With Valentine’s Day fast approaching, it made me think about one of the biggest advancements that technology has brought to the fitness industry. At the high level is in data collection - and this data has in turn helped us to better understand not only human physiology in general, but how each individual can maximize their efforts. But for me, at the heart of this revolution (pun intended) is the ability to track an individual’s heart rate. It helps indicate physical fitness, recovery, perceived effort, and opened a new chapter in the way people trained. Before we go much further, let's talk about the two primary methods of getting heart rate data today, and what some of the pros and cons of each are.

The first method and by far the most common is done by measuring the electrical activity of the heart in much the same way that an EKG does. Two sensors are placed in relative close proximity to the heart, and measure the minute electrical signals from the different sensor angles. It sounds complicated, but this is the core process used by the Polar HRM straps we've seen for years - the sensors are on either side of the center electronics, which primarily houses the battery, a small processor and transmitter. This particular method has several advantages; it is accurate enough to be used in a clinical setting, is very low power, has good error tolerance, is low cost, and durable. It is not without its limits though as it can only work within relatively close proximity to the heart, some people find them uncomfortable to wear, and smaller people (children, etc.) get inconsistent readings.

The second method and the one you see being used with almost all the wearables lately is done optically, by effectively reading the blood flow by the amount of absorbed and reflected light. Generally a device must fit snugly over the portion of skin being monitored to eliminate as much external light as possible, then light is generated (usually with an LED) and measured with a photo-diode or similar part. In terms of accuracy, it can be very close to the first method, but due to the nature of how the analysis takes place, it's delayed by several seconds. It's also unclear whether or not it's possible to generate an accurate RR-Interval optically - but on the flip side, it's possible to measure oxygen saturation of the blood using this same method (like a pulse oximeter). Another major advantage to this approach is that the sensor can be positioned all over the body - as of right now, there are sensors available for the wrist, finger, calf, forehead and ear. On the downside, it is more costly in terms of both money and processing power to do, it consumes far more battery power to operate, and it is much more susceptible to interference from light and other factors.

When wearables first arrived on the scene they were really nothing more than glorified pedometers, but as they've gained commercial success they've expanded into greater and greater functionality. The latest generation have started adding heart rate monitoring, and this is where the problems really started to begin from the consumer standpoint. Prior to this, there were chest straps or nothing at all - and so the choice was pretty clear. As wearables arrived, they didn't make a distinction between how their sensing worked versus what was already commercially available. With most (if not all) wearables, they are only able to check your heart rate every couple of minutes - and this is fine for their intended use case, allowing you to see how your heart rate fluctuates over the course of a day. But in terms of fitness, this is close to useless. Imagine trying to do a heart rate based interval run, where you checked your heart rate once every 5 minutes. To make matters even more confusing, new optical heart rate sensors came out which DO report real-time heart rate data (the MIO being a good example), and they smartly started to differentiate by calling it 'continuous heart rate'. And then you have some products like the Microsoft Band, that dynamically change the rate at which they check heart rate based on what they think you're doing - if you're sleeping it's 2 minutes every 10 minutes, if you're just doing whatever it's 1 minute every 10 minutes, and if you're working out it's every second.

But wait, the fun doesn't just end there - not all of the wearables will transmit that data real-time, so even if they are sampling in real-time, they may not be able to provide it to something like a treadmill. And there's now a myriad of different protocols being used - the original Polar one from the last 20+ years, then ANT/ANT+, and now more recently Bluetooth Low Energy (BLE or BT4.0). In the end this results in consumers having harder and harder times getting these devices to inter-operate - this wearable won't work with that app on those phones, etc. Almost none of these devices integrate with ACTUAL fitness equipment in any meaningful way - or if they do, it's only at the most surface level, like the summary of a workout from a treadmill.

The sad part is that we're not getting more accurate data from these new devices (in the fitness context), we're actually getting data that's less accurate in many cases. We're losing critical data, such as RR-interval, and instead replacing it with virtually useless data, like how many steps you've taken since you woke up. On the horizon we do have some interesting things coming - the two most notable being the AmpStrip and Apple's Watch. While the AmpStrip is a bit of an unknown, Apple has a good track record in recent years of really understanding a market and it's needs before introducing a product, so it could be one of the first to really get it right.

Watch the video below for my reviews on some popular heart rate monitors.