continuous core body temperature monitoring.

The sensor allows you to easily see how much your core temperature rises with effort, so you can train your body to adapt to internal and external heat.  You can also design personalized cooling protocols crucial to helping you sustain your power and pace on race day.  With CORE, you’ll be ready to perform at your absolute best in any conditions.

What’s in the box

CORE Sensor

USB magnetic charging cable

6 medical-grade adhesive patches

Clips to secure the sensor to HR monitor strap

Guide to setting up the CORE iOS / Android App

Medical use & safety

Medical use - The CORE sensor is not medCE or FDA certified and must not be used for medical nor diagnostic purposes. The CORE sensor can be sold as a clinical thermometer for use in the United States. Learn more here. 

Safety Warning - This product can expose you to chemicals including Nickel and Nickel compounds, which are known to the State of California to cause cancer, and Bisphenol A (BPA), which are known to the State of California to cause birth defects or other reproductive harm. For more information, go to


Explore the features of the CORE sensor

Real-time, accurate core body temperature monitoring

Access a new dimension of performance with crucial data you’ve never had until now.

ANT+ and Bluetooth compatibility with automatic data transmission

With CORE, you don’t have to learn a new device: the data already displays on your favorite sports tech.

Data storage in the Core cloud web app for analysis of trends over time

See how your core body temperature correlates with performance metrics so you can learn and adapt.

Accuracy backed and validated by clinical, lab and field tests

Elite athletes and coaches trust CORE to deliver key insights for training and racing. You can, too.

Technical Specifications

Technical Details

The innovative sensor technology is integrated into the compact and waterproof unit that can be comfortably worn during sports activities, at work, or all day long.

Compact Size: 40 mm width x 50 mm height x 8.35 mm depth

Weight: 12 grams

Provides medical-grade accuracy (based on ISO_80601-2-56, Mean Absolute Deviation of 0.21 °C)

Non-invasive (worn on the chest)

Not impacted by environment thermal influences

Battery life: 6 days continuous transmission 
time (up to 6 weeks with sleep mode)

Rechargeable lithium-polymer battery (USB charging cable supplied)

In Addition

Waterproof up to 1.5m (IPX7)

Bluetooth BLE & ANT+ Connectivity

Connects with: CORE iOS and Android App, WatchOS, Wear OS, Garmin ConnectIQ watches and bike computers, Wahoo bike computers, COROS watches, SUUNTO watches and more..


Frequently Asked Questions

Your muscles generate heat when they’re working hard.  Generate enough heat, and your core body temperature will rise. Your body will try to cool itself by diverting blood from the muscles to the skin where it’s cooled by sweat evaporation, which leads to decreased speed and performance. But you can minimize this effect in two ways. First, by monitoring your core temperature, you can make strategic cooling and pacing decisions during training and racing, helping you stay cool and maximize your performance. Second, you can use heat training to help you adapt to higher internal body temperatures come race day. This can lead to radically better performance - in one study, cyclists improved their speed by 8% in a time trial, after heat training for just 10 days prior to the race.*

The CORE sensor measures both core body temperature and skin temperature. Those metrics are displayed live in the CORE app and on compatible sports tech devices. The app and some Garmin devices also display the real-time Heat Strain Index, which shows the amount of heat stress the body is experiencing.

When you’re heat training, use CORE data to keep your core temperature within your heat training zone. During racing, CORE data can tell you when to use cooling strategies and when to reduce power/pace so that you don’t overheat.

Maximum benefits are gained by doing 10–12 sessions within 2–6 weeks. Most athletes will experience the majority of gains after 4–5 sessions and benefits can be maintained through the season with just 2–3 sessions per week. Each session should involve a continuous effort of 45–60 minutes within the heat training zone. This is the recommended course of training, though even less frequent heat training has been shown to be effective at improving performance come race day.

Heat training adapts the body to perform more efficiently at elevated core temperatures. It also builds blood plasma and hemoglobin, which increases performance (increased power at both lactate threshold and VO2max) in both cool and hot conditions alike.

The impact of heat on human performance has been thoroughly studied and understood. It’s well documented by sports scientists that heat training increases the body’s ability to cope with higher heat, to cool itself more efficiently, and to perform in both cool and hot conditions. Physiological changes include increased blood plasma and hemoglobin, increased sweat rate, and earlier onset of sweating. Learn more from this selection of relevant research papers.

The CORE sensor measures thermal energy transfer between the body and the environment. An AI-powered algorithm uses this data to calculate core body temperature with medical-grade accuracy. Extensive testing has validated the accuracy of CORE data against internal body temperature data collected with more invasive methods, like ingested electronic pills. This means that athletes can reliably use CORE data to understand what is happening inside their body, with a completely non-invasive wearable that’s the first of its kind. More information on Core’s accuracy can be found in the article Scientific Data Validating CORE’s Accuracy.

The CORE app is available on both iOS and Android platforms. The sensor is compatible with most watches and cycling computers from Garmin, as well as a selection of devices from COROS, Suunto, Wahoo, and Hammerhead. Functionality with Apple and wearOS watches is still limited, but improved. Training software with full compatibility include Today’s Plan,, and Golden Cheetah. The premium version of Training Peaks is also compatible. Please see the CORE Sensor Compatibility page for full details - we are continuously updating our list of compatible platforms and devices

To get the most precise data during sports activity, we highly recommend pairing with a heart rate monitor. Heart rate helps the sensor accurately convert measured heat flux into core body temperature. During everyday activity (ie. non-sports), core temperature data is accurate both with and without a heart rate monitor.

Get CORE Accessories

From spare charging cables to indoor heat training suits.