Frontier X Heart Rate Monitor

I cannot recall when I started to get ads for the Frontier X heart rate monitor. For some reason they looked like just another far-fetched gadget promising to make you faster while in the end just separating age groupers from their cash. Plenty of that in my news feed every day. It was after I finally got a diagnosis for my arrhythmia that I began to look past the hunky, buff, bare chested dude in the photo and dig into more detail. I decided that this thing might help explain the variation that I feel day to day, and provide feedback to help me determine what intensity I can perform at without slamming into that wall.

This brings us to my first of many little gripes about this product. The ads and web site describe user adjustable alerts in the form of vibrations, intended to set limits. I asked if I could set an alert whenever the unit sensed an irregular heart beat. I was told yes. Actually, the answer is no. There are two alerts, one buzz and two buzzes. You can set them for minimum or maximum heart rate or strain. That’s it.

Which brings us to strain. Basically, this is how hard the heart is beating. Not how fast, how hard it is squeezing. Based on information I gleaned from a couple of FastTalk podcasts on heart matters, strain is not a significant factor for endurance athletes. It becomes a factor when athletes are working against very high loads. Weight lifters. CrossFit folks. So far none of my workout data shows any issue with strain.

Frontier markets the X (the new model is called X2, I have not found what’s different) as a wearable EKG, but as soon as you dig in they point out that it is not really an EKG because it only receives signals from the chest area. A real EKG uses sensors all over your body. Oh, and I learned to call this thing an EKG and will use that here, but Frontier uses the American spelling for cardio and calls it an ECG. Same thing.

To date I have collected roughly thirty workouts. Not enough to draw any conclusions, but enough to share my experience and point out some trends.

One thing that really jumps out at me is the variation between workouts  in percentage of “other” heartbeats to “normal” (sinus rhythm) heartbeats. There are lots of legal liabilities for using something like this to diagnose a health issue. When it comes to arrhythmia, Frontier will only go as far as to say it spotted an irregularity. Results are placed in three categories: Normal, Other, and Noise, where noise means the signal quality was not good enough to recognise anything. I had one workout with a lot of noise, caused by the unit popping off of one of the chest strap snaps. As for “others,” they could be PACs, or A-Fib, or even something else. Usually I get some percentage of Others. As I said, I have not collected much data, but the variation is unsettling.

Since my cardiologist has identified my arrhythmia as PACs, from here on I will no longer use the Frontier term “other” and simply use PAC. You may experience other others.

Below is a table summarizing the data I have collected. Four columns that repeat, newest on top-left, snaking down on the left, then again on the right. I split the columns at the break between when I used the Frontier mostly for running, then only for cycling after I decided to abandon the run. 

The percentage of PACs metric ranges from zero to seventy five percent! That’s huge! It is not easy to see from this display but the distribution is fairly even if we use an exponential curve. I used buckets starting at 2, 4, 8, 16, 32, and 64, and excluded the zero. ones, and the seventy-five. The result was this distribution: 4, 8, 5, 5, 3. A bell curve with a poor fit. Almost a straight line with a lump. About all we can say is the rate of PACs most often falls around 5% to 10%.

I have yet to determine what is causing this variation. Here is an example of how puzzling it is. On 4/27 and 4/29 I did the exact same workout, moderate dose lactate threshold intervals on the turbo trainer in my garage. Same bike, same time of day. Except for the percentage of PAC heart beats these two workouts look identical.

When I study individual workouts, the feature that I notice first is that the rate of PACs increases dramatically when my effort suddenly drops. What I expected was an increase proportional to effort, but that is not what I see. Again, not enough samples to make solid conclusions, but what I see is a low incidence of PACs when intensity is constant, more when I back off intensity. It’s as if the heart is tripping over itself trying to slow down.

I am not going to zoom in on a particular point in a workout to demonstrate this fact. What I will do is share with you the HR track from the Hapalua half marathon, the race which led me to accept that I am better off walking. That day my PAC rate was 20%. The flood of PACs at the end are from after the finish, before I got around to switching it off. I walked the second half and the reduction in PAC rate is obvious. (I do not know what the thin red line indicates.)

Let’s compare that with my long run from the week before. The PAC rate was 8%. I don’t want to draw too great a conclusion, but just looking at the rate of PACs suggests why I felt great on the practice run and like crap in the race. Or you could say why I was so surprised I could not run the way I had the week before.

The ecosystem in which it operates is straightforward. The device can operate on its own. It will record many hours of data. I always carry my phone with me anyway, and find it easier and more reliable to control from the Android app. There is a similar app for the iPhone crowd. To really take advantage of all of its features You need to create an account on the Frontier website and upload your activity. Typically, for me at least, the data uploads from the device to my phone after I stop the session, then from there it makes its way to the website.

There is a lot more I could say about this device. Basically, it does what it claims to do. Regrettably it creates an entirely separate ecosystem of data collection and some useless AI derived training advice. You have to start recording before it sends HR data (Bluetooth), so the start of a strip never lines up with Garmin and TrainingPeaks charts. It will insist on installing an update when you start it, even though you are ready to go. This happened to me at the Metric Century Ride. I could not start recording HR data until the first aid station. 

The device arrived in an Apple-quality box, better suited to a new iPhone or a Rolex watch. The box included two straps, identical except one is red and one is black. I chose the red strap to make it easier to find in my collection. Last week the unit popped off the strap and refuses to attach, as if the springs are worn. I switched to the black strap, so far, so good. 

The device has an LED display. Can’t figure out why, because you can’t look at it while you are wearing it. Mine rarely works, anyway.

Here are my two biggest complaints, other than that the price is much too high. First, I wish there was a way to overlay these charts with Garmin data. Especially power, but also cadence. I love that it tries to sense breath rate. Can’t say how accurate it is, but that is a promising metric. Second, and this is a big one, it gives you a decent EKG strip, and it shows on the HR chart where it sensed irregularities, but it does not mark the point on the EKG strip where the irregularity occurred. You have to find it yourself. Not a big deal for a trained EKG technician, but the intended audience is everyday athletes who just want to perform well. I don’t see how this is going to help them.

The ability to wear an EKG on workouts and in races has the potential, in the hands of a trained technician or cardiologist, to better diagnose heart issues. Perhaps, with more data and experience, it will be useful in determining how to avoid high percentage PAC days. (PACs, or whatever arrhythmia you are managing.) Personally, I plan to keep using mine, even though I am not exactly sure what the benefits are. Time will tell.