Video summary

Garmin CIRQA Ultimate Scientific Review!

Main summary

Key takeaways

Product Review

Product reviewed

Garmin “Circa” (smartwatch/fitness tracker with optional bicep strap use) was reviewed using a scientific, reference-based approach, focusing on:

  • Heart rate during workouts
  • Sleep stage tracking
  • Night metrics, including HRV (heart rate variability)

The reviewer emphasizes that wear location (wrist vs bicep) strongly affects accuracy.

Key idea: the same device performs very differently depending on where it’s worn.

Testing approach / comparisons

Reference devices (treated as benchmarks)

  • Heart rate reference: Polar H10 ECG chest strap
  • Sleep stages reference: ZMax EEG sleep device

Devices used for context

Performance is also compared against other devices previously tested and competitors mentioned, including:

  • Fitbit Air, Whoop, Oura Ring
  • Apple Watch, Pixel Watch
  • Eight Sleep Pod
  • Garmin Forerunner 570/170

Key findings: Heart rate tracking in workouts (wrist vs bicep)

Cycling / spinning (very strong, especially on bicep)

  • Spinning/Bike (cycling)
    • Wrist correlation: 0.99
    • Bicep correlation: 1.00
  • Notes: wrist is already excellent; bicep is even better, with minimal/no deviations.

Running (bicep clearly better)

  • Running correlation

    • Wrist: 0.89
    • Bicep: 0.98

  • Notes:

    • Wrist shows more deviations, including spikes/jumps and interval tracking errors.
    • Bicep tracks interval drops correctly, with only minor start-up calibration issues.

Strength training / weights (wrist fails, bicep improves)

  • Strength training correlation

    • Wrist: 0.73 (very low)
    • Bicep: 0.91 (much better, though not perfect)

  • Notes:

    • Wrist misses many peaks and shows “strange” heart-rate patterns during lifting.
    • Bicep still has misses, but is clearly superior.
    • Examples:
      • Bench press tracked “quite well”
      • Push-ups seemed quite good (noting this is often difficult for wearables)

Relative performance vs other devices (overall)

Across four exercise types, Garmin Circa on bicep is described as one of the best performers (based on the reviewer’s prior correlations/percentiles).

Reported rankings/percentiles:

  • Wrist overall: better than 63% of devices
  • Wrist cycling: better than just over 50%
  • Wrist running: correlation 0.89, better than only 27% (meaning 73% did better)

On bicep, performance improves substantially:

  • Spinning: 1.00, better than 77%
  • Cycling: 0.96, better than 3/4
  • Running: 0.98, better than 63%
  • Weight training: 0.91, better than almost 70%

Summary scores / ratings (cardio)

The reviewer assigns “grades” based on average correlation over three cardio exercises.

  • Bicep heart rate rating: 98 → “great”
  • Wrist heart rate rating: 93 → “good”

Main drivers of the lower wrist score:

  • Running (and to some extent cycling)

Key findings: Sleep stage tracking (wrist vs bicep)

Accuracy by sleep stage (agreement vs EEG reference)

Wrist (Circa on wrist):

  • Deep sleep agreement: 81%
  • Light sleep agreement: 67%
  • REM agreement: 45%

Many “benchmark REM” segments are instead labeled as light sleep, deep sleep, or wakefulness.

Bicep (Circa on bicep):

  • Deep sleep agreement: 91%
  • Light sleep agreement: 69%
  • REM agreement: 58%

The reviewer reports performance improves significantly, but cannot fully explain why.

Sleep stage patterns described

  • Deep sleep: generally detected correctly on both locations (sometimes “excess” deep sleep)
  • REM: hardest on wrist; bicep is better, but still not perfect
  • Example nights:
    • Wrist missed multiple REM endings (e.g., 3 of 5 cycles ending in REM correctly)
    • Bicep improved REM placement with closer segment durations, though timing can shift

Sleep “tier” / position among competitors

Using a chart framework (sensitivity + worst-stage performance, where the worst indicator is REM):

  • Garmin Circa on bicep: second echelon
  • Garmin Circa on wrist: closer to third echelon

Additional notes:

  • Other Garmin devices the reviewer tested (e.g., Forerunner 570 on bicep) did slightly better.
  • Forerunner 70 improved relative to earlier tests.

