UP3 & UP4: The first truly wearable heart rate monitors

When it comes to heart rate monitors, many people are stuck between a rock and a hard place. Existing products on the market may offer a variety of features, but it’s all at the cost of wearability. Big, clunky form factors, short battery life, a manual heart rate capturing process and a lack of actionable insights are all consistent complaints. When developing UP3 and UP4, we set out to solve this problem and accomplish three simple things:

  • Create the most comfortable heart rate monitor in a form factor that users will actually wear to bed
  • Enable passive heart rate capture, with no need to change modes to capture heart rate
  • Make heart rate a relevant measure of health. We want to help users interpret their data, enabling them to make healthy choices and maintain long-term heart health

There are several ways to measure heart rate, ranging from standard stethoscopes to ECG monitors. The most common approach in the wearable category is using optical sensors, which shine light through the skin to measure heart rate. But optical sensors are power hungry and need a relatively large surface area to capture a good signal. What’s the result? Products with low battery life and uncomfortably large form factors. Right off the bat, we knew this was not the technology to meet our goals. We set out to achieve the smallest form factor possible, with up to 7 days of battery life.

Bioimpedance: Reimagine the measuring of heart rate 

Given the limitations of existing technology, our first challenge was to reimagine a new way of measuring heart rate. To truly deliver a wearable design we created our own sensor platform using cutting-edge bioimpedance technology. This is the foundation on which we built UP3 and UP4. Bioimpedance measures the resistance of body tissue to tiny electric current to enable the capture of a wide range of physiological signals including your heart rate. If you’ve ever measured your body composition such as fat content, this is very similar. Our choice to use bioimpedance technogy sets us apart in three key ways:

  • Battery life. Because bioimpedance requires significantly less power compared to optical sensors for same level of accuracy, we can deliver a smaller form factor and longer battery life
  • Physiological signals. A single platform utilizing bioimpedance sensors captures a wide range of signals: heart rate, respiration rate and galvanic skin response (commonly known as skin conductance)
  • Updatable technology. Given the versatility of the sensor platform, we are able to (and we will) unlock exciting new features with a simple, free, over-the-air firmware updates in the coming months.



Empowering users to take charge of their heart health
You hear a lot about heart rate these days. But a major challenge is making heart rate relevant to you. What is healthy? What is not? How can I affect that rate? Heart rate measures the amount of beats per minute, with blood pumping throughout the body upon each beat. But this is where it gets tricky – heart rate changes a lot throughout the day. 91bpm after a cup of coffee may not be high. But if you just woke up? 91bpm is quite high. Without context, it is very easy to misinterpret heart rate.

At Jawbone, we categorize heart rate into three buckets: heart rate during activity, resting heart rate and heart rate throughout the day.

  • Heart Rate during activity. Benefits of heart rate monitoring during workouts are well understood, and is primarily done amongst a small yet growing number of athletes to monitor their cardiac zones and recovery times. While helpful, it only represents a very small part of the heart health story.
  • Resting Heart Rate.  This is measured moments after you wake up, and before external influences such as coffee, stress and movement. Resting heart rate is a key indicator of the following:
    • Long Term Heart Health – A slower resting heart rate indicates a stronger and healthier heart where as a faster resting heart rate indicates potential risk of heart disease
    • Energy – A slower resting heart rate indicates more enduring energy
    • Metabolic Efficiency – A lowering of resting heart rate over a 4 week period indicates an increase in metabolic efficiency
  • Heart rate throughout the day: Various factors impact variations in heart rate throughout the day, and understanding these influencers and actively managing them is critical. A few examples are:
    • Food– Good nutrition keeps your arteries clear. And clearer the arteries, easier it is for your blood to flow through your body.
    • Hydration – Keeps your blood at just the right amount of viscosity to easily flow through your body.
    • Stress & Anxiety -Stress and anxiety burden your cardiovascular system and increase your heart rate.
    • Coffee – Consumption could cause an acute increase in your cardiovascular index

Our purpose is to help you develop healthy habits for long-term heart health. Heart rate during workout and heart rate throughout the day are easily influenced by external factors. Resting heart rate on the other hand is devoid of such external influences. And because managing resting heart rate is the single most important thing you can do to improve your cardiac health, that’s what we’ve focused on initially for UP3 and UP4. So out of the box, we will deliver resting heart rate as a measure of heart health. But very soon, we will unlock “passive” and “on-demand” heart rate – both updates that will come over the air – allowing you to see your heart rate at any time throughout the day.

It’s about more than heart rate

The human body is a complex system, and several physiological signals contribute to different stages of our bio-state. At Jawbone, we don’t think of signals in isolation. We think of it as a fabric of signals coming together, increasing the accuracy of our system. In this case, heart rate also plays a critical role in both sleep tracking and measuring caloric burn. We analyze your heart rate data captured by UP3 and UP4 to track and determine your REM and Deep sleep stages.

We also use heart rate coupled with our unique workout classification algorithms to calculate your caloric burn.

heart rate blog running

And our Smart Coach system will deliver personalized insights and guidance to coach you towards achieving optimal heart health. Because ultimately, our goal is to help you manage your cardiac health. With UP3 and UP4, we have designed truly wearable products that seamlessly integrate in your lifestyle and—most importantlyyou will actually wear 24/7.

For a deeper dive into how resting heart rate is the best measure of heart health, check out our latest blog post on finding meaning in resting heart rate.


UP3 by Jawbone

About The Author

Jayanth Chakravarthy

At Jawbone, Jayanth is focused on unlocking exciting new experiences deeply rooted in sensors, hardware, and wearables. Previously, he was @ Cisco designing telepresence, @ Abbott inventing heart implants and @ D-Rev developing affordable medical devices for poor. Ping him (@cr_jayanth) if you want to chat about wearables.