Frontier X2 Heart Rate Monitor Review: What Makes It Different From Garmin and Polar

The Frontier X2 is a continuous ECG heart rate monitor designed to give athletes significantly more cardiovascular data than a traditional chest strap or wrist based running watch. We put it to the test to see whether those deeper insights are actually useful for training and who will benefit most from them.

As a hobbyist athlete I often tend to approach my training with more of an obsessive approach than most other hobbyists.

Throughout my years as a runner I’ve read several books on training from some of the biggest running coaches out there (Coach Amanda obviously included) and have integrated little wrinkles from a few coaches into my own training.

I routinely plan out my training blocks months in advance, making sure I’m keeping within the regular accepted ranges of hard training between the easier chunks so that, barring any freak accidents the week of a race, I arrive at the starting line in the best possible shape for a PR attempt.

One aspect of training that catapulted me from a 2:24 half marathon to a 2:08 finish four months later was focusing on heart rate based training.

But what happens when the basics just aren’t enough?

Enter Fourth Frontier’s Frontier X2, a premium chest strap monitor that goes well beyond basic heart rate tracking. The Frontier X2 starts with continuous ECG monitoring, compared to PPG reading taken from a wrist monitor, which rely on changes in blood flow.

Designed for serious athletes but available to all, the Frontier X2 is a valuable tool for athletes who need a deeper, more serious look under the hood.

Frontier X2 Overview

The Frontier X2 is a chest strap monitor that allows you to dig deeper beyond what is readily available in most cases. The main upgrade over wrist-based heart rate monitoring is the use of continuous heart monitoring using ECG sensors, whereas a watch such as an Apple Watch, Garmin, or Coros use optical sensors which can be prone to big spikes during intense movements.

They’re also less accurate due to changes in skin tone or presence of tattoos, or even if your watch is just a little loose.

Zone Based Vibrational Alerts

One of the best features of the Frontier X2 is the real-time alerts you can set during a run.

It should be noted that you will have to set specific alerts for each type of run and you can only set one alert. For an easy run I would set an alert to let me know when my heart rate crossed into zone 3. It was a very handy feature that I put to the test at mile 7 of a long run where I planned a route with a long uphill climb.

During a threshold workout I was able to set an alert for when I crossed into zone 5, which was extremely helpful because I knew to take my foot of the gas a bit during the last minute of my sixth kilometer interval at my threshold pace.

Cardiac Age

One of the newly updated features is a calculation of cardiac age.

The X2 directly records ECG and derives metrics such as heart rate and HRV, while also tracking breathing rate and other training data. Fourth Frontier says it uses this data to generate additional personalized insights and scores.

Cardiac age sounds like the Frontier X2 can tell you how old your heart actually is, but think of it more as a wellness estimate. The device uses cardiovascular data to compare your heart and fitness metrics with expected values at different ages, giving you an easy way to understand how your numbers stack up.

For athletes, the more useful part may be watching that number as a trend rather than obsessing over the age itself. If your training and recovery habits are improving, seeing your cardiovascular metrics trend in a positive direction can provide another way to track progress over time.

Over the course of the two weeks I tested the Frontier X2 I saw my cardiac age go from 45 (my actual age), to 46.75 after a couple hot weather runs, to where it now sits at 44.84.

This isn’t a medical diagnosis or a replacement for cardiovascular testing from your doctor.

Tons of Training Data

Every tracked activity will produce a full ECG report when synced with the Frontier X app. You’ll also have access to your training load, calories burned, heart rate, breathing rate, heart strain, HRV, and a few others.

Training readiness was a feature I haven’t had on any of my previous wearables, but it is a great feature to have. It can be done first thing upon waking and it doubles as a relaxing breathing exercise. You’re “eligible” for a readiness score after three readiness activities; this gives the Frontier X2 time to establish a baseline.

Over time the Frontier X2 will “learn” more about you and you’ll see some changes in the metrics. Certain metrics such as heart rate variability (HRV), resting heart rate, and stress will vary daily.

Sleep Tracking

When worn during exercise the Frontier X2 strap was extremely comfortable. Adjusting the fit is easy and can be done while wearing it, but it does require a bit of shoulder mobility. The one place where I noticed the fit was not quite as comfortable was during sleep, which I did wear several times to track my sleep scores against my Garmin.

While the strap is comfortable, if you ever wanted to track your sleep within a few hours of a run in hot and humid conditions, the strap might not be 100% dry.

I noticed the sensor was not always tight against my chest during the night, but only when I would adjust to sleeping on my side. When sleeping on my back or almost face-down the fit was much better.

This made my heart rate vary quite a bit during the night. Most nights my average heart rate and HRV was within a comfortable range of my Garmin, but one night I saw my Garmin heart rate end up at 48 BPM and 58 on the Frontier X2.

Ease Of Use

Starting my watch and then starting the chest monitor is as easy as one-two – just make sure you remember to hit the blue button to start your activity if you don’t want to start it through the app. That was a piece of advice I was given before testing and I still missed it on three of my tracked activities.

The sleep-fit was the biggest drawback I noticed with the Frontier X2. After that, I did occasionally have trouble getting it to pair with my Garmin, which seems unusual based on other feedback and our previous tester had no issues.

Most of the Frontier X2’s features are free once you purchase the device. A monthly membership of $14.99 is required for VO2 max and sleep tracking. If you’re willing to give it time, those features can be handy.

The VO2 max, as is the case with other devices, is just an estimate. In early outings it will vary wildly, and even cause a little self doubt at how low the score can be after a hot and humid run, but it will eventually learn.

Have you tried heart rate training? Are you getting truly accurate data through a chest strap or winging it with a watch?

What to read next?

• Dry Needling, Muscle Scraping, and E-Stim: Do Actually Work for Runners?
• Heart Rate Training Zones for Runners
• Best Heart Rate Monitors for Running