Garmin HRM-600 Replacement Tested: Accuracy Issues Fixed?

The Garmin HRM-600 has been flagging accuracy problems for some users, specifically systematic heart rate errors and RMSSD underestimation that compromise HRV tracking. The5kRunner put a warranty replacement unit through a half marathon effort to see if the swap actually solves anything.

The short answer: mixed results. The replacement unit performed better in steady-state efforts, but the strap design remains a legitimate concern. Fit inconsistencies across chest sizes can cause the pod to shift, which directly affects optical and electrode contact quality during high-intensity work.

For HRV users, RMSSD underestimation is a serious problem. Whoop and Polar H10 both hold a strong reputation for overnight and resting HRV accuracy. If your HRM-600 is reading lower RMSSD values than expected, your recovery scores in Garmin Connect or third-party apps like HRV4Training will be skewed. That affects training load decisions in a real, compounding way.

Compared to the Polar H10, which sits around 30 to 40 euros and is widely considered the gold standard for chest strap accuracy, the HRM-600 at roughly 100 euros needs to deliver consistently clean data. The Coros Heart Rate Monitor is another option worth considering if you want reliable ECG-grade readings without the premium price tag.

Verdict: a warranty replacement may improve your unit, but the strap fit issue is structural. If accuracy is non-negotiable for your training, the Polar H10 is still the safer bet.