Fourth Frontier X2 vs Garmin HRM 600 – A Buyer’s Decision Making Guide
Both Garmin and Fourth Frontier have recently launched their best-ever straps with top-end features. But they have different top-end features, intended for different buyers, though there is overlap in their wider abilities.
TL;DR – Garmin’s HRM 600 digs deep into the technicalities and possibilities within its ecosystem, whereas Fourth Frontier X2 digs deeper into heart health.
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Tech Basics
Both are competent devices.
- Frontier X2: Continuous single-lead ECG, detects arrhythmias, ST changes, cardiac strain, standalone recording, display, button
- Garmin HRM 600: Traditional HR/HRV/R-R, advanced running dynamics, standalone recording, button
Health Basics
At the highest level of HR detail, Garmin Connect and its watches recognise the continuously varying time between beats (HRV/RR) at up to 5 data points per second (5Hz).
Fourth Frontier’s app saves 125 data points per second (25x as many), enough to fully reconstruct an ECG waveform with P-Q-R-S-T peaks and valleys.
Head-to-Head
Perhaps the most confusing aspect to explain is that you will read that HRV straps like Garmin HRM600 or Polar H10 are ECG straps – and this is not always true.
| Metric | Frontier X2 | Garmin HRM 600 |
| HR accuracy | Matches Polar H10 | Matches Polar H10 |
| HRV | Reliable long-term trends | Slightly under-reads at rest in my tests |
| ECG / Arrhythmia | Yes, doctor-ready PDFs | No (HRV/RR only) |
| Strain / Effort | Cardiac strain + haptic alerts | Workout intensity only |
| Breathing rate | Yes | Yes |
| Running dynamics | Basic Body Shock | Full (Step Speed Loss, etc.) |
| Compatibility | BLE only (phone + Garmin) | ANT+ & BLE unlimited |
| Battery | 24 h continuous ECG | 2 months daily / 60 h sport |
| Price (2025) | $405 (use discount) | $170 |
Buy Frontier X2 if:
- You’re concerned: You’re over 40, have family heart history,
- You want a safety backup: You train at high intensity and want the comfort of extra heart safety features
- You want to aid the medical diagnostic process: You want arrhythmia alerts and shareable ECG reports.
Buy HRM 600 if:
- You race, train daily in the Garmin ecosystem,
- You want watch-free recording for the Garmin ecosystem (e.g. gym)
- You want accurate swim HR
- You just need rock-solid sports HR + running metrics.
Garmin HRM 600
High-end, watch-free heart rate recording strap.
+other retailersVerdict
- Heart health priority > Frontier X2
- Pure performance + simplicity > HRM 600
- No budget limits & paranoid > both! Wear Frontier X2 for harder workouts
Fourth Frontier X2
24x7 ECG, Real-Time Alerts and Sports Tracking.
Last Updated on 27 January 2026 by the5krunner
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors.
I don’t think that Frontier X2 and HRM 600 should be compared. HRM 600 gives a bunch of running dynamic metrics, but a sampling rate of 5 Hz and a reporting rate of 1 Hz are quite insufficient for serious heart series analysis. Frontier uses a sampling rate of 125 Hz, similar to Polar H10 (130 Hz), so they should be compared. Polar records a full 1-channel ECG. Polar Sensor Logger is free and records ECG and accelerometer data but does not interpret the data. ECG analysis for Polar H10 needs a subscription (has a free tier), records ECG only, calculates ECG parameters, and detects ectopic beats, but it does not interpret ECG. It saves data in the European Data Format (a standard file format for the exchange and storage of multichannel biological and physical signals). It can also be used for 24-hour recording.
hi
yes i think you are right and have made an edit. I had heard that hrm600 does collect data at 100+Hz but never had it cofirmed other than in my mind. yes the 5Hz is a limitation of FIT files which backtracks to what garmin devices do i assume
i’m making this comparison to avoid confusion in some buyers minds.
yes a vs. H10 could be useful too. Fewer non sporty people are aware of Polar’s lab grade devices
Hi — please take a look at this paper: https://pubmed.ncbi.nlm.nih.gov/31004219/
You can copy‑paste a FIT file with good-quality R‑R intervals into ChatGPT and ask for R‑R interval (RRI)–based HRV analysis. RRI analysis can suggest ectopic beats and many arrhythmias, but it has limitations and usually requires ECG confirmation. Key points:
Ectopic beats (premature atrial contractions — PACs; premature ventricular contractions — PVCs)
Appear as isolated short R‑R intervals (premature beat), often followed by a longer compensatory pause.
