Frontier X2 review: The heart health powerhouse for data-driven athletes

As a regular runner who’s getting a little older, I’ve become more conscious of my heart health. It’s not that I’m overly worried, but I do want to keep an eye on things and make sure I’m not pushing myself too hard. That’s why I was pretty excited when the Frontier X came along – a chest strap that promised to give me a whole lot more than just my heart rate, and I’ve been using it since its launch.

With its advanced physiological metrics and real-time ECG tracking and heart health alerts, the Frontier X offers a unique blend of sports and medical wearable technology. But unlike traditional ECG devices, which are often bulky and cumbersome, this bit of kit is practical for daily wear and exercise.

Frontier X2

Frontier X2
Use code FFGNW25 at checkout for a 25% discount

Frontier X2

Recently, Fourth Frontier has introduced the second generation of the device. Building upon the foundation of its predecessor, the Frontier X2 aims to provide even more in-depth insights into heart health and athletic performance, but with a price tag that may not be for everyone.

What follows is my experience with the Frontier X2 after a few weeks of testing. I will also compare it to the original model and explore who this device is designed for. The aim is to shed light on what the Frontier X2 offers and whether it’s the right tool for you.

Frontier X2 typically sells for $549 on the Fourth Frontier website. Use code FFGNW25 at checkout for a 25% discount.

Jump to

Design & hardware
Functionality – how to use
Pros & Cons
The bottom line – is Frontier X2 worth it?

Frontier X2 review: Design & hardware

At first glance, the Frontier X2 appears identical to its predecessor. The core unit, which houses the device’s electronics, maintains the same (73 x 24 x 13 mm) dimensions and weight (25 grams), ensuring a comfortable and familiar feel. Elastic chest straps, one blue and one black, are also included, allowing you to swap them out as needed.

A closer inspection reveals a subtle change: the physical button on the core unit, previously red, now sports a vibrant blue hue. This minor alteration serves as a visual cue to differentiate the second-generation device, while maintaining a consistent design language. Beyond that I didn’t spot anything different in the looks department.

Frontier X2 review
Fancy packaging

The sleek packaging also contains a Micro USB charging cable and a quick start guide. Next to them you’ll find a one-year warranty and 14-day risk-free trial, giving you a bit of time to test out the device.

If you’ve ever worn a heart rate chest strap, Frontier X2 is no different. Attaching the core unit to the strap is a simple process: position the unit onto the pins in the strap and press firmly until it clicks into place. The adjustable strap mechanism allows you to easily achieve a comfortable fit just below the centre of your ribcage. The strap holds everything firmly in place, even during vigorous activity. 

The Frontier X2 core unit may not have the most modern design, but don’t let this fool you. There is some very advanced tech inside. Plus everything feels very robust, like it could easily survive a few accidental drops.

As far as water-resistance, the device is good for submersion up to 1.5 meters. So yes, you can even use it when swimming.

Frontier X2 vs Frontier X
Frontier X2 next to Frontier X

A simple interface with a questionable screen

The device’s operation is streamlined with a single physical button located on the underside. This button powers everything on/off, starts/stops activity tracking, and logs event markers. Additionally, a strip of LEDs on the opposite end provides status updates through different colors, indicating pairing status, power on/off, and more. The overall control scheme is intuitive and user-friendly.

One big difference between Frontier X2 and standard chest straps is the addition of a small screen on the core unit. Like on the first generation, the screen is primarily used to display battery life, mode status, and a post-workout summary of your activity. 

Not this might seem like a strange addition, and it is. I personally can’t see the point. Don’t get me wrong – this is more of an observation than a negative.

The screen’s positioning across the front of your chest makes it extremely difficult to read during exercise. Plus the strap will likely be sitting below a shirt or other garment. Even if you were looking at yourself in the mirror, it would not be easy to make out what the screen is displaying. If Frontier releases a third generation device, it may be an idea to do away with the screen altogether – as this may improve further the already excellent battery life.

