Fourth Frontier X2 Review: Your Heart’s New Best Friend?

This in-depth Fourth Frontier X2 review dives into the second-gen ECG sports strap (launched 2023) with accuracy tests and real-world insights. Use code THE5KRUNNER for 25% 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: 23 February 2025

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Fourth Frontier X2 Design: Built for Purpose

Unbox the X2 and you get two chest straps, a clip-on pod with a button, a color display, and a side charging port—all in sleek packaging. The retro look might not win beauty contests, but it’s rarely visible. What you’ll 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 sharable PDFs for your doctor. It’s a complete, consumer-grade ECG solution that’s accurate and easy to use, with free expert video sessions to 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: Color 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

I tested the X2 solo (no second strap) on an easy run. It logged normal rhythms 80.7% of the time, with 11.9% flagged as notable—potential doctor fodder. 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—like that 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 still syncs back.

Set custom alerts for heart strain, breathing, or HR—simple, effective, and safe. Share live ECG links with coaches or export 3-hour PDFs from the dashboard (see mine).

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.

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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: Can’t verify arrhythmia detection without a condition to test, but the data looks legit and doctor-friendly.

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 (25% 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 HR, unique ECG insights, and life-saving alerts. It’s not cheap, but for heart health and sports data, it’s unmatched. I’ll keep using it for tougher sessions—why risk it?

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