Clearer acceleration and lateral force feedback in Protern
Protern uses GPS data from the Protern Sensor to help coaches review speed, acceleration, and lateral forces together with video.
This data is collected in real training conditions. Outdoors, at speed, and across varied terrain. Small measurement variations are unavoidable. They are usually hard to see in speed itself, but they become very noticeable when looking at acceleration and lateral g.
To make these views more useful during daily coaching, as of January 22nd 2026, we have updated how speed data is handled across Protern.
What has changed
Speed data is now lightly smoothed before it is used anywhere in Protern.
This means:
- All displayed speed values use the smoothed data (e.g. instant, average and max speed)
- All metrics that depend on speed use the smoothed data (e.g. acceleration and lateral force)
- All overlays, graphs, and comparisons are based on the same updated values
The goal is simple. Remove small, rapid speed jumps that come from measurement noise, so the data better reflects what actually happened during the run.
What stays the same
Speed itself remains effectively unchanged.
In testing, we found the following:
- Average and Instant Speed changed by about 0.1%
- Maximum speed changed by about 0.4%
These differences are barely noticeable during data review. What does change is how cleanly the data reads when it is used to explain movement and forces.
Where this helps in Protern Video
Acceleration data-overlay
Acceleration is calculated from speed. When raw speed jumps slightly from point to point, acceleration becomes noisy and spiky.
With the updated speed handling:
- Acceleration overlays are smoother
- Short spikes are reduced
- The build-up and release of acceleration through the turn is easier to follow
The improved acceleration data has enabled us to release the following new overlays in Protern Video:
- Single videos: Acceleration & Path - Acceleration projected on the athlete's line for single videos
- Side-by-side videos: Acceleration comparison (absolute and relative)
Lateral g overlay
Another big improvement is in the lateral g overlay.
Previously, small speed variations could dominate the overlay, making it harder to explain what the skier was actually doing in the turn.
Now:
- Lateral g follows the rhythm of the turn more clearly
- Peaks align better with turn shape and timing
- Coaches can explain where force builds, where it releases, and how different runs compare, without having to explain away noisy spikes
Side-by-side comparisons
When comparing runs side by side in Protern Video:
- Acceleration comparisons are easier to read
- Lateral g comparisons are more consistent
- Differences between runs stand out without being masked by noise
This is especially helpful when comparing line choices, tempo, or execution changes.
Where this helps in Protern Web
Analyze runs – speed graph
In Protern Web, the speed graph in Analyze Runs benefits from the removal of small speed jitters.
This is most noticeable in Slalom and GS, where frequent direction changes can exaggerate measurement noise.
The result:
- Smoother speed traces
- Clearer sections of speed gain and loss
- Easier interpretation across runs
Analyze runs – acceleration graph
The acceleration graph in Analyze Runs also benefits. It now:
- Shows clearer trends across the run
- Avoids rapid up-and-down movement that did not reflect skiing changes
- Supports cleaner comparison between athletes or sessions
Tracking lateral force over time
For coaches who track lateral g across sessions or phases of training, this change provides a more consistent baseline.
While individual values may differ from older data, the new values:
- Better reflect sustained force application
- Are less influenced by short measurement jumps
- Make trends over time easier to trust
This change reflects clearer measurement, not a change in athlete performance.
Summary
This update improves how Protern presents speed-based feedback across our tools.
- Speed values remain effectively unchanged
- Acceleration and lateral g overlays are easier to read
- Comparisons between runs are clearer
- Trends are easier to explain during review
The result is data that supports coaching conversations, instead of distracting from them.
If you have questions about how this appears in your own sessions, the Protern team is always happy to help.