Frontier X2 review
Single physical button

Enhanced connectivity

The Frontier X2 offers a few different connectivity options for tracking your workouts:

  1. Smartphone app: The method involves pairing the Frontier X2 with the accompanying iOS or Android app. This allows you to start, stop, and monitor your workouts directly from your smartphone. The device utilises Bluetooth for communication. You can also get a live feed of your ECG, as a separate function.
  2. Standalone mode: Alternatively, you can use the Frontier X2 independently during your exercise session and sync the data to your smartphone afterward. This option is ideal for those who prefer to minimize distractions during their workouts. Or when its not practical to carry your phone with you.
  3. External heart rate monitor: This one is my favourite. The Frontier X2 can also function as an external heart rate monitor, transmitting your heart rate data to compatible third-party devices, including Garmin, Polar, Wahoo, Zwift, and Peloton products. In parallel, it also captures all the same data as in standalone mode and saves it to the on-board memory.

Notably, the Frontier X2 can connect to multiple devices simultaneously, supporting up to two third-party devices in addition to the smartphone app. Although most users may not require this level of connectivity, it’s a valuable option for those who utilize multiple fitness trackers or platforms.

It’s important to note that the device, like its predecessor, does not support ANT+ connectivity. But it now has Bluetooth 5.0. Which is an improvement over the original as it allows for 3 times the speed and greater range. There are also faster updates for heart rate on connected devices.

Frontier X2 review

Battery that won’t miss a beat

Battery life is excellent. On a single charge there is enough juice for continuously recording for up to 24 hours. So a bit of an improvement over the first generation. If you exercise every day for one hour with the chest strap, you’d only need to charge it once every two weeks. A full charge can be achieved in just 45 minutes.

During my testing, I found that topping up the device every 4-5 days for about 20-30 minutes was more than sufficient to keep it at 100%. Charging is done via a standard Micro USB cable, which is convenient for replacing if lost or damaged. This familiar charging method adds to the overall user-friendliness of the Frontier X2, ensuring you can easily keep it powered up and ready for your next workout.

Frontier X2

Frontier X2
Use code FFGNW25 at checkout for a 25% discount

Frontier X2

Frontier X2 review: Functionality

Setup & use

Setting up the Frontier X2 is a breeze. Simply download the Fourth Frontier app and create an account. Then pair your device. Your login credentials will also grant you access to the web dashboard, which offers a more comprehensive view of your data. For your initial workout, try tracking it directly through the app.

Attach the strap to your chest, turn it on, and the screen will display the time, a summary of your last workout, and battery and memory levels. Remember to dampen the sensors on the strap and your skin before each workout to ensure accurate data collection from the start. It is not absolutely necessary, but it does help. This practice is actually beneficial for most heart rate chest straps.

The smartphone app is very easy to use. Along the bottom are a few tabs. One is Home, which takes you to a screen with an overview of your stats, recommendations and selected forum posts. Next to that there is a tab that takes you to a feed of your workouts, a small plus sign which you need to click on in order to start manually activity tracking, a Community tab and a Settings tab.

Activity tracking – customising heart health alerts

Using your phone as a display is not very practical for certain types of exercise – such as running. But it can be a good option for those cycling, rowing and engaging in other types of activities. For runners, I suggest they use another option. Simply start and end the session by double-pressing the button on the device itself. As mentioned, everything will be stored on the onboard memory and you can leave your phone behind. Then simply sync Frontier X2 with your smartphone later on.

Those that want to initiate a workout via the app can do so via the small plus sign. After choosing your activity type (from the long list that includes run, cycle, walk, strength, etc.), you can customize alerts for Cardiac Strain and Breathing Rate by setting upper and lower limits. Or leave the default values. Exceeding these thresholds during your workout triggers a double buzz notification. 

Fourth Frontier emphasizes breathing rate, considering it equally important as heart rate during exercise, a claim open to debate. But the undeniable value of heart information is where Cardiac Strain enters the picture.

