Muse 2 forehead photoplethysmography agrees with Polar H10 for heart rate but overestimates ultra-short RMSSD

The forehead sensor tracked mean heart rate closely, but its one-minute RMSSD values were almost twice as high as the chest-strap values. That means the devices should not be treated as interchangeable for this short HRV measure.

Griadhi IPA, Suadnyana IAA, Wahyuni N.
medRxiv (preprint) · Publication date: 2026-10-08
Added to site: 2026-10-11
DOI: 10.64898/2026.10.05.26364782

Preprint posted October 8, 2026. Added to Neurofeedback.com October 11, 2026 after abstract review; not peer reviewed.

Modalities

Heart-rate variability measurement, Photoplethysmography

Clinical focus

Wearable measurement agreement, Ultra-short RMSSD

Population

Seated research participants; participant demographics were not provided in the checked abstract

Sample

28 seated recording sessions; the checked abstract does not state whether each session represents a unique participant

Intervention / method

Sixty seconds eyes open followed by sixty seconds eyes closed, analyzed with fixed processing and eleven sensitivity analyses

Comparator

Muse 2 forehead pulse intervals compared with Polar H10 RR intervals

Clinician summary

Mean heart-rate agreement was near perfect (ICC at least 0.999). SDNN agreement was good to excellent but positively biased by about 8 ms. RMSSD agreement was moderate (ICC 0.60), with Muse values higher in at least 27 of 28 sessions by about 18.5 to 19.2 ms. Tracking the eyes-closed change in log RMSSD was not demonstrated.

How to interpret the findings

This is a non-peer-reviewed preprint checked from its abstract and metadata. The ultra-short two-minute protocol may not generalize to clinical HRV biofeedback. Without simultaneous ECG, the study could not separate optical-sensor timing jitter from physiological pulse-transit variation. The checked abstract does not provide full participant demographics, funding detail or longer-session performance.

Equipment and disclosures

Muse 2 forehead photoplethysmography and Polar H10 RR intervals were compared. Naming the devices identifies the tested measurement methods and is not an endorsement.

The authors declared no competing interests. The checked preprint metadata did not state a funding source. Preprint findings have not undergone journal peer review.

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