Heart rate monitors have become very common in wearables recently, as consumers are coming to expect more from their wearable devices. Counting steps, calories and general activity levels is no longer enough for most wearables, particularly in devices like smart watches, audio earbuds (hearables), and fitness bands. The biometric sensor systems that provide heart rate monitoring in wearables today have far more capabilities than you typically see implemented in the wearable devices on the market. For example, most biometric wearables report some version of heart rate monitoring, either “spot” measurements of heart rate on demand or continuously monitoring heart rate throughout the day and during activity. However, if the biometric sensor is accurate enough, combined with suitable activity context, these same devices can provide much deeper insights and tracking that can provide a much broader picture of someone’s overall personal health.
The usage of biometric wearables you see in the market today is truly only scratching the surface of what’s possible. From Valencell’s perspective, “what’s possible” must be scientifically researched and validated. Users of biometric wearables need to be able to trust the insights and the guidance provided by wearables, which means the data needs to be accurate and that data needs to be used in the context of a use case that has been shown effective in diagnosing. For example, certain heart rate variability (HRV) patterns have been proven to indicate atrial fibrillation (research).
We believe the combination of highly accurate biometric data and scientifically validated use cases are the key to the next phase of growth in the wearables market across consumer and medical sectors. So let’s look at just a few of the more interesting use cases that are already scientifically validated, but we don’t see in many (if any) wearables on the market today:
Moving beyond 10,000 steps
The goal of getting 10,000 steps per day that is the focus of many activity tracking wearables is valuable in motivating people to get moving in general, but it’s an arbitrary number that began with no scientific validation behind it. Just counting steps or activity doesn’t provide insights on how hard that person is working to take those steps. 10,000 steps for me is different than 10,000 steps for an Olympic athlete. What’s more important is how your body is reacting to the activity you put it through. Namely, two people of the same body weight moving 10,000 steps may indeed be burning nearly the same calories, but the person moving at higher intensity (heart rate) will be improving their cardiovascular health and fitness more effectively. In fact, moving 10,000 steps at an intensity below your appropriate heart rate zone may have no demonstrable effect on your fitness at all!
This is why the American Heart Association and Center for Disease Control and Prevention both recommend 150 minutes of moderate or 75 minutes of vigorous physical activity per week.
The best way to determine the level of intensity of activity, and therefore how much time you spend in moderate-to-vigorous activity, is by measuring heart rate. Tracking the intensity of your overall activity throughout the week, rather than just the activity or movement itself is much more important. While there are a few products on the market with this feature (Garmin and Mio), we haven’t seen it catch on with many others yet. However, expect to see more wearables focusing more in the future on intensity levels over time.
Core temperature is a good example of a metric that has very clear and proven scientific value, but is logistically difficult to measure regularly in the field. You can get accurate measures of core body temperature with an oral or rectal thermometer or with a thermopile in the ear, but this is difficult to do when a person is physically active or on a job site, for example. However, it is possible to estimate core body temperature using only a series of heart rate measurements. These estimates of core body temperature have been shown to be accurate within 0.5 degree Celsius (research). While the model for estimating core temperature is not a replacement for direct measurement (literature comparisons of esophageal and rectal methods average LoAs of ±0.58 °C) the results suggest it is accurate enough to provide practical indication of thermal work strain for use in the work place.
This has numerous potential applications, including sports & fitness (preventing heat exhaustion and/or fatigue), health & medical (managing fever), to industrial safety (preventing heat exhaustion). And the technology for this exists today – the same technology that’s implemented in consumer wearables, combined with the proven science, can provide a very close estimate of core temperature.
Adaptations to training
R-R interval (a.k.a. heart rate variability, HRV, or the time between beats of your heart) is starting to get more attention these days and for good reason. It can provide tremendous fitness and health insights, as we discussed here. There’s quite a bit of research on this topic and this review provides a good summary. One application of this capability is to use the 7-day rolling average of HRV to monitor individual adaptations to training. Specifically, HRV can indicate if an individual is over-trained and needs to take a break or is under-trained and needs to push themselves harder to improve their fitness level. This has been used by professional athletes for some time, but it’s just now beginning to see traction in consumer devices. Valencell recently partnered with Firstbeat, who has some of the most advanced analytics around HRV for these purposes and our customers Jabra and Suunto have successfully implemented both technologies.
HRV has also been shown in clinical study to indicate motor skills impairment in sleep deprivation situations. There are some obvious applications of this capability to driving situations, as the authors of the study indicate:
“Hence, HRV measures could potentially be used to predict when an individual is at increased risk of attentional failure. Our results suggest that HRV monitoring, either alone or in combination with other physiologic measures, could be incorporated into safety devices to warn drowsy operators when their performance is impaired.”
There are other potential applications as well in military, pilots in flight, and industrial safety use cases as well that could prevent numerous accidents, injuries, and even deaths.
Each of these examples can be implemented today. Because researchers have already demonstrated that these use cases actually work, there are no science projects to complete. All that’s needed to make these use cases work is accurate biometrics, but recently, consumers could only get accurate biometrics from a chest strap – untenable for most consumers. With the recent advent of accurate optomechanical biometric sensor technology, now these use cases can be implemented in more convenient form-factors, such as armbands, wristbands, and earbuds.
If these or any other scientifically-validated use cases interest you, we’d be happy to discuss helping you build the user experience with highly accurate sensor data. Get in touch at email@example.com.