This proprietary metric, medically known as ST depression, measures oxygen deprivation in heart muscles. Consistently high values can damage heart cells and should be avoided, as they may lead to fibrosis or arrhythmias over time. Frontier X’s real-time buzz alerts warn users when they cross into this unhealthy territory.

Additionally, the Cardiac Rhythm feature uses ECG data to detect deviations, displaying a post-exercise pie chart of time spent in Blue (Normal Sinus Rhythm), Yellow (Other Rhythm), or Gray (Not Interpretable) zones. More detail is available in 20-second interval charts, flagging any suspicious changes.

This is the type of data that you will not get from any other heart rate chest strap. At least not in this easy to understand fashion.

There’s also an optional Share link. Click on that and you’ll get a link you can send to someone that will allow them to keep an eye on your stats in real time.

Once you’ve saved your preferences, click start and allow a few seconds for the first readings to appear.

For running or walking, the Frontier X2 smartphone app displays metrics such as Effort, Strain, Heart Rate, HRV, Training Load, Cadence, Distance, and Pace. The other sports are slightly tweaked versions of the same. I don’t think there’s much of a difference.

I put the Frontier X2 head-to-head with a Polar OH1 chest strap and the results were pretty impressive. The heart rate stats matched perfectly, so I’m confident that the Frontier X2 is the real deal when it comes to heart rate accuracy.

Frontier X2 review app

A useful feature is that a single press of the device’s physical button allows you to mark significant events during your workout. This could be anything from a sudden strain or difficulty breathing to simply starting a new lap. So that a feature to be aware of as it might be useful to you.

Post-workout stats

After your workout, give Frontier X2 a few moments to sync its treasure trove of data to your smartphone app. Then get ready to dive into a world of stats and graphs that go way beyond what you’d see with a typical heart rate monitor.

Training Load

To start off you get a weekly Training Load based on the time spent in different Breathing Rate zones. Its like a points system and you can view a chart of your progress. Fourth Frontier claims this method of calculating training load is more precise than using heart rate or power zones, citing research to back it up. For example, Breathing Rate is not effected by factors such as caffeine, lack of sleep, temperature, humidity and stress. All of these can cause distortions with heart rate based training.


Heart health and more

Click on the History tab for a list of all your individual workouts. Tap on any workout to get more detailed metrics. This is where it gets more exciting.

Sure, you’ll get the usual stuff like heart rate and calories burned, but it’s the unique metrics like ECG trace, Cardiac Strain, Cardiac Rhythm, and Body Shock that really set Frontier X2 apart. These are the type of insights you won’t find on “traditional” heart rate chest straps.

Things such as Cardiac Strain and Cardiac Rhythm give you an assessment of your heart health during exercise. For me, there were only a few irregularities that were flagged up – nothing to worry about.

The ECG trace, on the other hand, presents your activity in 20-second segments. Zoom in to pinpoint any flagged irregularities in your heart rhythm, or to examine the markers you set during your workout, which appear as vertical black lines on the graph.


Body Shock, in particular, deserves a shoutout. It measures the impact of each foot strike and letting you know if your form is putting undue stress on your knees or other joints. You’ll see how this impact changes throughout your workout, so you can catch any deterioration in your technique before it leads to injury.

The app itself is a data lover’s dream, with detailed charts and tables. You can even compare different workouts side-by-side to track your progress over time. And if you triggered any alerts during your workout, they’ll be waiting for you in the app, along with a plain-English summary of your overall performance and personalised recommendations for your next session.

Using the website dashboard

If you’re a data geek, the Frontier X2’s website dashboard is your playground. It takes everything great about the smartphone app and supercharges it, giving you a bigger, bolder view of your fitness journey. With its larger screen, you can dive deep into the wealth of stats and zoom in on details.

IBut the dashboard doesn’t stop there. It also throws in the Health Trends section, a feature that tracks your progress over time and uncovers hidden patterns you might have missed on the smaller screen.

