Video summary

Garmin CIRQA - First Tests!

Main summary

Key takeaways

Science and Nature

Scientific Concepts / Nature & Physiological Phenomena Presented

Optical photoplethysmography (PPG) for heart-rate sensing

  • Circa uses Garmin’s Elevate V4 optical heart-rate sensor plus a skin temperature sensor.
  • Measurement accuracy depends on:
    • Fit/placement
    • Arm motion
    • Signal interference during activities

Heart-rate dynamics during exercise

  • Running
    • HR changes rapidly (short intervals).
    • This introduces more variability and potential timing/peak-tracking errors.
  • Indoor cycling
    • Generally easier for optical HR sensors due to more stable movement.
  • Weightlifting
    • Most challenging on-wrist because of wrist movement and tension.
    • Leads to missed or artifact HR peaks.

Sleep staging & heart-rate–derived sleep metrics

  • Circa’s sleep stage algorithm is described as essentially the same as Garmin watches, with tuning differences.
  • Sleep analysis includes:
    • Heart rate
    • Heart rate variability (HRV)
    • Sleep stages
  • Placement expectations:
    • Wrist vs upper arm / biceps band is expected to yield comparable HR/HRV/sleep.
    • However, Circa’s sleep-stage behavior is specifically tested.

Data priority / signal fusion across multiple wearables

  • Garmin Connect uses a “primary wearable” concept rather than merging simultaneous signals.
  • If two Garmin devices record overlapping data:
    • The primary device’s data takes priority.
  • Rules also prevent duplicate activity display when auto-detected activity overlaps with manually recorded activity on another Garmin device.

Battery-life factors in wearable sensing

  • Power usage is affected by:
    • Timed activity recording
    • Connected GPS
    • Heart-rate broadcasting
  • Pulse oximetry (not central to Circa tests here) can reduce battery life by up to a couple of days, depending on:
    • Movement
    • Perfusion
    • Skin tone

Sleep/wake optimization

  • A smart alarm creates a 30-minute wake window and targets an “optimal point” for waking (timing optimization concept).

Methodology / Test Plan (as Described)

Question-driven evaluation before/around device arrival

  • How Circa behaves when used alongside another Garmin watch:
    • Priority rules
    • Synchronization
    • Duplicate handling
  • Whether Circa matches Garmin watches for sleep stage tracking.
  • Whether upper-arm placement changes measurements versus wrist wear.
  • Button functions, activity detection, and data handling in Garmin Connect.

Planned exercise tests after setup

  • Multiple rounds in the long-term plan:
    • Outdoor run
    • Indoor cycling
    • Weightlifting
    • Outdoor cycling
  • Heart-rate comparison to a reference:
    • ECG chest strap — specifically Polar H10 in initial results
  • Additional sleep-focused data collection:
    • Sleep HR, HRV, and sleep stages
    • Comparison of wrist vs biceps/upper arm

Initial real-world testing performed in this upload

  • Wear Circa on left non-dominant wrist (biceps band not yet available at the time).
  • Run comparisons:
    • Time series / plots of HR from Polar H10 (reference) vs Garmin Circa.

Key Findings from the Initial Tests (Heart-Rate Comparisons)

Indoor cycling (initial)

  • “Almost perfect” / very good alignment with the ECG strap reference.

Running (initial)

  • Mixed results:
    • Generally tracks HR dips well.
    • Observed issues:
      • Occasional deviation during dips/changes
      • Slight delay in detecting an HR increase at a moment
      • Occasional high peak detection errors / overestimation

Weightlifting (initial)

  • Challenging on-wrist:
    • Missed some HR peaks.
    • Produced an “early high peak,” suggesting a possible artifact (described as roughly double HR in one segment).

Featured Researchers / Sources (Named in Subtitles)

  • Rob
    • Speaker; described as a post-doctoral scientist specializing in biological data analysis
  • Garmin
    • Company; provided device details and answers
  • Garmin Connect
    • Garmin ecosystem that applies priority/sync rules
  • Fitbit
    • Mentioned as a comparison point for personalized/adaptive activity classification
  • Polar H10
    • ECG chest strap reference device used in testing

Related comparison reviewers/devices (not specific researchers):

  • Fitbit Air
  • Whoop Strap
  • Amazfit Helios Strap
  • Garmin Index sleep monitor

Original video