A runner pausing to check their watch on a mountain ridge at sunset.

Steady effort for SuuntoPlus™

Run Steady.
Finish Strong.

Constantin shows how your pace, NGP, speed, and heart rate move against your average effort, so you can spot drift before it costs you.

Why drift?
A Suunto watch showing Constantin's drift view with a green movement trend, red heart-rate trend, current values, averages, and heart-rate zone bar.
A runner with a red, jagged mountain-ridge-shaped graph line rising behind them. Constantin watch screen showing movement-speed and heart-rate drift trends.

Why drift?

Every Effort Drifts. Most Watches Hide It.

Your current number and average number each tell only half the story. Neither one shows the direction your effort is taking. Drift reveals it: whether you're gradually speeding up, slowing down, or holding steady, and whether your heart rate is creeping up while your movement still looks fine. Catch that early, and you can adjust before a slow fade or rising heart rate costs you at the finish.

The display

One Trend, Three Views

Drift shows movement speed and heart rate together. Pace and Heart Rate views zoom in when you want one signal without distraction. All three views share the same trend data, so switching views never resets the picture. Short press the upper button to move forward; long press to go back.

A Suunto watch showing Constantin's Drift view with movement-speed and heart-rate trends together.
  • Movement trend
  • HR trend
  • Current + average
  • HR zone bar

Good to know

The Details

For the curious and the practical — how Constantin works under the hood, the questions people ask, everything that's changed, and what to do if something feels off.

Algorithm

Constantin reads the same workout data your watch already records and picks the right movement metric for your sport: pace for road, track, and treadmill running; NGP (grade-adjusted pace) for trail and vertical; speed in km/h for everything else. NGP uses the Minetti (2002) running-cost model — the same basis as Strava's GAP — with grade clamped to ±45%.

Each line is your drift: how far your current value sits from your workout average, tracked over time. The watch hands Constantin a fresh sample about once a second; those per-second values are averaged into buckets, so brief spikes and GPS dropouts don't throw the line around. The chart auto-scales and re-centres on the present moment — that's why the green movement line and the red heart-rate line share one scale and meet at the dot on the right.

For the nerds — the exact numbers:

  • Sampling: about 1 Hz — one reading per second.
  • Buckets: ~12 s each for the first minute or so (the line appears quickly), then ~150 s (2.5 min) once warmed up; each point is the mean drift over its bucket.
  • Window: 4 history buckets plus 1 live point per line, so the trend reaches back about 10 minutes once it settles.
  • Refresh: redrawn every ~3 s, and immediately whenever your zone, metric, or data validity changes.
  • Normalisation: movement is clamped to ±270 s/km (±27 km/h in speed mode), heart rate to ±90 bpm.
  • Auto-scale: the largest on-screen deviation, plus 40% head-room, clamped to 8–100% of range, then applied equally to both lines — faster movement drawn higher, within about ±16% of the dial height.

The coloured bar on the right edge is your current heart-rate zone, in Suunto's standard zone colours — a higher zone draws a longer bar.

FAQ

Which watches does it work on?

All UI2 Suunto devices, Suunto 9 Peak Pro and newer — including Race (1 and 2), Vertical (1 and 2), and Ocean.

Where do I find it?

Open the Suunto app on your phone, go to the SuuntoPlus™ Store, and look in the Running section — you'll find Constantin there. New to SuuntoPlus™? See how to get started →

Does it cost anything?

No — Constantin is a free SuuntoPlus™ app. No purchase, no subscription.

Does it replace my normal sport screens?

No. It's an extra SuuntoPlus™ screen you open during a workout — your usual data screens stay exactly as they are.

Why can't I pause the workout?

While Constantin is the active screen, the upper button is remapped to switch between its views. To pause, cycle to a different data screen first, then use the button as usual.

Why do I see -- at the start?

Until your watch has enough valid speed or heart-rate data, values show --. They fill in within the first minutes as the workout settles.

