# SOLVED : Expose fractional\_cadence for runs (odd SPM values in custom streams)

**URL:** <https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653>\
**Category:** Feature Requests\
**Created:** [13 November 2026 10:43 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653 "2026-11-13T10:43:42Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Baptou](https://forum.intervals.icu/user_avatar/forum.intervals.icu/baptou/32/96081_2.png) [@Baptou](https://forum.intervals.icu/u/Baptou)\
**Post date:** [13 November 2026 10:43 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/1 "2026-11-13T10:43:42Z")

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Hi David,

Running cadence is stored per foot as an integer, so a doubled “Run Cadence” custom stream can only produce even SPM values (180, 182…), never 181. The FIT record message carries the half step in a separate field, `fractional_cadence` (field 53, values 0 or 0.5), and the standard formula is SPM = (cadence + fractional\_cadence) × 2.

I tried to read it from a custom stream with “Process fit file messages” enabled:

- `m.cadence.value` returns the integer per-foot cadence (e.g. 81)
- `m.fractional_cadence` is `null` on every record message
- `Object.keys(m)` returns numeric indexes (0…17), no field names, and indexing by FIT field number (`m[53]`) throws “Index 36 out of bounds for length 1”

So from a script there is currently no way to reach the fractional part, even if the file contains it. Example activity (COROS Pace 3): [Intervals.icu](https://intervals.icu/activities/i208782236)

Two possible fixes, either would be great:

1. expose `fractional_cadence` on record messages in scripts, like the other fields;
2. better: when parsing runs, fold it into the cadence stream (`cadence + fractional_cadence`), so the built-in cadence stream becomes e.g. 90.5 and a simple ×2 gives correct odd SPM everywhere (streams, interval fields, activity fields).

Thanks for the amazing platform.

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<div class="post-metadata">

**Author:** ![pepe](https://forum.intervals.icu/user_avatar/forum.intervals.icu/pepe/32/36539_2.png) [@pepe](https://forum.intervals.icu/u/pepe)\
**Post date:** [13 November 2026 12:57 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/2 "2026-11-13T12:57:22Z")

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> [@Baptou](#):
>
> `fractional_cadence`

Hi Baptou,  
Have you tried parsing , `icu.fit.record`?

```auto
{
  for (const m of icu.fit.record) {
    const cad = m['cadence']?.value
    const frac = m['fractional_cadence']?.value
    if (cad !== undefined || frac !== undefined) {
      const spm = ((cad ?? 0) + (frac ?? 0)) * 2
      data.setAt(m.timestamp.value, spm)
    }
  }
}
```

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<div class="post-metadata">

**Author:** ![Baptou](https://forum.intervals.icu/user_avatar/forum.intervals.icu/baptou/32/96081_2.png) [@Baptou](https://forum.intervals.icu/u/Baptou)\
**Post date:** [13 November 2026 14:59 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/3 "2026-11-13T14:59:14Z")

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Thank you for the script, it’s the right approach and I owe you an apology for my earlier reply: your script does work. I ran it on a Garmin activity from another account and it gives correct odd SPM values (the `fractional_cadence` field is there, 0/1 alternation when isolated).

What was confusing me: on my own COROS runs, the same script only gives even values, and the script preview showed decimals (163.6) that I mistook for half-step data; they were just the smoothed preview curve.

To get to the bottom of it, I decoded the original COROS PACE 3 FIT file outside Intervals: the record messages have cadence as an integer per foot, plus vertical oscillation, ground contact time, vertical ratio, step length and power, but **no `fractional_cadence` field (53) at all**. So COROS simply doesn’t write the half step; nothing is wrong with your script or with Intervals.

I’m keeping your version as the shared stream for my athletes (odd SPM on Garmin, even on COROS) and sending COROS a request to add field 53. I’ll post a short summary and mark the topic solved. Thanks again.

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<div class="post-metadata">

**Author:** ![Baptou](https://forum.intervals.icu/user_avatar/forum.intervals.icu/baptou/32/96081_2.png) [@Baptou](https://forum.intervals.icu/u/Baptou)\
**Post date:** [13 November 2026 15:02 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/4 "2026-11-13T15:02:17Z")

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Short version for anyone landing here:

- Intervals stores running cadence per foot as an integer. To get exact SPM (181, not only 180/182) you need the FIT field `fractional_cadence`.
- **Garmin writes it** : the script below gives correct odd SPM.
- **COROS doesn’t** : I decoded an original COROS PACE 3 FIT file, the field is absent. Even values only, nothing can fix that on the Intervals side. Request sent to COROS.
- Activities synced via **Strava** have no original FIT: the stream isn’t created at all. Connect the watch directly.
- The script preview shows decimals (163.6): that’s just the smoothed preview, not half-step data.

Custom stream, “Process fit file messages” ticked, then Actions → Reprocess file:

```auto
{
  for (const m of icu.fit.record) {
    const cad = m['cadence']?.value
    const frac = m['fractional_cadence']?.value
    if (cad !== undefined || frac !== undefined) {
      data.setAt(m.timestamp.value, ((cad ?? 0) + (frac ?? 0)) * 2)
    }
  }
}

```

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<div class="post-metadata">

**Author:** ![miguell](https://forum.intervals.icu/letter_avatar_proxy/v4/letter/m/85f322/32.png) [@miguell](https://forum.intervals.icu/u/miguell)\
**Post date:** [14 November 2026 13:39 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/5 "2026-11-14T13:39:03Z")

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There is perhaps an even simpler way to do this if you create a `FractionalCadence` helper custom stream first—that way, there is no need to check reprocess the FIT file checkbox and everything is run from memory for faster execution:

 ![image](https://forum.intervals.icu/uploads/default/original/3X/5/4/5428687bdf81ef8a882db26d8f3eef165f5c6830.png)

```auto
{
  const cad = icu.streams.cadence;
  const fract = icu.streams.FractionalCadence;
  const len = cad.length;

  for (let i = 0; i < len; i++) {
    const c = cad[i];
    if (c !== undefined) {
      data[i] = (c + (fract?.[i] ?? 0)) * 2;
    }
  }
}

```

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<div class="post-metadata">

**Author:** ![Baptou](https://forum.intervals.icu/user_avatar/forum.intervals.icu/baptou/32/96081_2.png) [@Baptou](https://forum.intervals.icu/u/Baptou)\
**Post date:** [14 November 2026 18:08 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/6 "2026-11-14T18:08:54Z")

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Hi, thanks for the suggestion!

Unfortunately it doesn’t work for me. I created the FractionalCadence stream first (record field fractional\_cadence, rpm, format .1f), then a second custom stream with your script. The result is still in steps of 2: the new stream is just a duplicate of the normal cadence, so the fractional part seems to be empty or 0.

I’ve given up on this for now, but thanks again for your help.

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<div class="post-metadata">

**Author:** ![miguell](https://forum.intervals.icu/letter_avatar_proxy/v4/letter/m/85f322/32.png) [@miguell](https://forum.intervals.icu/u/miguell)\
**Post date:** [14 November 2026 19:47 UTC](https://forum.intervals.icu/t/solved-expose-fractional-cadence-for-runs-odd-spm-values-in-custom-streams/133653/7 "2026-11-14T19:47:10Z")

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Unfortunately, it doesn’t work with Coros, Polar and Suunto wearables since they lack a fractional cadence stream, whereas Garmin, Apple, and Amazfit watches support it and works great