Frequent PACs/PVCs produce irregular RRI sequences and reduced HRV complexity.
Bigeminy/trigeminy produce alternating RRI patterns (short, long, short, long…).
Atrial fibrillation (AF)
RRI signature: markedly irregular RRIs with loss of periodicity and altered low‑frequency structure.
Poincaré plots lose stable sinus clusters; sample entropy is typically increased.
Atrial flutter with variable block
Fixed block (e.g., 2:1) → regular RRIs; variable block → patterned irregularity (repeating groups).
HRV metrics often fall between AF and normal sinus rhythm.
Supraventricular tachycardia (SVT) and paroxysmal tachycardias
Sudden sustained runs of shortened RRIs; HRV drops sharply during episodes.
Onset and termination appear as abrupt RRI changes.
Sinus arrhythmia and sinus node dysfunction
Sinus arrhythmia: physiologic respiratory-cycle RRI variation — high HF power.
Sinus node dysfunction (pauses/exit block): long RRIs/pauses, increased variance, intermittent very low heart rate.
Atrioventricular (AV) block
2:1 or 3:1 AV block: repeating RRI patterns (constant ratio), producing multimodal RRI histograms.
High‑degree or variable AV block: long pauses and grouped beating.
Ventricular tachycardia (VT) and ventricular fibrillation (VF)
VT: sustained series of short, often regular RRIs (rapid rate); HRV is minimal during the run.
VF: chaotic, highly variable or nonphysiologic RRIs; frequently not analyzable from single‑lead R detection.
Notes and caveats:
Accurate R‑peak detection is essential; missed or false detections can mimic arrhythmia.
Single‑lead RRI analysis cannot reliably distinguish PACs from PVCs (requires ECG morphology).
Short recordings may miss paroxysmal events; ambulatory/long‑term monitoring improves detection.
RRI/HRV findings are supportive; definitive diagnosis requires clinical ECG review.
Strong correlations to
Frequent PVCs
Sustained ventricular tachycardia (VT)
Atrial fibrillation (AF)
Long pauses (sinus node exit block or high‑degree AV block)
Fixed‑ratio AV block (e.g., 2:1, 3:1)
I have a Frontier X2, Garmin HRM 600, Polar H10, and Polar Verity Sense heart rate monitors. I think each are useful in various scenarios.
Sticking to the X2, I cannot use this device for running. Even with wetting the electrodes and keeping it tight, the X2 stuggles to discern heart rate effectively. The biggest issue is that when the data is even mildly noisy, it will report a heart rate of 0. This plays serious games with any algorithm. If you’re trying to track your training load or VO2 max, you need clean heart rate data. The X2 simply isn’t reliable for running.
For cycling, I have had great luck. 3 concurrent bluetooth connections is fabulous. When jarring movement is minimal, the ECG analysis is fantastic. I captured a 6-beat NSVT event that I was able to share with my cardiologist. You can’t do that with any of the other heart rate monitors in my collection. Capturing PVCs is usally very accurate as well, and the Frontier site is great at analyzing data since it will highlight where there is a break from normal sinus rhythm, for any reason.
The X2 samples data at 1000hz, similar to the Polar H10 and I would presume the HRM 600, although Garmin doesn’t publish that information.
One problem I have with Frontier is that they are not friendly when it comes to exporting your data. There are no options as of January 2026 to export a second-by-second summary of heart rate data via CSV. You can export an EKG file as a PDF. However, it is not machine readable since its just a series of images.
Regarding ectopic heartbeats, you can see them by looking at RR-intervals on sites such as runalyze. PVCs typically present as beats both above and below the baseline, usually with a deviation of approximately 50-100 ms due to their premature and compensatory nature. So, there are other ways to monitor your PVC burden during exercise if you don’t want to spend the money on the X2. However, an EKG readout is infinitely more actionable. So, your mileage may vary.