Fourth Frontier X2 Review: Your Heart’s New Best Friend?
This in-depth Fourth Frontier X2 review dives into the second-generation ECG sports strap (launched in 2023), featuring accuracy tests and real-world insights. Use code THE5KRUNNER for 30% off—grab it now at fourthfrontier.com (£321.75 / $428).
It’s not just a heart rate monitor—it’s a game-changer for anyone serious about heart health, from athletes to those with medical concerns. Curious? Let’s explore why it’s worth your investment.
Last Updated: 10 June 2025
Buy Now: fourthfrontier.com – 30% off with THE5KRUNNER
A complete solution for heart safety in your activities and beyond
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Price - 75%75%
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Apparent Accuracy - 95%95%
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Build Quality & Design - 80%80%
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Features, Including App - 95%95%
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Openness & Compatability - 90%90%
Verdict: The Fourth Frontier X2 combines sports tracking with ECG-grade heart monitoring—a rare combination for active individuals or those with heart concerns. For safety, performance, or peace of mind, the X2 delivers.
Fourth Frontier X2
24x7 ECG, Real-Time Alerts and Sports Tracking.
Pros
- Real-Time Alerts: Haptic buzzes flag heart events fast—stay safe mid-workout.
- Full ECG Tracking: Records 24+ hours of ECG, sharable live or as PDFs.
- Sports Precision: Matches top straps like Polar H10 for HR accuracy.
- Unique Insights: Heart strain, breath-based load—data you won’t get elsewhere.
- Broad Compatibility: Syncs with Apple, Garmin, Peloton, and more.
- Long Battery: 24 hours of ECG, recharges in 45 minutes.
- Rich App: Detailed stats and trends, plus doctor-ready reports.
- Near Medical-Grade: Catches issues wrist wearables miss.
Cons
- Pricey: £321.75 / $428—worth it, but a leap over basic straps.
- Manual Start: Easy to forget pressing the button pre-workout.
- App Clutter: Functional, but the layout could be slicker.
- Retro Design: Looks dated—though it’s hidden under your shirt.
- Fit Challenges: Some body types may struggle with HR/ECG pickup.
- Swim Caution: IP67 rating feels iffy for serious swimmers.
Fourth Frontier X2 Design: Built for Purpose
Unbox the X2, and you’ll find two chest straps, a clip-on pod with a button, a colour display, and a side charging port—all in sleek packaging. The retro look might not win beauty contests, but it’s rarely visible. You notice smart haptics that buzz for heart alerts and a battery that lasts over 24 hours of continuous ECG recording.
The app and online dashboard are packed with unique features—think detailed ECGs and shareable PDFs for your doctor’s review. It’s a comprehensive, consumer-grade ECG solution that’s accurate and easy to use, featuring free expert video sessions to help decode your data.
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Why Choose Fourth Frontier X2?
Think of it as a souped-up sports strap—like a Garmin or Polar, but with ECG superpowers. It’s unique because it blends athletic tracking with medical-grade insights:
- Sports Edge: Colour display, haptics, heart strain alerts, breath-based training load, and workout caching.
- ECG Power: Live monitoring, long-duration ECG PDFs, and auto-detected cardiac events.
- Safety First: Haptic buzzes warn you of thresholds or unusual heart activity.
It’s perfect for biohackers, cautious exercisers, or anyone needing doctor-ready data.
Deep Dive: ECG Charts & Workout Insights
On an easy run, I tested the X2 solo (no second strap). It logged normal rhythms 80.7% of the time, with 11.9% flagged as notable—potentially useful for a doctor’s review. Tap “View ECG” in the app, and you’ll see 20-second traces with ‘O’ markers for events worth checking.
Double-press the button during a workout to log a manual event, such as the odd flutter you felt. The ECG zooms in on key moments, like these four circled anomalies around 11 a.m. (learn more).
Workout Gems:
- Training Load: Uses breath rate (not just HR) for a smarter intensity score—novel and research-backed.
- Body Shock: Tracks mechanical stress to flag injury risk, akin to Stryd’s metrics.
- Heart Strain: Measures ST segment shifts (0.2mv+ signals issues like oxygen deprivation)—set it to buzz at 0.3mv and ease off if it does.
Rich & Safe Workouts
Double-press, workout, done—no phone needed. The X2 caches everything, buzzing for alerts and showing time, distance, and shock score on its OLED (upside-down, but who cares?). Pair it with your app or Garmin for GPS, and the ECG will still sync back.
Set custom alerts for heart strain, breathing issues, or heart rate—simple, effective, and safe. Share live ECG links with coaches or export 3-hour PDFs from the dashboard (see mine).
Feature Deep Dive: VO2max, Readiness and Sleep Stages
Additional features have been added for premium subscribers since this review was originally published, covering the key metric that defines your healthspan – VO2max.
Also added is a detailed look at nightly sleep stages, try to optimise DEEP SLEEP for muscular recovery and REM sleep for cognitive recovery.
Readiness is a third new metric that assesses your daily HRV deviation from your baseline; a too large negative deviation usually indicates that you are not coping with life’s stresses and encourages you to slow down to adapt and recover.
Have a deep dive read at the following link.
Fourth Frontier X2 – Leading ECG Strap gets VO2max Feature Boost – Deep Dive
Body Shock
Fourth Frontier X2 beat Garmin to add this new metric to their chest strap. While Garmin examines the impact forces themselves, Fourth Frontier considers how your body responds to the forces, including changes to your ECG.
Have a deep dive read at the following link.
BODY SHOCK – an innovative running metric from fourth frontier x2
Who’s It For?
Not just a sports strap—it’s a health guardian. Get it if you’re:
- Over 40 & Active: Extra Monitoring for Peace of Mind.
- Biohacker: Craving ECG-level workout data.
- Carer: Watching a loved one’s heart (Paula Radcliffe uses it for her mom!).
- Heart-Conscious: Managing a condition or gathering evidence for your doc.
Fourth Frontier X2
24x7 ECG, Real-Time Alerts and Sports Tracking.
Accuracy: Does It Deliver?
Sports HR: Matches Polar H10 and Garmin HRM-PRO Plus spot-on, with rare glitches (likely from dual-strap tests). It’s as reliable as any top chest strap.
HRV: Mixed results vs. Polar H10 on HRV4Training—low correlation, possibly due to timing or setup quirks. Still, it’s functional for trends.
ECG: I can’t verify arrhythmia detection without having an arrhythmia to test! However, the data appears to be legit and doctor-friendly.
April 2025: The FDA approves Frontier X Plus as a prescription device, allowing medical professionals to prescribe it to their clients. I.e. it’s accurate.
Why Buy Fourth Frontier X2?
Heart disease hits 48% of us—silent issues can strike anyone, even athletes. The X2 catches 85% of hidden arrhythmias, offering prevention over regret. It’s the only strap blending sports precision with continuous ECG—Garmin and Apple can’t touch that. At £321.75 / $428 (30% off with THE5KRUNNER), it’s an investment in safety and performance.
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Discount & Final Thoughts
The X2’s retro vibe hides a powerhouse: accurate heart rate (HR), unique ECG insights, and life-saving alerts. It’s not cheap, but unmatched for heart health and sports data. I’ll keep using it for tougher sessions—why risk it?
Fourth Frontier X2
24x7 ECG, Real-Time Alerts and Sports Tracking.
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