Sleep score (numerical)

  • Sleep score (bicep): 73 → “good”
  • Sleep score (wrist): 64 → “satisfactory”

Night HR and HRV (reliability)

  • Heart rate at night (wrist vs reference):

    • Works well in a narrow HR range (roughly 39–55 bpm mentioned)
    • Points are close to the reference

  • Heart rate at night (bicep vs reference):

    • Similar close tracking; overall differences are minimal

  • HRV:

    • Generally measured reliably on both locations
    • In higher HRV ranges, Garmin may show slightly lower values vs benchmark (possible algorithm difference)

User experience notes (button, detection, comfort tradeoffs)

Strengths / conveniences

  • Physical button is a major improvement:
    • Starts workouts reliably by tapping the device
    • Emits a small green signal
    • Reviewer reports no accidental clicks on either wrist or bicep
  • Reduces reliance on automatic activity detection, described as erratic:
    • Especially on bicep (e.g., missing long hikes)

Downsides / bicep wear visibility issue

When worn on the bicep with long sleeves:

  • You can’t easily see workout start/stop status
  • You must rely on vibration/light signals to confirm recording
  • Reviewer sometimes accidentally left workouts running longer due to limited visibility

Product design / availability / value concerns (especially straps)

Color note

  • Blue/black looks fine with the box
  • Red variant appears more like faded pink than the advertised dark red

Bicep strap cost and availability

  • Bicep straps are not cheap and are hard to get
  • Example pricing in Austria: around $60
  • Delivery can take weeks (though a “larger version” takes a few weeks)

Strap form factor

  • Not a standard buckle; uses a narrow fastener
  • Reviewer hopes for third-party strap options (e.g., AliExpress)

Value comparison

  • Fitbit Air on wrist can be $99 (often cheaper than buying Circa plus an extra strap)
  • Reviewer calls Circa “expensive,” but still suggests it’s worth it for best performance.

Overall pros

  • Excellent heart rate tracking on bicep, often near reference
    • Strongest for cycling/spinning, running intervals, and strength training peaks (relative to wrist)
  • Sleep stages improve substantially on bicep, especially:
    • Deep sleep
    • REM
  • Night HR and HRV tracking looks solid on both locations
  • Button-based workout start is reliable and more usable than auto-detection

Overall cons

  • Wrist placement underperforms, especially for:
    • Running (correlation 0.89)
    • Strength training (correlation 0.73)
    • REM sleep (only 45% agreement; wrist REM misclassification is a major weakness)
  • Bicep strap drawbacks: cost, limited availability, non-standard connector
  • Red color mismatch: looks faded/pink vs the box
  • If you rely on sleeves, confirming workout status visually can be annoying (must use vibration/light)

Verdict / recommendation

  • Best recommendation: Wear Garmin Circa on your bicep for training

    • Best heart-rate accuracy
    • Noticeably better sleep staging

  • If you only care about wrist-friendly night tracking: wrist sleep tracking is acceptable

    • Sleep stage score: 64 (“satisfactory”)
    • Night HR/HRV: good enough

  • Avoid wrist use for running/strength training if accuracy matters

    • Performance drops sharply, especially for strength (0.73) and REM sleep (45%)

Unique points by the (single) main speaker

The review is primarily attributed to Rob, a postdoc scientist focused on data analysis, who:

  • Emphasizes scientific testing
  • Tests both wrist and bicep wear
  • Provides quantitative results (correlations and agreement vs reference devices)
  • Suggests why bicep can improve results (less artifact/noise and a clearer HR signal), while acknowledging limitations such as limited data/coincidence
  • Highlights button vs auto detection as a key usability factor
  • Discusses strap cost/availability and the desire for third-party strap options
  • Mentions preferences for app/offline syncing vs Fitbit Air, including a sync reliability issue discussed in that comparison

Original video