Garmin HRM 600 vs Fourth Frontier X2: Which Chest Strap Wins

Two chest straps, two very different philosophies. The Garmin HRM-600 sits at around $130 and targets performance metrics for serious endurance athletes. The Fourth Frontier X2 pushes closer to $400 and positions itself as a clinical-grade heart health device. Both use electrical impulse detection via ECG-based sensors, not optical PPG, which is why chest straps remain the gold standard for accurate heart rate data during high-intensity efforts. Picking the wrong one means paying for features you will never use.

ECG Accuracy and Signal Quality

The HRM-600 uses Garmin's latest soft textile electrode design with improved RR interval capture. RR intervals are the millisecond gaps between electrical impulses, and accurate RR data is the foundation for HRV calculations. Garmin claims sub-5ms accuracy on RR intervals, which puts it in the same bracket as the Polar H10, long considered the benchmark for raw ECG accuracy on the wrist. The H10 still edges it out in controlled lab conditions, but for real-world training the HRM-600 holds up well across running, cycling, and swimming to 50 meters.

The Fourth Frontier X2 goes further. It captures a full single-lead ECG trace that you can export as a PDF, share with a cardiologist, and use for atrial fibrillation screening. That is a meaningful clinical step beyond what the HRM-600 or any Garmin strap offers. It also measures respiration rate via electrical impedance across the chest, a more direct method than the accelerometer-derived breathing rates you get from Garmin or Coros wrist devices. For athletes managing cardiac conditions or monitoring long-term heart health trends, that distinction matters a lot.

Performance Metrics for Training

The HRM-600 is where Garmin focused its engineering budget. Running dynamics are the headline: vertical oscillation, ground contact time, stride length, and the newer left-right balance metrics all transmit live to compatible Garmin watches like the Forerunner 965 or Fenix 8. Cyclists get power-adjacent data through breathing rate and training load estimation. The strap also feeds Garmin's Body Battery and recovery algorithms directly, improving those scores compared to using wrist optical PPG alone. If you are a triathlete training across three disciplines, the HRM-600 integrates tightly with Garmin's entire ecosystem.

The X2 offers solid HRV tracking and recovery scores but does not broadcast running dynamics. It connects via Bluetooth and ANT+ like the HRM-600, and it pairs with third-party apps including Garmin Connect, TrainingPeaks, and Apple Health. But if you want ground contact time data on your next interval session, the X2 cannot deliver that. It is not designed to. The tradeoff is intentional: Fourth Frontier chose depth on heart health over breadth on sport metrics.

Use Cases: Who Picks Which Strap

For a runner chasing a marathon PR and training with a Garmin watch, the HRM-600 is the practical choice. The running dynamics data feeds directly into form analysis, the RR accuracy keeps HRV scores honest, and the swimming waterproofing covers open-water brick sessions. At $130 it is also roughly a third of the X2's price. Coros offers the Coros Heart Rate Monitor at a lower price point with basic RR interval capture, but it lacks the running dynamics depth and the ecosystem integration of the HRM-600.

The X2 makes sense for a masters athlete who has been flagged for an irregular heartbeat, or anyone whose doctor wants periodic ECG data outside a clinical setting. It also appeals to Whoop users who want chest-level electrical accuracy instead of wrist optical PPG, since Whoop's 5.0 still relies on PPG and cannot produce an exportable ECG trace. For pure health monitoring paired with any watch ecosystem, the X2 fills a gap nothing else in this price range covers.

What neither strap does particularly well is long-term skin comfort across full Ironman-distance efforts. Both require conductive gel or a wet electrode in dry conditions, and the HRM-600's hard plastic module can bruise the sternum on efforts beyond four hours. Fourth Frontier has improved the X2's textile electrode strip in its latest revision, but fit variability across body types remains a user complaint in long-course triathlon forums. Battery life on the HRM-600 runs around 500 hours, while the X2 sits closer to 30 hours of active recording, a significant gap if you forget to charge between sessions.

The short verdict: buy the HRM-600 if you train on Garmin hardware and want actionable sport performance data at a fair price. Buy the X2 if heart health monitoring and clinical-grade ECG export are the priority and the price is not a barrier. There is no overlap where one clearly beats the other on all fronts. They serve different athletes with different needs.