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Your heart rate walking outdoors

Ongoing studyRecorded outdoors, at your own pace

This is an ongoing study. The figure will be updated here as more people are recorded.

OPTICAL

Accuracy

92.4%

Outdoor Walking Heart Rate Agreement

paired with an ECG chest strap on the same walk

Reference standard

ECG chest strap

Sample size

4 participants

Walking outdoors, the Ultrahuman Ring reads within eight beats a minute of an ECG chest strap, on average.

Ultrahuman RingECG chest strapbeats per minute
92.4%agreement with the chest strap
7.7 bpmaverage difference
67%of readings inside the ±5 bpm / 10% tolerance
81–137beats per minute the reference covered in study
Figure 1 — One continuous stretch from a single recording. The figures beside it are for the study as a whole, not for the stretch drawn.
-45-30-150+158090100110120130140upper limit of agreement (+16.2)lower limit of agreement (-20.9)average offset -2.4 bpmthe two devices averaged (beats per minute)ring minus chest strap (beats per minute)
Figure 2 — Every five seconds, against the chest strap
One dot is one paired five-second reading, as recorded, pooled across recordings.

Outdoors is harder than a treadmill and the reason is not effort. A belt holds your pace for you; a pavement does not. You slow at a kerb, wait at a crossing, lengthen your stride on a clear stretch — and every one of those changes has to be tracked rather than averaged over.

Cold matters too. The vessels in your fingers narrow when your hands are cool, and that is precisely where this sensor is reading from, so an outdoor number carries a penalty an indoor one does not.

Both of those show up as width rather than as offset in the scatter below, where the readings spread a long way either side of a small average. A kerb, a crossing or a clear stretch changes the pace in a step rather than a ramp, and two devices reading from two places reach the new heart rate a few seconds apart. The single stretch drawn above is one walk from one recording, and it happens to run high throughout; the scatter is every reading in the study.