Initially, the Health Trends section might seem a bit bare, but stick with it. After a couple of weeks of training, it’ll start to paint a picture of your fitness trajectory. Having said that, I do feel its more of a nice to have than a must have as it didn’t really help me with any groundbreaking realisations. But I am keeping an eye on it.

Using Frontier X2 with a 3rd party device

Pairing the Frontier X2 with a third-party device via Bluetooth, like my Garmin Forerunner 955, is another option. It works just like any other heart rate chest strap. But remember, data flows one way: from the Frontier X2 to your Garmin, not the other way around.

Since my original review was published Fourth Frontier have introduced functionality which allows users to connect their Garmin account directly with the Frontier X2 smartphone app. This is useful as it allows for syncing of GPS maps of your exercise from your Garmin account to the Frontier app and web dashboard.

Turning on the Frontier X2 doesn’t automatically start tracking, though. You’ll need to double-click the physical button to kick things off. So, with my Garmin, I switch on the Frontier X2 and wait for the connection to Garmin confirmation, get a GPS signal on the watch, and then double-click the Frontier X2 to start heart rate tracking. After a few seconds, I’ll start seeing the data on my Garmin, and then I start the workout. It might seem like a few extra steps, but it quickly becomes routine.

Beyond that there is nothing to do. When you finish your workout, you’ll need to end the activity both on your Garmin watch and on the chest strap (another double-click). Garmin has the heart rate data saved, while Frontier X2 has heart rate and all the other tracking data in its memory. So you can sync that afterwards to the Fourth Frontier smartphone app for detailed insights.

Apple Watch users get a special treat: a dedicated Frontier X2 app for choosing activities and controlling the device, plus real-time display of multiple Frontier X2 metrics right on the watch. It’s a feature I’m hoping to see on Garmin and other platforms soon.

Frontier X2 review

Continuous 24 hour ECG recording

Beyond tracking workouts, you can also use Frontier X2 as an ECG recorder. The special mode is triggered from the smartphone app. It is where the device crosses into purely a health wearable.

Current ECG devices, primarily watches and handheld units, are not ideal for exercise as they require the user to be stationary and provide lower quality data due to recording from the finger or wrist instead of the chest. Additionally, they typically only capture short ECG segments, unlike the Frontier X2, which allows for longer continuous recordings.

Frontier X2 ECG

Frontier X2 is a single lead ECG. But it more closely resembles the output from the V5 lead of a medical 12-lead ECG measurement. The ECG signal is sampled at 125Hz intervals which equates to once every 8 milliseconds, which is quite good. That’s particularly important considering this is the metric that is used to evaluate your heart health.

Frontier X2 ECG

When you finish the recording, you can tap into a detailed evaluation of the readings.

Frontier X2 ECG

There is no way for me to confirm the actual accuracy of ECG recordings. But I do have a few devices in my arsenal that can capture ECG – and the waveforms look very similar.

“In studies comparing the Frontier X2 to a Holter Device and 12 Lead ECG, the Frontier X2 picked up all abnormal heart rhythm changes (arrhythmias) found by Holter and 12-Lead ECG, and adequately measured heart rate and QTc changes.” states Fourth Frontier on its website.

For those that want to share their recording with a doctor or a loved on, Frontier X2 comes with an option to send remote readings. You’ll get a link which you email to the other person – once they click on it they’ll be able to follow your ECG in real-time. By the way, you get this same option when starting a workout via the smartphone app.

Frontier X2 review: Pros & Cons

Frontier X2 has a lot going for it. But it also has a few cons. Let’s list them.


