The unspoken limitations of smart rings in exercise tracking

Smart rings have gained popularity as compact and less obtrusive alternatives to smartwatches for tracking various health metrics. They excel in monitoring sleep patterns, stress levels, and overall wellness. However, they have not been as successful in providing accurate data for exercise, a domain where smartwatches still reign supreme.

The science of heart rate measurement

Both smart rings and smartwatches predominantly use a technology called photoplethysmography (PPG) to measure heart rate. In this method, a light source, usually an LED, shines light onto the skin. A sensor then measures the amount of light that is scattered back.

The principle behind this is that blood absorbs light, and every time the heart pumps, more blood flows through the vessels, causing more light to be absorbed. The fluctuations in the returned light are then analyzed to determine the heart rate.

Challenges in high-intensity activities for smart rings

Many smart rings will attempt to track your heart rate during exercise. Examples include the Oura Ring, RingConn and Ultrahuman Ring Air. Some of these even have a dedicated workout mode.

Unfortunately, you will find that this type of data is often inaccurate. Smart rings are simply not cut out for exercise tracking. There are a number of reasons for this.

The issue of increased motion

During high-intensity workouts, the rapid movement of hands or fingers can introduce ‘noise’ into the PPG signal. This noise makes it difficult to accurately measure heart rate. In contrast, smartwatches are less susceptible to such noise as there is less movement on the wrist.

A snug fit can improve the reliability of heart rate measurements. It minimises the ‘noise’ caused by rapid movements and may also reduce the impact of sweat on the PPG signal. However, this is more of a workaround than a solution, as it still doesn’t make smart rings as reliable as smartwatches for exercise tracking.

The complexity of blood flow dynamics

Strenuous exercise alters the dynamics of blood flow in the body. These changes can affect the clarity of the PPG signal, making it challenging for smart rings to provide accurate heart rate data. This is less of an issue for smartwatches.

The interference of perspiration

Sweat can refract light differently, complicating the PPG signal further. While this is a challenge for all wearables using PPG, smartwatches often have additional sensors that can compensate for these inaccuracies.

The impact of sampling rate

Another, little mentioned, factor affecting the performance of smart rings in exercise tracking is the sampling rate. This refers to how often the device collects data.

Due to their smaller form factor, smart rings have limited battery capacity compared to smartwatches. To extend battery life, manufacturers may opt to reduce the sampling rate. This compromises the accuracy of heart rate measurements, especially during high-intensity activities where rapid fluctuations in heart rate occur. In contrast, smartwatches, with their larger batteries, can afford to have higher sampling rates, thereby providing more accurate and timely data.

Final thoughts

A leap forward would be the ability for smart rings to connect to external heart rate monitors. This would allow for more accurate data collection during high-intensity activities, bypassing the limitations of the ring’s built-in sensors. However, no such devices currently exist on the market.

Essential reading: The best smart rings – health tracking from your finger

So if you are purchasing a smart ring, make sure you know why. These types of devices excel at recovery and sleep tracking. Many of them also do a decent job when it comes to steps and basic activity tracking.

However, smart rings are currently not the ideal for tracking strenuous exercise. Until they can either overcome the inherent challenges of monitoring such activities or offer connectivity with external heart rate monitors, smartwatches will remain the go-to choice for comprehensive exercise tracking.

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Marko Maslakovic

Marko founded Gadgets & Wearables in 2014, having worked for more than 15 years in the City of London’s financial district. Since then, he has led the company’s charge to become a leading information source on health and fitness gadgets and wearables.

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