Sports & fitness
Sports and Fitness was one of the first application areas to fully embrace connectivity.
Always-on wellness on the wrist: Polar's Loop and the nRF5340
20
May
2026
2026
Oslo, Norway
By harnessing the dual-core performance and dependable Bluetooth Low Energy (LE) connectivity of Nordic's ultra-low-power SoC, Polar has unlocked the full potential of its screen-free Loop fitness band
As a pioneer in wearable devices, Finnish firm Polar (Polar Electro Oy) has long since set the global standard. Headquartered in Kempele (Finland), Polar has spent the past five decades innovating wearable technology that combines accurate biosensing, science-based insights, and secure digital solutions to help people live happier, healthier lives.
From first-time users to professional athletes, Polar’s portfolio spans sports watches, fitness trackers, and heart rate sensors. Beyond hardware, the company offers web services for planning and analyzing training, activity, and sleep, along with the recently introduced subscription fitness program for adaptive, personalized training plans. Polar's audience extends well beyond elite athletes: recreational enthusiasts, everyday wellness users, businesses across industries, and the academic and research community all rely on the company's science-backed solutions.
“For nearly 50 years, our product philosophy has been deeply rooted in science,” says Ismo Savikoski, Vice President, Research and Development for Polar. “Polar was built on a reputation for dedication to exercise science and precision measurement technology.”
Meet the Polar Loop
The Polar Loop is a screen-free, subscription-free fitness band designed to make healthy habits feel effortless. Lightweight and comfortable, it blends into daily life while silently capturing round-the-clock heart rate, sleep stages and quality, daily steps, recovery and readiness insights, automatic workout detection, and training data. In essence, it is focused on wellness without distractions.
All data syncs automatically to the free Polar Flow companion app, where users can choose when to review insights, rather than being interrupted by endless notifications.
As Savikoski explains, “The innovative design lets users track their health without distractions, complement elegant looks, or pair it effortlessly with a traditional watch.”
While touchscreen fitness trackers are helpful for collecting and cataloging our daily biometrics, the constant notifications and ever-increasing screen time can take a toll on one's focus and well-being. As a result, screen-free wearables that track health have become a category of their own. Still, the challenge is in ensuring that the technology behind them can deliver reliable wireless syncing, multi-day battery life, and continuous, accurate sensing. In short, Polar set out to build a screen-free fitness tracker that feels effortless while staying genuinely powerful.
For the Loop, Polar selected Nordic's nRF5340 System-on-Chip (SoC), supported by the nRF Connect SDK.
…the nRF5340 SoC was viewed as a natural and trustworthy choice for Polar…and integrating with Zephyr has been a very positive experience, and the tools offered by Nordic were extremely helpful in product development
Ismo Savikoski, Vice President, Research and Development, Polar
Powering the Loop
Despite how simple the concept sounds, designing a screen-free fitness band is challenging.
“Our key priorities included selecting a component with dependable Bluetooth LE performance, adequate RAM capacity, required peripherals, and compatibility with the Zephyr operating system,” explains Savikoski.
For the Loop, Polar required a wireless platform capable of delivering dependable Bluetooth LE performance to ensure reliable data synchronization with the Polar Flow app. The solution also needed sufficient RAM to support continuously running, science‑validated biosensing algorithms, along with the right mix of peripherals to interface smoothly with sensors and other on‑board hardware. In addition, full compatibility with the Zephyr operating system was essential to help Polar streamline development and maintain flexibility. Using the Zephyr RTOS (Real‑Time Operating System) with the nRF Connect SDK accelerated iteration and ensured consistent Bluetooth LE behavior across updates.
Finally, because the Loop tracks heart rate, sleep, activity, recovery, and training around the clock, it also requires a component capable of managing simultaneous sensing, data processing, and wireless communication within a wrist-worn device.
Why Nordic
When asked why Polar chose Nordic components for the Loop, Savikoski explains, “….our evaluation concluded that Nordic demonstrated the most robust technical capabilities to meet our requirements.”
The nRF5340 is the world's first wireless SoC with two Arm Cortex-M33 processors. The 128/64 MHz application core – with 1 MB flash, 512 KB RAM, a floating-point unit (FPU), and DSP instructions – gives Polar the headroom and signal-processing performance needed to run continuous biosensing algorithms on-device. The dedicated 64 MHz network core, with its own 256 KB flash and 64 KB RAM, runs the Bluetooth LE controller independently, so radio activity never competes with sensor processing for CPU cycles. This delivers the dependable Bluetooth LE link the Loop needs for reliable syncing with the Polar Flow app.
Equally important, the nRF5340 is fully supported in Zephyr through the nRF Connect SDK, which pairs the Zephyr RTOS with Nordic-proprietary protocol stacks, hundreds of sensor drivers, networking services, security libraries, and a polished VS Code-based IDE. Together, the nRF Connect SDK and Zephyr RTOS shorten time-to-market and simplify maintenance for this implementation.
Nordic Semiconductor is one of the largest contributors to the Zephyr Project, helping shape the RTOS itself while continually optimizing it for Nordic wireless devices. As a result, this gave Polar's engineers a tested platform from day one, allowing the team to focus on algorithmic accuracy and minimalist user experience instead of reinventing low-level firmware.
“Integrating with Zephyr has been a very positive experience, and the tools offered by Nordic were extremely helpful in product development,” says Savikoski.
Moving forward
The Loop is the latest development in a long history between Polar and Nordic Semiconductor. With a shared commitment to scalable, reliable wireless solutions built on Bluetooth LE and solid developer tools like the nRF Connect SDK, this relationship will continue through collaborative projects and future products.
“Polar’s decision to utilize the nRF5340 System-on-Chip was based on a long and positive history with Nordic. Over the years, this relationship has established a foundation of trust and reliability,” concludes Savikoski. “Based on our positive experience with reliability and support, we plan to use Nordic in future products and confidently recommend them to other manufacturers.”