  • In-depth data: The Frontier X2 dives deep into physiological metrics, offering far more than a standard heart rate monitor. ECG, Cardiac Strain, Cardiac Rhythm, and Body Shock are just a few of the unique insights you’ll gain. They add a whole new element to your activity tracking.
  • Versatile use: Whether you’re using it independently, with the smartphone app, or paired with a third-party device like a Garmin watch, the Frontier X2 adapts to your preferences.
  • Accurate tracking: Heart rate data is comparable to trusted brands like Polar, ensuring reliable tracking for your workouts.
  • Workout insights: Body Shock analysis helps you identify potential injury risks in your form, while post-workout summaries and personalized recommendations guide your training.
  • Real-time alerts: The device buzzes to warn you of excessive strain or unusual heart rhythms, allowing you to adjust your workout intensity as needed. You might be suffering from heart rate issues that you might not be aware of. The idea of this wearable is to warn you if this is, indeed, the case. It also warns if your breathing rate goes up to much during exercise, as this can be damaging to your lungs.
  • Long battery life: A single charge lasts up to 24 hours of continuous recording, ensuring you won’t run out of juice during extended activities.
  • User-friendly app and dashboard: Both platforms offer easy navigation and in-depth analysis, with the web dashboard providing even more powerful tools for data exploration.
  • 24-hour ECG monitoring: Unlike other ECG devices, the Frontier X2 allows for continuous recording, giving you a comprehensive view of your heart health throughout the day.


  • Price: The Frontier X2 is a premium device with a price tag to match – particularly if you compare it to a standard chest strap. This makes it a significant investment for most users.
  • Screen usability: The screen on the core unit is difficult to read during exercise and may not be necessary for all users.
  • Learning curve: While generally user-friendly, the device’s advanced features and data may require some time to fully understand and utilize effectively.
  • Limited third-party integration: Although the Frontier X2 can connect to multiple devices, some features, like real-time display of metrics, are only available on Apple Watch.
  • No ANT+ connectivity: The device relies solely on Bluetooth for communication, which may be a drawback for users who prefer ANT+ compatible devices.

While the Frontier X2 delivers on its promises, I’m holding out hope that Fourth Frontier will release an armband version in the future, offering a more convenient alternative to the chest strap. And does away from the display – I feel there’s no need for it.

To help you understand how the Frontier X2 stacks up against other heart rate monitors and ECG devices, check out this handy comparison chart created by Fourth Frontier. It clearly outlines the key differences between each type of device,giving you a clear picture of what the Frontier X2 brings to the table.

Frontier X2 vs other devices

Frontier X2 review: The bottom line, is it worth it?

Frontier X2 isn’t for everyone. Its premium price might be a dealbreaker for casual users or those interested only in basic heart rate tracking. However, if you’re serious about understanding your body, training smarter, and potentially identifying underlying health issues, the Frontier X2 is a worthy investment. Its wealth of data, unique insights, and real-time alerts provide a level of detail that few other wearables can match.

While older individuals may find particular value in its features, the device’s appeal isn’t limited by age. Anyone curious about their heart’s performance during workouts can benefit from the detailed data and real-time feedback it provides. This includes athletes seeking to optimize their training, individuals recovering from cardiac events or injuries, or simply those who want a more comprehensive understanding of their overall health.

Frontier X2

Frontier X2
Use code FFGNW25 at checkout for a 25% discount

Frontier X2

You’ll get answers to questions such as: Am I overexerting my heart and lungs? Can I push harder? The thing even tracks the impact on your joints with each foot-strike, potentially preventing injuries. For those who push their limits during workouts, the reassurance of staying within safe zones is invaluable.

Then there’s the live ECG function. It adds another dimension, valuable for those recovering from heart issues or simply curious about their heart health. 

Ultimately, it boils down to what you’re after.

If heart rate tracking is all you need, a regular chest strap will do the job just fine, and at a fraction of the cost. But if you’re curious about other aspects of your health during exercise, the Frontier X2 goes above and beyond a simple heart rate monitor. It’s not a medical device, but it packs a punch when it comes to information and insights.

Price, where to buy

Frontier X2 typically sells for $549 on the Fourth Frontier website. Use code FFGNW25 at checkout for a 25% discount.

If the Frontier X2’s price tag gives you pause, the original Frontier X is a worthy alternative. The difference in features between the two is not big. It boils down to 3x faster wireless data sync on X2, along with faster updates for heart rate on connected devices, 30 hours vs 24 hours data storage memory and improvements in battery life.

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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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