Changelog

2.12 (2026-06-25)

  • The workout screen now has three switchable views: a combined drift view, a pace-only view, and a heart-rate-only view. The upper button switches between them (short press forward, long press back). All three views share the same collected data and the same trend chart, so nothing is lost when switching.
  • The heart-rate zone bar appears as soon as a zone is active, without waiting for the trend chart to fill.
  • Both trend lines share a common scale and meet at the same point on the right, making it easier to see how pace and heart rate are drifting relative to each other.
  • The trend chart now reaches further back, giving a broader view of how your effort is changing, with a marker showing where you are right now.
  • When GPS signal drops briefly, the chart holds its history instead of clearing — the trend stays visible until data returns.
  • When you stop moving without pausing the exercise, the pace trend line holds on the last valid sample while the heart-rate trend line keeps updating.
  • Trend values are averaged over each recording interval rather than sampled at a single moment, giving a smoother and more representative picture of your effort.
  • More stable alongside route navigation and other SuuntoPlus™ apps.

1.91 (2026-06-10)

  • The trend graphs now cover about the last 6 minutes instead of 90 seconds, with the most recent minute shown in detail and older minutes grouped into wider steps — so you see both what just happened and the longer trend.
  • Evened out the heart-rate zone arc so the steps between zones 1–5 look more consistent.
  • More stable alongside other SuuntoPlus™ apps.

1.87 (2026-06-03)

  • The heart-rate zone arc now uses Suunto's standard zone colors (blue / green / yellow / orange / red).
  • The arc now follows heart-rate zones only, which fixed instability when Constantin and ZoneSense were used together.
  • Runs lighter, especially alongside other SuuntoPlus™ apps.

1.72 (2026-05-27)

  • Redesigned the workout around three clearer views: drift, pace, and heart rate.
  • Easier-to-read pace and heart-rate graphs, showing the current moment, recent trend, and average together.
  • Added intensity zone arcs on the pace and heart-rate screens (using ZoneSense when available, heart-rate zones otherwise).
  • Smoother, more stable graphs during short stops and missing pace — including while navigating a route or running other SuuntoPlus™ apps.

1.57 (2026-05-15)

  • Steadier charts and a more responsive screen: graphs keep updating after short stops or missing pace, big pace spikes stay tidy at the chart edge, and the display holds up better at workout start and when switching views.
  • Removed the "AVG" labels while keeping the average reference lines.

1.42 (2026-05-09)

  • Early stability and readability improvements: steadier graphs, screen, and layout (including when switching views), easier-to-read pace and heart-rate trends, and lighter performance on the watch during workouts.
Known issues

Earlier versions could crash when several SuuntoPlus™ apps ran at the same time — especially with active route navigation. On Suunto Vertical 2, running three SuuntoPlus™ apps at once was enough to bring it down.

Version 2.08 re-architected how Constantin aggregates and calculates its data — trend values are now accumulated over each recording interval instead of being rebuilt on the fly — which made it much lighter and far more stable. From 2.08 onward it should hold up, even alongside navigation and other apps.

If you still run into a crash or anything that looks off, I'd genuinely like to know — please report it to [email protected] so I can take a look.

Built to Keep You Steady

  • Three Focused Views

    Drift, Pace, and Heart Rate views share the same collected data, so you can switch focus without losing the trend.

  • Pace, NGP, or Speed Automatically

    Road runs show pace, trail and vertical runs show NGP, and other sports show speed in kilometres per hour.

  • Shared-Scale Drift Trend

    Green movement and red heart-rate lines meet at the current moment, making relative drift easier to read.

  • Zone and Summary Steadiness

    The heart-rate-zone bar appears as soon as a zone is active, and workout summaries add average and variation scores.

A note from me

I Used to Push Too Hard

Hi — I'm Łukasz. I made this small app mostly for myself.

I've had migraines all my life, and in sport I was always the one pushing too hard, sure that more effort meant more worth. Chasing results just brought me injuries and more migraines. It took me a while to realize sport is meant to serve me, not the other way around.

So I built the simple thing I'd always wanted: a quiet nudge that shows me when I'm speeding up for no reason. Now I read the numbers to stay steady and kind to my body — not to fix myself.

Constantin is just that — the gentle companion I wish I'd had.

— Łukasz, szmigieldesign

Platform & setup

Ready When You Are

Works with UI2 Suunto devices, including the Suunto 9 Peak Pro and newer.

  1. Add it before you run.

    Add Constantin as a SuuntoPlus™ app on your watch ahead of your workout.

  2. Open it mid-run.

    Once your workout is running, open Constantin to check whether your effort is staying on track. Use the upper button to move through the Drift, Pace, and Heart Rate views.

  3. Give it a few minutes.

    Values may show -- until your watch has enough valid speed or heart-rate data. The trend fills in gradually as the workout settles.

New to SuuntoPlus™? See how to get started →