Why heart-rate quality matters for Riina

Optical PPG vs. electrical ECG

Most wrist-worn wearables use photoplethysmography (PPG) — green LEDs that measure blood-volume changes through the skin. PPG works well at rest and during steady-state cardio, but can struggle with motion artifacts during high-intensity or wrist-flexion-heavy activities like rowing or CrossFit.

Chest straps use electrical sensors (ECG-grade) that detect the heart’s actual electrical impulses. They are largely immune to motion noise and deliver near-clinical accuracy across all intensity levels. For Riina, this translates to more reliable zone classification and fairer scoring.

What Riina needs from your device

• Continuous HR samples — Riina requires beat-by-beat or at minimum 1 Hz heart-rate data during a workout. Devices that only record summary averages are not compatible.
• Platform integration — the device must sync workout data to Apple HealthKit (iOS) or Android Health Connect so Riina can import it.
• Accurate zone transitions — Riina’s scoring algorithm weights time spent in higher HR zones more heavily. If the sensor lags on zone transitions or drops beats, your score will be off.
• Low artifact rate — spikes, dropouts, and flatlines corrupt the time-in-zone calculation. Fewer artifacts = fairer scoring.

Getting the best signal from optical sensors

• Wear it tight — a loose band lets ambient light leak under the sensor, causing noise. Snug but not restrictive.
• Wear it higher — position the watch 1–2 finger-widths above the wrist bone where the skin is flatter and has better perfusion.
• Avoid tattoos — dark ink absorbs the green LED light and degrades the PPG signal significantly.
• Warm up first — cold skin constricts surface blood vessels. Start easy for 2–3 minutes before intense efforts to let the sensor lock on.

When to choose a chest strap

If you primarily do HIIT, CrossFit, rowing, or any workout involving rapid wrist movement, a chest strap like the Polar H10 will produce noticeably cleaner data. It pairs to your phone or watch via Bluetooth and the HR samples flow through to HealthKit or Health Connect the same way native wrist data does.

For steady-state running, cycling, or walking, modern optical sensors from Garmin, Apple, and Polar are accurate enough that you will not see a meaningful scoring difference versus a chest strap.